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SERVICING - HIFI - i Electronic c. ~ z house number C: ~<'CS -~ :a :::, c. Convert a CB radio i for amateur use ~ .!!! <I: >, .c "0 Q) a; iii "c, £ 5-element FM antenna Matchbox crystal set Hifi review: Yamaha's brilliant new CD player - - Plus - the Original & Best TV Serviceman, Vintage Radio, The Way I See It, the Evolution of Electric Railways High Performance In Your Shirt Pocket! 3 1/2 digit LCD Display Ranes Max Res Accurac Vdc Vac Ade 100µV 1mV 100µA 10mA 100µA 10mA 0. H2 200mV-1kV 2V-750V 200mA 10A Aac 200mA 10A Ohms 200r.!-2Mr.! Display also has Low Battery & Over-Range Indication 0.5% + 1dig 0.75%+5dig 0. 75%+ 1dig 1.5%+5dig 1%+5dig 2%+7dig 0. 75%+ 1dig Built In Diode Check, Lo-Power Ohms & Continuity Test Beeper Memory Function for Relative Readings (DM6235 & DM6335) Autoranging Manual Ranging Over-Ride (DM6235 & DM6335) One Year Warrant Hold Reading Function (DM6335) 10A Range Automatic Current Limiting Overload Protected to 1000Vdc/750Vac $88.80 $99.60 Look At The Low Pricesl DM6135 Autoranging 3 1/2 digit 1OA ac/dc DM6235 As above with Memory function and Range Hold Prices include 9V Battery and High Quality Silicon Rubber Test Leads with Screw-On Alligator Clips DM6335 As above with Data Hold l0MQ Input Impedance Gotta Gatta GoldStar Dealer enquiries welcome. Call (02)736 2243 Recommended prices only including Sales Tax $118 • 80 You've Gotta Getta Goldstar from : M.,L John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 N.S,Y\', Ames Agency 699 4524 • J Blackwood & Sons• George Brown 519 5855 Newcastle 69 6399 • Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebson 707 2111 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Pty Ltd 698 4776 • Petro-Ject 569 9655 • David Reid 267 1385 • Digitel 709 6511 • Geoff Wood 427 1676 N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 QUEENSLAND Auslec (07) 854 1661 • G. Brown Group (0 7) 252 3876 • Petro -Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff Electronics 341 4655 • L.E.Boughen 369 1277 • The Electronics Shop (075) 32 3632 • Thompson Instruments (Cairns) (070) 51 2404 • Nortek (Townsville)(077) 79 8600 S.AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 0391 • Petro-Ject 363 1353 TASMANIA George Harvey (003) 31 6533 (002) 34 2233 VICTORIA Rad io Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301 • A.W.M. Electrical Wholesalers• Petro-Ject 419 9377 • J Blackwood & Sons 542 4321 • Factory Controls (052) 78 822 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044 OCTOBER 1 988 FEATURES THIS STEREO FM transmitter can broadcast your favourite CDs to your personal portable or to your car's AM/FM radio. It's based on a single chip so that it's easy to build. Details page 14. 4 Electronics & Brock's BMW Blaster by Leo Simpson Sensors monitor the car's performance 20 Yamaha's Brilliant New CD Player by Leo Simpson Uses 8-times oversampling for improved specs 76 The Evolution of Electric Railways by Bryan Maher Pt.12: Queensland's powerful new electric locomotives PROJECTS TO BUILD 14 Build an FM Stereo Transmitter by John Clarke One IC lets you listen to CDs on your W alkman 28 High Performance FM Antenna by Bob Flynn 5-element design fa~ improved fringe area reception 52 The Classic Matchbox Crystal Set by Steve Payor Super-sensitive circuit pulls in the stations 64 The Led-Light House Number by John Clarke Turns on automatically at dusk IF YOU CAN DO BASIC metalwork you can build this high-performance FM antenna. It's a 5-element Yagi design that's just the shot for fringe area reception. See page 28. _ _, . , _ _ , . _ _ _ _ A > > ~ .,_,-i'::,~' ❖,_..,. SPECIAL COLUMNS 8 Vintage Radio by John Hill Checking out the power supply 36 The Way I See It by Neville Williams Fly by wire: is it safe from electromagnetic interference? 44 Serviceman's Log by the original TV serviceman Curing woolly pictures at Wollongong 84 Amateur Radio by Garry Cratt Convert a CB radio to the 28MHz amateur band ¼i ... ~-~ ~'•,-: .. _~--·~ ~t __ ,: • - .- , ~ " ~;;~ ,+1V'N.'$"'#>'-"',ili;'/ ~ «¼~ ,. P///<%% YAMAHA'S NEW CDX-1110 CD player features 8-times oversampling for unrivalled linearity and brilliant signal-tonoise ratio. Our review starts on page 20. DEPARTMENTS 2 Publisher's Letter 3 Mailbag 61 Subscription Page 70 Circuit Notebook 81 Back Issues 90 Product Showcase 97 Ask Silicon Chip 99 Notes & Errata 100 Market Centre YOUR HOUSE WILL BE easy to find at night with this house number. It uses LEDs that turn on automatically at dusk and then turn off again some four hours later. Construction starts on page 64. OCTOBER 1988 1 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby Photography Bob Donaldson Editorial Advisory Panel Philip Watson , VK2ZPW Norman Marks Steve Payor, B.Sc., B.E . SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Magazine Printers Pty Ltd, Waterloo, NSW 2017 . Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Typesetting/makeup: Subscription rate: currently $42 per year ( 12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue . Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 * Recommended and maximum Australian price only. 2 SILICON CHIP PUBLISHER'S LE't-lER Those wonderful infrared remote controls Ever stopped to consider just how wonderful some electronic products are? My favourites are the remote controls for my VCR and TV set. And I know that anyone who has a remote control for their TV set loves it too. Don't like that program or that advert? Just zap it and something else is on the screen. Have you ever stopped to watch how people use their remotes? Some people have it on the table in front of them and they stab the buttons viciously to erase the offending images. Others hold the remote control in their hand and derisively thrust the unit at the TV as they zap the program off the screen. Or perhaps they just casually render the talking head voiceless so that adverts can be ignored. And consider how handy it is to be able to "fast forward" through the commercials when you are watching a videotape. So attached to the remote am I that I become irritated if I can't immediately reach it while I am watching the Teev. But aside from the utter convenience, remote controls are a wonderful piece of technology. First of all, they employ one or two infrared light emitting diodes which are pulsed on and off at a rate of around 10kHz or so. The pulses are actually a serial data stream corresponding to the button you've pushed. Each button, and there may be 40 buttons or more on some complex remotes, has its own special data code. These pulses of infrared light from the remote transmitter (you could almost think of them as pulses of heat) are received by an infrared detector (diode or phototransistor) inside the appliance and converted to an electrical signal. This is fed to an amplifier which filters out all the noise and then passes it to a decoder. Normally the decoder is a dedicated microprocessor which puts out digital signals in response to your commands. Some of these digital signals will be converted to analog signals, to change the volume setting or the DC voltage to the varicap tuner in the VCR or TV set or to do some other task. All this happens within a few tens of milliseconds of you pressing a button. And when you're not pressing a button, the encoder chip inside the control is quiescent, draining perhaps only a fraction of a microamp from the batteries. No wonder the batteries last a long time. We've come to accept this wonderful technology as nothing special. It's just one of the features of electronic appliances. But next time you pick up your remote control to zap an advert, think about the complex series of electronic events you set in motion as you push the button. And we just take it all for granted. Leo Simpson MAILBAG Non-serviceable appliances Maybe even an advert in the I sympathise with the comments classified section of this wonderful electronics journal might be the way. about non-serviceable appliances, Please. minor and major, in The Way I See It Grant Lockie (June 1988). It is evident these are Mangakino, NZ designed for the consumer throwSorry, but we really have sold out of away market and that this market acthe January issue. If anyone has a cepts such a philosophy. spare copy, we'd be happy to pass it on The label "no user-serviceable to our reader (free of charge, of parts inside" is perfectly honest, as course). they do not contain bulbs in bayonet sockets. "Refer servicing to qualified On aesthetics and attenuation personnel" is positively a compliAs usual, another enjoyable issue ment! of SILICON CHIP has come out this "Return to supplier for repair" is, month. I gather from reading the on the other hand, dishonest outside Studio 200 Control Unit articles it the warranty period for this breed of would be a superb piece of hifi gear throw-aways as the exercise is, by but I was bit taken aback by the definition, pointless. The genuine ex- starkness of the control markings on ception relates to ionisation type (the the front panel. I feel a few abbreviabest) smoke detectors, although tions would have looked better (ie, truthfully, they are not hazardous. bal, mon, vol) and the Source label "Not able to be repaired" or under the selector eliminated as this similar appears occasionally and is is self explanatory. economically, but not usually The same goes for the use of the technically, honest. tone defeat switch which is obvious While glued assembly makes simply by using it - why not label it repair difficult as with the more ex- "defeat". Your logo would have lookotic "snap" construction, heat- ed nicer in a not-so-heavy block print rivetting is fairly easy to undo and re- . or some other fancier writing and I do and if one were able to find a real hate the line under the name. engineering shop anymore, the If I make this unit I will make my "weird" screwdrivers are probably own front panel for sure as obtainable. Also, a toolmaker could everything else is great. Hope you supply one if a repairer wanted to use don't mind the criticism; it keeps you it often enough. on your toes. You are probably closest to the One other point: why don't you attruth when you consider the legal tenuate the CD input. If you have 2 aspect; ie, that of the manufacturer volts output from CDs and a line input providing no "reasonable" ~eans of of 240mV, won't this mean that the repair to exempt itself from any con- volume control would be turned down sequent liability. more for CD than for other inputs? I realise you don't get overload with P. B. Webster, VK2BZC the volume control ahead of the rest Lake Cathie, NSW of the circuitry but one would have to Craving for a January issue remember to turn it down more for · Thanks for your fast response to CDs. my order for a subscription and back Keep up the good work and looking issues. I have now read them all and forward to next month's issue. in a word, "cracker". Unfortunately, Paul Gee Orient Point, NSW you were not able to supply a copy of the January issue, so now it's time to Nah, we don't mind criticism. Weigget on my knees and beg, grovel, nore most of it anyway. We think the plead and, if necessary, . prostrate labelling on most hifi equipment is far myself and even pay unreasonable too small to be easily readable by most of the population. Be honest now: can amounts of hard-earned for maybe a spare slightly dog-eared old office you read the control labels on most hifi copy, or a return from a newsagent gear when at arm's length? If you can, you are fortunate. from the back of beyond. SILICON CHIP, PO Box 139, Collaroy Beach 2097. There is no need for attenuation of CD signals. Remember that the 2 volt RMS (2.B volts peak) output only occurs on very loud musical peaks; normal program levels are a great deal lower. What this means is that there is usually not much difference in volume settings as you switch from phono to tuner to CD and so on. It just isn't a problem. And if you attenuate the signal, there will inevitably be a reduction. in the signal-to-noise ratio. Commercial stereo amps normally don't attenuate either. Query on circuit diagrams I was most impressed with the July 1988 issue of SILICON CHIP particularly the presentation of the Discolight. I find the circuit diagrams in your magazine well laid out and easy to follow. I have just one small quibble. Shouldn't the inputs of the unused CMOS gates be shown tied high or low? I am sure they actually are tied one way or the other on the printed circuit board but possibly they should be shown on the circuit too. Keep up the good work. A. Lackey Collaroy Plateau, NSW We agree that unused CMOS gate inputs must be tied high or low otherwise it is possible that they may oscillate. They are tied on the printed board of the Discolight. However, we make a special effort to make the circuit diagrams uncluttered and easy to follow. That means that we leave out the more or less extraneous details, such as unused CMOS gates. After all, showing these gates would not aid understanding of the circuit, would it? UHF remote transmitter/receiver Why does the UHF remote transmitter/receiver operate on 304MHz? Perhaps I missed seeing it but I found no information in your magazine which explains this point and, for example, discusses the choice of 27.145MHz for commercial garage door operators etc. I suspect that the Department of Communications and the Standards Association of Australia have an influence and I would appreciate a Continued on page 96 OCTOBER 1988 3 BROCK'S BMW: ELECTRONICS UPDATES On October 2nd, millions of Australians will watch the motor racing at Bathurst. In particular, their eyes will be on Peter Brock and his co-drivers. Computers will be watching him too as he strives to get the very best out of his BMW M3 sedan. By LEO SIMPSON Just how do you screw the very maximum performance out of a racing sedan over a distance of 1000km without running the risk of blowing it up before the finish? That is a question which continually haunts racing drivers and their backup teams as their cars hurtle around the track. More than any other driver, Peter Brock has always managed to perform this task to the optimum. They don't call him "Peter Perfect" for nothing. That he has won more races than anyone else is a tribute to his superb feeling for motor cars. He has been able to judge just how hard to push a car while still keeping enough in reserve to be able to finish the race. In other words, there is more to winning a race than just being able to go fastest around the track. But as motor racing becomes more competitive, even superlative drivers like Peter Brock need more than just the "seat of their pants" to keep them out in front. And this is where computers are being brought into the picture. Not that computers have not been involved in motor racing for a number of years. Most of the cars circulating around the track at Bathurst this year will have one or more on-board computers in their ' ' engine management systems''. These systems are used to control the ignition timing and fuel injection. The problem with existing engine management systems in cars is that they don't tell the driver anything about the state of the engine. They have been designed that way so that they are as unobtrusive as possible. But even if the engine management system did provide This diagram shows the main components of the Netcomm Racing Modem System. The system can cope with more than 60 sensors on the car. PC UHF RADIO 4 SILICON CHIP feedback to the driver, he would still want to know more, about the state of the tyres, brakes, suspension and so on. If racing drivers had this information about their cars' condition, they could push them a lot harder. In the meantime they have to err on the side of caution if they are to finish a race. Overcoming this lack of information has been a joint project between leading data communications manufacturer Netcomm Pty Ltd and Peter Brock's BMW racing team. Netcomm and Brock are in the process of developing a comprehensive monitoring scheme which will give real-time information about virtually every aspect of the car during a race. Called the Netcomm Racing Modem System (RMS) it was first featured in the car driven by Murray Carter in the 1987 Bathurst 1000. This year it will be featured in the Mobil BMW car driven by Brock as well as Murray Carter's Ford Sierra. Racing Modem System As the name suggests, the RMS is based on modems but there is far more to it than that. The basic rac- DATA .. CAR COMPUTER SENSOR 4FHE PIT CRE Peter Brock in the BMW M3 sedan at Oran Park on Sunday 28th August. Brock won this race. Will the Racing Modem System give him the edge to win at Bathurst in October? (Paul Buchtmann photo). ing modem system consists of a bank of sensors placed around the car, an on-board computer, a modem and a UHF (ultra high frequency) transceiver. The computer converts all the signals from the sensors into a digital data stream which is fed via the modem into the transceiver. The transmitted information is picked up at the pits by another transceiver and modem and fed into a computer where it is displayed on a video monitor for constant analysis by technicians. As the race progresses, technicians can monitor every aspect of the car and thereby are able to spot problems before they become disasters. Sensor functions Just to show how comprehensive the monitoring is, the various sensors and their functions are listed, as follows: • Engine tachometer: measures engine revolutions up to 9000 RPM. This is one of the screen displays used on the Apple Macintosh to display car sensor information. Note the thermometer displays for temperature readouts and the dial displays for speedometer and tachometer readings. (Paul Buchtmann photo). OCTOBER 1988 5 A laptop computer can be used to replay data recorded during a practice or race session using the Netcomm Racing Modem System. In this way, the driver can optimise his performance on the track. This photo shows how the Netcomm modem and UHF transceiver are installed under the dash of peter Brock's BMW sedan. The modem transmits at between 2400 and 9600 baud. (Paul Buchtmann photo). • Speedometer: measures up to 300km/h. • Backward/forward accelerometer: measures the acceleration and braking forces on the car and driver. • Up/down force: measures the downward force applied to the car by the spoilers. • Left/right accelerometer: measures the cornering forces on the car and driver. • Engine oil pressure. 6 SILICON CHIP • Engine oil temperature. • Fuel pressure: measures the pressure of the fuel delivered to the injection system. • Fuel temperature: measures temperature of the fuel to determine if vapourisation is occurring. • Water temperature: measures the temperature of the water as it passes from the engine to the radiator. • Detonation: an acoustic sensor monitors for the onset of this critical condition. If detonation occurs at racing speeds it can destroy the engine. • Exhaust gas: measures the carbon monoxide content of the exhaust gas. • Exhaust port temperature: each cylinder exhaust port is measured. This is another critical engine parameter. The piston heads are run at a temperature which is at times just below melting point. • Relative horsepower: a figure obtained from the existing engine management system on the BMW. • Battery voltage. • Battery current. • Fuel pumps: monitors which pump is operating. • Fuel flow: measures the rate of fuel consumption. • Gearbox oil pump. • Gearbox oil temperature. • Engine bay temperature. • Differential oil cooler pump. • Brake temperature: brake discs will glow red hot when braking at the end of the straights. If the calipers become too hot there is a risk that the brake fluid will boil. • Brake pedal pressure. • Brake pad wear. • Brake lockup: determines if the wheels lockup under braking. • Wheel spin: determines if the rear wheels lose traction under acceleration. • Throttle position. • Cabin temperature: air conditioning is not a feature of racing sedans. • Air temperature: measures the ambient temperature around the car. • Humidity: measures the ambient humidity around the car. • Air pressure: measures the atmospheric pressure. • Driver temperature: measures body temperature. • Driver heart rate. • Tyre temperature: the temperature of the tread casing of all four tyres is measured. If it exceeds a critical level, the tyre will disintegrate. • Tyre pressure. • Shock absorber temperature: each shock absorber is measured. If shock absorbers get too hot they cease to work properly and the car's handling suffers accordingly. This photo shows the prototype Netcomm system as used on Murray Carter's Nissan in 1987. • Vibration: measures vibration of the car body. That adds up to more than 45 sensors although we understand that some of these are not yet on the car. Tyre pressure monitoring is a particular problem; just how do you measure pressure in a spinning tyre? Netcomm weren't saying. Tyre temperature, on the other hand, is measured by infrared pyrometers spaced a critical distance away from each tyre. They have to get the spacing just right. Too far and sensitivity is degraded; too close and the oscillating wheel will rip out the sensor. Many of the sensor functions are already provided by the existing engine management system on the BMW and its anti-skid braking system (ABS). But that still left a great many others which have had to be installed. Processing the data Signals from the sensors are fed to a data acquisition computer which can accept up to 66 inputs. The computer is based on an 8-bit microprocessor with 32K of ROM (read only memory) and BK of RAM (random access memory). The computer prescales the inputs (ie, attenuates or amplifies the signal for optimum data transmission) and then performs analog-to-digital conversion. The digital data is encoded with a parity system for error correction - most important in a telemetry system of this complexity. The resulting 8-bit parallel data is then converted to a serial data stream to pass via an RS232 port to the Netcomm modem. The FSK (frequency shift keyed) signal from the modem is then fed to a transceiver (a combined transmitter and receiver) transmitting in the 470MHz band. The transmitted signal is picked by another transceiver in the pits area of the track and the detected signal fed to another modem to produce an RS232 signal fed to the port of a Apple Macintosh. This is specially programmed to display the information from the car sensors. Graphic displays Rather than just display the information as numerical quantities, the computer is programmed to display the information graphically. Hence, there are displays on the screen, to depict a speedo, tachometers, various thermometers to show the many temperatures be- ing monitored and so on. In this way it is easier for the technicians to monitor any changes just by glancing at the pointers, thermometer levels etc rather than having to pick specific figures off the screen. Not only is all the sensor information able to be displayed on the screen, it is stored in the computer for later more detailed analysis. Of course the Racing Modem System is heavily used in practice and training sessions. During these times the drivers can really push the car to the limits and beyond. This enables the technicians to build up comprehensive information about the onset of failure all the car's systems. It remains to be seen whether the Netcomm Racing Modem System gives Peter Brock and his team the necessary edge to win at Bathurst. But one thing is certain - it will be used on more racing cars in the future. •~ Our thanks to Netcomm Australia Pty Ltd and Communications Solutions Australia Pty Ltd for their assistance in the preparation of this article. OCTOBER 1988 7 VINTAGE RADIO By JOHN HILL Checking out the power supply The power supply must be carefully checked out before switching on a vintage radio. The components most likely to be at fault are the electrolytic capacitors, most of which should be replaced as a matter of course. Although only a few parts are involved, the power supply is a common source of problems in vintage radios. It should be carefully checked out before power is applied, as a fault here can quickly cause damage to critical components. Most mains-operated valve radios have three separate secondary windings on the power transformer. These secondary voltages are used as follows: 5 volts for the rectifier filaments, 6.3 volts for the heaters in the other valves, and a high tension (HT) winding ranging from 285 to 385 volts a side (equivalent to 570 volts, centretapped). The 5V and 6.3V AC supplies are wired straight from the transformer to the filaments and heaters. However, the high tension supply must be rectified to give a high-tension DC supply for the anodes and screens for the various receiving and outpuf valves. A vacuum tube rectifier of the full wave type (two diodes in the one envelope, with the cathodes joined together) is used for this purpose. Now the figures presented in the preceding paragraphs work in with a good many Australian-made sets from the mid 1930s-1950 era. Fig.1 shows a typical circuit configuration but there are other variations. For example, some rectifiers require a cathode voltage of 6.3V AC, not 5V. Similarly, not all radio valves use 6.3V heater supplies. There are 2.5V valves, 4V valves and 12V valves in some late model sets. In these radios, the low tension voltages on the transformer will be different - but that's about all. The high tension voltage will still be well in excess of 250 volts. The output from the rectifier valve will not be pure DC but does contain some 100Hz hum. The amount of hum will depend on the degree of "smoothing" provided by the following filter network. Whilst mains hum can be eliminated completely, most radio manufacturers settled for reducing it to a reasonable level. This smoothing of the rectifier output was accomplished in several ways. The most common method in the older valve radios involved filtering the rectified DC with a choke and two high-voltage electrolytics, as shown in Fig, 1. Both the choke and the capacitors help to smooth out the ripple, which reduces the intensity of the hum. In later radio designs, a high-wattage resistor was often used instead of the choke. Electrodynamic speakers The heart of many an old set's high tension supply - a 5Y3G rectifier valve. Other common rectifier valves lilcely to be found in vintage radio sets are the 5Y3GT, 280, 80, 5Z3, 5U4G, 6X4, 6X5GT, 83V and the 5V4G. 8 SILICON CHIP Most radios made up to the late 1940s incorporated the high tension choke in the loudspeaker, where it served a dual purpose. As well as smoothing out the rectified DC, the current flowing through the choke Sets from the late 1940s and early 1950s used a chassis mounted choke. Spare chokes come in handy from time to time. Many high tension chokes in early valve sets doubled up as a field coil in the loudspeaker. This derelict electrodynamic speaker shows the field winding to be a large coil of fine wire. provided the magnetic field for the ''electrodynamic'' loudspeaker . This type of loudspeaker was used before the devolpment of permanent magnet speakers. Electrodynamic loudspeakers are not without their problems, but more about that some other time. If a radio set has a permanent magnet speaker, then the choke will be bolted to the chassis somewhere. A choke looks like a small transformer but only has two connections. It is nothing more than a large coil of wire with an iron core. An open circuit choke, whether it be in the field coil of the loudspeaker or a separate choke unit, is frequently a problem with a 40 or 50-year old radio. Often the set has been stored unprotected for years in an outdoor shed. This can Fig.1: this power supply configuration was standard in many Australian valve radio sets. Be wary of the rectified HT and the high-voltage transformer secondaries - these voltages are potentially lethal. CHOKE '--- -- - --+-...r12·16 + 350VW! HT +250V APPROX 12-16 + 350VW! promote corrosion where the fine wire of the choke coil joins the leadout wires, but this is not the only mishap that can happen to a high tension choke. The point is, if the choke becomes open, that effectively disconnects the high tension supply to the valves and a very mute set is the result. A burnt-out winding is another common cause of choke failure. I remember once observing smoke quietly pouring out of a choke within a minute or so of switching the radio on. The set seemed to be working fairly well, yet the choke was overheating enough to produce visible smoke. If prolonged operation under these circumstances is allowed, the choke will soon burn out. The cause of this problem is usually a faulty capacitor; eg, a faulty electrolytic on the choke output, or a faulty paper capacitor on the HT line. As we've seen in a previous episode, the waxed paper dielectric that separates the two layers of foil breaks down and causes electrical leakage between the plates of the capacitor. This breakdown can result in anything from slight leakage to a complete short circuit. The more current through a leaky capacitor, the greater the current flow through the choke. Hence, a choke can be overloaded if the set has defective capacitors. It is good practice to replace all paper and electrolytic capacitors when restoring old valve radios - particularly those capacitors which operate with high voltages across them. Replacing chokes It will be fairly easy to replace a choke that is attached to the chassis, but the job will be more difficult if the choke forms part of the loudspeaker. In the latter case, you will have to replace the loudspeaker as well and that usually means substituting a modern permanent magnet type unless you happen to have a suitable spare. So, before switching an old radio on, it is a good idea to thoroughly check out the high tension supply if there's a short somewhere, you could wreck a perfectly good elecOCT0BER 1988 9 Replacing a power transformer is not difficult if it is clearly marked like the one in the middle. In other cases, you will have to first identify the primary winding, then locate the other windings by making voltage checks. i ~ The speaker field coil can be mounted under the chassis if an old set is converted to permag (permanent magnet) speaker operation. Make sure that the choke is properly secured. trodynamic loudspeaker. If in doubt, put a milliamp meter in the choke circuit and find out what's going on. Most chokes that are fitted to a 5-valve receiver are rated at 60 milliamps . Remember, it is quite normal for a choke or speaker field coil to become warm when in use but it is not normal for it to become hot or to give off smoke. By the way, the HT voltage on the output side of the choke should be about 250 volts DC and this can be 10 SILICON CHIP quickly confirmed using a multimeter. If the voltage is higher, it may be caused by a non-standard component replacement (eg, a replacement choke or loudspeaker of the wrong impedance) and something should be done to correct the situation. Adding a resistor to the high tension line could solve this problem. Electrolytic capacitors Electrolytic capacitors are an important part of the high tension sup- ply. As previously mentioned, a shorted electrolytic can soon wreck the choke or the speaker field coil. The rectifier valve could also be damaged due to excessive power dissipation - the anodes will get red hot. Although I recommend that all electrolytic capacitors be replaced, this may not be strictly necessary in all cases. In post-war sets, you may be able to get away with the original capacitors. They should be thoroughly checked though. A visual inspection is a good starting point when checking electrolytic capacitors. It will be fairly obvious if the fluid inside the capacitor has been leaking: the seal at the positive end of the capacitor will be cracked or punctured in some way. Any capacitor that shows signs of leakage must be replaced, even if the set still appears to be working OK. Old electrolytics should also be checked for electrical leakage and this can be done using an ohmmeter set to the tkn scale. When the test probes are applied, a good electrolytic will initially cause the meter needle to rise dramatically (half scale deflection or more), then fall back to almost zero as the capacitor reaches full charge. A reading of several megohms indicates a good electrolytic with very little leakage. However, old electrolytics that have not been in use for many years often show a much higher reading on the meter. In many cases, this _ high degree of leakage is only temporary. Putting the capacitor back into service helps to reform the aluminium oxide dielectric inside the capacitor and it often works normally again. You can check whether the capacitor has been reformed by another leakage check. After the set has been running for five minutes, turn it off, let the capacitor discharge and do another leakage check. If the leakage is still high, the capacitor should be replaced. A final check for an old electrolytic is a capacitance test. Many digital multimeters have a capacitance function up to 20µF or thereabouts. Be warned though; without the correct polarising voltage, the measured capacitance will only be a guide. Remember also that old electrolytic capacitor tolerances were very wide (typically + 100% to - 50%}. It is a good idea to always discharge the electrolytic capacitors before working on a set. However, don't do this by directly shorting the capacitor terminals with a screwdriver blade or similar instrument. Discharging a capacitor in this manner can cause internal damage due to the high discharge current involved. A far better method is to use a lOkO resistor fitted with a couple of probes. This will limit the current to a safe value. The rectifier valve The rectifier valve itself must not be overlooked in this discussion on high tension. A rectifier may light up OK but that doesn't mean that it will work properly. Filament type rectifiers have specially coated filaments that give off high electron emission at relatively low temperatures (red heat). This coating is easily seen by looking into the glass envelope of the valve. Such a visual inspection is a reasonable way to determine the general condition of the rectifier, excluding short circuits and other nasties. If the filament is white, the coating is intact. If the filament is bare and metallic looking, then the coating has either burnt off or has fallen off. In some cases, the filament coating can be seen in bits and pieces drifting around inside the glass envelope. What the foregoing really means is this: if the filament is bare, the electron emission will fall to such a low level that the rectifier will not pass sufficient current for the set to operate correctly. In many cases, low volume in a valve receiver is the result of abnormally low hightension voltage due to a worn-out rectifier valve. Simply replacing the rectifier will boost the volume considerably. Much the same can be said about rectifiers with indirectly heated cathodes. The cathode is coated and, if this coating has cracked or SPECTACULAR ELEASE vifa NEWSA-100 SPEAKER KIT Since the introduction of VIFA speaker kits in Australia in 1985, thousands of speakers have been built with superb results. VIFA is now proud to release four new speaker kits ranging from a mere $399 to $1199 per pair including cabinets. Never before have speaker kits been so popular in Australia than after the heavy devaluation of the dollar. Similar fully imported quality loudspeakers are today typically 2-2½ times more expensive. And these speakers may very well be using Danish VIFA drivers anyway, as VIFA supply more than 50 of the world's most respected loudspeaker manufacturers with drivers. But why the big savings? Because fully imported speakers suffer from 25% import duty, 20-30% freight, 30% sales tax and 28% handling charges (typically). So if you would rather put your money into better quality than in other people's pockets, VIFA speaker kits are the only way to go. Are they difficult to build? No, the kits are supplied with all parts needed including fully built crossovers and pre-cut flatpack cabinets ready to assemble. No soldering or carpentry skills are needed, just a Phillips head screwdriver, some simple hand tools and a few hours of your leisure time. Are they as good as people say? Read the reviews, listen and compare with any other speakers twice the price or more. Need we say anymore? VIFA for the quality conscious audiophile. For full details please contact Sole Australian Distributor: SCAN AUDIO Pty. Ltd. P.O. Box 242, Hawthorn 3122. Fax (03)4299309 Phone: !03l 4292199 (Melbourne) 02 5225697 (Sydney) 07 3577433 (Brisbane) 09) 3224409 (Perth) Stocked by leading stores throughout Australia Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Whv design circuitry which requires additional components to achieve a specific capacitance; we can wind exactly the capacitance you need to match your design criteria within the ranges of 10pF to 1µF and up to 10,000VDC. Capacitors are manufactured to 0.25%, 0.5%, 1.0%, 2.0%, 2.5%, 5%, 10% and 20% and are priced according to tolerance. All capacitors are tested to 2.5 times the rated voltage. Interested? Call us now on: (02) 938 4690 OR Cut out and post this coupon to ~--------~---. I Yes, I am interested in your capacitors. Please post me details of the following values: II ... /... VDC ... / ... VDC . /. VDC . 1 . VDC I Name (Please print) I Address I I I I I Box 7 40 ~ B . r_o_~_v_a_~_._N_.s_.w _ . _2_1o_o___ L~~~~~~~~~~~J Post Office OCT0BER1988 11 There are many high voltage connections underneath the chassis. Don't take unnecessary risks when working on the high tension supply, as the voltages are potentially lethal. Old electrolytic capacitors can cause serious problems in the high tension department. Their replacement is always a good move. worn away, the performance of the valve is suspect. Naturally, a valve tester can save a bit of guesswork in this regard. However, a good many restorers work without such an instrument and a visual inspection followed by an in-circuit check will do the job just as well. Power transformers Power transformers in old radios are usually very reliable. However, they do break down occasionally and the usual problem is a burnt out primary winding. If the primary or any of the other windings has broken down, the only 12 SILICON CHIP solution is to replace the transformer. This is another situation where it pays to have a good supply of spare parts. Radio wrecking is a very important aspect of vintage radio work and every restorer should have a good range of power transformers on hand to cope with emergencies. Changing a transformer over is a fairly simple job if the connections are clearly marked. However, in many cases, there is nothing more than a bunch of multi-coloured wires emerging from the transformer. This means that a bit of circuit tracing is required to identify the leads. This can be done by trac- ing the leads back to the 240 volt AC line, the rectifier filament (5 volts), the rectifier anodes (285 volts) and the valve heaters (6.3 volts). The connections on the replacement transformer may also need sorting out. The primary leads are usually the leads closest to the core. Once these have been identified, the unit can be temporarily connected to the mains and the remaining windings identified using a voltmeter. Note that, in most cases, the high-voltage secondary winding will be centre-tapped. Take great care when making these measurements. Both the mains and HT secondary voltages are dangerous and getting tangled up with them could well be the last thing you do on this earth. In fact, it's a good idea to terminate all leads from the transfomer in a terminal block before applying power. It should only be installed in the chassis after the leads have all been identified. Another way of identifying transformer leads is to apply an AC test voltage to one of the lowvoltage' secondary windings (either the 5V winding or the 6.3V winding). The leads to these windings use stout single-strand copper wire, so they're easy to identify. All you have to do is to apply the test voltage (say 6.3V AC) to one pair of leads that have the same colour code, then identify the remaining leads using a multimeter. It doesn't matter which lowvoltage secondary winding you feed the test voltage into. If you guess correctly and feed a 6.3V test voltage into the 6.3V winding, then all the other voltages will be correct. But if you pick the 5V winding, all the other voltages will be high by a factor of about 1.26 (ie, 6.3 + 5). If you use a test voltage other than 6.3V AC, the expected output voltages will be scaled accordingly. Finally, always remember to disconnect the power supply and discharge the electrolytics before working on the set. If you follow this simple safety routine you will live to enjoy your hobby for some time to come. Next month's vintage radio topic will be on loudspeakers. ~ The Mini-mitter is a miniature stereo FM transmitter using just one integrated circuit and powered by one 1.5V penlite cell. You can connect your CD player to the Mini-mitter and then listen to your favourite CDs anywhere in the house, via your Walkman personal portable. By JOHN CLARKE & LEO SIMPSON How would you like to listen to your favourite CDs and records via headphones without being tethered to your stereo system? Maybe you want to wash the car, mow the lawn or vacuum your house while you listen to your favourite music. Clearly, a Walkman-style cassette player will let you listen via headphones while you work but who wants to go to the trouble of dubbing a record to tape every time the mood hits you. Or maybe you have a portable CD player and you'd like to listen to CDs via your car radio. Most car radios do not have connections for an external program source so that 14 SILICON CHIP can be a real problem. If you have these problems, the Mini-mitter is the answer. You can connect it up to your stereo system and broadcast your own stereo music program on the FM band; ie, 88-108MHz. The Mini-mitter puts out a flea-power signal (around 200 microwatts or so) but that is enough to give clean stereo sound over the average portable FM radio within a range of 20 metres or so. You can use it in your car with a portable CD player, to avoid making any connections to your car radio. Just connect the CD player up to the Mini-mitter and tune in your car radio to the correct frequency to hear the program of your choice. The Mini-mitter is built into a small case and powered from just a single 1.5V AA size cell. Two RCA sockets are provided at one end of the case for the left and right audio channels. At the other end, there is a length of wire which is the transmitting antenna and there is a slide switch to turn the Mini-mitter on or off. Inside the case, there are a couple of trimpots to adjust the level of the left and right channel audio signals. These are important to obtain minimum audio distortion, especially when listening to compact discs. There are also internal adjustments to vary the transmitter frequency anywhere within the 88 to 108MHz FM band. We'll talk about these later. As you can see from the specs, battery cost will not be a problem. A normal penlite cell should last for many months even if you use it for several hours every day. A single IC provides all the .......,,s ____*___*_________ .01 .01 'T'l41-t-pF__..._L2.., i .001 18 F OUT * LEFT IN 47pF ,.. IC1 BA1404 RIGHT INPUT ~ 1.5V VR3 50k LEFT INPUT er t.J ANTENNA DSC lO * * 15pF osc=----41 1 RIGHT IN MPX OUT 14 PILOT OUT 13 10 + JJOpF 16VW _ STYRO ... 4.7pFJ ' AUDIO BIAS 2 MOO IN 12 10 DSC AUDIO RF BIAS GNO 4 3 8 + .,. * C1 15pFI 2·10pF -:- FREQUENCY TRIM ":" .,. 16VWJ .OOl+ L1 ,L2: 1.5T, 0.62mm DIA. ENAMELLED COPPER WIRE ON 5mm FORMER WITH F16 CORE .D1'i * CERAMIC FM STEREO TRANSMITTER Fig.1: the key component in the circuit is the BA1404 FM stereo transmitter IC from Rohm Corporation. This chip includes a 36kHz multiplexer plus all the necessary input amplifiers, mixers and oscillators required for FM stereo transmission. Specifications Operating voltage ... ..... .... ..... .. ....... ... .... .. ..... ...... .... .......... ... 1.5V Quiescent current ... ... ... .. .. .... .... .. .. ... .. .. .. ..... .. ..... ... .... ......... . 3mA Harmonic distortion ..... .. ........ .. .. ..... .. ...... .. . 3% for 200mVp-p input Stereo separation ........... ..... ......... .. .. ... ...... ... ... ... .... 45dB at 1 kHz Frequency range ..... ........ ... .. ... .. ....... ... ......... .. 88 .1 to 107.9MHz necessary functions for FM stereo transmission. This includes input amplifiers. 38kHz multiplexer. mixers and oscillators. Naturally there are a number of passive external components but the resulting circuit is very compact. How it works Fig.1 shows the complete circuit of the Mini-mitter. It is based on a BA1404 integrated circuit made by the Rohm Corporation of Japan. The circuit works as follows. The left and right audio signals from the program source (CD player, tape player etc) are connected to trimpots VRl and VR2 to set the input signal levels. These are coupled via a parallel network of a 47k0 resistor and .OOlµF capacitor to provide the standard 50µs pre-emphasis applied to Australian FM signals. Put simply, pre-emphasis is a defined amount of treble boost applied to the signal before it goes into the transmitter. Then, when the signal is received and demodulated, an equivalent inverse order of treble cut, called de-emphasis, is applied before the audio signal is fed to the tuner outputs. The result is an improvement in the high frequency signal-to-noise ratio, which means a reduction in audible hiss. The pre-emphasised audio signals are then coupled via a series 4.7µF capacitor and 100 resistor to the left and right inputs of the IC, pins 18 and 1, respectively. The 100 resistor is there as a " stopper" to prevent latch-up due to RF signals on the input leads. The internal bias supply for the audio input amplifiers is filtered by a lOµF capacitor connected to pin 2. To provide the 38kHz multiplex oscillator, a miniature 38kHz crystal (same physical size as a 32kHz watch crystal) is coupled via a lOpF capacitor between pins 5 and 6. The oscillator's bias supply is decoupled by a l OOOpF (.OOlµF) capacitor connected to pin 4. To provide a balance setting for the multiplexer, VR3 , a 50k0 trimpot, connects between pins 16 and 17 of the IC. The multiplexer output from pin 14 and the 19kHz pilot signal at pin 13 are mixed using series resistors and capacitors to set the correct phase and level to the modulation input at pin 12. The modulator oscillator tuned circuit components are those connected to pins 9 and 10; ie, L1 and associated capacitors. Cl , a 2-lOpF trimmer capacitor, provides fine O CT0 BER 1988 15 The completed assembly mounts inside a small plastic case to give a really compact assembly. The small trimmer capacitor (at end of pen) allows fine tuning of the transmitter output frequency. Fig.2: here's how to mount the parts on the PCB. Keep all leads as short as possible and note that some of the parts are mounted endon to save space. The coil formers for Lt and L2 are installed from the underside of the PCB. adjustment for the oscillator frequency. Inductor 12 and a 47pF capacitor at pin 7 form the tank circuit [ie, a parallel tuned circuit) for the RF amplifier. The output signal to the antenna is coupled via a 4. 7pF capacitor. One of two antennas may be used. If the transmission path is very short, you will find that a single wire 15cm long will suffice. For a more effective transmission, a simple dipole can be used, as described later. Construction The Mini-mitter circuit is built onto a small printed board (coded SC06-1-1088-1) measuring 4 7 x 16 SILICON CHIP 60mm. The board is housed within a plastic case measuring 83 x 54 x 28mm. A Scotchcal label can be attached to the lid of the case to indicate the controls. Start construction by checking that the PCB will neatly fit into the case so that it is supported on the stops of the PC guides. The stops are provided for mounting a printed board horizontally, as we have done, but they need to be lowered by a bout 4mm, to give sufficient clearance for the battery and its holder. You can achieve this by judiciously cutting away the guides with a pair of side cutters. If the PCB is too wide it can be filed down to size until it fits neatly into the case. The PCB requires two 5mm holes for the coil formers for 11 and 12. These formers are installed from the underside of the PCB and are glued in position [using nail polish or 5-minute epoxy). You can now insert and solder the IC as shown on the overlay diagram [Fig.2). The 1.5-turn coils can then be wound onto each former. These are wound by first stripping the enamel from one end of the wire and soldering it in place. Wind on 1.5 turns and insert the free end of the wire into the PCB. Cut it to length, strip off the enamel insulation and solder. Both coils are wound in the same way. Once the coils have been wound, the remaining parts can be installed as shown in Fig.2 . All the resistors are installed end-on [ie, vertically) and so is the 330pF polystyrene capacitor. Ensure that the four electrolytic capacitors are oriented for correct polarity. If you can't obtain a single AAcell holder you can make one by cutting down a dual AA-cell holder. The holder is cut in half longitudinally to provide a single holder. The spring in the negative end is soldered into the PCB while the positive end is connected to the PCB using a stiff piece of copper wire looped over and soldered to the clip socket. Once the PCB is complete, install it in the case and mark out positions for screwdriver access holes for the trimpots, VRl and VR2. You should also mark out holes for the panel RCA sockets and switch. The switch is mounted very close to the base of the case so that it does not foul the PCB. Drill holes for the sockets and trimpot level adjustment holes. The switch is mounted using small selftapping screws into the mounting flanges. The frequency adjust hole in the lid is found after attaching the label artwork to the lid and drilling at the hole position provided. Now wire up the switch, RCA sockets and antenna. The antenna can be a simple dipole [ie, an indoor FM antenna) or a single length of wire [about 15cm would be suitable) connected to the antenna terminal. For a dipole, the second How an FM Stereo Transmitter Works Fig.3 shows the block diagram of a stereo transmitter as typified by the Mini-mitter. The left and right channel inputs are applied to trimpots and then to 50µs preemphasis circuits (to provide treble boost above 3kHz, to the Australian FM standard). After pre-emphasis, the left and right signals are fed to buffer amplifiers and then to the multiplexer which is driven at 38kHz. This produces a sum (L + R) signal and a difference (L - R) signal which is amplitude modulated on a 38kHz carrier. The carrier is suppressed to provide a double sideband suppressed carrier signal. The (L + R) and (L - R) signals are mixed with the 1 9kHz pilot signal which is derived by dividing down the 38kHz oscillator signal by two. The resulting composite signal is then frequency modulated onto a carrier frequency in the FM band. Once filtered and amplified in the RF amplifier, the signal is transmitted via the antenna. Fig.4 shows the spectrum of the composite stereo signal. The L + R signal occupies the frequency range between O and 1 5kHz. The double sideband suppressed car- ANTENNA (L +R)+(L-R)coswst +Kcoswpt MULTIPLEXER PILOT MIXER .,. RF MIXER OSCILLATOR Fig.3: block diagram of an FM stereo transmitter, as used in this project. The accompanying text explains how it all works. LEVEL L+R L-R 0 15 19 23 PILOT L-R 38 53 FREQUENCY (kHz) Fig.4: frequency spectrum of the composite transmitted stereo signal. Note the pilot tone at 19kHz. rier signal (L - R) has a lower sideband which extends from 23-38kHz and an upper sideband from 38-53kHz. There is no subcarrier at 38kHz. The pilot carrier at 1 9kHz is also shown. The pilot tone is used by the receiver to reconstitute the 38kHz subcarrier so that the stereo signal can be decoded . connection goes to the earth track adjacent to this antenna terminal and is soldered to the underside of the PCB. You can buy a ready made dipole antenna from Jaycar (Cat. 1 T-3002) or Arista outlets (Cat. FMAl). VR3 should initially be set to the centre position. Now insert a 1.5V AA cell into the battery holder and check that there is 1.5V across pins 3 and 15 with a multimeter. Initial checks Operation can initially be checked with an FM tuner set to an unused frequency near the centre of the band. Insert slugs into 11 and 12 and adjust both so that each slug is about 2mm below the top of the former. Now adjust the 11 slug until the tuner receives the signal. This can be detected by the level and/or This close-up view clearly shows the winding details for L1 and L2. The PCB clips into guides running down each side of the plastic case (see text). OCT0BER1988 17 ..I L + ff!il~ SC 06-1-1088-1 + ffl!HIHs LEFT RIGHT FREO.e ADJ. LEVEL LEFT ~~ ON OFF LEVEL RIGHT ., + STEREO FM TRANSMITTER i 1~1~ + r Fig.5: actual-size artwork for the front panel. Fig.6: actual size PCB artwork. PARTS LIST 1 PCB, code SC06-1-1 088-1 , 47 x 60mm 1 plastic case with plastic lid, 83 x 54 x 28mm 2 RCA chassis mounting sockets 1 AA cell holder 1 1.5V AA battery 1 sub-miniature slider switch 2 Neosid 722/1 5mm coil formers 2 Neosid F1 6 4mm ferrite cores to suit formers 1 38kHz miniature crystal 1 BA 1 404 Rohm FM stereo transmitter IC 1 1 00mm-length of 0.63mm enamelled copper wire Capacitors The two small holes in the end of the case allow screwdriver access to the level adjustment trimpots, VR1 and VR2. A third hole in the lid of the case provides access to trimmer capacitor Cl for frequency adjustments. tuning meter on the FM tuner and/or by a stereo light indication. The L2 slug is then adjusted for maximum signal. To set the transmitter on other parts of the band, the slugs must be low down into the coils for the low frequency end of the band and conversely, higher for the high end of the band. Note that both slugs should be set in similar positions in the former for best results. The coils are slightly interactive so that adjusting one will affect the other. For fine tuning, use the trimmer Cl. The slugs can be secured in position using a very small amount of candle wax. Alternatively, some 18 SILICON CHIP dental floss inserted into the former before the slug will help stop movement. To adjust the input level trimpots, connect a program signal to the RCA sockets and listen to the output from the tuner, preferably via headphones. Adjust the trimpots so that distortion is not present on loud signals. This is easy to do because when the distortion is present it sounds awful. If you have an AC millivoltmeter and sine wave oscillator you can also set trimpot VR3 for maximum separaiion between channels. If not, just leave VR3 centred as this will be close to the optimum setting. 2 2 3 1 3 1 2 2 1 2 1 1 0µF 16VW PC electrolytic 4 . 7 µF 16VW PC electrolytic .01 µF miniature ceramic .0 1µF metallised polyester .001 µF metallised polyester 330pF polystyrene 4 7pF miniature ceramic 1 5pF miniature ceramic 1 0pF miniature ceramic 4. ?pF miniature ceramic 2-1 0pF trimmer capacitor (Philips 2222 808 11109) Resistors (0.25W, 5%) 1 x 1 00kD, 2 x 47kD, 1 x 2. 7kD, 2 x 1 on, 1 x 50kD miniature vertical trimpot, 2 x 1 0kD miniature vertical trimpots Miscellaneous Small self-tapping screws, hookup wire, tinned copper wire. <at>HITACHI 20MHz/lmV $830 ExSa!esTax $996 me tax m··· Wouldn't you pay a bit more for features like this? So good we give the full Spee! Display CRT Graticule Quality Hitachi engineering O Two year Warranty o Includes two quality Hitachi probes o Tough all metal case and front panel Ideal for servicemen - small footprint and light weight (31Ox37cJx130mm 6kg) o Extensive triggering facilities including TV sync and vertical mode for steady traces when input frequencies differ widely o Free 55 page operating manual with circuit diagram o Poteritial External Intensity Modulation Vertical Deflection Sensitivity Bandwidth MAX. Input Voltage Input Coupling Input Impedance Display Mode CHl Vertical Signal Output X-Y Operation Sensitivity Bandwidth Phase Difference Horizorital Deflection Sweep Time Range Trigger Trigger Mode Trigger Source Trigger Sensitivity Order now. Call Sydney (02) 648 5455 32 Parramatta Rd, Lidcombe 2141 Fax (02)6471545 TelexAA24949 P.O.Box14Lidcombe2141 Melbourne (03) 480 0111 72-74 Chifley Drive, Preston 3072 Adelaide (08) 354 0588 Brisbane (07) 277 4422 Perth (09) 325 9333 I BB.L ] Bell Test & Measurement The measure of quality A Division of Bell-lRH Ltd (inc in N.S.W.) Prices subject to change without notice Internal , 8 x 10 div (1 div = 1 cm) , Horizontal and vertica l center lines further marked in 0.2 div increments, mark ing for measurement of rise tl me Accelerating Rise Time o 6-inch recta ngular. Trigger Coupling Trigger Slope Calibrator Power Supply Ambient Temperature Dimensions Weight MTBF Accessories Supplied 2 kV. Voltage : 5V o r more. Effect ive bandwidth : DC to 2 MHz. Max . inpu t voltage: 30V (DC+ AC peak}. 5m V/di v to 5V/d iv in 10 calibrated steps ± 3%. lmV/d iv, 2m V/d iv ± 5% when using x 5 magnifier. Uncalibra ted co nt inuous co ntrol between steps 1 : < 2 .5. DC t o 20 MHz 1-3 dB). DC to 7 MHz (- 3 dB) when using x5 magnifier. 17.5 ns. 50 ns when using x 5 magnifier . 300V {DC+ AC peak) or 500Vp-p AC at 1 kHz AC,GND, DC. 1MS1 approx . 25 pF. CH1, CH2 {n ormal o r invert), ALT. CHOP, ADD Voltage : appro x . 20mV / div in t o 50!1 Bandwidth: 50 Hz t o 5 MH z (-3 dB) i nto 50!1. CH1 : X-axi s. CH2 : Y-a xis. 5mV/ div to 5V /div. 1mV/div, 2mV /di v w hen using x 5 magnifier. DC t o 500 kHz 1-3 dB ). 3° or less from DC to 50 kHz . 0.2 µs/ div t o 0 .2s/d iv in f9 ca librated steps e 3%. 100 ns ±5% w hen using x10 magnifier (20 ns and 50 ns uncafib rated) . Uncalibrated con ti nuous co ntrol between steps 1 : < 2.5. Automatic {sweep runs in absence of a triggering signa l and for signa l below 30 Hz), Normal {sweep runs when triggered ), TV' V. TV-H. CH1, CH2, V -MODE, External, Line. 20 Hz to 2MHz 12 MHz to 20MHz I CH 1 and CH 2 i 0 .5 di v I 1.5 div I 20mV I E.x ternal I I BOOmV I AC. + or Square w ave. Vo ltage : 0 .5V ± 3%. Frequency: A pprox. 1kHz V olt age : 100/ 120/220/240 V ± 10%. Frequency : 50/60 / 400 Hz. Power consumpti on : approx . 30 W. Rated range o f use : +10 to 35° C. Limits of operation : 0 to 50° C. Storage and transport : - 20 to 70°C. 310(W) x 130IH) x 370(D) mm. 12.2 X 5. 1 X 14.6 in. Approx. 6 kg/ 13.2 lb. 20 ,000 hours for target value. Two AT-1 0AJ 1.5 p ro bes, Fuse , Power cable , I i Operation manua l. I HIFI REVIEW YAMAHXS BRILLIANT COMPACT DISC PLAYER You've heard of 2-times oversampling and 4-times oversampling in CD players. Now there is 8-times oversampling, as featured in Yamaha's top of the range CD player, the CDX-1110. It provides unrivalled linearity and a brilliant signal-to-noise ratio as we found when putting the CDX-1110 through its paces. By LEO SIMPSON When CD players were first introduced five or so years ago, the available 16-bit digital-to-analog converters were pushing the very limits of VLSI (very large scale integration) technology. Linearity was a real problem, especially at signal levels below - 60dB with respect to the maximum output level of 2V RMS. So much so, that one of the biggest players, Philips, elected to use a technique called "oversampling" which enabled them to use 14-bit D-A decoders. Philips claimed (and reviewers confirmed) that this technique gave results as good or better than available 16-bit decoders. Philips also opted to use dual D-A decoders 20 SILICON CHIP and thereby was able to claim an advantage of no phase delay between channels at the higher frequencies. There was a further advantage in that the filtering required to remove the sampling artefacts was less severe. That was then. In the intervening years, many manufacturers have used the oversampling technique to improve on the performance available from 16-bit decoders. Yamaha has used 2-times oversampling at 88.ZkHz while more recently they and some other manufacturers have employed 4-times oversampling, at 176.4kHz. Now Yamaha have leapfrogged all the rest by introducing their 8-bit oversampling machines which run at 352.BkHz. Why so high? We're not going to delve into all the technical background because it would make this article too long but there are three reasons to increase the sampling rate to 352.BkHz. First, improved linearity; second, better signal-tonoise ratio; and third, very low sampling artefacts in the audio output of the player. There are a number of other technical advantages but as far the user is concerned, those listed are the important ones. As spectacular an advance as the jump to 8-times oversampling may seem, that is not the whole story as far as this new CD player from Yamaha is concerned. It also offers 18-bit D-A conversion and digital control of the output level. What's that you say? How can a 16-bit CD player have an 18-bit decoder? We'll come to that later. Presentation The styling and presentation of the latest CD player from Yamaha is very much in the mould of 16-BIT NO OVERSAMPLING / " \ V SIGNAL I DIA \ CONVE RTER OU TPUT I WAVEFORM AFTER DIA CONVERSION '-ERROR WAVEFORM OF ABOVE SIGNAL (DISTORTION) HI-BIT 8 TIMES OVERSAMPLING AT 352 .8 kHz SIGNAL WAVEFORM AFTER DIA CONVERSION DIA CONVERTER OUTPUT ERROR WAVEFORM OF ABOVE SIG NAL Fig.1: these photos and diagrams show the difference between normal 16-bit sampling at 44.lkHz and 8-times oversampling at 352.BkHz. Notice that the steps in the re-constituted audio waveform are much smaller and sampling artefacts to be filtered out are greatly reduced. Manufacturer's Specifications Audio section Frequency response ....... ... .. ....... .... .. 2Hz to 20kHz within ±0.3dB Total harmonic distortion .. .. .......... .. ...................... less than .002% Signal-to-noise ratio ... ... .. ... ...... ... ... ... .... .... ... ............... ..... 118dB Dynamic range ....... ... .... ............ ..... ...... .. .... ...... more than 1 00dB Wow & flutter .. ... ... ......... .... .... .. .... .. .. .. ..... .. ........ .. . unmeasureable Channel separation .... .... ... ...... ..... more than 1 00dB (1 kHz , 20kHz) Maximum output voltage .. .. ... ......... ... .. .. .. .... .... .. .. ... .. .. 2 volts RMS Output impedance ...... ... ... ..... ..... .... .. ....... ........ ... ... ... .... . 4 7 ohms Headphone output .... .. ........ .............................. 3 volts/150 ohms Internal system Optical pick-up .. ..... .......... ......... .... .......... ... ..... .. .... .. 3-beam laser Error correction system ........................ ..... ............ .. .. .. .. .. ... CIRC Digital-to-analog conversion ... ...... ....... ....... .... .. .. twin 1 8 -bit floating Filtering ..... ... .. .... .. ........ .. .... : .... . hi-bit digital & 3rd order active filter I ! Volume control General Dimensions ...... ...... .. ...... ... ......... .. ............ 435 x 120.5 x 418mm Power consumption .... ....... .. .... ........ ................. ...... ....... 30 watts Weight .... .... ... .. ... ....... ... .... ........ ..... ... ......... ....... ... ........ . 14.2kg previous models although it is notably larger and heavier. In fact, it is currently one of the largest and heaviest CD players available. It is made to look even larger by its massive feet although they are not quite as noticeable as they appear in our photograph. As can be seen, the CDX-1110 offers comprehensive facilities although, for remote control, you can directly select any of the first 24 tracks of a disc. For tracks above 24, you first hit the 10 + button twice (or more) and then a button between 1 and 9. (some test discs have over 50 tracks). If you've listened to a disc many times and know it well, you can "freshen" it up by listening in "random play" mode. Three repeat modes are also available. You can repeat a single track, the whole disc or a track excerpt, as marked by two pushes of the A - B button. The latter repeat mode is very fast, with almost no gap between the end and start of the repeated passage. This can be handy for music students or when testing loudspeakers. If you ' re taping a CD, the CDX-1110 will insert a 3-second gap between tracks. This makes it easier for the tape player to subsequently find particular tracks (in those machines with automatic music selection). You can also program the order of play, up to 24 tracks. And how many of you have CDs on which there is a track you really hate? The CDX-1110 copes with that. By using the Delete button you can program it to leave out the track or tracks which are "on the nose". So much for the play facilities. Most users will probably not use the controls on the machine but use those on the remote instead. It's much easier and you don't need 20:20 vision to see the control labelling. the most part, these are in line with those offered on previous Yamaha models. We'll just touch on the highlights of the playing facilities, all of which are also available on the infrared remote control. As can be seen from the photo, you can directly select any of the first ten tracks via buttons on the front panel. On the The Yamaha CDX-1110 is one of the few machines on the market with full volume control via the remote handpiece. It's a beauty. Yamaha make the point that the digital volume control is more precise, offers better tracking between channels and lower noise but I just like it for the convenience. It increases (or decreases) the signal level in 0.4dB steps and has a total range of more than 70dB. The remote control has no less than 44 buttons but it is still quite easy to use although it would be better with a bigger "Play" button. OCT0BER1988 21 18-bit conversion Inside the Yamaha CDX-1110: note the two transformers in the power supply and the large player mechanism which has a locking lever for safe transport. The same could be said of the buttons on the machine itself; the Play button needs to be made bigger or more obvious so that you don't have to peer at the front panel to find it. Output facilities On the rear panel, the CDX-1110 has two pairs of RCA outputs, both of which are variable in level via the digital volume control. One set of outputs is labelled "direct" while the other is "filtered". The difference between the two is that the latter has an analog low pass filter to remove digital sampling artefacts (that is, noise at the sampling frequency). Yamaha state that they have pro_vided the choice of two outputs because some people prefer the "softer" sound of the filtered output while, on the other hand, the direct outputs have the advantage of minimum phase error. In addition to these analog stereo outputs, the CDX-1110 has two digital outputs, for ultimate connection to a separate D-A converter, should a better unit be available in the future (perish the thought). One 22 SILICON CHIP of these outputs is via a conventiomi.l RCA phono connector while the other is via an optical fibre connector, for true isolation. The mains supply connection is via a sheathed two-core flex with moulded two-pin plug. The unit is double-insulated. Interior details Removing the lid of the CDX-1110 reveals a very busy interior with lots of interconnecting wiring between the various printed boards. The power supply is unusual in a couple of respects. It has two power transformers, both quaintly labelled "massive power supply" . The other point is that the supply employs shunt regulators instead of the more usual series regulators. Yamaha state that this is because the shunt regulators have a lower output impedance than series regulators, particularly at high frequencies. The implication we draw from this is that the shunt regulators are better at suppressing digital "hash" and therefore result in a better signal-to-noise ratio. Having covered the key features of the CDX-1110, we still have yet to explain how the unit manages to employ an 18-bit D-A converter instead of a 16-bit converter, oversampling or not. In reality, Yamaha has combined an 18-bit digital filter (which performs the 8-times oversampling) in conjunction with two 16-bit D-A converters, one for each audio channel. Yamaha has taken advantage of the fact that the two most significant bits from the 18-bit filter are only present during the loudest parts of the program signal. Normally then, the top 16-bits of the 18-bit signal are fed direct to the two 16-bit D-A converters. When one or both of the two most significant bits is not present, operation is shifted to accommodate the two least significant bits while the gain of the associated audio amplifier is changed by a factor of 0.25 to compensate for the change in signal level. The result is a much improved signal to noise ratio. This clever scheme is shown in Fig.2. We can vouch for the fact that it works - the CDX-1110 has a phenomenal signal-to-noise ratio. It also has improved linearity at very low signal levels. Interestingly, the way in which the 18-bits from the digital filter are manipulated to make them compatible with the 16-bit D-A converters is not the end of the story. Yamaha use the same technique to provide the remote volume control referred to earlier. To change the signal level, the signal is varied in level while it is still in digital form, by manipulating the bit levels. Very tricky. On test In use, the CDX-1110 is great. The transport mechanism works very smoothly and quitely. And it has the fastest access times we have yet to come across. Switching from track 1 to track 25 on a 25-track disc takes less than two seconds. That's really fast. Sound quality was absolutely tops, from either the Direct or Filtered audio outputs. The difference is very small although it is discernible to the keen-eared Th e top 16 bits are sent directly to the DIA converter DIA converter drops operat,on level by up to two bits to accommodate digital filter output j j : 114 L______ ___ J l Output Gain lowered by 114 High Level Signal Low Level Signal Fig.2: these diagrams show how the 18-bit parallel signal from the oversampling filter is switched to the 16-bit D-A converters (only one shown). When the lower 16 bits are switched to the converter, the output amplifier gain is reduced to compensate for the shifted operation. listener - but only when switching directly between the two. On the test bench, the CDX-1110 really shines. Paradoxically, it presented us with less problems in confirming its specifications than many other CD machines we have tested. The reason is that the digital sampling artefacts are so high in frequency that the normal 20Hz to 20kHz bandpass filter of our AC millivoltmeter ignored them. As a matter of interest, the 352.8kHz residual signal is - 60dB with reading being .005% at 20kHz in one channel. Verifying figures for channel separation was no problem . Yamaha specify - lO0dB. We achieved around - 103dB or better over the whole frequency range. Signal-to-noise ratio Signal-to-noise ratio is the big one. Yamaha specify this at a stunning - 118dB. Six months ago there was no way we could verify this, respect to full output. Yamaha quote the frequency response as being flat from 2Hz-20kHz within ± 0.3dB. None of our test discs go below 20Hz but within the range 20Hz to 20kHz we were able to confirm that the Yamaha's unfiltered outputs were considerably better than ± 0.3dB. In fact, the response was only .03dB down at 20kHz. The filtered outputs were not quite so precise but well within Yamaha's spec of ± 0.3dB. Yamaha's spec for harmonic distortion is a little vague, a figure of .002 % being quoted, with no reference frequency. Our measurements yielded figures very close to or equal to .002 % for most of the frequency range, with the highest All functions of the CDX-1110 player can be selected by the infrared remote control. with available test equipment, commercial or otherwise. Now we can, with our own AC Millivoltmeter. For unweighted measurements (band limited from 20Hz to 20kHz) on the unfiltered outputs, we measured -114dB and - 117dB for the two channels. For "A" weighted measurements, these figures improved to - 116dB and - 118dB respectively. Strangely, the figures were not quite as good for the filtered outputs: - 11 ldB and - 113dB unweighted, and - 113dB and -115dB "A" weighted. That slight degradation may be due to the op amps in the analog filter stages. For those who have just read those figures and find them a little meaningless, let's put them in perspective. That figure of - 118dB with respect to the 2 volt RMS reference signal represents a noise signal of just 2.5 microvolts (2.5 millionths of a volt)! That makes the Yamaha CDX-1110 the quietest piece of audio equipment available, that we know of. Unbelievable. Linearity is another key test of the Yamaha 18-bit technology. If it doesn't come through here, it isn't worth doing. Well it does. On the linearity test tracks of the Technics CD-001 test disc, we measured an error of - 0.4dB at the - 80dB level. At the - 90dB level, we measured errors of between - ldB and - 1.2dB, depending on whether direct or filtered outputs were connected. These results are easily the best we have ever measured. No problems with tracking tests were encountered as far as the test disc was concerned. Nor did we expect any. Well, how would you sum up the Yamaha CDX-1110? Clearly, the objective measurements show it to be one of the best machines available today, regardless of price. And subjectively, it's right up there among the top machines. You'd need to own a really top amplifier and loudspeakers to do it full justice. Recommended retail price of the Yamaha CDX-1110 is $1899. For further information, consult your local Yamaha retailer or Yamaha Music Australia Pty Ltd, 17-33 Market Street, South Melbourne, Victoria 3205. Phone (03) 699 2388. 16] OCT0BER1988 23 Electronic Australia Kits KA-1109 Electric Fence KA-1115 30<1N amp module KA-1116 30/JN power supply KA-1117 30<1N speaker prntector KA-1119 Transistor tester KA-1220 Signal •acer KA-1230 Zener diode tester KA-1390 Freq. counter 50MHz KA-1392 Prescaler 500M Hz KA-1428 Funcion generator KA-1430 Vocal canceller KA-1505 TAI Han effect KA-1506 Transistor asst ignition KA-1508 KA-1522 "f:it~ KA-1535 ~itionkiUer KA-1550 uxe car alarm KA-1556 Ultra sonic move det. KA-1500 Railmaster controner KA-1574 30V 1Ara,wer supply KA-1582 House arm KA-1595 Ditta/ capacitance meter KA-1598 40 inverter 121230V KA-1610 300W inverter 121230V KA-1630 12V lamp flasher KA-1635 AM/FM stereo tuner KA-1636 AM/FM remote control KA-1650 Playmaster 60/60 KA-1652 Blueprint 60/60 KA-1660 Electric fence KA-1670 Light saver KA-1675 Saaecher car alarm KA-1677 Audio oscillator (metered) KA-1681 3 band short wave radio KA-1682 Dual track power supply KA-1683 Battery monitor KA-1687 Electronic rain gauge KA-1688 Electronic strotiosoope KA-1689 Ex~. power supply KA-1690 DI ox KA-1691 TV colour bar/pattern gen KA-1692 Voice operated relay KA-1693 Metronome KA-1694 VolUcontinuity test KA-1695 AC/DC Millivoltmeter KA-1696 Econ. Temp probe DMM KA-1697 Utility timer KA-1 698 Tran, FET, Zener lest KA-1699 Bench amp- signal trace KA-1700 Power transistor tester KA-1701 RF detector r,.ooe KA-1702 50MHz Dig req meter 23.50 $119.95 $105.00 $23.50 $21.50 $27.95 $16.95 $169.50 $46.50 $129.50 $24.95 $44,95 $42.50 $29.95 $115.00 $23.50 $89.50 $34.95 $109.95 $89.50 $169.00 $85.00 $99.95 $249.00 $12.95 $599.00 $99.50 $329.00 $369.00 $59.50 $15.99 $34.95 $165.00 $79.50 $129.95 $14.95 $49.95 $13.95 $26.95 $39.95 $169.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $99.00 !i~~~n;i Handy 100I. Will clip 10 and hold small nuts, bolts, washers, etc. Cat. TH-1842 WAS $6.50 If • • , f ._ f/_l NOW $4.95 IC EXTRACTOR~ --~ One piece metal construction, ' Y )~ 8 - 40 pins, .' ; t .' Cat. TH-1818 WAS $4.25 NOW $2.95 SAVE $1.30 , · ;/ I J/ J/ ,, j/ v· Government Instrumentalities, Schools, Public Companies KA-1703 KA-1704 KA-1705 KA-1706 Line Filter FM Receiver Stroboscopic Tuner Cheap capacitance meter $39.95 $55.00 $47.50 $16.95 Australian Electronics Monlhly Kits KM-3015 LisleninJ post KM-3030 Ultrafld ity preamp KM-3040 Dual ~ed modem KM-3042 Spee synthesiser KM-3050 Workhorse amle KM-3056 1OOW module ess MFets KM-3061 Miaophonereeamp KM-3063 Uo satellite ecoder KM-3064 Octave EQ mod KM-3065 RS true 232 interface KM-3067 NiCadchar~ KM-3068 FMminder g $39.95 $359.00 $169.00 $43.50 $35.00 $79.50 $36.95 $55.00 $59.95 $27.95 $24.95 $11.95 Electronics Today International Kits KE-4014 Mixer preamp KE-4023 Si~nal Spkr protector KE-4029 Ni ad baltery,1aarger KE-4033 Temperature obe KE-4050 ETl480 50W amp module KE-4052 ETl480 1OOW amp mod KE-4048 ETl480 power supply KE-4200 5000 power amp KE-4204 5000 1(J octave ~aliser KE-4220 ETl499150W Mos et amp KE-4405 ETl581±i-15V power sup KE-4666 RS232 Centronics inter/I KE-4690 ETl342CDI KE-4698 4 sector house alarm KE-4711 Mini FM transmitter KE-4722 RS232 Commodore KE-4724 Parametric equaliser KE-4725 Solder iron temp control KE-4728 Ring tone customiser KE-4729 Guitar preamp KE-4730 Solar gen pisupply KE-4733 Active Crossover $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $219.00 $109.50 $27.50 $32.50 $79.50 $29.95 $9.95 $16.95 $23.50 $39.50 $29.95 $45.00 $12.95 $39.95 Silicon Chip Kits KC-5010 Capacitance meter KC-5012 Car radio power supply KC-5013 1GHz Digi Freq meter KC-5015 Telephone ringer KC-5016 Speed control/dimmer KC-5017 24 to 12V converter KC-5019 100W amp module KC-5021 Protector car alarm KC-5023 Low ohms adapt DMM KC-5027 KC-5028 KC-5029 KC-5031 KC-5032 KC-5033 KC-5034 KC-5035 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 Ph meter Train controller CD Hiphone amp Optical tacho DISCO Light Srudio 200 Preamp Remote for Car Alarm Plasma discharge Wireless doorbell TX Wireless doorbell RX Universal power supply Vader Voice Speaker phone Jaycar Kits KJ-6502 Syntom drum synlh KJ-6504 8 channel mixer KJ-6505 Console Psupply above KJ-6531 2801 lfJ octave Eq. KJ-6535 2010 1Oband stereo Eq. KJ-6655 Hall EffectTrigger kit KJ-7000 Red light Hasher $49.95 $89.00 $24.95 $49.95 $159.50 $229.00 $79.50 $229.00 $16.95 $42.50 $12.95 $19.95 $89.00 $42.50 $595.00 $119.00 $239.00 $169.00 $49.95 $19.95 $27.95 $28.95 $299,00 $19.95 $18.95 $59.00 $38.95 $79.50 $29.95 FAMOUS TOWERS BOOKS FROM JAYCAR TRANSISTOR SELECTOR • Hardcover • Over 27,000 listings Cat. BM-4554 ' JAYCAR Soldering Kit Designed for general purpose soldering . This ktt includes a 30 watt 240V so ing iron and quality metal stand · sponge, a !<lngth of solder all solderwick. $29.95,. SAVE ~ $35 DIGITAL IC SELECTOR $29.95 DIODE & SCRINDEX Quartz Crystal Clock Movement • AA battery that lasts for 1 year • ±15 seconds/month accuracy • NEW MODEL • Hook for wall mount • On/off switch SUPPLIED WITH 3 SETS OF HANDS Cat.XC-0100 • 1CYs of 1000s of SCR's, Triacs, Diodes & DIACS listed Cat. BM-4560 $29.95 IC INDEX • Reference book for both linear and digital IC's, ~ . Cat. BM-4562 - ~ ...._ $29.95 OPAMP& LINEAR EPROM Eraser • Over 5000 linear IC's with specs etc. Cat. BM-4556 ~~ ~ $29.95 Great replacement electret mic inserts for tape recorders, etc. Handy for hobby projects. Includes data sheet and application circuit. Operated from a single 1.5V battery. 10mm diameter. 50Hz 15kHz. Cat. AM-4010 $1.95 10+ $1 .65 ea Ideal for the hobbyist and handyman. Our lowest price 240 volt quality iron has a stainless steel barrel and is supplied wtth free solder. Spare tip Cat. TS-1453 $4.95 Cat. TS-1450 ONLY $16.95 • Spees on 13,000 IC's Cat. BM-4558 11 you wish to purchase from us, simply send us your official order and we will give you a complimentary 30 day account. ''Hot stick" Soldering Iron $12.95 e------l! o----0 . . q BACK IN STOCK SPEAKER CLOTH <!!!'!!!!!!!!!!I!!! BNC Male 10 double binding posts/Banana sockets Cat. PA-3666 $9.95 ea 10+ $9.50 ea BNC Female to Double Banana Plugs Cat. PA-3668 $8.50 ea 10+ $8.00 ea Up until now, if you wanted speaker cloth you had the choice of black or blackl We now have available brown speaker cloth. Top quality, acoustically transparent. Cat. No Colour Size Price CF-2751 Black 1 x 1m $9.95 CF-2752 Black 1 x 1.7m $13.50 CJ:-2755 1 x 1.7m $13.50 SAVE ON GENUINE CANNON WE'RE OVERSTOCKED!! 3 Pin Line Male Cat.PP-102~ $4 ==I...~ -~ -~ ~ SAVE $1.25 3 Pin Line Female Rack Cabinets - see our catalogue Rack Frames - Seaourcataloguefor full details for full details 44mm Natural Cat. HB-5411 44mm Black Cat. HB-5410 88mm Natural Cat. HB-5413 88mm Black Cat. HB-5412 132mm Natural Cat. HB-5415 132mm Black Cat. HB-5414 132mm Economy Black Cat. HB-5402 each $65.00 $65.00 $75.00 $85.00 $90.00 $95.00 $72.50 5+ $62.00 $62.00 $71.00 $80.00 $85.00 $90.00 $67.50 Cat. Cat. Cat. Cat. Cat. Cat. 6 unit frame (370mm) Panel set for 6 unit 18 unit frame (907mm) Panel set for 18 unit 30 unit frame (1450mm) Panel set for 30 unit w- Cat.PS-1032~ ~ ~ ~ 3 Pin Chassis Plug Portasol soldering iron, bring it into any Jaycar store for a FREE gas refill ~I PP-1020 SAVE $1.25 3 Pin Chassis Cat. PS-1030 ~ i Socket $4.50 SAVE $1.45 SAVE30%ON BUG BOXES DATAKPCB PRODUCTION Now available. Make printed circuit boards from magazine pages or original artwork. See our catalogue for full details. KIT ONLY $99 $6.95 TAL 50 pieces Cat. RG-5003 es: (10 of each) 0.047, 0.056, 0.068, 0.082, 0.1 European Made MAINS FILTER BARGAIN 10+$8.95ea DIALDRUM/ EVER ONLY $159 About 20 dial drums and 2.5 metres of dial cord. CORDPACK All for only $5 Cat. HM-3130 ~~- NORMALLY $3.75 each NOW ONLY $10 for 10 or $1.50 each cat. LT-3020 BELOW NORMAL W HOLESALE PRICE PRESS RELEASE tJJearCustomer, There are times when due to circumstances beyond our control some advertised products may not be in stock when our a d s appear. We suggest you phone to check availability. DIGITAL PANEL METER CATALOGUE A brand new 18 page Lascar catalogue is available from the Australian representative, Jaycar Electronics. The catalogue features the latest Surface Mount Technology DPM's from Lascar • ■ the wo rld's leading DPM manufacturer. Panel meters are available in both liquid crystal and LED-type displays. All DPM's come complete with snap-on bezels. Full technical information Is • 300 watts RMS into 4 ohms provided for the 50-odd products • 200 watts RMS into B ohms described. K~ includes PCB, heatslnk & components Contact Jaycar branches or Head Cat. KA-1115 Office for a free copy of the catalogue. 300 WATT PLAYMASTER AMP KIT SAVE $10 NOW $109.95 Telephone~ 300 WATT POWER Diverter ~~ •SUPPLY Includes transformer, rectifier and filter caps . NEWMODEL Cat. KA-1116 This professional quality product will automatically transfer Incoming calls to another telephone number. Your business will not lose any important calls If you move, as incoming calls can be diverted to your new office address. Two telephone lines are required while the _ _ _ _ _ _ _ _ _ _ _. . YT-6510 is not Telecom approved it is a Outdoor Baluns • 300 to 75 ohm complete with small length of cable to attach antenna and F59.connecto, for coax connection. A GREAT WAYTO NEVER BE OUT OF THAT ODD GREENCAP AND SAVE A PACKET AT THE SAME TIME '------------J CORDLESS PHONE LOWEST PRICE TV INSTALLERS BARGAIN $6.95 TAL 50 pieces Cat. RG-5002 lues: (10 of each) 0.018, 0.022, 0.027, 0.033, 0.039 I • $6.95 Values : (10of each) 0.0068, 0.0082, 0.01, 0.012, 0.015 $9.95 ':/ ~t $6.95 Values: (10 of each) 0.0027, 0.0033, 0.0039, 0.0047, 0.0056 • 4 amp 240V PCB mount • For full details see last months ads Cat. MS-4008 originally selling for $269 Don't ever run short of that greencap again. 5 easy to buy, low cost packs which represents a considerable saving over individual prices. Each pack contains 1o of each value and packs cover the complete range from 0.001 uF to 0.1 uF. Values: (10 of each) 0.001, 0.0012, 0.0015, 0.0018, 0.0022 TOTAL 50 pieces Cat. RG-5001 BUG BOX Cat. HB-63 ONLY $4.15 SAV LSI BUG BOX cat. ONLY 5.55 SAV BUG CASE Cat. HB-6366 ONLY 6.95 SAVE 3 BUG CAGE COVER ONLY $4.85 SAVE $2.10 Jaycar Introduces the Easy way to Buy Greencaps TOTAL 50 pieces Cat. RG-5000 See our catalogue for full detai Cat. HB-6370 $109.50 $49.00 $139.50 $89.00 $169.50 $ 129.00 If you own a $4.25 ' - l _ _ _ ~ SAVE $1.25 " - $a HR-5210 HR-5215 HR-5220 HR-5225 HR-5230 HR-5235 SAVE $10 NOW $95 SPEAKER PROTECTOR KIT Cat. KA- 1117 SAVE $2 NOW $21.50 very well made product. A 7.5V AC adaptor is provided. Cat. YT-6510 WAS $249 NOW $219 ·1 RS232 TO CENTRONICS ADAPTOR • Interface a printer to RS232 serial port of your computer • Includes PCB, DB25 A/angle plug & components. Cat. KE-4666 SAVE$2.50 NOW ONLY $30.00 NEGATIVE ION GENERATOR A METER FOR ALL SEASONS 240 volt - SAVE $50 For full specs on all of these products see our 1988 catalogue. Cat. YX-2905 ECONOMY POCKET :t.J~ • 20,000 ohms/Volt • Size 80 x 50 x 30mm Cat. OM-1001 1-l- "'(,j~ 5"1.JC $17.50 LOW COST MODEL • 10,000 ohms/Volt • 12 ranges Cat. QM-1015 Indoor TV ~ Antenna i; UHF/VHF/FM ~ The ultimate indoor antenna - built-in mixer for UHFNHFIFM - wide frequency band from 40MHz - 890MHz. Directional fine tuning possible with variable direction inner reflector - easy to mount - 75 ohm impedance with coaxial cable anc! plug. Cat. L T-3130 \ SAVE $3 ONLY $31.95 Solar Powered Exhaust Ventilation Remove gas, fumes, humidity, etc by using the suns free power - solar. It will remove about 35 cubic metres of air every 1/2 hour in bright sunlight. Ideal for: • Boats •Caravans• Port-a-loos • Greenhouses • Sheds• Holiday homes• Backyard dunnies • Kitchens • Weekenders, etc. Cat. YX-2500 SAVE$5 OCTOBER ONLY $44.95 MicroChart SELLOUT Bye-bye MicroCharts. Over the years we have sold hundreds of MicroCharts, but now the time has come and their time is numbered . M icroCharts are professional, comprehensive, plastic summary cards packed with key time-saving information on: microprocessors, electronics, programming, and tools for busines s. • Solid plastic • lasts a lifetime • 2 comprehensive sides • Crystal clear printing • Instant access to data you need See our 1988 catalogue for full details. • "C" Language Cat. BM-8512 • Basic Intro Cat. BM-851 0 • 8080 & 8085 Cat. BM-8501 • 6502 (65XX) Cat. BM-8502 • Z80 CPU Cat. BM-8500 • 8086 & 8088 Cat. BM-8508 • Alogrithms Cat. BM-8504 • How to sample Cat. BM-8514 • Wordstar Cat. BM-8506 Thinking about investing in a VIFA speaker kit? Let Jaycar tempt you in to making that decision in October. SAVE UP TO $100 PER PAIR. All our stores have the new upgraded Vffa kits on demonstration, so drop in and have a listen. Remerrber, you willpay about twice as much for similar pre-built imported speakers. In fact they will probably have Vita speakers in then anyway. See our 1988 , catalogue for full details. ,. (Demonstration speakers are not at Concord). SA 130 3 way kit complete with tabinets and crossovers. 130W RMS power handling. Cat. CS-2465/CB-2467 SAVE $100 ONLY $1099 pr J $26.50 POPULAR MODEL • 20,000 ohms/volt • 10A DC range Cat. QM-1022 -t~ . "-'"''-~~ ~\:\)I $39.95 ULTIMATE ANALOGUE • Transistor tester • Centre zero adjust • Peak to peak & RMS Cat. QM -1050 $79.95 10A DIGITAL • Tran sistor tester • Vinyl case Cat. QM-1530 $89.95 CAPACITANCE TESTER • 10A digital • Transistor tester Cat. QM-1540 $129 4.5 DIGIT 10A • Transistor tester • Diode tester • Data hold Cat. QM-1560 $179 TOP DIGITAL • With frequency counter • Capacitance tester • Transistor tester • 20A current • High impact case Cat. QM-1555 SA-100 2 way kit complete with cabinets and crossovers. 100W RMS power handling. Cat. CS-2460/CB-2462 SAVE $70 ONLY $729 pr $159 DIGITAL AUTO TUNE-UP TESTER • RPM & dwell on 8,6,5, and 4 cylinder and more Cat. QM-1573 $139.50 DIGITAL L-C TESTER • Cap range 2 to 200uF • LC range 2mH to 20H Cat.OM-1575 $219 DIGITAL AC CLAMPMETER •400 amp • LCD display Cat. QM-1570 $139.95 SA-70 2 way kit complete with cabinets and crossovers. 70W RMS power handling. Cat. CS-2471/CS-2472 SAVE $50 ONLY $449 pr J' ALL ONE PRICE WERE$12.50 ~ NOW $9.95 , :~· 0 • SAVE $2.5~ },(~~ ··· -:.\ , SA-50 2waybookshettkltwith ,/i''t,~_-i., _, · ··... 'cabinets and crossovers. 30W RMS W 0 n't ),'¾j-'•·4" · ' ,:. ,. power handling. ' ;..;f<t . /. ~- '°''.· Cat. CS-2450/CS-2452 last ·c·-\:' -<- ··' ,6~"~-·-~-, • t.\_ . ,. SAVE l_ong :t,~~ ~-~$ 20 !liB'lf~~t~~tONLY $379 SPEAKERPHONE Ref: Silicon Chip Sept 1988 High quallty hands free telephone adaptor that works extremely well. Full kit including box, panel, isolating transforme r and all parts. Cat. KC-5040 ONLY $89 Thin Insulation Tape 10mm diameter x 20 metres long. Japanese made and black In colour. Flame retardant and cold and weather resistant. LIMITED QUANTITY Cat. NM-2805 ONLY 60t roll SAVE $7 on ADCOLA 240V Soldering Irons S30 12 wan Cat. TS -1492 ONLY $29.95 SAVE $7 S50 16 wan Cat. TS-1494 ONLY $32.95 SAVE $7 SOLAR ENERGY SENSATION * .,. DUE EARLY OCTOBER .. 0.45 VOLT SOLAR CELL MODULES ·*;i •, - .. to utilise , Size 75 x 45 x 6mm Cat. ZM-9005 ;) $6.50 10+ $6.20 ea ~ ,., . .• * * $29.95 SOLAR PANELS··*· " 2 Models ) , 6 volts <at> 240mA · ' 12 volts <at> 120mA These are quality made solar panels with aluminium picture framing around the edges for durability and ease of mounting. The solar cells themselves are covered by a clear resin for long life. Each panel measures 327(L) x 165(W) x 18mmthick. SOLAR EDUCATION KIT 12 volt panel Cat. ZM-9008 Cat. ZM-9009 <at> 120m A $79 The solar panel in the lid will charge up to 4 x AA NiCads in a fairly short time. It is ideal for yachts, campers or anywhere where 240V is not available. It is NO DEARER than an ORDINARY NiCad charger but takes about the same time to charge in reasonable sunlight. Cat. MB-3502 Size: 65(W) x 30(H) x 95(D)mm WAS $17.95 NOW $14.95 *. complete with: • Solar cell module • Solar energy booklet explaining the whys and hows of solar energy • Small DC motor • Screws and nuts • Wire with motor clips • Coloured spinner discs • Paper earoplane and bird models • Plastic turntables with 4 sizes, 5/8", 1", 1 1/2" and 2" • Plastic fan-spinner Discover for yourself how to harness the nergy of light and employ It in countless practical applications. Solar energy uses are limited only by your imagination. Cat. KJ-6690 ONLY $9.95 Loudspeaker P.A. Bin Enclosure Designs Book J' ·, Fane Acoustics UK, makers of speakers for the likes of Pink Floyd, David Bowie, Genesis , Iron Maiden etc. have produced an absolutely fantastic book on P.A. bin designs. The book begins with construction info in general, i.e. what materials to use, how to join timber, how to brace the cabinets, sealing, lining, wiring, crossovers, impedance matching, etc. The second section includes 22 separate detailed designs for: reflex cabinets, horns, wedge monitors, folded horns, w bins etc. Designs accommodate 10", 12", 15" and 18" speaker components. This book is cram packed with information. Save a fortune and build high power P.A. bins for yourself and friends. SOLAR PLANT TURNTABLE No more lopsided plants. Promote healthier well developed plants. Will handle up to 15 kg of weight. Also ideal for store window displays. Cat. YX-2503 $17.95 Cat. BF-4150 ~'~~' ■ 1 VISA $14.95 HEAD OFFICE MAIL ORDERS POST & PACKING 115 Parramatta Road Concord 2137 P.O. Box 185 Concord 2137 ~o ~~49~9 ~ ~.~~ Telephone (02) 747 2022 HOTLINE (02) 7471888 $25 $49.99 s 4.50 Telex 72293 FOR ORDERS ONLY $50 $99.99 $ 6.50 0 100 _FA_C_S_I_M_IL_E~(0_2~)_74_4_0_7_6_7_ _ _ _T_O_L_L_FR_E_E_(D_D_8)_0_22_8_8_8_ _v_ER_s__ __s_10_.oo_ _ - - , • 1 * Now you can experiment with solar energy ... the energy source of the future. Our solar education kit is designed to let you build your own solar models. This kit comes 6 volt panel<at> 240mA $79 Solar Battery Charger . How often have you been away on holiday leaving your car at home, and when returning finding your battery as flat as a tack I You need to push the car out of the garage, down the driveway and out onto the street so you can connect jumper leads, or wait an hour or more for the NRMAIRACQ/RACV to arrive. Well, with this handy gadget all that is gone. When you park your car for extended periods (i.e. 4 or more days) simply plug this into your cigarette lighter socket and sit the unit on the dash board, or near the window of the garage. When you return home - no more dead batteries. The unit consists of solar cells in a housing with 1 metre of cable and cigarette lighter plug. Cat. MB-3503 Size 96 x 65 x 6mm Cat. ZM-9006 10+ $3.75 ea *"· ' -,, ·.,,:... SOLAR CAR-BATTERY BOOSTER 0.45V 1000mA $3.95 '.~9. FREE power '.ro~ the sun. *l· 1 !. . Ideal for experimenters. Connect in series or parallel if you wish. Terminal strap enables easy connection to other cells. Two handy sizes 0.45V 400mA *' . Jaycar proudly intr?_duces a range of direc.t imported solar pro.ducts ;~I~ , MAIL ORDER VIA YOUR fr ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 L--------------------------------------' SYDNEY • CITY 117 York St. (02) 2671614 · Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 • 12 GORE HILL 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 • Mon-Fri 9 - 5.30 Sat 9 - 4pm CARLINGFORD Cnr. Carlingford & Pennant Hills Rd (02) 872 4444 Mon-Fri 9 • 5.30 Thurs 8.30 pm - Sat 9 • 2pm BURANDAQLD 144 Logan Rd (07) 393 0777 Mon-Fri 9 • 5.30 Thurs 8.30 - Sat 9 -12 CONCORD 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 - 12 MELBOURNE-CITY Shop 2, 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 HURSTVILLE 121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 -12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 12 Build this 5-element FM antenna How's your FM reception? Not up to scratch? You can greatly improve matters by building this 5-element Yagi antenna which is designed specially for the FM band. By LEO SIMPSON & BOB FLYNN It's amazing isn't it. So many people spend thousands of dollars on their hifi equipment and then just string up the simple dipole antenna that came with their receiver or tuner. It really is a waste. After all, most people know that to obtain 28 SILICON CHIP good TV reception, they need a good antenna installation. Well, the same applies for FM. If you want the best sound quality, you need a good antenna. Sure, if you live in a strong signal area, you might get away with just a tap off your existing TV antenna but a separate FM antenna will always give a better result. The problem is: what antenna to buy? There are very few available and of those that are, few are suitable for fringe areas. To be specific, the most common FM antenna available is a 3element Yagi which gives, at best, about 6dB gain with respect to a simple dipole. These are OK in strong signal areas but we wanted more gain. We also wanted more directivity to cope with poor recepFig.1: this diagram shows all the details of the 5-element antenna. At top is a plan view while the other diagrams show hardware and element mounting details. ► . . E E B ~ a: ,f;l E ita: E E E \::! . .s .s ;! ~ a: ,- w ~ iS IlliS 9 :;; w ~ a: a: 0 0 E .s ::. ... 0 ,f;l ,f;l a: iS !!i N ..,~ = z N -L BOOM 2222mm A A C A A 19 19 ... N ~ ... N ... N 50 63D 627 363 ~ 0 562 J ~694 69/ FOLDED DIPOLE INSULATOR 3mm ACRYLIC -==------------Jil -------- -----'140D -":.:....- - ------- - - -- -~...-----------~~- ~ DIPOLE TOP PIECE - 1 REQO. 642 680 DIPOLE BOTTOM PIECE - 2 REQO. I 0 19 19 50 3/16" x 70mm WHITWORTH SCREW I 0 FOLDED DIPOLE SPACER - 1 REQD. 19mm SQ. ALUMINIUM TUBING MATERIAL:- FOLDED DIPOLE, IHRECTORS ANO REFLECTOR : 10mm DIA.; 1mm WALL THICKNESS, ALUMINIUM TUBING BOOM : 19mm SQ., 1.8mm WALL THICKNESS , ALUMINIUM TUBIIG 0- FASTENERS : STAINLESS STEEL FOLDED IHPOLE BOTTOM PIECE 0 REFLECTOR ANO DIRECTORS TO BOOM CONNECTION 3/16" x 60mm WHITWORTH SCREW FOLDED DIPOLE TOP PIECE FOLDED IHPOLE ENO 0 ; 42 IHPOLE ENO PIECE 2 REQO. =,, ELEMENT BG x 13mm STAINLESS STEEL SELF-TAPPING SCREW BOOM SPLIT WASHER I 0 FM ANTENNA FOLDED DIPOLE TO BOOM CONNECTION OCT0BER1988 29 Fig.2: the dipole insulator plate has wing nut terminals to connect 300!1 ribbon or a 300!1 to 75!1 balun. The plate is made from Perspex, Lexan or other acrylic material. The square boom makes mounting easy. more directional. To put it another way, it has a narrower acceptance angle. This means that reflected signals coming in from the side of the antenna will be suppressed. This is worthwhile because the more suppression you can obtain for reflected signals, the less distorted the resulting stereo sound will be. In other words, if you have problems with distorted sound from some FM stations (due to reflected signals or "multipath" ), you should be able to obtain a worthwhile improvement using this antenna. Another reason to build this antenna is to improve on the signal available from a normal 3-element array. While a gain figure of about + 2dB with respect to a 3-element array may seem modest, it can make a substantial difference to the apparent signal-to-noise ratio when receiving weak stations. Tools you will need Fig.3: this topside view of the antenna shows how the folded dipole is attached to the square boom. Note the short section of aluminium tubing which acts as a spacer between the underside of the boom and the dipole insulator plate. Whitworth or other machine screws hold it all together. tion conditions where multipath is a real problem. After looking at what's available, we decided to design and build our own. Actually, we ended up building a number of variations before settling on the design presented here. The new antenna is a 5-element Yagi array. It has a folded dipole, a 30 SILICON CHIP single reflector and three directors. It has an estimated gain of between 8 and 9dB gain with respect to a dipole and an improved front-toback ratio compared to a 3-element array. Narrow acceptance angle As well as an improved front-toback ratio, this antenna also is Most enthusiasts will have all the tools needed for this project. You will need a hacksaw, electric drill and a vice. It would also help if you have a drill press but you can do without. Apart from an antenna clamp (U-bolt and V-block bracket), no special hardware or fittings are required. Making and assembling this antenna is very straightforward. If you have all the materials available you can probably do it in a single afternoon. The diagrams of Fig.1 show all the details of the 5-element antenna. These diagrams show the dimensions of all the elements and the various hardware bits you will have to make to assemble the antenna. At top is a plan view showing the length of all five elements and their spacing along the boom. Fasteners After a few years' exposure to the elements, many antennas are in a poor state. Aluminium may not "rust" but it does corrode, particularly in seaside areas or in metropolitan areas where there is a lot of industrial fallout. This corrosion can be a lot worse if you don't use the right screw fasteners. We recommend the use of What is a Yagi antenna? The Yagi is not a new antenna design by any means. It was developed by H. Yagi and S. Uda at Tohoku Imperial Univers ity in Japan in 1926. In the VHF (very high frequency) bands, of which the FM band (88-108MHz) forms a small part, most antennas depend on electrically resonant elements; ie, elements which are a halfwavelength at the frequency of interest. In its simplest form, the Yagi consists of a dipole element and an additional slightly longer parasitic element behind it, called the reflector. More complex designs have shorter parasitic elements in front of the dipole and these are called directors. The reflector and directors are referred to as parasitic elements because they also resonate over a frequency range similar to that of stainless steel screws throughout, whether for machine screws or self-tappers. They do cost a little more but they last indefinitely. Don't, on any account, use brass screws. When used to attach aluminium elements these will corrode away almost before your eyes. Nor do we recommend galvanised, bright zinc or cadmium plated steel screws. In seaside areas these can be visibly corroded with just a few days' exposure. In rural areas, well away from the sea or city pollution, you can probably get away with galvanised screws but the antenna will last longer if you paint it. Starting work Before you start, make sure you have obtained all the aluminium and hardware listed in the Bill of Materials. After all, you will be frustrated if you get half-way through and find you can't progress farther because you lack screws or some other item. Get 'em all before you start. Cut the boom to length first. It is 2222mm long. It is made of 19mm square aluminium tubing which the dipole. Part of the electromagnetic ene rgy they capture is re-radiated and picked up by the dipole. Hence the director and reflectors add considerably to the signal which is picked up by the dipole on its own. By suitably dimensioning the reflector and directors, it is possible to determine the overall frequency coverage of a Yagi antenna, its gain and its directional characteristics. In general, the more elements in a Yagi array, the higher will be its gain and the smaller the forward acceptance angle . There is a law of diminishing returns though. Above a certain number of parasitic elements, no useful increase in gain is obtainable . There is a definite tradeoff between the practical size of a Yagi and the amount of gain it provides . makes drilling and assembly easier. (Yes, if you are experienced in metalwork and have access to a set of V-blocks and a drill press, you could substitute 25mm diameter tubing for the boom). While you're at it, cut the folded dipole spacer which also uses the 19mm square tubing. It is 50mm long. You should have a piece of tubing about 120mm left over as scrap. Don't throw it away. It will come in handy later. Now cut the 10mm diameter tubing for the director, three reflectors and parts for the dipole. Remember the old adage about "measure twice and cut once". It's hard to lengthen elements that are too short. Note that the three directors are all the same length, 1270mm. Next, centre-punch the boom for all holes prior to drilling. Note that the boom is 2222mm long and the total of the element spacings along the boom is 2182mm - see the plan diagram on Fig, 1. Mark the hole centre position for the reflector element first, 20mm from one end of the boom, and then work your way along. If you have a drill press which Bill of Materials Alumini um 2.3 metres of 19mm square aluminium tubing with 1 .8mm wall thickness 8 .5 metres of 10mm diameter aluminium tubing with 1 mm wall thickness Hardware 1 piece of thick Perspex, 1 20 x 40 x 3mm 1 U-bolt and clamp to suit mast 4 8G x 13mm screws 2 8G x 32mm screws 2 3/16-inch Whitworth roundhead screws 70mm long 1 3/16-inch Whitworth roundhead screw 60mm long 2 3/ 16-inch Whitworth roundhead screws 32mm long 2 3/16-inch Whitworth roundhead screws 1 9mm long 7 3/16-inch ID split or lockwashers 7 3/16-inch Whitworth nuts 2 3/16-inch Whitworth wing nuts 2 3/16-inch ID flat washers Note: all screws, washers and nuts to be stainless steel Miscellaneous Mast and wa ll mounts or bargeboard mount (hockey stick style) , 3000 to 750 in-line balun (for outdoor use). semi-air spaced coax cable (Hills SSC32 or equivalent). plastic cable ties, silicone sealant. lets you drill all the element holes square through the boom you are fortunate. If not, mark the hole centre positions on both sides of the boom and drill from both sides. If you don't get the element holes lined up properly, you will have the elements skew-whiff. A few words of advice on drilling is appropriate here. Drilling in thin wall aluminium can be a problem and many people will tend to end up with holes that are more triangular than round. The way around this problem is to drill all the large holes (ie, all 10mm holes) undersize and then ream them out to the correct size using a tapered reamer. OCT0BER1988 31 though because the dipole should be assembled and mounted on the boom first. Making the dipole Fig.4: the ends of the folded dipole are fabicated using 42mm lengths of aluminium tubing shaped to mate with the upper and lower pieces. They are held together with a 70mm long machine screw, nut and split washer. Fig.5: the mast clamp and V-block assembly can be purchased from electronic parts or automobile accessory retailers. Use galvanised types if possible. Avoid cadmium plated or zinc plated clamps which tend to rust out. Be careful when reaming holes out though because it is quite easy to get carried away and then end up with holes that are oversize. Use a scrap piece of 10mm tubing to test when the holes specified at 10mm are the correct size. 32 SILICON CHIP Each director element and the reflector is held in the boom with a self-tapping screw, as shown in diagram A of Fig.1. Drill a 3mm hole at the centre point of each element but only through one side. Don't mount the elements on the boom yet The folded dipole is made from five pieces of 10mm aluminium tubing, three long and two short. The detail of its assembly can be seen from the diagram at the bottom of Fig.1. Two short tubes, shown as diagram E on Fig.1, are cut and shaped so that they key in with the top and bottom elements of the dipole. Further detail is shown in the photo of Fig.4. The top and bottom pieces of the dipole are held at each end with a 70mm long 3/16-inch Whitworth screw, together with a nut and lock washer. At the centre, the lower halves of the dipole are terminated on a insulating plate (shown in diagram D of Fig.1). This plate is made of 3mm acrylic (Perspex or Lexan). The dipole halves are each secured to the insulating plate with a 19mm long 3/16-inch Whitworth screw, nut and lockwasher. Terminals for the dipole are provided with two 32mm long 3/16-inch Whitworth screws, each fitted with a nut and lockwasher plus a wing nut and flat washer. The insulating plate is secured to and spaced off the main boom via a section of square tubing, shown as a "folded dipole spacer" in diagram F of Fig.1. The insulating plate is secured to the spacer with two 8-gauge 32mm long self tapping screws which go through the spacer and into the boom. The top piece of the dipole is then secured to the boom with a 60mm long 3/16-inch Whitworth screw, nut and lockwasher. The details of the dipole insulating plate and fixing to the boom can be seen in the photos of Fig.2 and Fig.3. Note that while we used a white Perspex, you could use a piece of clear material if that is what you have on hand. By this time the antenna looks just about complete. You need to add the antenna clamp, to enable it to be attached to the mast, and you will need a 3000 to 750 balun to match it to 750 coax cable. You can use 3000 ribbon if you wish and omit the balun, but to obtain the Fig.6: do you have trouble drilling round holes? You'll do better by drilling the holes undersize and then reaming them out to exact size with a tapered reamer. most interference-free signal, we recommend coax cable for your installation. Unfortunately, many antenna clamps are sold with a cadmium plated and passivated finish. These have a "gold" finish. This may be adequate for inland areas but they soon rust in sea air. We may seem to be paranoid about corrosion but since the SILICON CHIP editorial offices are only a few hundred metres from the seaside we are very aware of just how quickly antennas can rot away. If you can, buy antenna clamps that are heavily galvanised. These last a lot longer than the cad-plated jobs. U-bolts and clamps intended for auto exhaust systems are generally quite good in this respect. But be aware that zinc " plated" fittings are not as rust resistant as galvanised types. Zinc plated fittings have a smooth bright appearance while heavy galvanising is unmistakable - it has quite a rough appearance. If you really want to gild the lily, go to a ship's chandlers and buy stainless steel U-bolts and clamps. They'll last forever; well just about. We suggest that the ends of all the elements and the boom be Fig.7: the reflector and director elements are attached to the boom using self-tapping screws. All screws, nuts and washers should be of stainless steel to avoid corrosion. stopped up with epoxy adhesive (eg, Araldite), putty or silicone sealant. This will stop them from whistling in the wind. Better still, you can buy Delrin plugs to suit the square aluminium tubing. These look neater. You might also consider painting your antenna, if you live in an area where corrosion is a problem. We suggest you leave the antenna for a month or so to weather it and then paint it with an etch primer. Finish it with an aluminium loaded paint such as British Paints "Silvar" . Installation When you have finished your antenna you need to carefully consider its installation. There is no . point in going to a lot of trouble making it if you don't install it properly. Try to install your new antenna well away from existing TV antennas as these can have quite a serious effect on the performance. Similarly, nearby metal guttering, electric cabling, metal roofing or sarking (ie, reflective insulation such as Sisalation) can have a bad effect on antenna performance. Don't forget the effect of a hot water tank which may be lurking just beneath the roof tiles. If you live on a busy street, try to install your antenna as far away as possible from the traffic side of your house. That way you will minimise ignition noise from passing traffic. Finally, install the antenna as high as possible above the roof and guttering. If that is a problem, try to install the antenna so that it is at least a half wavelength away from the nearest metallic object such as guttering or roofing. This means a distance of about 1.5 metres away from guttering. Take care when installing the antenna. Safe working with ladders is particularly important. Take your time and don't take risks. You don't want to end up in hospital. Line up the antenna so that it is aimed at the main FM stations of interest. If you are really keen, you could also consider installing a rotator, to obtain the very best reception from all stations. If you are using 3000 ribbon, use spacers to hold it away from the mast, otherwise you'll lose signal. If using coax cable, tie it to the mast with insulation tape or cable ties, to stop it flapping in the wind. ~ OCT0BER1988 33 D DIECAST BOXES Diecast boxes are excellent for RF shielding, and strength. Screws are provided with each box . H11451 100 x 50 x 25mm . $ 5.95 H1 1452110x60x30mm $ 6.50 H t 14531 20 x 65 x 40mm . $ 6.95 H 11 46 1120x94x53mm . $11.50 H11462188x 120x78mm ... $13.50 Ht 1464 188x 188x64mm ... S29.50 H 10382 3 x 4 x 2 inches H10383 3 X 4 X 3 inches H10384 3 x 4 x 4 inches H1 03853x4x5inches H10386 3 x 4 x 6 inches H10387 3 x 4 x 7 inches H10388 3 x 4 x 8 inches H103893w:4x9inches H103903x4xl0inches . . . $ 5.50 $ 6.50 $ 7.50 7.95 $ 8.50 . $ 9.50 $ . $10.50 $10.95 . $11.95 UTILITY BOXES HORWOOD METAL INSTRUMENT CASES (ROUND HANDLES) 8416N H10461153x 102x203mm $18.95 84/BN H10462 203x 102x203mm S19.50 84110N H10463 254 K 102 x203mm S19.95 8411 2N H10464 305x 102x203mm $22.95 Plastic boxes with aluminium tops. · and available in four sizes. Very popular lor projects and very ecconomical! H10101 150x90x50mm $ 3.25 H10102 195x113x60mm $ 4.50 H 10103 130x68x41mm $ 2.75 H10105 83x54x28mm $ 1.95 H 10110 120x65x38mm $ 2.95 H10112 120x65x38mm (Metal top) $ 2.95 CROSSOVER NETWORKS CPF CONTINUOUS POWER FILTEA SPIKE ARRESTOR The Fortran C PF Filtered Electronic Spike Protector provides a protective electronic barrier for microcomputers. printers, telephone systems and modems electronic typewriters, audio and stereo systems and other sensitive electronic equipment . The CPF provides protection from dangerous electrical spikes that can c~u~ anyth~ng lrom_obvious damage (like 1mmed1ate equipment failure) to less obvious harm that can drastically shorten a system·s life. CPF's superior circuitry design and semi conductor technology reSIX)nds instantly to any potentially damaging over-voltage. ensuring safe trouble free operation . Additionally, CPFs filtering capability helps eliminate troublesome and 9316N H1 0467 153 K 76 x 228mm $16.95 H10465 203 Ht0466 254 H10468 305 H 10470 430 93/BN x 76 x 228mm 93110N x 76 x 228mm 93112N x 76 x 228mm 93/17N x 76 x 228mm Cat.X10088 $29.95 FREE POSTAGE FOR SILICON CHIP READERS THIS MONTH MINIMUM ORDER OF $50 APPLIES JUST QUOTE THIS ADVERTISE MENT $29.95 MINIATURE HOBBY VICE • Lever operated suction grip base for instant mounting and portability • Mounts on smooth non-porous surfaces. Cat.T 12458 ... only $6.45 K&WMETAL INSTRUMENT CASES Used in many projects, these cases have hammertone finish and are both versatile and ecconomical H10478 125 x 40 x 65mm . S 5.95 H1 0479 150 x 55 x 95mm . S 6.95 H 10480 100x92x130mm ... $ 8.95 H 10481150x55x100mm ... $ 7.95 H10482200x80x130mm .. . $ 9.95 H1 0485255x92x 155mm ... $14.95 H10487255x 165x 155mm . $16.95 H10489305x 105x2QOmm . $16.95 SPECIFICATIONS : 4 ~~:::u~~:ra~e~ 1 DC Prima,y Cunent: 4·2A (24V input ~-~e MASTER RACK MOUNTING CABINETS These superb rack mount cabinets will give your projects a real professional appearance! Just look at these features ... • All dimensions conform to the International Standard • All alumir,ium construction • Choice of black or natural finish • Deluxe brush finish anodised front panel • Removeable top and bottom lid • Ventilated lid Horizontal Depth : 254mm A = External Front Panel Height mm B = Mounting Hole Centres mm C = Internal Chassis Height mm A B C Finish Cat.No. Price 44 34 38Natura1Ht 0401 $59.50 88 57 82Natura1H10402 $69.50 132 89 126 Natural H 10403 $79.50 44 34 38B!ack H10411 $65.00 88 57 82Black H10412 $75.00 132 89126Black H1041 '.3 $85.00 • Charges from 1 lo 100. C. AA. AAA. N. and up to 3 x 9V batteries at the same time. • Dual colour LEO in first three compartments to designate 1 •SV or9V. • 240V ACl50Hz. • Approval No. N10637 Cat.M23525 . ........ $59.95 STEP DOWN CONVERTER DC-DC ~fnfi;:~~ POCKET SIZE BATTE RV TESTER • Tests all 9V to 1·SV batteries including button cells. STEREO WIRELESS TRANSMITTER This unit was developed to allow portat?le compact disc players to be used 1n cars by transmitting the ~e;g~~t~;e~utp~tc~~~:~gi_r~fir in also transmit any mono/stereo signal ~~"::c7ivh ~adphone output to any 8 SPECIFICATIONS : • Input 3·5mm stereo phone plug . Impedance 32 ohm . • Mono/stere<:> switch has plug mounting chp. • FM Transmission approx . 90·35MHz (Tuneabfe 89-91 MHz) • Range 15 metres. {below 1SmV/m at 100 metres) • Power 1 ·5V AAA size batteries (100 hours continuous use) • Size72 x 38 x21mm • 12dB attenuation •Crossover point 800 and 5,000 Hz • Impedance ohms 0825 PLUG WALL PLATE • Fitted with OB25P plug. (AS232) • Anodised aluminium plate. • Includes mounting hardware. P10944 $11.95 a $24.95 Cat. A 16005 3 WAY 150 WATT CROSSOVER NETWORK • 16d8 attenuation • Crossover point 350 and 3.000 Hz • Impedance 8 ohms Cat. A16007 $34.95 t-.r. _, TEXTOOL SOCKETS P1701616pin ............... $14.95 P17024 24 pin . ... $18.50 P17028 28 p;n .... .... ... ... . $24.95 P17040 40 p;n . .. $29.50 A16100 Use these quality, all metal, Piezo tweeters for great top end sound in your band speakers, disco sound system, etc. Rated at 30 watts RMS. · in a system they will handle over 100 watts RMS. Two sizes to choose from : Size: 4 " x 101,-2•· Impedance : 8 ohms Rating : 30 watts RMS Response: 1.5kHz-14kHz Dimensions: 102x267x 177mm Cat. C92082 Normally $49.95. This month only $39.95 Size: 3"x T Impedance : 8 ohms Rating : 30 watts RMS Response : 2kHz • 15 kHz Dimensions: 76 x 177 x , 45mm Cat. C92084 Normally S29.95 This month only $24.95 Dealers, OEM's, etc., phone (03) 543 2166 for wholesa~ prices PIEZOSIREN • 4 piezo units in a high impact plastic cabinet • Input 12V DC - 200mA • Output 115d8 at 1m, dual tone • Compact size 105 x 85 x 45mm • Smart design suits interior use Cal . S15071 ............. ... . $24.95 () -, OMNI-DIRECTIONAL WIRELESS MICROPHONE Tuneable : 92 - 104MHz Freq. Response: 50 • 1SkHz Range: Over 300 feet in open field . Modulation: FM Power Source: 9V Battery Type : Electret Condenser. Dimensions : 185 x 27 x 38mm Weight: 160 grams Cat. A 10450 .. ... .... ... .. .... . $19.95 $69.95 • Requires no crossover and handles up to 1OOW! • Sensitivity : 100dBI0 .5m RS232 GENDER CHANGERS ~tJ~ifo'f~~ns~~ Jfnfi~:cT~ matt $119.95 . $11.95 SUPER HORN TWEETER Built around a heavy duty heatsink this unit features the latest transistor A16160 $9.95 $11 .95 10A STEP DOWN CONVERTER DC-DC SPECIFICATIONS: Input Voltage : 24V DC Output Voltage: 13·8V DC Primary Cunent : 11A (24V input, 10A output) Output Current: 8 Amp continuous rated (12Amax .) Size: 125(W) x 50(H) x 175(0)mm Weight: 900 grams P10947 $7.95 • Requires no power source. M23521 $99.95 black . 2WAY60WATT CROSSOVER NETWORK • Fitted with DB25S socket. (RS232) • Anodised aluminium plate. • Includes mounting hardware. • 12dB attenuation • Cross over point 2,300 Hz • Impedance 8 ohms ==r~J~=.sbatterysizes Ou~itu:fi:!ent : 4 Amp continuous rated (5·5A max .J Size : 125(W) x SO(H) x 90(D)mm Weight: 450 grams A16155 DB25SOCKET WALL PLATE $4.95 MIDRANGE HORNS SUPER DELUXE BATTERY CHARGER ~ ✓1P~~ BUIit around a heavy duty heatsmk this umt features the latest transistor 1 ~r!t8tfo ftenS~8~ matt black with a unique mounting bracket makes it the best in its class. Cat.A16001 3WAY60WATT CROSSOVER NETWORK S21.50 • Ideal for holding components. and other small/light objects . 2WAY60WATT CROSSOVER NETWORK Cat.A16003 A10031 (10 discs) $12.95 A10032 (20 discs) $19.95 $18.95 $9.95 3WAY60WATT CROSSOVER NETWORK • Holds 10120 compact discs in Iheir cases • lnterlockillQ modular design allows vertical and horizontal interlocking • Discs slide into place horizontally making lilies easy to read. • Wall mount or free standing . $17.95 P10940 • 6d8 attenuation •Crossover point SOO and 5,000 Hz • Impedance 8 ohms COMPACT DISC STORAGE UNITS $3.20 • Fitted with 5 pin DIN socket. • Anodised aluminium plate. • Includes mounting hard•Yare . • 6dB attenuation • Crossover point 5,000 Hz • Impedance 8 ohms Cat.A16002 $69.95 Designed for car burglar alarm backup battery. Allows the back-up battery to be charged from the car battery and isolates the back-up battery by not allowing the back-up battery to drain back to the car battery A 12095 A 10011 ~~ena~,~;";!~Tir:~£~~:r~:c!sn~ lamps, and the like that threaten the ~ormance and shorten equipment hie of unprotected electronic components. SPECIFICATIONS : Electrical rating : 220·260 volts (AC) SOHz 10 Amp Splke/AFI Protection: 4 ,500 amps for 20m/second pulses . Maximum clamping voltage: 275V differential mode. CAR BATTERY ISOLATOR HORWOOD MET AL INSTRUMENT CASES (SQUARE HANDLES) Enables a portable CD player or portable TV to be played through any car speaker system by using the cars cassette player. Reduces the risk of thett. Just plug in when required , and remove when you are finished. Hard wiring not needed . Crossovers are essential for multiway speaker systems, otherwise your bass will be ~egraded by inter• modulation distortion and cone break up, and your treble will be distorted by bass components. These c:-ossovers are designed to channel only the frequencies that each driver can properly handle. Read the specifications to choose the correcl one for your need . FREE STANDING, FOLD UP MAGNIFIER An ecconomically priced " hands free "' magnifier. lets you take care of all those tricky fine detailed jobs so often encountered in electronics, or any of many other practical uses such as home , work , hobbies etc. Cat. T1 0020 Normally $14.95 SPECIAL. ONLY $12.95 • Saves modifying or replacing non-mating RS232 cables. • All 25 pins wired straight through Cal . X15650 Male to Male Cat. X15651 Male to Female Cat . X15652 Female to Female Normally $14.95 each Only$9.95 DB9GENDERCHANGERS • Saves modifying or replacing non mating DB9 connections • All 9 pins wired straight through X 15640: Male to male X15641: Male to Female X15642: Female to Female only$14.95 : i~~d~i:;s~M$ 3kHz-30kHz • Size 96mm diameter Cat. C12102 Normally $12.95 SPECIAL. ONLY $9.95 ,.JE ~ '" -~ ,..- P.A. SPEAKERS Low dual cone, wide range . 200mm (Sin.). Ideal for public address, background music, etc. Tremendous Value at these prices! ........ Cat.C12000 1·9 10+ $6.95 $5.95 RS232 WIRING ADAPTOR BOX • • • • Male to female 25 (?etachable plug on leads 2 mini jumpers Ideal for experimenting or temporary connections Cat. X15665 ...... Normally $49.95 Only $44.95 008 335757 TOLL FREE MAI LOR DER HOTLINE FOR CREDIT CARD ORDERS! LOCAL ORDERS & INQUIRIES CALL (03) 543 7877 SILICON CHIP KITS NOW AVAILABLE FROM ROD IRVING ELECTRONICS! HIGH ENERGY IGNITION SYSTEM FOR YOUR CAR LOW OHMS TESTER FOR DIGITAL MULTIMETERS Want to accurately measure low value resistors down to 0·01 ohm? This simple adaptor circuit wilt do the Job. It plugs directly into your digital Is your car still limping along with outdated Kettering ignition? What? You are still cleaning points, adjusting the dwell, checking timing and all that 7 g~i:7g n~~~ and forget those tune-up hassles. ~~:~j~~~~ ~~~t~~n """"""""" $47.95 multimeter. J$ ~ - ' , •• .... ~ ">. ~ ~ i/ HEADPHONE AMPLIFIER FOR CD PLA YEAS ; ~ - - ··- LAB SUPPLY $28.95 t ~-D.._j DUAL TRACKING 18·5V POWER SUPPLY Take a squiz at this! A dual tracking power supply of modest cost giving up to +- 18·5V DC. It has voltage metering, a LED dropout indicator and short circuit protection. $97.50 Does your compact disc player lack a ~:~~.: =~~:,~ ~d1fs~~;fo"the Fully variable 0-40V current limited 0-5A supply with both voltage and current metering (two ranges: 0-0.SN0-5A). This employs a conventional series-pass regulator, not a switchmode type with its ~~~l~i~ie ~~~~~~?t~~?nng ~tt,;~~~~'cf system switching between laps on the transformer secondary. (ETI May'83) ETI 163 Cat.K41630 ..................... $249 .............. ,,, .. ,,, .. ,, $22.95 l~e~ta:;g~(~r~~~,,~ters audio Cat. ..... ...... .. .. .......... ... ... MOTORCYLCE INTERCOM OVER 500 SOLD! Motorcycling is fun, but the conversation between rider and 8 1 ~~~ lhij~~t~~~om and you can converse with your passenger at any time while you are on the move. There are no "push-to• talk" buttons , adjustable volume and DIGITAL CAPACITANCE METER Mk.2 THE SCREECHER CAR BUGLAR ALARM Here is a low cost car alarm designed with a new deterrent strategy. Instead of using the alarm to try to draw the attention of passers-by to the felony in progress, this alarm sounds inside the car, to deafen the thief and make ii too uncomfortable to proceed with pinching the vechile! (86a19, EA August ·a6) •Note:The RIE kit contains quality silk screen printed and prepunched front panel ANO an exclusive High Intensity Display! (85cm9a, EA August '85) HANDS-FREE SPEAKER PHONE Here's a hands-free telephone that anyone can afford. With the ~~v~~=~~~~~~~~~%] the phone to your ear. And if you are ~~~~~~~~~;f~~ 0ci~~.ntinue with .................. P.O.A. SLAVE FLASH TRIGGER .. ..... FREE POSTAGE FOR SILICON CHIP READERS THIS MONTH MINIMUM ORDER OF $50 APPLIES JUST QUOTE THIS ADVERTISE MENT $49.95 detects the flash and triggers a5econd (slave) flashgun. It's easy to build and very affordable. .............. P.O.A. .... MUSICOLOR IV 50 W AMPLIFIER MODULE (ETI 480) ~[~~plh~~:i:f ;~~~7tf~ity control plus opto-coup1ed switching Cat . K44880 ....... Normally $31.80 ~El1~~~-i~ Jf~~e (Heatsink optional extra) $114.95 SPECIAL, $21.95 100 W AMPLIFIER MODULE (ETI 480) Cat. K44801 ...... . Normally $34.80 SPECIAL, $28.95 POWER SUPPLY TO SUIT Without transformer ...... WALK-AROUND THROTTLE FOR MODEL RAILWAYS HEADPHONE AMPLIFIER f~~~~!rf~~~~:~;~n. :wt~~~rr~~~· ~~~utt~ It's equYvalent commercial units, and features eight separate inputs, individual sector control, battery back up and self-test facility. Specifications: • ~~~a~f;~~rs with LED status This clever adaptor circuit plugs into your digital multimeter and can measure capacitance up to 2·2 microfarads. .......................... P.O.A. MUSICOLOR IV Add excitement to parties, card nights and discos with EAs Musicolor IV light show. This is the latest in the famous line of musicolors and it offers features such as four channel "color organ" plus four channel liqht chaser, front panel LEO display, internal microphone, single sensitivity control plus opto-coupled switching ~win:u~~i~ r,~~e , cat.Ka1oao. \ .. .. $114.95 MULTI SECTOR ALARM STATION Protect your home and possessions from burglars with this up to the CAPACITANCE ADAPTOR FOR YOUR MULTIMETER PROTECTOR CAR BURGLAR ALARM This refined car burglar alarm has just about every feature you could want but is easy to build. It incorporates internal and external ::r:~ =~~~s=-:f .................. 11~~· ignition P.O.A. $22.95 PRACTICE WITHOUT ANNOYING THE FAMILY' If you ptay any type of electronic Want to build a walk-around throttle for your model railroad layout? This one offers a host of features including P.O.A. 15V DUAL POWER SUPPLY AUDIO TEST UNIT KIT Just about everyone these days who has a stereo system also has a good cassette deck, but not many people are able to get the best performance from it. Our Audio Test Unit allows (81A010) (EAOct '81 ) Cat. K81 10 1 .................. (Heatsink optional extra) g~~:rnr~~r SPECIAL, $15.95 • Two delayed entry sectors . • Variable exit, entry and alarm time settings: entry delay variable between 10 and 75 seconds; exit delay variable between 5 and 45 seconds; alarm time variable between 1 and 15 minutes. • Resistive loop sensing: suits both normally open and normally closed alarm sensors. • Battery back-up with in-built charger circuit. • Built-in siren driver. The RIE ktt lncludea a 1uperb printed and prepunched metal ~:i1=!::;~~n=!::~r~:, K85901 $134 without batt81)' back'-!) SPECIAL, $115 K85900 complete kit . only $159 SPECIAL, $129 This simple project is suitable for 1 :o~:t;~/~~~J:~¥~~g~f;r~! • (ETI 581 , June '76) Cal . K45810 .. .... .. .. .... .... . $34.95 $59.50 LOW-COST BIPOLAR MODEL TRAIN CONTROLLER Add excitement to parties, card nights and discos with EAs Musicolor IV llght show. This is the latest in the famous line of musicolors and it offers features such as four channel "color organ " plus four channel ll~hl chaser, front Cat.K81080 ................. $29.95 Have you ever desotdered a suspect transistor, only to find that it checks OK? Trouble-shooting exercises are often hindered by this type of false alarm, but many of them could be avoided with an "in-circuit" component tester, such as the EA Handy Tester. (EA Sept .'83) 83TT8 Cal. K83080 ....... Normally $18.95 tf~s t~~~bYi~~~~f~!~~=~~orde(s response for a given tape or alternatively, it allows you to find out which tape is best for your recorder. MUSICOLOUR IV ~fe When your camera's ltashijun fires, this simple device automat1cally Cat. K86081 ... ................ TRANSISTOR TESTER $99.95 ~~sAe~!b.!i~u~gic2 Cat. K84020 . $9.95 Updated from the EA March 'BO issue, this Digital Capacitance Meter checks capacitor values from 1pF to 99.99uF over three ran~es. Its main features include a LEl~n9i;;i~~i.t and a bright 4 digit Cat. K85090 .. ... ... .... .. .. .. . ::!~7~. b~~~ music direct, without degrading the sound queltty. 1W AUDIO AMPLIFIER KIT A low-cost ~eneral-purpose.1 watt audio amphfier, suitable for instrument, this headphone amplifier will surely interest you. It will let you practice for hours without upsetting the household.or you can use it to monitor your own instrument in the midst of a rowdy jam session. (EA Feb.'84) 83MA11 Cat. K84111 ....... ....... ..... $39.95 Here is a simple model train control for those enthusiasts who desire something better than the usual rheostat control. It provides much improved low speed performance and is fully overload protected, yet contains relatively few componenets. Best of all, you don·t need to be an electronic genius to construct it. (80TC12) (EA Dec ·00) Cat. K80120 $39.95 ELECTROSTATIC HA2ARD DETECTOR KIT It's called electrostatic hazard and if !~~~~~~r;!~?C ~~~:~~~il~:;;~t~~~ the poor device is never likely to be quite the same again. So, out of a very ordinary collection of bits and pieces, ETI has fashioned a black box that wilt sit quietly on a corner of your bench for years at a time and beep when ever high tension appears. It may save you a Jot of trouble, particuly if you ever work with CMOS. {ETI 173 May '86) Cat. K41730 ... ...... ......... $54.95 READY-SET-GO LIGHTS A simple project for starting slot car ~;ci~~~::&;:~::~rse~r::ional random delay between the amber and green. (ET! Oct.'84) ET! 277 $24.95 EA AM STEREO DECODER AM stereo is now broadcast in Australia on an experimental basis . This add-on decoder wori<s with the Motorola C-QUAM system. (EAOct.'84) 84M510 Cat. K84100 ...... Normally $26.95 SPECIAL, $16.95 CRYSTAL CONTROLLED TV PATTERN GENERATOR ZENER TESTER LEb~u~du~~~~!~· ~~~~:lso check (ETI May'83) ETI 164 Cat. K41640 ............. .... .. $11.95 ~i!~eo'K.rt~ :t, ~~ELAIDE NOTE : (tr1ces may vary 1111ersta1e due to lreigh1COSIS) MAIL ORDER, Local Orders: (03) 543 7877 Interstate Orders: (008) 33 5757 All Inquiries: (03) 543 7877 CORRESPONDENCE, P.O. Box 620, CLAYTON 3168 Telex: AA 151938 Fax, (03) 543 2648 - MAIL ORDER HOTLINE 008 335757 fTOLLFREEJ /STRICTLY ORDERS ONLY) Cat. A simple low cost add-on for your multimeter. This checks zeners and reads out the zener voltage directly Rod Irving Electronics MELBOURNE: 48 A'Beckett St. Phone (03) 663 6151 NORTHCOTE, 425 High St. Phone (03) 489 8866 CLAYTON: 56 Renver Rd. Phone (03) 543 7877 SOUTH AUSTRALIA, Electronic Discounters P/L, Anyone wishing to obtain the maximum performance from a colour TV reciever needs a pattern generator. Why not build this superb unit which provides five separate patterns; dot, crosshatch, checker ~~~~·.P~:YR~f!f, fn~u~~~ear~~:;? ABS type case! (80pg6, EA June '80) Cal. K80033 ................... $99.95 LOCAL ORDERS &INQUIRIES f03J 543 7877 POSTAGE RATES, $1 - $9.99 .. .. .... ....... ... , .. .... $2.00 $10 - $24.99 , .. .. ... ...... .. ...... $3,00 S25 - $49.99 $4.00 $50 - $99.99 .... . .. ... ... . $5,00 $100 - $199 .... . ....... .... . ... $7.50 $200 - $499 $10,00 $500 plus ....... ............ ... .. S12.50 ~=l~t;;:,~~~s!~Y;. ~!:~rr~::~,. :::~~~:~t':K::~~~':'a~:'." be All sales tax exempt orders and wholesale Inquiries to: RITRONICS WHOLESALE, 56 Renver Rd, Clayton. Ph. (03) 543 2166 (3 !Ines) Errors and omissions excepted. Prices and specifications subject to change. :~~:a~s~T~~~~fk>~~~~~:!s Machines. 'Apple is a registeredtr~. ;~=~!:~~';{;d tradmarks ol thew ■EEZ THE WAY I SEE IT By NEVILLE WILLIAMS Fly by wire: is it safe from electromagnetic interference? Future aircraft, ships, trains and road vehicles are likely to be guided and controlled by electronic rather than mechanical means. But while electronic systems may be reliable in themselves, it has yet to be shown that they can be fully protected from electromagnetic interference. We know what can happen if the brakes fail or the steering linkage comes adrift in a present-day tourist bus. It can easily end up in the creek at the bottom of the hill! A similar fate could befall its future electronically controlled counterpart if the data circuits from the driver's cab to the road wheels were to be corrupted by a chance signal from a high-power mobile transmitter in the adjacent traffic lane. There is certainly no lack of precedent for accidental transmitter or other electromagnetic breakthrough into all sorts of electronic equipment, from radio receivers to radio telescopes. Ask any design engineer or service technician who's been around for a while; it's something that they have always had to live with! The question is not so much why interference should be a potential problem with electronic control systems but why it should not be, based on a mass of past experience! The vital difference is that whereas to date, electromagnetic breakthrough has merely been embarrassing, frustrating or mildly expensive, it is much more serious 36 SILICON CHIP when the lives of passengers are directly involved. Fly-by-wire concept In aircraft, electronic control or the so-called "fly by wire" concept has been around for some time but I first encountered it in 1984, when researching an article on Australia's then-new FA-18 Hornet attack fighter. Up until then, I must confess, the term fly-by-wire seemed to relate more to the woven steel cables strung from the cockpits to the control surfaces of ancient biplanes the cables that helmeted pilots religiously checked before take-off. In the present context, and certainly as applied to the FA-18, the word "wire" has to do with control circuits. These take over from the usual mechanical or hydraulic links, conveying encoded instructions from the cockpit to the flight computers and thence to actuators coupled to the various control mechanisms throughout the plane. The computers process and execute instructions from the pilot while optimising - or configuring - the plane for take-off, landing, or J:!Ormal flight, taking into account the constantly changing fuel/ weapons load. Being connected also to strain gauges and other status indicators, they can intervene to protect the airframe from excessive forces, unless deliberately overridden by the pilot to cope with emergencies. Like a super "George" (auto pilot) the flight control computers can be programmed to relieve the pilot (or crew) of routine tasks, freeing them for activities which call for intuitive human reaction - a major requirement in a combat aircraft as complex as the FA-18. Indeed, in more radical military designs, where aerodynamic stability has been deliberately sacrificed for sheer get-up-and-go performance, the planes are reputed to be virtually unflyable without constant computer monitoring and intervention. The bottom line is that the desired end result can be achieved much more efficiently with a dedicated all-electronic control system, than by attaching separate electronic modules to otherwise conventional mechanical and hydraulic linkages. The allelectronic fly-by-wire approach is lighter, more accessible for automated system checking, and capable of higher redundancy to cope with possible airframe damage, especially in combat aircraft. Passenger, cargo planes Modern airliners like the new A-320 Airbus are also being designed around fly-by-wire technology but with emphasis on operational The Switch to UHF TV On the NSW South Coast My perception of the Australian radio/TV broadcast scene was recently altered by a couple of weeks spent holidaying on the NSW mid-north coast. The winter days were pleasantly mild but whatever else the area may have going for it, a surfeit of broadcast entertainment is certainly not one of them. Back in Sydney, most residents have access to five local TV stations, eight AM-stereo radio stations and about as twice as many FM stations, if one includes the community broadcasters. At most times, if one wants to look or listen, there's a reasonable chance of finding something to fit the mood. But in the unit where I was staying, despite a newly installed antenna/booster system, only two worthwhile TV signals were available - from the ABC and a regional commercial station. As for radio, the score was the noise-free ABC regional transmitter on the FM band and on AM, Radio National from the ABC, plus the local commercial broadcaster and an assortment of other signals that were only just listenable. In that short list, the role of the economy, reduced crew requirements and detailed monitoring of the flight envelope, both to assist pilots and to counteract possible errors of human judgment. According to news reports, one of the demonstration routines for the new A-320 Airbus has been a low-level fly-over at reduced speed and in such an attitude as to be inadvisable, if not hazardous, under ordinary manual control. It therefore came as quite a shock when a brand new A-320 recently crashed in full view of spectators. It was apparently performing just such a manoeuvre an event that gave rise to speculation that the flight computer system may have "crashed" a few critical seconds before the plane it was controlling! The item concerned the plight of a small group of viewers in the southern highlands of NSW, who would be affected by the pending re-deployment of TV stations in the adjoining lllawarra area of NSW from their present VHF channels to UHF - to make room for new FM radio services. Preliminary tests had indicated that the UHF signals might not reach this and other small communities that were currently able to receive the VHF transmissions. Naturally, the residents were upset. Admittedly, the DOTC is planning to explore some of these problems before the VHF transmitters are actually switched off but how isolated small communities will fare in the all-UHF era is the subject of assurances rather than guarantees. What I found disturbing in the admittedly off-the-cuff TV interview was the facile dismissal of the viewers'objections: (1 ). They were fringe viewers who'd been lucky enough to receive useable signals from the VHF transmitters. They might not be so lucky with the UHF service. (2). The government has made other provisions for fringe viewers. All they need to do is to install a dish and pick up services direct from the satellite. Not surprisingly, the viewers concerned were unimpressed by the idea of having to spend $2500-odd to receive fewer TV services than at present - the ABC and SBS only. While the DOTC has a job to do, it is to be hoped that they will be no less keen to advise and assist the disadvantaged as they may be to "pull the plug" on the VHF services by the due date. I support in principle more intelligent long-term . use of the VHF/UHF bands. But the need for a full complement of FM radio broadcasters is not so urgent that TV fringe viewers need to be summarily disadvantaged. The matter may possibly have been clarified before you get to read this but in the meantime, I was intrigued by further speculation that radar blips or other powerful radio signals may have corrupted the plane's control logic at a critical moment. Such an eventuality was named as the most likely reason for the puzzling crash of a West German fly-by-wire Tornado fighter in 1984, killing both crew members. They certainly appeared to have ignored warnings to keep well clear of ultra-powerful radio transmitters near Munich carrying transmissions for the "Voice of America" and "Radio Free Europe". It is true that both military and commercial aircraft carry communications and radar transmit- ters, some delivering quite high RF output. It can also be assumed that precautions would have been taken at the design stage against possible breakthrough into the flight control system from these sources. It does not follow, however, that filtering, shielding and isolation from identified potential inter£erence will guarantee ,immunity at all times, from other external sources of a different frequency, spectral content and power level whether unintentional or deliberately hostile. Just consider the following: • Interconnecting leads can act as receiving antennas, especially at frequencies to which they happen to be electronically resonant. • The growing use of plastics rather than metal in aircraft con- ABC is crucial and as if to emphasise the point, chairman David Hill chose that same period to announce plans to provide additional program services in the area. His positive note was in sharp contrast to the attitude of a staff member of DOTC (Department of Transport & Communications) who had been quoted in a TV news item a few days previously. OCT0BER 1988 37 THE WAY I SEEIT-CTD struction may cause on-board wiring to be less effectively shielded. • While much more compact and efficient, solid-state equipment is relatively vulnerable to high level electromagnetic radiation - suggested as a reason why some Russian combat aircraft are reputed to use valves for critical functions. Problem that won't go away After many years in the business, I have no illusions about the persistent and intrusive nature of unwanted interference affecting electrical signals. As already suggested, it has always been with us in one form or another. I find it difficult to believe that it will suddenly and obligingly disappear from the present scene. In the 1920s and 1930s, when half the fun of radio was in logging weak and distant stations, we had to battle daily with atmospheric and man-made "snap, crackle and pop"! Oh yes and with heterodyne whistles from other listeners' regenerative detectors. In the 1940s and 1950s, with a rising emphasis on car radios and mobile 2-way equipment, we had to deal with vibrator hash, silence the ignition of the host vehicle, and put up with the invisible cocoon of interference that surrounded many other vehicles on the road. For good measure, rural vibrator-powered receivers involved a parallel set of problems. The preoccupation with television in the 1960s and 1970s exposed the pattern of harmonics being radiated by most old-style amateur transmitters, while the CB radio boom, which followed, emphasised the vulnerability of contemporary consumer equipment generally to nearby radio frequency emissions. In Britain, for example, official complaints about interference from CB radio transceivers averaged several thousand per month during 1981/82! More recently, computer and other digital equipment has added a further dimension to the conflict between wanted signals, "dirty" power lines, and the complex clutter of extraneous electromagnetic radiations which is poised to corrupt the flow of encoded information. This leads to further observations: • Digital equipment can itself be a frequent source of interference. • Some CD players radiate enough RF to noticeably desensitise the associated FM tuner in a hifi system. • Sydney airport radar caused major hassles for engineers when setting up the UHF TV relay channels in Kings Cross. • A Sydney sound studio recently encountered serious hash problems from newly installed switchmode power supplies. • People fitted with heart pacemakers are warned against certain environments which might affect the electronics. • Lightning strikes or near misses are still a fact of life, as pointed out in "Serviceman's Log" (August 1988, page 31). It's all a matter of EMC In European technical parlance, if not elsewhere, discussion of such problems is commonly lumped under the heading "EMC". This is short for electromagnetic compatibility, or the compatibility of particular technologies and/or items of equipment with the overall electromagnetic environment. It involves both sides of the equation: (1). The ability of electrical or electronic equipment to operate efficiently without needlessly polluting the already cluttered electromagnetic environment. (Strictly speaking, even a clinically clean transmitter complicates the environment by emitting yet another signal). (2). The ability of electronic equipment to function normally, unaffected by extraneous electromagnetic energy, natural or man-made - a critical consideration in the present context. Despite countless discussions and conferences over the years, at national and international levels, it is doubtful whether governments and industry have handled electromagnetic compatibility any more deftly than other major environmental issues. Historically, we've tended to put up with RF interference problems - output and input - until they've become utterly intolerable and even then, settled for corrective measures that didn't involve dipping too deeply into the too hard basket! Rather than tackle spurious emissions head-on, it's been easier to maintain the S/N ratio by progressively upping the power of transmitters around the world, thereby complicating the electromagnetic environment in another way. As mentioned in the August issue, it took decades for the Australian Government (and others) to give their inspectors effective control over RF sources other than regulation transmitters. In Europe, the EEC group is at odds over standards, with full legal implementation still two or three years away. Wise after/before the event? If there's one lesson to be learned from contemporary environmental debate, it's that we tend to barge ahead on the basis of present need (or fad) only to later concede that more consideration should have Any new technology certainly hos to be a lot better than what was aboard the Tornado fighter that crashed in Germany in 1984. 38 SILICON CHIP 'Problems? ... and you don't have our I20page catalogue . .. Modern fighter aircraft use fly-by-wire technology but is it sufficiently developed for civilian passenger aircraft? been given to the consequences of so doing. It's easy enough to be perceptive after the event, but ever so much harder to correct the situation when the damage has been done. Now - not later - is the time to debate this whole fly-drive-ride by wire push. Does it represent real progress or the use of high technology for the s.ake of commercial exploitation? It may seem utterly presumptuous for a mere technical columnist in a magazine to query the judgment or the motives of the world aircraft industry or, in longer term, the manufacturers of ships, trains and road vehicles. But in effect, the question boils down to this: • Have electronic engineers associated with those industries really overcome, once and for all, the perennial problem of electromagnetic interference? • Can they guarantee that their electronic control circuits are totally proof against penetration and corruption by all conceivable extraneous sources of electro-magnetic radiation? • Assuming that reality falls somewhat short of perfection, can they be confident that a functional all-electronic control system can be at least as reliable as the most proven conventional methods? Any new technology certainly has to be a lot better than what was aboard the ill-fated Tornado fighter in 1984. The mere fact that the crew had been warned to keep away from the Munich transmitters indicates that the control equipment was known to be vulnerable to high-level electromagnetic radiation. In terms of EMC - electromagnetic compatibility - how much better is the equipment aboi:trd the FA-18, the A-320 and other comparable aircraft in 1988? Drive-by-wire cars? If it is appropriate to speculate about aircraft which are technologically up front in terms of design, production standards and maintenance, what is the likely position in relation to road vehicles and, in particular, to the ordinary family car? How compatible will it/they be in an increasingly cluttered electronic environment, especially after encounters with some of our local "she'll-be-rightmate" mechanics? In considering this subject, it certainly isn't reassuring to read reports in overseas journals of obscure malfunctions in vehicle cruise and engine management systems, which appeared to be due to electromagnetic interference. Those would be annoying, frustrating, perhaps expensive but a similar malfunction directly affecting control of the vehicle could be disastrous. Best we ask the questions now, rather than wait until we're behind the wheel! A promising way of "hardening" communications and control equipment (reducing its vulnerability both to the electromagnetic environment and to deliberate zapping) would be to replace the "wires" with optical fibres. Maybe we should shift the emphasis to flying-riding-driving by glass! ~ At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. Video plugs and sockets ... Video extension speakers . . . Video flyleads ... Video RF interference filters .. . Video splitters ... Indoor antennas ... Video switching units . . . Down convertors . . . Video speaker controllers . . . Video camera lights . .. Video tape rewinders ... Video cine adaptors . . . Video head cleaners . . . Video splicing kits . . . Video storage cases ... Video dust covers . .. Video leads .. . Searl plug leads ... Video dubbing kits .. . Video headphones . . . Video shotgun and wireless microphone systems . . . Pre-amplifiers with video inputs .. . Video camera stands . . . Just about anything you want. ... Try us ... NOW! Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARISTI\. ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 OCTOBER 1988 39 ,--------------------------------, I I Why Waste Your time With Other Suppliers Altronics Can Deliver Any Of The Quality Products To You Tomorrow - Just Phone Your Order Toll Free 1 I J kO' D On 008 999 007 I a~/ Direit~~e II Country Clients Please Allow Additional 48-72 Hours I I 1 I I ~--------------------------------- Microprocessor Controlled Detector Clips On To Sunvlsor Invisible from outside your vehlcle - this lantHtlc high apec Radar Detector Detects X and K Band Radar up to an Amazing 13KM This super compact "Sunvisor clip on" Microeye Detector is virtually invisible from the outside of most vehicles at normal eye heiaht hence its very unlikely yours would attract the attention of a thief (or the Gendarmes for that matter) However, please remember that use of Radar Detectors is not permitted in some states. MICRO EYE VECTOR The First Detector With GaAs Diodes DC Brushless Fan 120MMx120MMx38MM Brush less, Electronically Commuted DC Motor Voltage 24V DC Current 330mA Speed 3100 RPM Air Flow 23 C.F.M. Noln Level 32 dbA Until now, GaAs diodes have only been used in I sophisticated military radar equipment. The Microeye Vector is the first consumer electronics product equipped with this new technology. Why GaAa Diodes Make The Difference • Lower threshold allows for a better signal to noise ratio • Lower signal conversion loss • Higher barrier reduces noise. Quite simply GaAs diodes increase the sensitivity of the Microeye Vector.•Using the latest digital processing technology the unit will filter out and ignore emissions from 80% of poorly designed Radar Detectors that emit microwaves. • Simply plugs into your cigarette lighter socket. • Clips onto sunvisor • Detects Mobile Radar Equipment. • Highway/ City Modes switch allows monitoring of City or Highway conditions. Normally $29.98 This Month S24 .DO F 1040 6 or More $20 •• Ultra High Power Capacity Polypropylene Ba•• Drivers Save 25% This Month 12" (300mm ) Model 100 Watts continuous input 150 Watts intermittent input Impedance 8 Ohm Sensitivity 93db Weight 3620gm 9 9 $ s4 9 9 C 3070 Normally S139 Acceaaorles Included:- Visor bracket • Velcro • Cigarette lighter plug. 21 Day Money Back Guarantee. 1 5 " (375 mm) Mode l !~=~~~i~:~J~~nt input 412 Normally High Performance ALC Wireless Microphone Our incredible ALC Mic is • Cardiod -Uni Directional Pick-up pattern• Freq.Res.: 30Hz-15KHz • carrier Frequency .Adjust Range: 8 1 one of the most exciting products for '88. Wireless Mics suffer from overmodulation distortion with too higher input sound level making them unsuitable for high grade vocal entertainment use of ALC (Automatic Level compressor) fixes all this. w ~:~;,;;·$1~;:~,,s:;~;i;; ~:1: S99 .00 Super Bargain Save $50 Fantastic Negative Ion Generator There have been volumes written about the benefits of negative ions combating air pollution, cigarette smoke etc. can be very beneficial to Asthma sufferers. Our great little Rover generates billions of ions per second! Includes tester. W 120 Watts continuous input ~g;075 $17; elght $ j 111\\1 149 /ii ~filfi f~l~~~:~~<at>r~~E.I~lI quick stocks are limited. These are the Genuine Grain Oriented Toroid Transformers as un d In Electronic Australia Protects Toroidal Power Transformers Why • Torold? • Smaller size and weight to meet modern "Slimline" requirements. • Low electrically induced noise den,anded by compact equipment. • High efficiency enabling conservative rating whilst maintaining size advantages. • Lower operating temperature. • Simple , quick single boll mounting Dimensions and Weight 180 VA Model• 110 Diam . 45mm H. 1.8Kgs Lead s 200mm 300 VA Model• 125 Diam . 45mm H. 25Kgs Leads 200mm 160 Watt Models 300 Watt Models! S65 A 0990 s29 =,.'. ~ 10 up cat.No. S62 ea SEC.V M 3050 M 3055 M 3060 12 + 12 18 + 18 25 + 25 ~;g !tS $79 Cat.No. M 3085 M 3086 M 3088 ~~~ 10 up $75 ea SEC.V 12 + 12 18 + 18 25 + 25 !g:~ ,;}{ ~~~:~== :: ; · :· tl■lr}_· ; 1111: I:;··•· :·::: ···. -··•· ··.·Jtr ·\·> ·•·•···•·•·· ·· ;: ·=·:·r <X .·: r·.•.··.,- · • · ❖ ~ •. ·::r•·•·• •··•· ·r•·;,·•·=·•·.,.\,••··· A Great New Product From Altronics For '88 The Fantastic Pin Point Ultrasonic Cleaner ' ~<at> c\ofs, conne ""?u\ef ~e\a'/s,;...ucn co••: nes, "o ,.. c,ean 5'l-l1\c ses a ce•s, G,as ? 'l-le\\e{'/ \e\ Je n t1'o t1'1JC Design Award Winner Awarded the Good Product Design Award for CETDC in 1987. This fantastic Ultrasonic cleaner can earn its cost a hundred times over in cleaning Computer Connectors, PCB's, Switches, Relays, Jewellery, Glasses, Watches etc. How Does It Work? The Pin Point Ultrasonic Cleaner uses a transducer generator to produce millions of activated microscopic cleansing bubbles, which· blow dirt, grease & grime off surfaces, and deep into cracks and holes. This personal ultrasonic cleaner won't scratch precious jewellery or glass. Comparison studies made by hospitals, commercial businesses and industry show ultrasonic cleaning proves better and safer than a,ny conventional method. But don't take our word for it. Test the Pin Point Ultrasonic cleaner yourself . Pop your dirty watches , glasses, connectors etc. into the cleaners stainless steel basin, add a cup of tap water, and three minutes later see the difference. The results are instantly revealing . SPECIFICATIO NS Power Supply : 240V 50Hz Power Consumption : 300mA Frequency : 40 +/-2KHz Dimensions : 224 x 114 x 124mm Capeclty: 570ml Weight : 1kg Body Materlal: ABS Plastic Tank Materlal : Stainless Steel (SUS 304) On/Off: 3 Minute Auto Timer. •••••• I Amazing Price Breakthrough * RF Signal Generator Great Saving On #·i:C•l*l#hil◄ •! 1 1013 · Quality Solderless Breadboards Frequency Counter Sensation 150MHz Frequency Counter A frequency counter is invaluable for the accurate alignment and testing of many modern electronic circuits. is a winner. SPECIFICATIONS: Frequency Range: 100k - 150MHz in 6 ranges RF output level 1OOmV RMS Accuracy +/-3% Modulatlon: Internal (30% depth) - 1KHz• External - 50Hz - 20KHz • Crystal Locked Oscillator ' NOW SPECIFICATIONS: Freq.Range: 10Kz - 150MHz Gate Time 1 sec. 6sec. Accuracy +/-1 count Max.Input 20V P- P Sensitivity: • 10Hz - 30MHz - 25mv-100mV • 10MHz - 150MHz - 100mV - 300 • Power requirement-9V DC at 100mA S199 a 1520 S18O.00 Stop Data Crashes And Corrupted Software "Squeeky Clean" Mains FIiters An investment in one of our fantastic 'Squeaky Clean ' Mains Filters could save you a small fortune with your computer system.Protects Hardware end Software from mains voltage spikes caused by lighting, transmitters, electric motors, welding, machinery etc. Anyone who has to re-build 3 weeks of software programming will cherish the aquisition of one of these fine mains filters . Energy Authority Approved . P 8160 4 Outlets Each individually filtered. A must for 'serious' computer installations e.g. for Schools, Business etc. • Loading Rating: Continuous 10 amps, with circuit breaker at 240V P 8150 Slngle FIitered AC . • Outlets: 4 GPO's Double Outlet Model individually filtered. Just the shot for home computer or for individually located peripherals e.g . remote printer, computer terminal etc. Loading Rating: 10 Amps Max. load at 240V AC • Outlets: 2 GPO 's single filtered . $269 640 Holes P 1005 $12.50 640 + 100 Holes P 1007 $14.50 640 + 200 Holes P 1009 $16.95 400 + 1280 Holes Accepts up to 16 x 16 pin OIL IC's Terminals for PS Connections. P 1012 $43.50 SOO +1920 Holes Accepts up to 24 x 16 pin OIL IC's Metal Back ing Plate for Shielding of sensitive circuitry. P 1015 $65.00 High Definition Computer Monitor Superb "Goldstar Pro" Non glare naturally, & screen character resolution well worthy of mating up with top end personal or professional computers. • Compatable with IBM, Apple, Commodore Computers • Excellent for small business applications • Exceptionally clear & stable display • 80 characters 25 lines display. CDT Non glare phosphor P31 green Input composite video 1V P-P Input Conn . RCA Jack Input Imped. 75 Ohms or high imped. (switchable) Video Bandwidth 18MHz Horlz. Reaolutlon 900 lines at centre external control• brightness contrast 129 Now s .DO D 1115 Amber Screen -~·:·;,~ . : t ~ ~ ; , - :. Great Kit Projects To Build Many Just Released For 1988 Ja~k/~~~~t~ell Brllllant Performance Stereo Pre Amp 111111111 ::: Universal High Power Amplifier Module (See SC Dec'87) ?}W. } J ! Ft :::•1::: ] ii Studio 200 Stereo Control Unit (Slllcon Chip June/July'88) Out-Performs Commercial Units Costing $600 Plus :::•••1 ::::::a:::: 11 The Studi·o 200 Stereo Control Unit is companion to the studio 200 stereo power amplifier (or other power amps). It features slim single unit rackmount profile, treble, bass, balance, input selector, tape monitor switch, stereo/ mono switch and volume control. Inputs include phono, tuner, CD, VCR and tape loop. I! I K5015 :1: 11:• 1 s229 High power rugged reliable design featuring low distortion and inbuilt speaker protection All components, including output transistors mount on a single PCB. Suitable for high quality guitar amp, public address or in a high fidelity stereo amplifier. Kit includes angled heatsink bracket, main heatsink and unlike other kit suppliers, the in-built Poly-, switch for loudspeaker protection. General Purpose Pre-Amp This unit contains· all necessary components to complete:- • A Phone Pre-Amp with RIAA freq. response• A tape Pre-amp with NAB response • A microphone Pre-amp with either 40 55 or 80db of gain.• Or a Pre-amp for just about anything! Power 10-40V DC High 100db Ripple I:I i•l lil i Jro;.I Rejectio~ ::::::::::::or, s18.so 5510 1,,.. j/1, db/ }/ 0.{ :::::::=::,Q =:: Active Direct lniectlon Box itii JI Ellmlnates Annoying Hum Pick up} (!tee EA Oct'87) ,:,:,:,:::::w i t fai: J\i\i; i :••··••:•1 \ 0. \It Calling A!I Audio Purists K 5010 This : ; : ~ ~ ; ; ; ; ; : ;,;~ic;~~h; ~s. ; ;r You 5399 Per Channel Power Ampllfler .,.,_.,_::= _'_,_,_••• :,_:,•. ""' : ar \ii(::. •_9.:1 i t)•"• - Featurea: • In-Built speaker protection• Toroidal Transformer (low hum)• Black Satin Finish • Low leakage power supply capacitors • Housed in Rugged Custom Chassis. Specifications: • Output Power 100W into 8 Ohms Freq. Res.(at 1W) 20Hz-50KHz + or - ldb Input Sensitivity 870mV Harmonic Distortion (20Hz-20KHz) 0.1% Slgnal To Noise Ratio 100db or Better Protection 5A fuses plus RDE245A Polyswitch Damping Factor (without K 5550 $ 45 .00 H' h E I ltl S t lg (S~:~ff1l on %~Ip ~.ny'88)ys em _P_o_1_ys_w_i_tc_h_e_s_)_1o_o_<w_i_th_P_o1_y_sw-itc_h_e_s_J_10_0_._s_ta_b_1_111_y_u_n_c_o_n_d_it-io_n_a_1._--,,f II•II ,Jj( \ 1:•: :1 :::: I Extend~ the life of plugs Dlscollte (See SIiicon. Chip July/Aug'88) Add Some Colour To Your Next Party [~I~t~~~~~;:: 1i electric guitar pickups, -: synthesizer etc. to low level balanced outputs to be fed over long lines. Features: Professionally screen printed • Earth isolate ·: switch • 15db pad • Phantom ;:::;:: :,:•· powering plus internal 9V bat. )C:: & points, increases power & improves fuel economy. Suits 4,6 & 8 cylinder engines. Install one into your car & start saving $$$ from the very first day. K 4015 s43.so : :• m111•11e::1g11F::11&1:: : n1:1m1:1m~:::::::: ~:;:;~•1~::'.:~ ~::;:: The Screecher Car Alarm (See EA Aug'86) Ear Splitting 110clb Modulated Tone K 4360 s39 .95 Now our top selling car Alarm. Two Sensor inputs-Normally open and normally closed enable,simple connection to door, bonnet, Boot light, switches etc. The Protector Car Alarm (Slllcon Chip Feb'88) Save Over $100 On An Equivalent Commercial System Feature•: Internal & External Sirens • Dash lamp flasher • Battery back - - - - - - - - - - - - - - - - - - - - - - - - - - - • • up• Delayed .& Non delayed inputs• Ignition killer• Easy to build & install. sa-we $SS \ \he co• o"cornrnerc\al ol 1ua\eo\l (See EA Mag.Jan '85l eQU • Super Low Price on Famous EA 8 Sector Alarm Svstem Kit FHIUrN: • Alarm has 8 separate input circuits - 8 sectors can be monitored independently. • Each input circuit is provided with an indicator LED and a sector On/Off switch. • Individual sector isolation allows the user to have some areas of the premises habited while others remain protected e.g. Inside Off/Outside On . • Inputs accept both normally closed and normally open sensors. • Two inputs provided with an entry delay between 10-75 seconds) . Internal t,ip warning buuer-alerts owner/ occupant of pending alarm operation- . great for the " forgetful " amoungst us. This buzzer is pre-settable between 5 and 55 seconds prior to Alarm. • Unique circuit detects automatically when any N/ O or N/ C loops are either open circuit or dead short. • ·II· eomeone trying to bridge Bench Top Power Supply 3-30V to 1 amp Max.with variable current llmlt FEATURES: • Output 3 to 30V at 1A • Short circuit protected • Load switching• Current limiting . Dual scale meter• Housed in our Delu xe " ABS " instrument case . SPECIFICATIONS: • Output Voltage - 3 to 30V • Output Current - 0 to 1 amp (fully variable)• Load Regulat ion - Better than 0.2% from Oto full load • Output Ripple-Less than 2mV RMS. KIT K 3210 rHd awltch .. etc. • Switched output can be used to sand a silent alarm through an auto-dialler circuit or similar. K 1900 S 5065 149.50 (without Back Up Battery) KIT $ (12V 1.2AH Backup Battery) Now Only 24V To 12V DC $15.00 Converter (Slllcon Chip Dec'87) Laboratory Power Supply Enables 12V appliances like stereos, 2 way radios, CB's etc . to operate from a 24V battery. • Operates from 18V-30V. Output is 13.6V at 5 amps. KIT K 3255 -f 59 .OD K3300 3-5 Volt• at up to 5 Amp• $ 195 Designed by Electronics Australi~. this supply has been one of our most popular kits. Our version incorporates refinements and 1s now housed 1n an attractive, tough " ABS" instrument case. This all new compact version has been made possible by the use of a highefficiency Toroid Power Transformer. So you win I.our ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlca Kit 11 fully drHled and punched. Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister 436 0422 Perth 09 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PIHH Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by Individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors . Don't forget our Expre11 Mell and Phone Order Service - tor the coat of a locel cell, Bankcard, YIN or MMtercerd holder, cen phorie order tor Nm• day d..petch. STANDARD DELIVERY a PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 7 days from day you post order to when you receive goods $7.00 OVERNIGHT JETSERVICE - We process your order the day received and despatch via. Overnight JelHrwlc• Courier for delivery next day Country areas please allow additional 48-72 hours Weight limit 3Kgs (3Kgs covers 95% of Orders). $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1) . When phone ordering please request " Insurance" . TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight JetHrwlce we deliver next day. ?') }{'\' WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B .Electronlcs & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 F~rmer Electronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electron ics 346133 QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronlcs ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics :::;::j::: :'):::::::: : :.:.,:\.:.\.:,:.:,.: ',.:.:,:.:,:.:,.::.:.:.:.:.:.:.':. Reid SA :;:;~88 T~~::~~ F~~;A~~ct~~:~~: ~a~e6yo:~42;3~U~J!~ST:;·~~:r:~E~8 rvse~u■ Electronics COUNTRY !~ 3~:~El~~~hoo~!c:a~~~~: 31~~~ALL~ S~ re ;l~~tr~:~~~ ■ 2671385 CARINGHAH COFFS HARBOUR Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NELSON BAY Nelson Bay ~;=~;; A woolly picture at Wollongong For those of us who service TV sets in a big city served by several transmitters, all carefully sited and delivering signals of about the same strength at any one location, life is (relatively) simple. But not so for our collegues who work in fringe areas, where customers seek the best of both worlds. This train of thought was started by a story from a colleague who works in and around the Wollongong area on the NSW south coast. The story itself, while interesting in its own right, was made even more interesting because of the way it highlighted the many problems encountered in this area. But before getting stuck into the technical problems, we first need to set the scene. For the benefit of those not familiar with this part of the world, the City of Wollongong is some 70km - as the crow flies - south of Sydney. (I've never been able to work out why the poor old crow has been given the job of making these measurements or, for that matter, how he goes about it. Perhaps he does it on the basis of so many wingbeats to the kilometre?) Anyway, the accompanying sim- ple map should help put the reader in the picture. Given reasonable terrain, 70km is not a great distance for a TV signal but, in this case, the terrain is anything but favourable. Wollongong city is at sea level, and sits immediately below an escarpment, some 300 metres high, which runs parallel to the coast and only a few kilometres inland. As a result, the advent of TV in Sydney (using channels 2, 7, 9 and later 10) saw a forest of tall masts, fitted with high gain antennas and amplifiers, which sprang up in Wollongong and the coastal suburbs to the north and south. As might be expected, the results were patchy and unpredicable. While Smith might receive excellent pictures, poor old Jones next door could often get little more than snow. \ 44 SILICON CHIP This situation prevailed for some years, during which time both the residents and the local TV sales and service industry learned to live with it. And, in many cases, they achieved results which, in theory, should not have been possible. In short, the population had become Sydney TV orientated. Eventually, the powers that be presented the area with its own TV channels: channel 4 (94-101MHz) as the commercial channel and channel 5A (137-144MHz) as the ABC channel. Both these bands, regardless of their geographical allocations, have been controversial; channel 4 because it occupied part of the "international" FM band, and channel 5A because it transgresses certain international satellite channels, and is adjacent to the amateur 2-metre band (144-148MHz). But controversies aside, the channels have in general served the area well. The two transmitters are located on Knight's Hill, some 700 metres above sea level and about 30km sou' sou' west of Wollongong. They also serve areas to the south, such as Nowra, Jervis Bay, Ulladulla and even further down the coast, as well as inland. In theory, of course, the locals should have been content with these two channels since, officially, the Sydney channels were never intended to serve that area. But human nature being what it is, and considering the history of Sydney reception, most wanted the best of both worlds. And very nice too, if you can get it; four commercial channels plus the ABC puts you one up on Sydney viewers. (By the same token, many Sydney clubs and hotels have channel 4 and 5A antennas pointed at Knight's Hill to take advantage of Sydney sporting events not broadcast locally). Knight's, Hill er~· eKiama Nowra /~~ . ateman's Bay Fig.1: this map shows the area, south of Sydney, involved in the accompanying story. The Sydney TV transmitters are at Gore Hill while the Wollongong transmitters are at Knight's Hill. But satisfying this desire wasn't always plain sailing. In some cases it worked out very well, often by default, but in others it presented a host of problems. Signal strength problems and around Wollongong itself, since the antenna is pointed towards Sydney and the local signals are approaching from the rear and the side. In addition, the antenna is not cut to favour the local signals, so there is enough natural attenuation to prevent problems. But not always. As we move south from Wollongong the distant signals get weaker but, because the local transmitters are moving around to the front of the antenna, their signals get stronger. And as we said earlier, there is conflict between channel 4 and channel 9. The main reason appears to be the nearly two-to-one frequency relationship between the two channels. While the second harmonic of channel 4's vision carrier falls short of channel 9's vision carrier, some of channel 4's video content would reach it. Anyway, the practical result is that, with too much channel 4 signal, channel 9 becomes unwatcha ble. As these problems became apparent the TV antenna industry responded with a range of "traps" designed to control channels 4 and 5A, and having different orders of attenuation. The first one offered provided 30dB attenuation and, when this proved to be too severe for many localities, was followed by 20dB and lOdB models. These helped a lot but were not adequate in all localities. Which only serves to highlight the difficulties encountered in this and similar areas; each case has to be treated on its merits and installations tailored to suit. Which brings us to the specific situation that started this story, and which the reader will be better able to appreciate against the background we have just set out. In fact, from here on, the story is best handed over to my colleague. This is how he tells it. Colleague's story The story really started about 15 years ago, and concerns a customer who lives at Ulladulla, about 85km south of Knight's Hill and about 180km from the Sydney stations at Gore Hill. I helped him install a new TV set when he moved into the area at that time. His home is on an excellent site and I felt sure that Sydney's signals would be readily available. But he wasn't interested and, in fact, for a few years was content to watch the two local channels, using nothing more pretentious than a pair of rabbit ears. I don't like rabbit ears. Signal strength notwithstanding, they simply cannot provide a clean Broadly, the problem is one of having to cope with vastly differing signal strengths and the risk of cross modulation caused by powerful local signals mixing with weak distant ones. In particular, there is conflict between channel 4 in Wollongong and channel 9 in Sydney. A popular set-up for Sydney reception is a phased-array antenna, such as the Hills model CA16, feeding a suitable amplifier, usually masthead, on the tallest practical mast. These antennas are cut to resonate around channel 9, but are broad enough to cover 7, 8, 9, 10 and even 11 in some circumstances. This arrangement is often good enough to cope with both groups of signals. This is particularly so in OCT0BER1988 45 SERVICEMAN'S LOG signal in all circumstances. Movement of venetian blinds and other metal objects, or even people, can create all kinds of ghosting problems. As a result, I continued to urge him, over the years, to fit a decent antenna. He succumbed in the end and I fitted a simple 4/5A antenna on a "hockey stick" mast mounted on the bargeboard of the house. And even he had to admit that the improvement was worthwhile. He was happy enough with this for the next couple of years, then suddenly, about 10 years ago, expressed a desire to receive the Sydney channels. I suspect that the advent of some sporting events, available only on these channels, prompted this decision. Anyway, I was confident I could provide a suitable installation. I chose a Hills CA16 phasedarray antenna, mounted on a 5-metre length of masting, and feeding a Standard Components MH20 masthead amplifier. This produced excellent signals from the Sydney channels, apart from channel 9, which suffered severe cross modulation from channel 4. This came as no surprise, having come to grips with the problem previously in this area. The solution called for yet another trap filter which had been developed by the antenna manufacturers, following representations from myself and other servicemen. Initially, we had tackled the problem using the lOdB or 20dB 4/5A filters already mentioned. This was tricky enough in itself because the strength of the channel 4 signal as fed to the amplifier can be quite critical. Too little attenuation can wreck channel 9, while too much 46 SILICON CHIP can put channel 4 into the noise. And the gap between these limits can be quite narrow. But there was an even bigger problem, involving channel 5A. For a couple of reasons, channel 5A's signals are significantly weaker out of the antenna, to the point where they can be well into the noise by the time channel 4 is under control. One reason is that 5A's signals are naturally weaker in this area, an official DOTC survey listing them as lOdB down on channel 4. By my observations this figure may be a little high, but there is at least a 6dB difference. The second reason is that this phased-array antenna favours channel 4 rather than 5A; probably because, being cut for channel 9, it favours channel 4 on a harmonic basis. Anyway, whatever the reason, channel 5A can be down anything from 6dB to lOdB. So, on a worst case basis, channel 5A could be 20dB down on channel 4, and even in the most favourable circumstances is going to be 12dB down. By itself, this difference can usually be tolerated. But add 10 to 20dB attenuation caused by a filter needed to control channel 4, and 5A is well and truly into the noise. The new filter, designated FL300-4, was designed to attenuate channel 4 only, by 18dB. I have no details of its response curve, but it is reasonable to assume that it would be level within a few dB over the bandpass. It was a simple device, on a printed board measuring about 25 x 60mm and consisting of four resistors, three fixed capacitors, a trimmer and three printed inductors. It was enclosed in shrink plastic for external moun- ting, but I chose to mount it in the amplifier housing. And it worked. Channel 4 was eliminated from channel 9, and channel 5A was left in the clear to provide a clean picture. So everyone was happy. Lost colour End of story? No, the beginning really. As I mentioned, all that happened about 10 years ago and was virtually forgotten until recently. Then the customer was on the phone with the complaint that he was losing colour on channel 4. My first reaction was to enquire whether it was only channel 4 that was faulty. (Some customers will insist that a fault is on one channel only, for the simple reason that they only ever watch that channel!) On being assured that channel 5A and all the Sydney channels were OK, my next reaction was to suspect faulty fine tuning for channel 4. On this basis, I told the customer to check the fine tuning and see if this made any difference. If that didn't work, then I would have to make a call. Well, it didn't work and he was on the phone the next day to report this. So I headed for the hills. I'd taken care to pack the field strength meter because, even at that early stage, I had a feeling that the fault was likely to be associated with the antenna. I found the situation essentially as the customer had described it, and quickly convinced myself that there was nothing wrong with the set. So I disconnected the coax from the set and made some field strength measurements on the channel 4 signals. The vision carrier (95.25MHz) was running at 54dBu (0dBu = 1µ V) which was possibly a trifle low, but not ELECTRONIC COMPONENTS +5 I -5 ; ill -10 ,_ ~ "' " \ - 15 -zo 80 We stock a wide range of electronic parls / '- / V • For service • For Hobby • For Transmitters • For Receivers \ I '- 85 95 90 100 Also in stock: 105 110 Valves for Transmitters - 6146, 8950, 4X150, 6JS6, 811 and many others. FREQUENCY (MHz) Fig.2: response curve of the channel 4 filter. As can be seen, it gives a pronounced dip at 100MHz. seriously so. But the sound carrier (101.75MHz) was down to 35.5dB and, while it is normally down significantly on the vision carrier, I felt that this was more than it should be. And if something was lopping off the top of the response curve it would show up as a weak sound carrier, but could also mean a weak chominance sub-carrier. So it was up the ladder and onto the roof to lower the antenna for a thorough inspection. This revealed nothing significant. Nor were there any other visible faults , such as bad coax connections, or the like. So it looked like something funny in the ampiifier or the filter. The filter was the easiest to check, by the simple process of removing it. This brought the vision carrier to 73.5dBu (a jump of just on 20dB) and the sound carrier to 59.5dBu (a jump of 24dB). Of course, channel 4 was now back to full colour. But poor old channel 9 was the loser with cross modulation from channel 4 very much in evidence. The vision carrier increase was not unreasonable for an 18dB filter, but I was suspicious about the sound carrier which had recovered an extra 4.5dB gain compared to the vision carrier gain. This seemed to confirm that there could be something amiss at the high frequency end of the filter bandpass, as I had already half-suspected. As far as the immediate situation was concerned, the easiest thing to do was leave things as they were, while I took the filter back to the workshop for a more detailed check and consideration of what best to do. Back at the bench I fed signals from the generator through the filter and into a suitable level meter. Selecting an arbitary zero reference at B0Mflz I took a series of readings across the bandpass. The results are shown in the accompanying graph and the point that stands out is a marked dip at 100MHz which is virtually the chrominance sub-carrier frequency (99.7MHz) and which is no less than 16dB down from reference. Just why the filter had developed this dip was a mystery. A visual examination revealed nothing and a detailed component-by-component check would have taken more time than I could spare at that stage. So I simply pushed it to one side. Antenna trap The important thing was to decide on the best solution. Simply fitting a new filter was one option, but I decided to try another approach which I had developed more recently. In many cases, it has proved to be perfectly adequate. This involves making a simple trap from a length of coax; a quarter wavelength long at the appropriate frequency [allowing for the coax velocity factor) and which is connected across the amplifier input terminals. The other end is Valves for receivers , made by Rhode & Schwarz, Siemens & Collins. R-388, R-390(A), R392 and more. Mail order welcome D. Dauner Electronics 51 Georges Crescent, Georges Hall 2198, NSW Phone: (02) 724 6982 Telex 178 401 TV TECHNICIANS & SERVICE COMPANYS Have your PHILIPS VARICAP TUNERS (ELC2060) Repaired or Exchanged ONLY $17.oo ea TEN or MORE $15.oo Quick service 3 Months Warranty Send Faulty Tuners Cheques and money orders + P&P $2 .00 to: -:T.V.TuNERS) 216 Canterbury Road, Revesby 2212, Sydney Australia Phone: (02) 77 4 1154 OCT0BER1988 47 SERVICEMAN'S LOG left open and, by reason of the quarter wavelength dimension, makes the device look like a short circuit at the chosen frequency. The "Q" of such a trap is quite high - too high for this application - so the trick is to cut it for a lower frequency, about 88MHz in this case . This normally provides enough attenuation to prevent cross modulation but has little effect on frequencies above the channel. This offers another advantage. There are several Sydney FM stations in this segment, and these are well received in good local positions. The ability to use the TV antenna for these signals is a bonus which customers appreciate. Happily, this approach worked in this case and I had the customer's system back to normal in a couple of days. It is not, of course, a panacea, but when it works it has the advantage of low cost, simplicity, and reliability. A convenient form of coax is the very thin Teflon dielectric type, the higher cost being of little consequence in this application. End of story Well, that's my colleague's story and I think the lesson to be learned is that there is no one answer to the problems encountered in such areas. The successful serviceman or technician is the one who has a whole range of options available, most born of long experience in the area, and a good understanding of the basic principles involved. From my own bench For a change of scene, here is a short report from my own bench about a puzzling case of sound distortion in a TV receiver. The first one occurred several years ago and I have had about eight since then. Naturally, after the first one, they presented no problem. I had intended to write about this on many occasions but, for one reason or another, never managed it. It was only when another such case landed on the bench a few days ago that I was reminded of my good intentions and resolved to procrastinate no longer. That first case involved a Sanyo 6603 colour TV set but I hasten to add that the fault is not confined to any one brand. The lady who owned it was basically an ABC viewer but occasionally chose a commercial program if it appealed to her. And this was the first vital clue because her complaint was that, FOR A Ct\~~GE OF see.NE HE'RE. IS ~ SHOR, 'R£POR.T' FROM W\'1 OWN 'gE.NCH•o• 48 SILICON CHIP while the sound was perfect on the ABC, it was distorted on one of the commercial channels. (I can't be certain which one; most likely channel 9, but I would stand corrected on that. In any case, it doesn't alter the sense of the story}. It was convenient to make a house call on that occasion, and I f?und that the customer's description of the fault was quite accurate, except that the distortion was far worse than she had led me to believe. But why distortion on that channel only? The picture was first class but I checked the fine tuning anyway, just in case of something silly in that department. All I learned was that, by detuning the channel to the point where the picture had virtually vanished, the sound was significantly improved, although it was still a long way from perfect. Then the penny dropped. That particular channel had just enjoyed a blaze of publicity as a result of its being the first to introduce a stereo sound system. So that was it; I'd have been prepared to wager a new picture tube to a dud diode that for some reason, yet to be determined, this set didn't like the stereo sound signal. Well, that was a start, but there was still a -way to go. What would cause a set to respond to a stereo signal in this way? With the stereo system only recently introduced, it was a real brain teaser to try to visualise how this might happen. The stereo signal I had followed the technical discussions which had preceded the selection of the system, so I was familiar with its basic theory. And to refr_e sh the reader's memory, our TV stereo system uses a second sound carrier alongside the main one, approximately 242kHz higher in frequency; more exactly, 242 .1875kHz ± 1Hz, if my memory serves me correctly. (All right, all right, I looked it up}. To maintain compatibility, the main channel carries a left plus right (L + R} signal (mono receivers thu_s receive a normal mono signal} while the second channel carries a right only (2R} signal. In a stereo receiver, these two signals are SIF AMP . & DEMOD . IC151 AN340 or LA1320 SYNC. DRl\11 0202 2SC5: 18'- ., """ fl90 1' 3300 FRO'"4 SW90 18 l TO A UOIO OUTPUT Uh' fll:('11.' Fig.3: portion of the sound IF channel of the Sanyo 6603 showing the IF amplifier and demodulator chip (IC151), the sound IF transformer (T151), and the quadrature coil (T152). matrixed together to recover the separate left and right channels. Which is all very well as basic theory, but was not much practical help right then. For one thing, I couldn't be sure whether I had a one-off situation - ie, a fault in this particular set - or whether there was something in the design of this model which made it incompatible with the new system; something which nobody had foreseen when the set was designed. I finally decided that the faulty design theory was the lesser possibility, particularly as I had heard nothing of any such probl~m elswhere. But, if it was this particular set, where did I start looking? I fished out the manual and turned to the sound IF section of the circuit, the relevant portion of which is reproduced here. The main portion is the sound IF amplifier and demodulator chip, IC151 (AN340/ LA1320}, and I had to consider the possibility that the fault could be in the chip itself, or in any one of a dozen or so associated minor components. But my strongest hunch was that it was simply an adjustment problem, if only because such maladjustments, while rare, are not unknown in the mono scene, where they cause varying degrees of distortion. And, while in theory at least, such adjustments should be made using a sweep generator and CRO, experience has taught me that it is usually possible to make a perfectly acceptable adjustment, in the field, with nothing more than a keen ear and a little care. The two adjustments I had in mind involved the sound IF transformer, T151 , which feeds the sound IF to pins 1 and 2 of IC151 , and the sound detector transformer (quadrature coil) between pins 9 and 10. Based on experience I tackled the latter first. TETIA TV TIPS National TC1401 A Symptom: Bottom foldup . Linearity can only be corrected if height is reduced almost to minimum. Voltage on TR454 collector low at 80V instead of 91 V. Cure: C-463 , a 22µF 250V electro , open circuit. This capacitor is the bypass on the main rail to the vertical output and its loss drops the rail voltage , as well as introducing excessive negative feedback. A vital precaution in making such adjustments is to first note and mark the position of the core or slug, then move no more than one turn initially to judge the effect. Further adjustments can then be made if necessary but one should always be in a position to return to the original setting. In this case, one turn was enough to produce a dramatic improvement, so I kept going until I passed the obvious peak, then returned to that point. And for the moment, that seemed to be the answer. But had I found the right peak? Was this the main sound channel or the second channel? Confident that I could return to this setting when I needed to, I turned the adjustment back to where it had been, then beyond this until I found another sound channel. Subjectively, it was hard to pick the difference between the two, but I reasoned that the first was more likely to be the right one, so I reset the core to this position. Then I moved to T151 and gave it a slight tweak, which was all it seemed to need. Finally, I switched the set to the ABC, which I knew was not even experimenting with stereo at that time, and was happy to note that the sound was perfect here also. Undoubtedly, had I picked the second channel instead of the main channel, this test would have revealed it. So that solved that problem and, as I said earlier, I have had about eight such cases since._ All have responded completely to this simple adjustment routine. As to why the fault occurred in the first place, I can only guess. One possibility is that the adjustments simply drifted, and it is true that most of the sets had been in use for several years. On the other hand I am more inclined to the idea that the adjustment was out from day one; not far enough out to upset a mono signal, and therefore capable of passing final test, but far enough out to allow a distorted version of the second channel to be heard. That's all we have room for this time around; see you next month.~ OCT0BER1988 49 T H E MUSICAL T E C H 'For us the realistic reproduction of music is the essential promise' Saul B. Marantz THE CL MATCH ASSIC BOX CRYSTAL SET By STEVE PAYOR Have you ever built a crystal set in your life? If you've never a built a crystal set before, this is the one to have a go at. You '11 be surprised at just how well it performs. This interesting little project is easy on the budget but big on satisfaction. And it won't cost you a cent to run after it's finished, even if you let it play continuously until the year 2088. Make no mistake about it, this crystal set is a real, working AM radio receiver, not just a nostalgic novelty. Until the invention of electronic amplification, the humble crystal set was the only form of wireless reception in use. Circuit development reached a peak around the 1920s and the "Super Crystal Set" described in the March 1988 issue of SILICON CHIP is a typical example of the type of receiver used for shipto-shore communications over thousands of miles. Simpler crystal sets, using only a single tuned circuit, were used for listening to domestic broadcasts and the crystal set described in this article is in the same category. It's cheap, easy to use, and capable of receiving all local broadcast stations at worthwhile volume. There is a price to pay for free entertainment however. First, you have to string up an antenna and provide a fairly good earth. Second, you will have to find a pair of sensitive, high-impedance headphones. More about the headphones later. Indoor antenna Our new crystal set has been designed to work with 15 metres of hookup wire as an indoor antenna. In most cases just draping it around A1 MATCHBOX CRYSTAL SET Fig.1: the complete circuit for our matchbox crystal set. Unlike most other crystal sets, it uses variable inductance tuning to give constant bandwidth and volume over the entire tuning range. The headphones should be high-impedance types (see text). a skirting board will do the trick. But if you live in a poor signal area it may be necessary to run the wire out the window and up and away from the house. In any case, stick to a length of 15 metres to start with, because the antenna capacitance and resistance form an integral part of the tuned circuit. As you can see from the circuit diagram and photographs, the tuned circuit consists of an inductor, wound on the outside of a matchbox, in parallel with a fixed capacitor and the antenna capacitance. The inductance is varied over a wide range by sliding two pieces of ferrite rod in and out of the matchbox. The ratio of minimum to maximum inductance that can be achieved in this way is about 4:1, which is not quite enough to cover the entire broadcast band in one go. This band extends from 531kHz to 1602kHz; ie, a 3:1 frequency ratio which requires a 9:1 change in inductance. We solved this problem by providing an antenna tapping, A2, at the centre of the coil. This tapping is used when tuning the top half of the band, and the antenna capacitance is transformed to an equivalent capacitance of only 32pF or thereabouts. When the antenna is connected to Al, the full antenna capacitance (approximately 135pF) is in parallel with the tuned circuit. This effectively doubles the tuning capacitance and shifts the tuning range down to cover the bottom half of the band. The two antenna tappings also perform another vital function they enable us to optimize the antenna coupling for each tuning range. The subject of antenna imOcT0BER 1988 53 1~NJ~~:Els El--0 400 EQUIVALENT TO EART!!J:""° ... · V 135PF 300uH FIXED SIGNAL INDUCTOR Fig.2: equivalent circuit for a 15-metre long antenna. It can be represented by a 135pF capacitor in series with a 400 resistor and an AC voltage source. pedance, and its loading effect on the tuned circuit, is perhaps the most important consideration in the design and operation of a crystal set. So let's start by considering the antenna as an electrical circuit. Equivalent circuit Fig.2 shows the equivalent circuit of our 15 metres of hookup wire at broadcast band frequencies. The wire is too short for its inductance to be significant at these frequencies. Thus, the antenna can be effectively represented by a capacitance of 135pF in series with a small voltage source [the received signal) and a certain amount of resistance. This resistance can be broken down into two parts. The major component is just the highfrequency resistance of the antenna wire itself. The other component is the "radiation resistance", which represents the coupling of the antenna to the surroun~ing space. The total series resistance of our 15-metre indoor antenna [including the earth connection) is about 400 at 1MHz, of which only a few ohms is the actual radiation resistance. Thus the antenna's efficiency is quite low. One way to increase the antenna efficiency is to make it longer and higher. The wire resistanc:::e increases in proportion to the length, whereas the radiation resistance goes up with the square of the effective height above ground. This should answer the old question "why is a longer antenna better than a short one?" . 54 SILICON CHIP Fig.3: the traditional "textbook" crystal set. The need for tap-changing as the set is tuned makes operation awkward. If we could run a very thick antenna wire straight up to a height of a quarter of a wavelength (75 metres at 1MHz), we would find that the series inductance would exactly cancel out the capacitive reactance. Thus, the only impedance left would be the radiation resistance, about 370. To achieve this ideal performance, this antenna would also require a perfectly conductive ground plane - a copper disc 150 metres in diameter would be near enough! Believe it or not, at a distance of 20km from a typical broadcast station, such an ideal antenna would receive more than 20mW of power. This is enough to provide quite respectable sound level from a loudspeaker! Obviously such an antenna system is not practicable, but one should bear in mind that a crystal set needs the best possible antenna PARTS LIST 1 wooden matchbox 9 metres 0.355mm (27 B&S) enamelled copper wire 5 solder lugs 1 polystyrene or silvered mica (low loss) capacitor; approximately 1 OOpF 1 germanium diode, OA47, OA91 , OA90 or equivalent 4 miniature alligator clips Miscellaneous 1 5 metres of insulated hookup wire for antenna, additional wire for earth lead as required, highimpedance headphones (see panel) . and earth system to function effectively. A microwatt of received power will provide good volume with a sensitive pair of headphones, a nanowatt is perfectly listenable, and a signal of around 50 picowatts is just readable. A good earth For the record, this crystal set will receive stations at listenable volume with less than a metre of antenna. However, it won't work at all without an earth connection, for the simple reason that the antenna current has nowhere to flow. One can get away with a large metal object buried in damp soil, but since dirt is not as conductive as metal the best ground connection would be a large metal grid, laid on or under the ground, and stretching as far as possible in all directions. Domestic water pipes fit this description admirably. Selectivity and coil tappings Sharpness of tuning is always a problem with simple crystal sets the resistive component of the antenna impedance and loading by the diode circuit both tend · to reduce the selectivity of the tuned circuit. One solution to the problem is to provide several taps on the inductor, as in the typical "textbook" crystal set of Fig.3. If we tap the antenna and diode into the coil a few turns from the "earthy" end, the tuning will be very sharp because the loading will be negligible. But the signal coupling will be correspondingly small. Selectivity and "Q" Factor The "Q" or Quality Factor of a tuned circuit is the ratio of its centre frequency to its -3dB band., width (see Fig.4). For example, a tuned circuit with a centre frequency of 1 MHz, and a -3d8 bandwidth of 1 0kHz, has a Q of 100. Normally, a Q of this magnitude is only just achievable with a welldesigned low-loss inductor. The unloaded Q of the Matchbox Crystal Set at 1 MHz was measured at around 95 to 98. Conveniently, Q is also equal to the ratio of the impedance of either the inductor or capacitor (they are equal at resonance) to the resistance causing the energy loss in the tuned circuit. For example, consider again a circuit with a Q of 100 at 1MHz. If the tuning capacitance is 1 00pF, it has a reactance of -j16000 at 1 MHz and the inductor has a reactance of +j1600O (253µH). For a Q of 1 00, the equivalent series resistance of the tuned circuit is 1600/100 = 160. The equivalent parallel resistive load would be 1600 x 100 = 160k0. (Fig.5.) Thus a high-Q tuned circuit must have very little series resistance (in the coil for example), and a very high parallel load resistance. The unloaded Q of the Matchbox Crystal Set is almost entirely determined by the coil resistance which, as we have just calculated, is about 160 at 1 MHz. Compare this with the DC resistance which is only about 1.30! When the crystal set is in use, the Q is considerably lower, because of the combined loading The optimum tapping points can be found by experiment but (and here's the catch) they vary with each frequency setting. For example, at the low frequency end of the band, one might obtain best results with the antenna tapping at 100% (ie, at the top of the coil) and the diode at about 60% of the turns. At the high frequency end of the band, the optimum antenna tapping may be only 10%, and the diode tapping about 25%. BW AMPLITUD OdBl+-----t-~ Q= folBW lo FREQUENCY RESONANT FREQUENCY Fig.4: the "Q" of a tuned circuit is the ratio of its centre frequency to its - 3dB bandwidth. 25311Ht:D OR~ lo = 1MHz Q = 100 Fig.5: equivalent high•Q tuned circuits (Q = 100 at 1MHz). of the aerial resistance and the diode circuit. With a 5k0 headphone load and a 1 5-metre antenna connected to "A2", the Q of the Matchbox Crystal Set was measured at around 50 at 1MHz, giving a -3dB bandwidth of 20kHz. Since the typical minimum separation between local broadcast stations is about 50kHz, this would put the interference from an adjacent carrier at -14dB. Unless the wanted signal is very weak, the major component of the interference will be ultrasonic, and therefore inaudible, so you will find that the Matchbox Crystal Set has adequate selectivity for most applications. There are three reasons why the tappings change so much. First, the RF resistance of the antenna wire increases with the square root of the frequency (due to the "skin effect"). But worse than this, the radiation resistance goes up with the square of the frequency. Thus, the damping effect of the antenna resistance is considerably greater at the top end of the band than it is at the bottom end. Second, to obtain the same selec- tivity at the top end, the tuned circuit needs to have a "Q" three times higher than at the bottom end. Finally, to make matters worse, the impedance of the L and C elements is three times higher at the top end of the band. The result is that we need to reduce the effective antenna and diode loading by more than a factor of nine as we tune up the band. For this reason the fixed inductor/variable capacitor approach is just about the worst arrangement possible. The only reason why this circuit is so popular is that variable capacitors are ·(or were) readily available. Variable inductors, on the other hand, were something you had to make yourself. Variable inductance is best If we want a tuned circuit that maintains constant selectivity with the antenna and diode connected to a fixed tapping point, the first thing we must do is use a variable inductor instead of a variable capacitor. Oddly enough, all of the earliest crystal set designs used variable inductors. These were invariably quite cumbersome affairs, using either a sliding contact arrangement or a pair of coils which slid or rotated inside one another. Nowadays, making a variable inductor is almost too easy, thanks to the availability of low-loss RF ferrites. With a fixed tuning capacitor and a variable inductor, the impedance of the L and C elements is three times lower at the top end of the band. This means that, for a given loading, the tuned circuit Q will automatically be three times higher. In practice, the effect is not quite this good, since we have ignored the resistive losses in the coil itself. Another problem is that the loading is not constant. Remember that the antenna resistance increases with frequency, so the optimum tapping point still needs to be moved, although over a much smaller range. This design solves the problem by electrically "moving" the A2 tapping as the tuning is adjusted. Although this tapping is nominally half-way up the coil, the effective OCTOBER 1988 55 Headphones for the Matchbox Crystal Set Owning a good pair of highimpedance headphones is a must for any crystal set enthusiast. You may get lucky poking around the disposal stores, but most of the headphones you are likely to find will have a fairly low impedance Don't let this worry you too much . If you find a sensitive pair in good condition, then a small audio transformer with the appropriate turns ratio is all you will need to turn them into a first class pair of crystal set headphones. The most sensitive type to look for are those with a "balanced armature" mechanism and a light aluminium diaphragm . Old telephone earpieces of this type are excellent and, even allowing for the losses in the impedance matching transformer, they are just about the most sensitive transducers ever made. Next, in order of decreasing sensitivity, come the even older style of headphones with sheet iron diaphragms. These are still being manufactured in 20000 impedance, but the sensitivity is not as good as it was in the old days. Next come the older style of "modern" headphones, the ones coupling varies depending on how far the ferrite rods are inserted into the top of the coil. When the rods are only partially inserted, the inductance of the top half of the coil is greater than the inductance of the bottom half. Also, not all of the magnetic flux from the bottom half of the coil passes through both halves - some of it leaks out the sides of the matchbox. Thus, the effective tapping is less than half-way up. When the ferrite rods are fully inserted, all of the flux flows through both halves of the coil and the effective tapping point is exactly half-way. So our "fixed" antenna tapping actually "moves" whilst we are tuning from station to station. There is an obvious advantage of this tuning system - it's dead easy to use. As a bonus, the Matchbox 56 SILICON CHIP with small 80 loudspeakers in them, and very large earpads. A good scheme is to connect both 80 drivers in series (get the phasing right) and use a 1 k0:80 transistor radio type audio transformer (eg , the M-0216 from Dick Smith Electronics). You may lose a little bass response, but you will have a pair of 20000 headphones. Note that the DC resistance looking into the matching transformer will be a lot less than 20000, so the transformer looks like a short circuit to the DC voltage from the rec'titied carrier. Actually, it is not quite this bad because the diode still has a few thousand ohms of forward resistance. Nevertheless, it is worth taking some steps to avoid excessive damping of the tuned circuit. Fig.6 shows how a series resistor can be added to bring the DC resistance up to 2k0. A bypass capacitor prevents any attenuation of the audio signal. This technique can also be used to make a pair of medium impedance phones from a couple of old telephone earpieces. These Crystal Set automatically maintains a constant bandwidth and volume over its entire tuning range. There is a second and not-soobvious bonus: we can accurately mark a tuning scale on the sliding part of the matchbox. This is normally not possible with an "ordinary" crystal set, since a slightly different tuning scale is required for each antenna tapping - hardly worth the bother! Actually, the Matchbox Crystal Set has two tuning scales, one for the top end of the band (with the antenna connected to AZ), and one for the bottom end (with the antenna connected to Al). As you can see from the photographs, both scales are almost linear, and all of the Sydney stations are spread out quite nicely across each range. The same will apply for other locations. " 20000" 1k·BO AUDIO HEADPHONES TRANSFORMER HEADPHONE DRIVERS 80 Fig.6: this diagram shows how to convert a pair of low impedance headphones into 20000 highimpedance headphones. All you need is a small audio tran~former, a resistor and a capacitor. 0.22·0.47 BALANCED ARMATURE TELEPHONE EARPIECES 200 (0C) Fig.7: this circuit will give good results with 200 telephone earpieces. have an AC impedance of a few hundred ohms each, but a DC resistance of only 200. Connected as shown in Fig. 7, they perform surprisingly well, although with 'a proper matching transformer Once your crystal set has been calibrated, the tuning scales will always be spot on, so long as you maintain a fixed antenna length. Diode circuit For the sake of simplicity, the AZ tapping is used for the diode as well as the antenna. Loads of between Zk0 and 10k0 are about right for this tapping. If you intend to use a very high impedance load, such as a pair of piezoelectric "crystal" earpieces, then connect the diode to the top of the tuned circuit (ie, to Al). The load resistance with crystal earpieces will be somewhere between 100k0 and lM0. Headphone impedance At this point we should explain why the headphone impedance required for crystal sets is always DIODE IN~&T PIEZOELECTRIC TRANSDUCERS 4.7k-10k Fig.8: a 4.7kll-10kll resistor should be added in parallel with piezoelectric transducers to prevent distortion due to insufficient shunt resistance. the results are phenomenal. If you don't want to go to all this trouble, try a pair of piezoelectric transducers. Murata make some very sensitive piezo inserts which are easy to fit into any old-style headset. These are available (along with lots of other goodies) from Orpheus Radio, RSD 898, Ballarat 3352. Telephone (053) 34 2513. Piezoelectric transducers have the opposite problem to electromagnetic transducers - they have an infinite DC resistance, and a fairly low AC impedance. Electrically, a typical pair of piezoelectric transducers in parallel looks like a 0. 1µF capacitor. If you connect them to the diode without a load resistor, all you will hear is a faint, distorted crackling. very high, compared with the impedance of modern high-fidelity headphones (usually 80 to 320). Why can't we just move the diode tapping way down towards the bottom of the coil and use low impedance headphones? The answer is we could, if we could find a diode with a resistance of about 100 at a forward voltage drop of say lOmV. The best all-round diode for crystal set use is the gold-bonded germanium type OA47. At lOmV applied voltage, a typical device exhibited a forward static resistance of 26k0 and a reverse resistance of 3 lk0. So, for signal voltages of ± l0mV, no effective rectification takes place. When the voltage was increased to lO0mV, the forward resistance dropped to 7k0 and the reverse resistance increased to 73k0. Rectification now takes place but, for Fig.8 shows the demodulated signal envelope as delivered by the diode into a load which has too much capacitance and not enough shunt resistance. Severe audio distortion results because the capacitor can't discharge rapidly enough to follow the audio frequency variations. Adding a 4. 7k0 to 1 0kO resistor in parallel with the transducers will fix this problem. Last, but not least, you might like to try a pair of "crystal" earpieces. These use tiny crystals of a naturally-occurring piezoelectric salt and their impedance is very high. A pair connected in parallel will only need a shunt resistance of between 1 0OkO and 1 MO for best audio quality. Often, the reverse leakage of the germanium diode alone will be sufficient. reasonable efficiency, a load in excess of 10kO is necessary to prevent undue loading. There are two possibilities for improved rectification with low impedance loads. One is the so-called "backward diode", which is really a zener diode with a reverse breakdown voltage of 0V. These are normally used only in microwave detectors and are hard to come by. Another approach is to use a battery and potentiometer to bias a silicon diode into forward conduction. By adjusting the bias, you can select the best compromise between forward and reverse resistance for a given load. This approach was often used in the past, especially when using a "carborundum detector". This was a diode made from a crystal of silicon carbide with a sharpened steel point sticking into it. It needed This old telephone earpiece was converted to high impedance operation using the circuit shown in Fig.6. The parts all fit in the plastic housing. a forward bias of about 1V for best results. However, high impedance headphones and an ordinary germanium diode are still the most convenient arrangement. If you want to, you can make a suitable pair of phones using currently available parts (see panel). What, no .00tuF capacitor? Conspicuous by its absence from the circuit diagram is the usual .00lµF capacitor across the headphones. This is included in all the "textbook" circuits to provide RF filtering of the audio output, but its presence is usually undesirable. The impedance looking into a rectifier with a capacitive filter is close to half that of the load resistance, so with our headphones already lower than the optimum load resistance, this capacitor only makes things worse. By contrast, an inductive filter can increase the effective load resistance to slightly more than the headphone resistance. A lmH or 2.5mH RF choke in series with the diode may well improve the performance with low impedance headphones (eg, lkO or even 6000) - at least in theory. In practice, the choke can be left out as there will be sufficient inductance in the headphone windings or in the matching transformer. Construction Let's begin construction by locating a suitable matchbox. This OCT0BER1988 57 glue is incredibly tough, and it is the only one which can take soldering temperatures without embarrassment. Start with the three lugs on the "antenna" side of the matchbox. Spread an ultra-thin smear of Urethane Bond on the matchbox, and a little more on the solder lugs. Position one lug at each end, and one exactly in the middle. Leave the box standing on its side for several hours until the glue hardens. Next, turn the box over and glue the two headphone lugs exactly opposite the "A2" and "E" lugs, checking the location with a ruler. Stand the box between two heavy objects to keep it level until the glue sets. The tuning scale was carefully hand-drawn on the inner part of the matchbox. Note the diode running across the centre of the matchbox and the polystryrene capacitor between the "Al" and "E" terminals. L1,L2 = 37 TURNS, 0.355mm DIA. ENAMELLED COPPER WIRE, CLOSE WOUND. 100pF TUNING CAPACITOR FERRITE RODS GLUED TO INSIDE OF MATCHBOX TRAY f \ V ' SOLDER LUGS GLUED TO MATCHBOX COVER WITH URETHANE ADHESIVE. Fig.9: here's how to build your matchbox crystal.set. Each of the coils consists of 37 turns of 0.355mm guage wire, but other wire gauges can also be used (see text). is not so easy as it sounds because wooden matchboxes are scarce these days, and the cardboard ones are a little too flimsy to wind a coil on. In any case, you will need to make up a wooden "dolly" to prevent the box from being crushed during the winding. Carefully plane a block of wood so that it just fits tightly inside, then glue a short piece of broom handle to it and put it aside. Next, give the insides and outsides of both halves of the matchbox a coat of Satin Estapol or similar clear polyurethane finish. This strengthens the assembly considerably. Allow it to dry overnight, then lightly sand all over with 600 58 SILICON CHIP grade paper to smooth any furry bits. The top coat of Estapol will be added later, when the coil windings, etc are in place. Meanwhile, prepare the five solder lugs by firstly tinning them - this will minimise the amount of soldering heat needed later on. Once tinned, thoroughly scrub away all traces of the flux resin with a tissue and methylated spirits, then bend the lugs through 90° as shown in the photographs. Glueing the lugs The best glue for this job is Dow Corning "Urethane Bond" (formerly sold under the Selleys label). This Winding the coil The recommended wire gauge is 0.355mm (27 B&S) but don't worry if you don't have the exact size good performance can be obtained with any gauge from 0.315mm to 0.5mm (28 B&S to 25 B&S). Of course, the number of turns that will fit in the available space will vary, but the appropriate choice of tuning capacitor will compensate for any variation in inductance. For example, on one prototype, wound with 0.355mm wire, two coils of 37 turns each just fitted between the lugs. This crystal set required a tuning capacitor of l00pF. A second prototype was wound with 0.5mm wire. The two coils ended up having only 23 turns each, and a 270pF tuning capacitor was required. Performance wise, there was little difference between the two windings, although the second set had a slightly restricted tuning range, and it preferred a lower headphone impedance. When it comes to winding the coil, you can use one of two methods. Either wind each half of the coil separately, terminating the wire on the solder lugs as you go, or wind the whole lot in one go, with a few extra turns across the central gap which can be snipped out later. Keep a heavy tension on the wire all the time, and don't let go or you will find yourself having to start all over again. In fact, it's a good idea to have on hand several short pieces of masking tape, for holding flanges, and soldered the end of the antenna wire to it. A band of flat elastic keeps the wire in place when it is wound up. For the earth lead, we suggest that you use a few of metres of wire with a miniature alligator clip at one end, and a large jumper lead clamp at the other end, which can fit around the kitchen tap, or a water pipe. Initial testing We made up an antenna reel using a tin can with a couple of large "Milo" lids as flanges. The headphones were put together from a pair of discarded telephone headsets and a small audio transformer. the wire in place should you need to stop for any reason. It isn't necessary to count the turns, just fill up the available space between the lugs with a neat, close-wound layer of wire. When the time comes to solder the wire to the lugs~ you can temporarily anchor the turns in place with more masking tape, or secure the windings with "Super Glue" or a tiny smear of "Araldite". Thoroughly scrape and tin the ends of the wire, and solder them to the lugs with a minimum of heat. Mounting the components The diode runs from the middle "A2" lug, across the front of the matchbox, to the headphone lug on the other side. Bend the leads neatly to follow the shape of the box. The tuning capacitor runs down the side of the matchbox, between the "Al" and "E" lugs, but its exact value needs to be determined experimentally, so do not solder it in place at this stage. The only other components are the two pieces of ferrite rod, but first they need to be cut to length. Ferrite is quite hard and brittle. About the only way to cut it is to file a groove right around the rod and then break it by hand. Trim the rod if necessary by rubbing it on a sheet of silicon carbide paper (wet or dry), using kerosene as a lubricant. Check that both pieces fit snugly lengthwise down each side of the "drawer" part of the matchbox. If everything is correct, give them a wipe over with methylated spirits, then glue them in place with 5-minute AL'aldite. By the way, any type of round or flat ferrite rod will do, providing it is "antenna" grade ferrite. Accessories The crystal set is now ready for testing but first we need some accessories to complete the setup. Number one on the list is a suitable pair of headphones, and we have prepared a panel describing a number of practical alternatives. Fit a pair of miniature insulated alligator clips to the headphone leads. Next; measure out 15 metres of medium or heavy duty hookup wire for the antenna, and fit a miniature alligator clip to one end. You may wish to secure the other end to some sort of spool, so that you can wind the antenna up without getting it thoroughly tangled. We made a spool from a tin can with two large "Milo" lids as Now for the exciting part. Connect up the antenna, earth and headphones, and temporarily attach a 100pF capacitor to the "Al" and "E" terminals with a pair of short clip leads. Check the coverage of the top end of the band with the antenna connected to the "A2" tapping, then the bottom end with the antenna connected to "A 1 ". If you are missing some stations off the top end of the band, you will need to reduce the tuning capacitor, and vice-versa. A small assortment of capacitors will provide quite a variety of values if you Handy Hints Hint #1: nail polish is a handy item in your workshop. It will secure a pointer to a dial cord, prevent a knot in a dial cord from coming undone, or can be used to lock screws in place. Nail polish can also be used to anchor the terminations on small coils and to permanently set trimmer capacitors and potentiometers. Hint #2: to hold small components while you solder them together, use a large spring clip (normally used for holding papers together). The spring clip can either be screwed to your work bench or to a solid block of wood to stop it. from moving around. Hint #3: having trouble getting a replacement tip for your Tandy, Dick Smith or Scope temperature-controlled iron? Many of the tips for these brands are interchangeable. Take your old tip with you to compare it with the new one to make sure it matches. OCT0BER1988 59 This view shows how the two ferrite rods are glued to the inside of the matchbox tray. Any type of round or flat ferrite rod can be used, providing it is "antenna" grade ferrite . connect them in series and parallel combinations. Once the required capacitance has been determined, it can be made permanent, but make sure you use a low-loss capacitor. A loss factor of less than .001 % at 1MHz is desirable. The best capacitors are polystyrene, silvered mica, or NPO ceramic types specifically designed for RF work. Finishing touches The ruggedness of your Matchbox Crystal Set can be improved by giving the lower parts of the solder lugs, and the area around them, a thin coating of epoxy. Use slow-setting Araldite, and spread it thinly and evenly with a pointy instrument. It will flow out smoothly and set crystal clear if you warm it up a little while it is setting. A warm window sill in the afternoon sun is ideal. Put a little of the epoxy oh the diode and capacitor as well but don't bother to coat the coil windings - these are best held in place with a final coat of Satin Estapol. Before you get out the Estapol, stick some small pieces of sticky label material on the matchbox and label the terminals "A 1" , "A2", "E", " Phones" and "Phones" with your neatest writing. Don't use a spirit-based felt tip pen - use drawing ink or similar water-based 60 SILICON CHIP The matchbox crystal set is tuned by sliding the tray up or down to change the inductance of the coils. A good earth connection is vital for correct operation. medium. Also, now would be a good time to draw a tuning scale on the sliding part of the matchbox, so that it will be protected under the final coat of Estapol. Calibration As you can see from the photographs, we managed quite a comprehensive tuning scale. This was hand-drawn over the first coat of Satin Estapol with Rotring drawing ink and a fine pen. This surface takes ink beautifully if it is pretreated to render it slightly hydrophilic (ie, to make it attract water). Just moisten a tissue with saliva (yes, that's right), rub it all over the Estapol, and then wipe it dry. If the cardboard is darkly coloured, you can stick some white label material over it, or use one of the decorative white or silver inks available at most artists' supply shops. Next, consult a list of AM broadcast stations (in any recent DSE catalog for example) and make a short list of all the stations in your area and their frequencies. Log as many of the stations as you can, drawing a light pencil line against the edge of the matchbox for each one. Draw a base line on the scale and measure the positions of all the station lines relative to it. Next, plot a graph of these measured distances against the listed carrier frequency of each station. Carefully join the points with a smooth curve. You can now read off the position of any intermediate frequencies (eg. every 50kHz or lO0kHz), as well as the exact position of any stations which happen to be too weak to be received from your location. Transfer all this information with ruler and pencil onto the sliding part of the matchbox, and ink it in. If you make a mistake, it can be cleaned off with a moistened cotton bud. Be careful of smudges - the ink takes a long time to dry on this surface. Finally, give both halves of your crystal set a final coat of Estapol all over, keeping clear of the exposed parts of the solder lugs of course. Operational hints Although the circuit should be tuned by moving the ferrite rods in and out of the top of the matchbox, you can also tune in the same stations by moving them in and out at the bottom. The difference here is that the lower half of the coil will have a greater inductance, effectively moving up the "A2" tapping. This will give you more volume, but less selectivity - the stronger stations will be noticeably louder but some of the weaker ones will be lost altogether. Use whichever setting suits you best. ~ Don't miss a single issue IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. * * * * * Constructional Projects for the Enthusiast Amateur Radio by Garry Cratt The Serviceman's Log The Way I See It Hifi Features & Reviews FREEPOST * SUBSCRIPTION COUPON Subscription to commence in._ _ _ _ _ _ _ _ _ _ _ __ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree~------------------Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ __ 1 year (12 issues) D $A42 2 years (24 issues) D $A84 NZ & PNG (airmail) D $A65 D $A 130 Overseas surface mail D $A62 D $A 1 20 D $A 130 D $A240 Australia Overseas airmail Enclosed is my cheque/money order for $ _ _ _ or please debit my D Bankcard Card No. I D Visa Card I I I I I I I I I I I I I I I Subscription Hotline We can accept your subscription order by telephone . Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date. Detach and mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 I Signature _ _ _ _ _ _ _ _ Card expiry date_/_/__ • No postage stamp required in Australia. 0;}/ d'tJ I ~-------------------------------------~ OCT0BER1988 61 $10 Off Infra-Red Controller! Here's great value: you'll save $10 on the superb AEM 240V Infra-Red Controller. Gives dual action (on/off) control on any mains device (TV, lamps, etc etc) from up to 12m away. Both sections (transmitter and receiver) supplied (and spare transmitters are available). Exclusive DSE kit includes special case & panel. Cat K-3428 ---- WAS $59.95 s49es Spare Transmitter To Suit: sges Just in case you lose yours - or want to give control to more than one person. Cat K-3429 TV Cro Adaptor Handy Zener Tester When zeners are new, you can sometimes read the type number. Sometimes. When they're a little older ... And how do you know if they're zenis goodus or zenis cactus? With a Zener diode tester, of course. 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Visitors would no longer have to peer through the murk with torches to find your abode. Your house number would welcome them with a cheery glow. By JOHN CLARKE & LEO SIMPSON Most homes are hard enough to find during the day when you can see the house numbers but at night it's a different matter. How many times have you peered through the dark trying to find a particular street number? It's even worse on wet nights when rain and darkness combine to make street . numbers virtually impossible to see, even if you have torch. Now, at least as far as your own home is concerned, you can do something about it. You can build the LED-Light, a street number that glows in the dark. It turns itself on automatically at dusk and then turns itself off again about 4.5 hours later. We've even incorporated an automatic brightness feature so that the LEDs (light emitting diodes) are brightest at dusk and then dim down significantly so that they are not too bright on the visitor's eyes. That might seem like gilding the lily but when you have upwards of 50 or more LEDs glowing in the dark they can seem painfully bright. But more of that later. The LED-Light is powered from the mains via a 12V AC plugpack rated at 300mA or more. Using low voltage AC means that you could mount the LED-Light on your letter box and bury the wires carrying the 12V supply directly beneath the soil. In some areas, mounting the LED-Light high up on your home's front wall might be a better idea, in case some light-fingered technofreak takes a fancy to it. Either way, running the wires to it will not be a problem. We built our prototype LED-Light into a standard plastic jiffy box measuring 198 x 113 x 63mm and the LEDs are all fitted onto the lid, as can_ be seen from the illustrations. A light dependent resistor (LDR) senses whether it is daylight or not and operates the circuit accordingly. Our prototype was made for one of our staff members who lives out in the sticks; hence Lot 14. The circuit A light dependent resistor senses the approach of darkness and turns the LEDs on for a preset time. Make the figures big enough so that they can be easily seen from the street. 64 SILICON CHIP You might think we've gone right over the top with the circuit for the LED-Light considering that it uses five ICs, four transistors and five diodes. Well, they're real cheap ICs so that is not a problem. The circuit can drive up to 64 LEDs which is enough to cater for 4 or 5-digit street numbers (or Lot or RSD numbers, if you're out in the bush). The circuit has three functions: light sensing, a long interval timer and a brightness modulator. Light sensing is provided by the light dependent resistor LDRl and ICl ; the long interval timer consists of IC2 and IC3, while the brightness modulator is IC5, Q3 and Q4. IC4 lets the three circuit functions work together, to determine whether the LEDs are on or off, bright or dim. The light dependent resistor NUMBER THAT GLOWS 01-04 4x1N4002 12VAC FROM PLUG-PACK + + 470 10 16VWr 16VW.:r ~t}' J .,. 100k +12V 4xRED LEDS PER ROW (64 LEDS TOTAL) 16 4011 10 CK 4 8 .,. .,. 10 + 2 16VW:r 3 +12V +12V LDR1 ORP12 .,. 8 56k IC1 555 2 + .,. .,. 15k B E~C VIEWED FROM BELOW ~- .,. 470k 10k .,. .o~I .,. LED-LIGHT HOUSE NUMBER Fig.I: the circuit can drive up to 64 LEDs which is enough to cater for 4 or 5-digit street numbers. LDRl and ICl provide the light level sensing, IC2 and IC3 form a long interval timer, and IC5, Q3 and Q4 vary the LED brightness. LDR1 and a series 33k0 resistor form a voltage divider which is monitored by pin 2 (and pin 4) of IC1, a 555 timer. When LDR1 is exposed to light, its resistance is low and therefore pins 2 and 4 of IC1 are held high. As the level of illumination decreases (like, when it gets dark) the resistance of LDR1 increases and so the voltage on pins 2 and 4 begins to fall. When the voltage on pin 2 drops to about 4V, IC1 's output at pin 3 goes high. It remains high for as long as pin 2 is at 4V or below. In pitch dark, the resistance of LDRt is likely to be several megohms which means that pins 2 and 4 of IC1 will be below 1V. Pin 3 of IC1 is connected to pins 12 and 13 of NAND gate IC4c and pin 6 of IC4b, another NAND gate. NAND gate IC4c functions simply as an inverter, so that when pin 3 of IC1 goes high, pin 11 of IC4c goes low, pulling the reset pin (11) of IC3 low too. This lets the timing interval start. It also turns on the LEDs via IC4b, Qt and Q2. We'll come back to IC4b later. Long interval timer IC2 is another 555 timer IC which is connected to oscillate at about 0.5Hz. This means that it produces a train of positive pulses at its pin 3; one pulse every two seconds. These pulses are fed to the clock input (pin 10) of IC3, a 14-stage divider. This OCT0BER1988 65 5-second delay set by the 470k0 resistor and 10µF capacitor connected to pins 6 and 7 of IC1. Brightness modulator The LEDs are inserted into tight-fitting boles in the lid of the case and wired in series groups of four. Our prototype used 55 LEDs but you will probably need a lot less than that for your house number. As noted above, the brightness of the LEDs is varied depending on whether it is dusk or pitch dark. At dusk, the LEDs are at maximum brightness and as it gets darker, they are dimmed down significantly. This function is performed by IC5a, a dual operational amplifier. IC5a monitors the voltage across LDR1 and its output at pin 1 is used to vary the voltage at pin 5 of IC5b which operates as a Schmitt trigger oscillator. It runs at up to about 2kHz (depending on the degree of darkness) and its pulse output drives transistor Q3 which drives Q4 and the LEDs. Thus IC5 controls the duty cycle of the LEDs. At dusk, when the LEDs are brightest, they are on 100% of the time. When it is pitch dark, they are on about 50% of the time. This is when they are being pulsed on and off at about 2kHz. Transistor Q4 switches on and off the positive supply to the LEDs and is driven by Q3 via oscillator IC5b. Power supply Power for the LED Light is derived from a 12VAC plugpack. This feeds a bridge rectifier consisting of diodes Dl to D4. The rectifier output is filtered with a 1000µF capacitor to supply the LEDs. For the remaining circuit, the filtered rectifier output is regulated with a 12V 1W zener diode, with further filtering provided by a 4,70µF capacitor. The 10µF capacitor is for extra supply bypassing adjacent to the ICs. The light dependent resistor (LDR) is mounted at full lead length on the PCB. When the PCB is later clipped into the place, the leads of the LDR are bent so that its face protrudes through a hole in the side of the box. divides the incoming frequency by 214 or 16,384. The result is that after about 4 hours 30 minutes the output at pin 3 (Q14) of IC3 goes high. The signal from pin 3 ofIC3 is fed to NAND gate IC4a, connected as an inverter. So when pin 3 of IC3 goes high, the output of IC4a, pin 3, goes low. This drives pin 5 of NAND gate IC4b and thereby turns off Qt, Q2 66 SILICON CHIP and the LED display. IC4a also drives pin 4 of IC2 which then inhibits any further oscillation. The output of IC3 stays high until next morning when light hits LDR1 and IC1 delivers a reset pulse to pin 11 (ofIC3). IC1 will not respond immediately if car headlights strike LDR1 for & few seconds. This is because of the Construction We built our LED-Light into a plastic utility case measuring 198 x 113 x 63mm. All the circuit components, with the exception of the LEDs, are mounted on a printed circuit board coded SC03-1-0988-1 and measuring 104 x 103mm. Assembly of the PCB is a simple matter of inserting the parts into the board and then soldering."Begin by installing the wire links, resistors and diodes. Then do the capacitors and transistors. PARTS LIST 1 plastic utility case, 198 x 113 x 63mm 1 PCB coded SC03-1 -0988-1 , 104 x 103mm 1 12VAC 1 A plug pack 64 5mm red LEDs (see text) 1 ORP12 cadmium sulphide cell (LDR1) Semiconductors 1 4020 14-stage ripple carry binary counter 1 4011 quad 2 input NAND gate 2 555 timers 1 LM358 dual op amp 1 BC558 PNP transistor 1 BC548 NPN transistor 1 BC338 NPN transistor 1 BC328 PNP transistor 4 1 N4002 1 A diodes 1 1 2V 1W zener diode Fig.2: here's how to mount the parts on the PCB. Because the LEDs are wired in groups of four, you might not need all of the 4 700 resistors shown. Note that the corresponding 4700 resistor must be increased to 8200 for a one or two-LED set, as outlined in the text. Note that the diodes, transistors, electrolytic capacitors and ICs must be oriented as shown on the overlay diagram. Don't bend the leads of the 1W zener diode, D5, close to its body to fit it into the holes on the board. This component can get warm depending on whether the LEDs are off (which means that the supply is lightly loaded) and whether the mains voltage is high. To enable D5 to cope with expansion when it does get warm, install it with an expansion loop at cine end. The light dependent resistor LDR1 is soldered into circuit with its leads sufficiently long so that it can be mounted with its face protruding from the the side of the box. Checking the circuit Before wiring all the LEDs into the circuit and installing the unit in the box, it is a good idea to check that the circuit board functions properly. If you check it out now it will be much easier than trying to troubleshoot it later. So leave off the rainbow cable connecting the LEDs until the following checkout procedure has been done. First check that all solder joints on the board are up to scratch and that there are no solder bridges between tracks or breaks in the tracks themselves. Then connect a 12V AC or DC plugpack capable of delivering 300 milliamps or more. You can use a 12V bench power supply if you like, as it will work just as well. If you are using a bench supply, adjust it to deliver about 14 volts which will cater for the voltage drop in the diode bridge (about 1.2 volts). Now use your multimeter to check voltages around the circuit. D5 should have close to 12 volts DC across it. With your multimeter's negative lead on the negative end of D5, check that + 12V appears at pin 8 of ICs 1, 2 and 5, at pin 14 of IC4, at pin 16 of IC3 and at the emitter lead of Qt. Now cover LDR1 to prevent it being exposed to light. If you have an analog multimeter (or a digital multimeter with an analog scale) you should be able to check that IC1 is oscillating at about 0.5Hz. Leave the meter set to the same DC voltage scale and place the positive Capacitors 1 1OOOµF 25VW PC electrolytic 1 4 70µF 16VW PC electrolytic 3 1 OµF 16VW PC electrolytic 1 .01 µF metallised polyester Resistors (0.25W, 5%) 2 X 470k0, 4 X 100k0, 1 X 56k0, 1 x 33k0, 1 x 15k0, 1 x 1 OkO, 2 x 5.6k0, 3 x 1 kO, 18 x 4700, 1 x 330 0 .5W Miscellaneous Solder, tinned copper wire, 300mm of 1 8-way rainbow cable. lead on pin 3 of IC1. The pointer should flick up the scale to 12V about once every two seconds. You check the frequency divider operation of IC3 in a similar manner. Place the negative lead on each output in turn. Pin 9 (the Qt output) should rise to 12V every four seconds or so; pin 7, every 32 seconds; and pin 5, every 64 seconds. You ·could check every available divider stage (not all stages have pin outputs) in this way if you wanted to but it would be very timeconsuming and a fairly pointless exercise. Once you've demonstrated that the early divider stages of IC3 are working you can be sure it is OK. OCTOBER 1988 67 Note that IC2 will oscillate whether or not LDR1 is exposed to light but IC3 will not work unless LDR1 is covered. This is because IC3's reset input, pin 11, is high (ie, at + 12V). You can check the action of LDR1, IC1 and IC4 by covering and uncovering LDRt. With LDR1 covered, pin 3 of IC3 and pins 12 and 13 of IC4 should be high. Pin 11 of IC4 and IC3 should be low. Five seconds after LDR1 is uncovered, all these points should change state;, ie, pin 3 of IC3 and pins 12 and 13 of IC4 should go low and so on. Having got this far, we've practically checked the whole circuit. Now wire one LED and a 10k0 resistor in series between one of the 4700 resistors and the common line from the collector of Q5 (this line is along one edge of the board, adjacent to the row of 4700 resistors). Note that the LED comes on when LDR1 is covered and goes out five seconds after it is uncovered. Good. Its brightness should also visibly dim as LDR1 is completely covered. I OOOIMIODD-GOOOOD-GO .,, I Fig.3: this is the full size pattern for the printed circuit board. Wiring the LEDs The LEDs are mounted on the lid of the case and can be arranged in any manner required. Up to 64 LEDs can be accommodated. We arranged the LEDs on our prototype close together but they can be spaced further apart for better readability at a distance. The LEDs are inserted into tightfitting holes in the lid. Wire the LEDs in series in sets of four with the anode of one connected to the cathode of another. If the last set of LEDs is not four, then the series resistor supplying that set will need to be altered. For three LEDs, the resistor can remain at 4700, for two and one LED sets, use an 8200 resistor. You can run the wires from the LEDs to the PCB using multi-way rainbow cable. A hole is required in the base of the case for leads from the 12VAC plugpack and another close-fitting hole is needed for LDR1. The unit is now ready for final testing. Connect up the power and test that the voltage across the zener diode is about 12V. Now test 68 SILICON CHIP Stout pieces of tinned copper wire can be used to connect the commoned anodes of the LEDs together. Keep the wiring tidy to avoid confusion. that the LEDs light when LDR1 is covered. They should remain lit for five seconds after LDR1 is again exposed. Finally, the case can be weatherproofed using silicone sealant over the cord entry and around the edges of the lid. Delete options Just like some new cars have "delete" options then so has this circuit. If you are not buying the kit you can save a few dollars by leaving out the automatic brightness feature. To do this, delete IC5, transistors Q3 and Q4 and the 10 resistors and .OlµF capacitor associated with these active components. A link should be wired in place of the collector and emitter leads to Q4. ~ Nicad ~ Battery -.!.!~~-=- ••• Charger a (NJ{f.rrl} rans Mein, powered. ch•rges 6 x AA or AAA High Qunlity from C.I.C. Co. s19 80 betterie, i n 14-16 hr,, vith LED indica1or>. ca1 02-2012 a..~ for rndlo control Tamiya curs etc. Plug-1n replacement i, Cat 1300mAH end et thl, price, 02-1090 \JOU could efford 2 e, ,pere,. 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Cat 16 - 3445 9P skt lo 25P plug .. Cat 16-3447 0~DT Ei~c ~" HIGH QUALITY }:· ~~~~tmtg beoe CetOl-5312 NON-RESETTABLE 2 ◄ V DC .. $5.50 ee 24 V DC Chassis 19-5011 ...$6.SOea 11 O VAC Chaooi, 19-5012 ... $ 5.00ea 220 V AC Chaosi o 19-5013 ... $ 5 . 95 ea Bug 1 0+ Less 1 0\11 HEAVY DUTY - --~ pin size connector. 15 PIN Mule Cat 01-09'17 11 4/6/8" Honeycomb Cone ~ ~ri:R5~ euto reoet, 12Vdc oper. c-1 TYPE CONNECTORS 12V RED. HLUE. ORANGE. IDEAL FOR ALARMS etc . •Build your o'w'n system at 1o'w' cost I Hu 25 ea siren. entry/exit delay, S )!~~~m~ into car redio for high quality. ou1pu1. Reduce cone breakup, excellent be,, sound, RMS power ret1 ng, . All 8 ohms i mpedence . LOOK AT OUR ADVERT HERE EVERY MONTH! 22K end - of-line reoiotoro, N.0/N.C . i notentenddeley, Inbuilt Extro loud 08 9 AsusedonnewlBM type computer, etc . 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Higheot Quelity end fully guerenteed . 200xl45x40mm Buffer : De1e: Pover : 256K or 2x12BK o1orege 4K bytes/second maximum Z40Yec or 9Vdc •1 500mA Macintosh® CABLES Re91st,r•d trad, rn~rk of Appl, Compu tpr- ~ :~~ :~ ;:i~t;r m:~ c=) ( lmege""riter I, ll or some other,) o·• $10.95 Pl u, to printer $10. 95 ·; · • (lmege'w'riter I, II or ,ome others) Plu,tomode m • HALOGEN CENTRONICS P A R - L L E L ca104-1592 z buffers (total 2 95 Custom m11de to order here ; n Oz relay s'w'itching for home,, security, neon siqns etc Cat 04-0110 Weterproof for outdoor,. $16.50 CASSETTE SALVAGE and REPAIR KIT CASSETTE Complete ,et of cassette perb'W'ithsplicing bar end tape end bh1des . Cet 01-0430 REPAIR KIT r:;..i rfiiil ~ "ij ~ $2.95Eech ~ TELEPHONE EXTENSION BELL 10 Metre leed for remote locat ions 'w'ith \JS type plug. Aust pl ug -8depter on l y $5.52 eo $22.so Cot 24-3001 Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Off peak indicator for hot water systems How many times have you run out of hot water from your off-peak hot water system? It most commonly happens when the rellies (relatives) are staying and use all the hot water before you even get up, leaving no hot water for the most important shower of the day - yours. This circuit provides a visual indication when the hot water system is switched on so you have some idea when it will be safe to venture under the shower head. It monitors for the presence of control tones on the 240V mains and switches on a LED. The circuit is powered by a 9V AC or 12VAC plugpack which picks up the control tones. Diode Dl half wave rectifies the 12.6VAC from the transformer and the resulting DC is filtered using a 470µF capacitor. A 7808 regulator sets the voltage at 8V. Control tones picked up by the +8V 9-12V AC PLUGPACK + IC2 70 SILICON CHIP DUT.,_8_~ NE567 22k 1k 0.33'+ transformer are coupled via a .0039µF capacitor and a 47k0 resistor to the input of ICl. This is a non-inverting amplifier with its gain set by the 22k0 and lkO feedback resistors at pin 2. The amplifier is biased to the half supply point by the two lOkO resistors connected to pin 3. Both the .0039µF input capacitor and the 0.33µF feedback capacitor filter out the 50Hz signal from the mains supply but allow the lkHz control tones to pass. Output from the amplifier connects to the input of IC2, an NE567 phase locked loop. This provides a low output from pin 8 whenever the IC detects or locks onto a set frequency. In this circuit, the lock frequency is lkHz as set by the .039µF capacitor and 27k0 resistor at pin 6. When control tones are present, the signal is amplified by ICl and detected by IC2. The resultant low output from pin 8 of IC2 drives the off peak indicator LED. r-----------------+---..--+---+15V Audio overload detector Here is a circuit which indicates whenever an audio signal exceeds a specified threshold value. It is useful to indicate clipping levels on a power amplifier, mixer or microphone amplifier. It indicates the overload by flashing a LED for about 200ms for each overload peak. The circuit comprises three ICs. ICl is used as a precision full wave rectifier, IC2 as a comparator and IC3 as a timer. The precision rectifier uses a CA3140 connected as an inverting amplifier. A diode is connected in series with the output and within the feedback loop. The CA3140 is specified here because its inputs 3 IN 1.5k 220k IC3 555 INPUT .,. i.,. OVERLOAD LED 1M can be pulled below its negative supply line (pin 4). Opei'ation is as follows: when the input goes low, ICl functions as an inverting amplifier with a gain of - 0.5. Diode Dl is forward biased. When the input signal goes positive, the output of ICl goes to ground and Dl is reverse biased. The signal is then passed to the output via the 3k0 and 1.5k0 resistors. .,. In this case, the op amp is effectively out of circuit and the output signal is half the input signal. So the CA3140 in conjunction with diode Dl provides full wave rectification and a gain of 0.5. Op amp IC2 compares the output voltage from the precision rectifier with the reference voltage set by trimpot VRl. When the rectifier voltage exceeds this reference 1k 10k MAXIMUM ADJUST IC1 555 VR2 1M 10 RESET .,. 4.7 + K 4 013 680k 01 8C548 014 2 0.120min 3 0-240min _ S 2 .,. . 16VW.r- Long interval timer Many applications call for time intervals which are too long for a standard 555 timer circuit. In practical terms, it is limited by the leakage of normal electrolytic capacitors to time intervals of no more than about 15 minutes. For longer intervals, you need to resort to a long interval timer such as the XR2240 or the circuit presented here. It uses a 555 timer to drive a 4020 14-stage ripple counter. ICl is connected as an astable timer (ie, it oscillates continuous- voltage the output of IC2 goes low and triggers a 555 timer, IC3. The 555 timer is connected as a monostable so that the output remains high for about zooms each time it is triggered. The zooms period is set by the 220kn resistor and lµF capacitor at pins 6 and 7. The output of the 555 at pin 3 drives the LED via a lkO resistor. The input voltage to the circuit should be limited to an absolute maximum of 15 volts peak-to-peak. Note that the input impedance of the circuit is rather low at 3k0. To function properly, the circuit should be driven by a low impedance source. Subscribers Are you about to change your address? Please advise us by the middle of the month to ensure that your next issue arrives at your new address. ly). Its output is divided by IC2, the 4020, with division ratios set by switch S2. The division ratios are 2048 at pin 15, 4096 at pin 1, 8192 at pin 2 and 16,384 at pin 3. To obtain a 30 minute period, as set by S2, ICl is set to oscillate at 1.13Hz by adjusting trimpot VR3. With this setting, S2 can also give time periods of 60 minutes, 120 minutes and 240 minutes. The high output from S2 is used to turn on Q2 and the associated relay. The output is also fed back to Ql which switches on and pulls pin 4 of ICl low, stopping it from oscillating. So once the selected time period has been reached, the output at S2 stays high and ICl does not oscillate. S1 provides a reset function. When S1 is closed, pin 11 of IC2 is pulled high. This resets all its outputs low. This turns off Ql and allows ICl to oscillate. The O. lµF capacitor connected to pin 11 also provides a "power on" reset function. When power is first applied, the O. lµF capacitor is effectively a short circuit so that pin 11 is pulled high for a short period, to allow reset to occur. Trimpots VRl and VR2 are provided for fine adjustment of the time period. SAFETY WATCH Safety Watch will be an occasional feature in SILICON CHIP drawing attention to issues of electrical safety in the workshop and home. Electric shavers should be checked Electric shavers are so reliable that it is easy to become blase. The power cord should be very carefully examined from time to time to check for any cracks in the insulation. After all, remember that these appliances are used in wet environments and so the possibility of a shock from a cracked power cord is high. If the cord shorts, there is also the danger of burns. In one case, the power cord was found to have a serious break in the insulation of the removeable 2-pin female plug. The cord was normally wrapped around the shaver after each use and so the crack was hidden in a permanent bend in the reinforced section of the plug. There is no satisfactory repair for this situation. Do not attempt to tape it over as further flexing will lead to breaks in the insulation of both conductors and ultimately they will short. The cord must be replaced and the faulty cord disposed of. The same comments apply to other appliances which use removeable cords; eg, cassette players and radios. OCT0BER1988 71 Brand new ~ 240V50Hz Synchronous Motors CLEAR STYRENE UTILITY BOX This water clear box consists of two matching halves . Overall dimensions (both halves) are 63(L) x 40(W) x 25(D)mm. The boxes are Ideal for storing small components or housing ve,y small projects. As they are clear they would, for example, make a good housing for a photo llash trigger. Low cost and limited quantities. We have made a SCOOP PURCHASE of Double Pole Squirrel Cage motors with rubber shock moue.:lng plate (which can be removed if necessary.) The motor is supplied with an on-off switch (also removable) and features a 4mm diametm hard steel drive shaft, 21 mm long (with mounting plate removed). These motors are Ideal for fans or when reduced, in applications requiring a Cat.HB-6065 4 ~~•,":,r f;:,lii. i. • ' / • 4 "> :,1., r, : ~ .. for $1.00 iflRlU/fJ© ~~!M~/fJ ifO©!M :B~c;.-~N" • BICENTENNIAL LIGHTS WHAT A FLOP! We really believed everybody would jump at the chance to illuminate their gardens. But nol So, they have got to go. 12 volt operated, 6 metres long, 20 lamps. See our ads July for full details. WAS$49.95 Out they go at $29.95 1/2ANRCA LEAD? Well, not quite. These are a stereo lead, (figure 8 shielded) with two RCA plugs on one end and tinned stripped leads on the other. Leads with 2 RCA plugs on both ends sell for $4.95. Cat. WA-1040 ONLY$1.95 10+ $1.75 each RUGt SAVINGS 41®® mm.W G JENJEIB.&i.IL JFUJIBJF(O)§JE A UJII» II(0) A.IMCJF IffiihlB?.<GAIIN Completely built, this module measures 63 x 35mm, has a high input irrpedance and high gain. Runs on 9V and requires a 15 ohm load. Supplied with full specs and data. Made In England! Cat. M-0292 ONLY$3.95 10+ $3.50 each We have a small quantity of 15 ohm 5" x 4" speakers to suit. Otherwise just use two 8 ohm speakers in series. Cat. AS-3013 $3.95 ZENER DIODE BARGAINS BARGAIN No.1 1 watt Pkt 25 12 volt Cat. ZR-1370 $2.95 SAVE $5.80 BARGAIN No.2 6 volt 500mW Pkt 50 Cat. ZR-1372 $2.50 SAVE $10 NORMALL V $29.95 NOW Tonearm cable. Yes, we've finally n able to locate a small quantity of core tonearm cable. This cable is · led together and total diameter is $14.95 CLOCK MOVEMENT WITH BUILT-IN PENDULUM DRIVER This module measures 87mm long x 55 wide x 35mm deep and uses 1 x AA battery. Clock movement Is supplied with 3 sets of hands, and pendulum Is a suspended arm within the module which swings back and forth. A suitable pendulum can be attached to the bottom of the arm. Flt your own custom dock face. Great for novel applications. WAS $22.95 Cat. XC-0103 NOW $16 · · . SAVE $6. TRANSFORMER BARGAIN ULTRA THIN SHIELDED CABLE This 100VA unit measuring 1D0(H) x 90( x 75(D)mm features a rrounting bracket that enables you to mount rt vertical or on its side. Primary winding is tapped from 200-240 volts. Secondaries are 1 x 16V. 1 x 12V. Both would be minimum 2 amps. Cat. MM-1812 Qualtty English made shielded cable with a total diameter of 1mm. Ideal for screened wiring in small spaces I Packet 5 metres WAS $14 SAVE $5 NOW $9 Jaycar 12V/ .,,-1> 300VA SINE ~~ WAVE Inverter NOW AVAILABLE wave• and this unit gives a genuine 300VA, not less. The Jaycar Sine Wave Inverter has tremendous surge capab ilny. It will, for example, stan a small refrigerator. We are very proud ol this Aust ralian made and designed product. The price, however, may have to rise soon, so · hurry! Cat. Ml-5020 $399 SALE 01 I/; ~ ;;;;;; ,._ (~ "' 'I!) Chassis mount socket on bakelite with . ____________ Features Mylar drivers, sponge earpads, metal 3.5mm stereo plug. Cat. AA-202 1 WAS $29.50 Cat. WB -2310 NOW $17.95 SAVE39% SA880 Mylar drivers, freq . repon se GREEN RECTANGULAR 20Hz-25kHz. Quality muff pads . LED BARGAIN Cat. AA-2022 NORMALLY 40C each WAS $39.50 OCTOBER PRICE 1-10 20eea 11-99 16eea 100-999 14e ea 1000+ 12eea including taxi Cat. ZD-1765 NOW $24.50 ~~ , . OCTOBER SPECIAL # Cat. TH-189 1 ~ fl//1)~ 1 fi ( ~ 1 125mm flush cutters Cat. TH-1892 / $7.95 -~ SAVE$2 POINTED TWEEZERS / / SAVE $1 / 1 11' QN_L ~ 1.95 tSi\l""""ll;i(~f) /1 t__lfv®~~ ' 1 -' ~ economy plug . NOW $39.50 SAVE 34°/4 For full details see our catalogue. SAVE 38% ~ ..-~ " JUST ARRIVED QUALITY NIPPERS $7.95 SAVE$2 WAS$59.50 -«\._~~ ---------■.,,,,"fiW!i.,1/ 211%11~7!:.■.. Cat. TH-1765 RCA SOCKET Top of the range, excellent sound. Qualtty phones. Cat. AA-2023 ONLY $2.50 130mm wire nippers Now you can enjoy SIN E WAVE power at AROUND 85% EFFICIENCY for much the same cost as inferior square HEADPHONES SA888 Similar to those used on those expensive gold audio leads. Clearly marked in red or black. RED Cat. PP-0236 BLACK Cat. PP-0237 Now ~ou can have _all the benefits of t~~; g~e~r ~~:sJ;;~~~~e~\mport is durable, stylish and compact, measur- $3.50 ea 1O+ $3.20 each WIRE WRAP KYNAR WIRE ON SPOOLS We have been after this for years, and have finally lound it. It's high quality SILVER PLATED (other companies sell wire wh ich isn ot silver pl<)ted) on 50 foot spools. Available in 4 colours. RED Cat. WW-4340 BLACK Cat. WW-4341 BLUE Cat. WW-4342 ing only 110mm in total length. It simply plugs directly into the cigarette lighter socKet in your car. lt can generate large amounts of negative ions 1or purifying air , and scme ozone for eliminating odour. Jaycar's direct importing cuts out the middle man and saves you money. SPECIAL INTRODUCTORY OFFER ONLY $34.95 Cat. YX-2910 / ONL'?$s."so/ ~ NORMALLY 36i ea 1/2 PRICE ;- · _· _' _ 10 FOR $1 SAVE 73% PLASTIC · W { ·-';' · per reel 1/2 PRICE FEET -~ ~ ..Th•a•t·s•o•nly•1•3•ep•e•rf•oo•tl---CIGARETTE PLUG amps, Ideal for turntables, speakers, large etc. Easy mounting wtth one 4 mm USUALLY $1 .20 OCTOBER SPECIAL 60i ea diameter bolt or self tapper. Diameter 35mm at base. USUALLY SSC ea ocTOBER ONLY 1O+ 35C ea BA CK AGAIN! White Cone Midrange Our rrost popular midrange. Large sealed back wtth extra clear crsip midrange. 110mm, 80 watts RMS power handling, 95dB sensitivtty, 10oz magnet, freq ."resp. 31 Hz - 7kHz, resonant freq. 310Hz. ' Cat. CM-2080 1986 PR ICE eat your heart out Dickll ONLY $22.50 Polypropylene Cone Midrange We've been able to lower our price on our high power midrange. Black Poly cone. Huge 10oz magnet. 5" diameter. Specifications: Power handling 100 watts RMS system Resonant Freq. 570Hz Sensitivity 96dB Freq. Rasp. 570Hz - 7kHz Cat. CM-2085 $24.95 r . ; . . ; ~ ~ 40i each Cat. HP-0830 Build ·;our own, or use for spares. Oualtty Japanese made DPDT push on/ push off switch rated at 125V 3 amp. Complete with black round knob. These are commonly used as on!off power switches fo r mains products, and normally cost about $4 • $5. Javcar has a quantity availam:e for only $t.95. Cat. SP-0730 $1.95 ea WAS $6.95 NOW $4.95 SAVE $2 Cat. KJ-7100 10+ $1.75 ea 12V CAR ANALOGUE CLOCK MOVEMENT "P<at> <at>[}{][Ml ~ □ L'Zl ®Wl~©~[Q) ©<at>~~ FOR THE PRICE OF ECONOMY COAX Yes. for a short time only, you can purchase HIGH QUALITY air spaced 75 ohm coax for the same price as our economy 75 ohm cable. Normally tts $1.20 per metre, but you can buy it for only 80e per metre. Or, ~ you buy 50 metres or more, it's only 60e metre. That's half price! ao;~;tre 50m or more 60t metre ~ u MASSIVE SCOOP PURCHASE! Grab a quartz crystal car clock wtth a set of automotive style hands at a price that will astonish you I Once a'gain our suppliers huge loss is your gain! Convert that broken/unreliable or inaccurate mechanical clock in your car to space age precision I ade in West Germany by VDO, the odule measures roughly 45 x 38 x 40 ep. The compact size virtual ly sures that nwill fit in any space! ntit strict! limited! A JAYCAR/SILICON CHIP EXCLUSIVE KIT .P LASMA DISCHARGE DISPLAY Ref: Silicon Chip August 1988 Jaycar and Silicon Chip have combined to produce a low cost but spectacular plasma discharge display. At the heart of the kit is an exclusive rare-earth gas chamber specially made for this kit. This gas chamber is specifically designed to produce a spectacular red, violet and orange continuously moving light show. It's like nothing on earth I You will absolutely amaze your friends and family. The Jaycar kit of this project includes the rar&-earth chamber, mounting plinth, EHT transformer and inverter electronics. A 2-3 arrp 12V DC power supply is required. (A battery charger is ideal). You can have this 9Xclusive kit, complete for the amaz ing low price of only $2991 Call in to one of our stores for a demol Cat. KC-5035 SA VE $26.50 on 500MHz Frequency Counter Kit Ref: EA Dec 81/Feb 82 For October only you can purchase the 50MHz frequency counter kit at $169.50 and for an extra $20 we will supply the 500M Hz prescaler (worth $46.50). This represents excellent value. Counter Kit KA-1390 $169.50 Prescaler KA 1392 $46.50 NORMALLY $216.0 BUY BOTH FOR ONLY $189.50 SAVE $26.50 ~r' l)l(flAtFREJJJJfNCY/PfRIODMiTtf< NEW LOW PRICE $229 "'"'"' SAVE $70 Saving s made because of mass production of this sensational product! '(• NOW $79 July/Aug MODEM KJT Normal Price $379.00 Power Supply $49.95 $428.95 $199 • SAVE AN AMAZING $22 BUY BOTH FOR ONLY Cat. KE-4715/4716 . ',._ I . "'' i~. cj) CLOCK MOVEMENTS WITH BUILT-IN MELODY MODULE ~~ ~ ~ WAs $99 PASSIVE INFRA RED DETECTOR - PRICE BREAKTHROUGH It had to happen II Jaycar was the first to offer pulse count P IR's and lately we were the first to offer pulse count for less than $100. We are proud to announce another first in PIR's. A QU ALITY PIA FOR ONLY $69.95 FULL PRICE Sure, you are probably thinking "but what about the quality and reliability" . There's nothing worse than an alarm system that false triggers, you know the old story about the boy who cried wolf. We have extensively tested the units and have no doubt about their quallty and operation ability. Features & Specifications • Dual element pyroelectric sensor • 24 dual element detection zones in three :ayers • Wide angle 90" multi layer coverage • 12 metre range • Operation voltage 7.5 · 16V DC • Tamper protected • LED Indication • Size 65(H) x 84(W) x 46(D)mm • Colour beige • Relay output ~ • 3 month guarantee ~ Cat. LA-5017 ONLY $69.95 $30 LESS THAN ANY PIR WE KNOW OF .t,- ~~~ " • irrpedance input unit measuring to well over 50MHz. All parts mount on the one PCB. The Jaycar kit includes case, front panel and all specffied parts. Cat. KA-1 702 ~= f" WAS$299 LOW COST 50MHz 4 DIGIT DIGIT AL FREQUENCY METER 'f:: 6 ~~~:::i~u;~~ hly ~ sensitive, high Y:>. ET/ ~eg:JiC:C~5JNTELLIGENT s~.,.c ~ ',l"-w'" ~-,1,"''I•' · CATALOGUE '·~~-~--· 132 pages of electronic goodies. Hyou don, have our catalogue or if you've lost It call in to any of our showrooms for a free copy. (And a lollie if you have to wait). OR send a large SAE to PO Box 185 Concord 2137 and we'll post you one. 6.3 VOLT MES GLOBES Don1 miss this bargain. OEM's Bruce Routley (02) 747 2022. NORMALLV 50~ THIS MONTH 4 for $1.00 10 for $2.00 . CARUNGFORD . OPEN 'TIL 2pm SAT • 0.1 MONOLITHIC :J■i ----------TOP SHOPPING AT JAYCAR CAP SALE We have available a pack of 0.1 monolithic capacitors with short leads at a very special price. The leads vary from 1.5mm long to 5mm long. The 1.5mm are fust long enough to go through a circuit board. ONLY $7.95 for 100 NORMALLY $16.50 per 100 Cat. RC-5496 I'! Jaycar will purchase your surplus stocks of components and equipment. We are continually on the lookout for sources of prime quallty merchandise. CALL GARY JOHNSTON OR BRUCE ROUTLEY NOW ON (02) 747 2022 These are widely used In Personal computers. Sorry about the price, but thes are genuine European plugs. They are so new the Asians haven, copied them yet. Cat. PP-4007 $14.95 Outdoor Irifra Red .Motion Detector Ideal for both residential and commercial appllca.tlona, Completely seff contained an easy to Install. Designed to mount directly to a standard round junction box. The unit wtll autorTIP•lcally turn on two floodlights when someone walks within th detector range. Ideal security system to protect loved ones and property. Delectlo range Is 40 feet long by 60 feet wtde. Ugh wtll stay on for a mlnlmum of 1o seconds up to 15 minutes (adjustable). Works only at night. Globes not supplied. cat. LA-5132 ONLY$139 FM TRANSMITTER (l\flNI l\flTTER) Refer: Silicon Chip October 1988 Listen to your compact discs playing at home on your Walkmanl This project transmitts the input signal on FM which can be picked up by the FM radio in a Walkman. Uses one IC and delivers about 200 microwatts. Full kit. Cat. KC-5041 ONLY $29.95 POWERMATE2 Refer: EA October 1988 Revamped version of original Powermate power supply. Delivers clean, crisp regulated 13.8V DC at up to 5 amps. Full kit. Cat. KA-1707 $119 1GHz DIGITAL FREQUENCY KIT Complete kit. $299 Cat. KC-5013 I I 100WATT AMP MODULE UTILISING POLYSWITCH IC: :J '2 If f_,t:,;:! u ~, • SPEAKER PROTECTION Silicon Ch ip December 1987 .':' r.j"'•t-, . •Refer: Kit includes PCB, all components r v,.,•-· , ONLY $39.50 480/100 Capacitor discharge gn ltion system for - - - - y o u r car 4 9 cat. KE- s o Playmaster/Jaycar 60/60 Blueprint Amp $79.50 ~E ~A ~ D~E~L~U~X~E..C~A1111R ~ ALARM $369 Hundreds sold. See our 1988 catalogue for full details. $89.50 • 300/300 full duplex plus 12oon5 half duplex Cat. KM-3046 .ACTIVE 'DIRECT INJECTION " DI BOX Full of features. See our 1988 catalogue for full details. Cat. KA-1690 $34.50 DIGITAL CAPACITANCE METER $85 POWER SUPPLY TO SUIT Cat. KE-4048 $29.50 TRANSFORMER , Ref: EA August 1985 • Checks values from 1pF to 99.99uF over 3 ranges Cat. KA-1695 $33. Cat. MF-1095 ' UNIVERSAL SPEED CONTROL ·« ,_ ' __ ... •.\Oi _:;.~•- · q Control • eleclric drills, fans. electric blankets, lamp dimmers , soldering irons. PC board pre-built. Full kit only. ~~~' ~t • ~• ~ - - -~_!__I_ V/SA : F· !MasterCard. --- '., 100 watt module Cat. KE-4052 1 .. •<• . I. $21.50 Cat. KA-1652 .SUPER SIMPLE MODEM $27 .50 r: Tests transistors, SCR's and diodes. Cat. KA -1119 Cat. KA-1550 STILL AVAILABLE 480/50 50 wait module ! PULSE SHAPED CDI $8.95 Cat. KE-4050 ~ See our 1988 catalogue for full details $38.95 FABULOUS ETl480 AMP MODULES IN CIRCUIT ~·.,_ •• TRANSISTOR .., i 1.., f • TESTER i ; •• -< ' Cat. KS-6502 (less polyswitch) and heatsink bracket. Cat. KC -5019 Polyswitch to suit Cat. RN-3418 ONE OCTAVE EQUALISER MODULE 10 band graphic equaliser module with 10 slider pots S $ Cat. KM-3064 AVE 5 NOW $54.95 •. Handy Teslf"f ··sYNTOM" DRUM SYNTHESIS · ~ ~ -~ HEAD OFFICE 115 Parramatta Road Concord 2137 Telephone (02) 747 2022 Telex 72293 FACSIMILE (02) 744 0767 MAIL ORDER VIA YOUR MAIL ORDERS PO Box 185 Concord 2137 HOTLINE (02) 7471888 FOR ORDERS ONLY TOLLFREE (008) 022 888 fr POST & PACKING - - $9.99 s 2.00 S24.99 S 3.75 $49.99 S 4.50 $50 $99.99 S 6.50 OVER St00 St0.00 SS $10 $25 ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY - CITY 117YorkSt. (02)2671614Mon-Fri 8.30 · 5.30 Thurs 8.30 pm • Sat 9 • t2 GORE HILL t88 Pacific Hwy cnr Bellevue Ave (02) 439 4799. Mon-Fri 9 - 5.30 Sat 9. 4pm CARLINGFORD Cnr. Carlingford & Pennant Hills Rd (02) 872 4444. Mon-Fri 9 • 5.30 Thurs 8.30 pm· Sat 9 · 2pm BURANDA OLD 144 Logan Rd (07) 3930777 Mon-Fri 9. 5.30 Thurs 8.30 • Sat 9 - 12 115Parramatta Rd (02)7453077 · Mon-Fri 8.30 · 5.30 · Sat 8.30 · 12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 • 5.30 Fri 8.30 · Sat 9 • 12 121 Forest Rd (02) 570 7000 · Mon-Fri 9 . 5.30 Thurs 8.30 pm· Sat 9 · 12 SPRINGVALE VIC 887-889 Springvale Road Mu/grave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 . 5.30 Fri 8.30 • Sat 9 · 12 ! CONCORD HURSTVILLE THE EVOLUTION OF ELECTRIC RAILWAYS Of all Australian railways, the Queensland system has in recent years been the most innovative. Its significant achievements include the introduction of a powerful new electric locomotive, a triple bogie unit rated at 2.9MW. Electric locomotive design began in Europe 85 years ago using a single motor and rod-drive copied from steam locomotives. These proved to be immensely strong but incapable of high speeds because of the long fixed chassis mounting the driving wheels. Accordingly the two-bogie type was introduced where each axle is 76 SILICON CHIP driven by its own motor. To obtain sufficient pulling power for freight service, three driven axles (six driving wheels) per bogie were used. Locomotives using two six-wheel bogies have been constructed using six traction motors, with a total power up to 10,000HP (7.46MW). This wheel arrangement is known in Australia, USA and Europe as the Co-Co type. "C" indicates three driven axles per bogie and "o" means that no non-driven wheels exist. In Switzerland the Re6/6 nomenclature would be used instead, where "R" indicates high speed capability, "e" stands for electric and 6/6 shows that there are six driven axles out of a total of six. The Co-Co design has reigned supreme worldwide for all heavy service but it does present problems, particularly on the winding narrow guage (3 feet 6 inches, 1067mm) tracks which make up the Queensland rail system. There are two particular problems: (1). On tight curves the 3-axle bogies incur considerable friction between wheel flanges and the rail inside edge. Wear on both the rails FACING PAGE: CUT-AWAY drawing of a 3000-class triple-bogie locomotive. A lot of equipment is included in the body, including a large transformer ◄ which steps down the 25kV AC overhead supply. (Drawing courtesy Clyde/ASEA- Walkers). and the wheel flanges can be high. (2). The long bogies also cause considerable track deflection which means that maintenance to the permanent way is a constant problem. These two problems could be solved if 2-axle (Bo-Bo) locomotives were used but the greater axle loading could not be tolerated on Queensland's light tracks. The BoBo design also presents a problem in that for a given loco weight, less tractive effort is available before wheel slip is encountered, than for a Co-Co design. Built by Clyde/ASEA-Walkers, this powerful new 2.9MW electric locomotive was the first of a new generation for Queensland Railways. The triple 2-axle bogies allow the loco to negotiate tight curves and give less track deflection than a conventional Co-Co design. Tri-ho locomotives The solution was a really innovative design involving a Bo-BoBo design - that's right, three 2-axle bogies, sometimes called a Tri-Bo configuration. This has one 2-axle bogie at each end of the loco and one in the middle. To allow the loco to negotiate curves, the end bogies swivel as you'd expect while the middle bogie slides from side to side under the loco chassis. This permits the wheels of the centre bogie to self-align with the track for minimum sideways friction. The centre bogie carries one 'third of the total weight, with flexible cables joining the traction motors to the control circuits in the body above. Maximum sideways deflection on the centre bogie, on the tightest curves, is ± 200mm from the centre-line of the loco chassis. With twelve wheels, all driven, six traction motors and short bogie wheelbase, many locomotive designers see this type as ideal. For a given loco weight, it has the same axle loading and tractive effort as a Co-Co design but it has the advantage that each bogie carries only one third of the locomotive weight (rather than half in a Bo-Bo or CoCo design). This point is important in the design of short bridges and culverts. Before electrification, the Queens- RE DTE CONTROL EQUIPMENT ELii'ffllit'rcs CUBICLE Fig.1: this diagram shows how the major equipment is arranged inside the new Queensland Railways 3000 class locomotives. The two end bogies pivot in the normal way while the centre bogies can move sideways by 20cm in either direction to enable the loco to traverse curves. land Railways were transporting over one million tonnes of coal each week from huge open-cut mines in the Blair Athol, German Creek, Curragh and Blackwater districts. From there, the coal was hauled to the ports of Gladestone, Dalrymple Bay and Hay Point, for shipment to the world. Record tonnages were being hauled by the coal trains, pulled by up to six diesel electric locomotives. Each loco was rated at 1.65MW giving a total of 9.9MW (13,270HP) per train. Their huge consumption of diesel fuel was a prime factor in the decision by the Queensland Government to electrify all the state's coal lines. Queensland Railways engineers then faced a number of important questions: (1). What axle loading (weight per axle) and weight per bogie can be withstood by the track, bridges and track bed? (2). What tractive effort and power would be needed in each loco and how many locomotives to use per train? (3). What electrical system to use, what voltage, frequency, AC or DC, and what type of control? (4). Can the one locomotive design perform all the required tasks: express passenger, heavy coal and freight trains? High voltage AC Because of the long distances over 1490km of track was to be OCTOBER 1988 77 ELECTRIC RAILWAYS - CTD electrified - a single phase 25kV AC 50Hz system was adopted. With 25kV AC used on the overhead contact wire, the necessary track substations can be spaced at large intervals. To further reduce the current (and voltage drop) the QR system uses an arrangement of 50kV feeder cables to supply centre-tapped trackside transformers. These produce the 25kV supply for the train overhead contact wire. The 50kV AC feeder supply is derived from the State Electricity Commission's 132kV 3-phase supply fed to substations spaced at about 50km intervals. Locomotive manufacture The State government split the contract for manufacture of the electric locomotives between two Australian companies. The Clyde/ ASEA-Walkers group is building 70 locos, to be known as the 3500 class, at their Maryborough works. Comeng (Commonwealth Engineering) is building the remaining 76 locomotives, to be called the 3100 class, at their Salisbury engineering works. As all locos have the same major specifications, the two classes together are conjointly called the " 3000 class". Both classes make use of microprocessors and high power gate-turn-off thyristors (GTOs) to control the traction motors. Each loco carries a 4.5MV A transformer which steps down the 25kV overhead wire supply to several fixed voltages between 400 and 800 volts with lower voltages for controls and auxiliaries. Each locomotive is equipped with six 495kW (664hp) direct current motors. These are four pole compound wound with compensator windings and interpoles. The whole locomotive is therefore rated at 2.9MW continuous power at the rail. These are geared for a maximum speed of 80km/hour and can produce a continuous 260kN of tractive effort at 40km/hour or a maximum short time rated starting tractive effort of 375kN (84,000lb). The Clyde/ASEA-Walkers group are using ASEA motors while the Comeng company use Hitachi. The motors have series field windings to maximise starting torque and separately excited low voltage shunt field windings to achieve precision control. Bogies Each of the three bogie frames is fabricated from structural steel with critical control and inspection of all welds to ensure long life free of fatigue problems. Primary suspension is by chevrons of rubber which are backed up by helical spring secondary suspension. These afford good isolation of motors and body from track irregularities and vibrations. Traction rods transmit acceleration and braking forces from the bogies to the body. The complete bogie design is vital to the achievement of minimum axle-to-axle weight transfer during acceleration. This allows both motors in each bogie to be driven equally hard without one wheel pair slipping. Thus maximum tractive effort for a given loco weight can be achieved. GTO thyristors As already mentioned, the Queensland 3000 class are controlled by GTO thyristors. Fig.2 shows the essential circuit for the motor controls. Each motor armature is fed by two series phase controlled thyristor bridges connected in series. Each thyistor bridge is fed from a secondary winding on the main transformer. Another secondary winding supplies another thyristor bridge for The Comeng 3100 class is similar to the Clyde/ASEA-Walkers 3500 class but uses Hitachi motors instead of ASEA motors. Comeng is building 76 of these Tri-Bo locomotives at its Salisbury works. 78 SILICON CHIP 25kVAC SDHz DYNAMIC BRAKING RESISTOR REPEAT TRACTION MOTORS 4,5,6 REPEAT MOTORS 2 AND 3 11 OVDC SUPPLY TD MICROPROCESSORS, CONTROL, BRAKES, CRITICAL FUNCTIONS -----1 + 'T' DYNAMIC BRAKING BATTERY CHARGER 110v: SERIES FIELD MOTOR No.1 ..J.. -:; SHUNT AELDS MOTORS 4,5,6 AUXILIARY SUPPLY 3-PHASE 415VAC SOHz ----------''W------TD S NT MoTt:s 2 FlEJ-~s3 , ---------------------------,-\-----SEPARATELY EXCITED SHUNT FIELD MOTOR No.1 WHEEL RAIL Fig.2 partial schematic of the electrical system within the 3000 class locos. SCR chopper circuits are used to control the power to the six traction motors. The locos have dynamic braking but do not employ regeneration to put power back in the grid. the shunt field windings of all traction motors. The phase control signals are derived from microprocessors which take into account the acceleration or braking demands from the driver. The main thyristors are cooled by forced oil flow in , the Clyde/ASEAW alkers locomotives while forced air cooling is used in the ComengHitachi versions. Electrical power for the microprocessors, controlling electronics, running lights and other vital functions comes from the onboard l lODC battery supply. Brakes In formulating the concept of a locomotive for heavy-haul freight, general freight and also passenger service, the designers had little scope for innovation in brake design. Dynamic braking can certainly be provided . on the locomotive, saving wear on brake blocks throughout the train, but for final stopping and emergency use full air brakes are needed. As the new locos will haul both new and old rolling stock, standard air brake systems must be provided. To allow for multiple operation of locomotives by one driver, the braking controls are mounted in a separate rack in the loco and remotely controlled by pneumatic lines from either driver's cab. For dynamic braking, as Fig.2 shows, the armatures of the traction motors are disconnected from the thyristor bridges and connected to heavy duty low resistance braking resistors. The traction motors now act as DC generators, with the degree of braking controlled by the power applied to the shunt field windings. Multiple operation Up to six locos may be used on heavy coal trains with three locos at the front and three near the middle. These coal trains can be up to 2km long! Control for two or three head-end locomotives from any driver's cabin is via a 44-wire cable connecting the adjacent locomotives. Control for the three locos a kilometre away in the middle of the train is by LOCOTROL II, an ingenious radio control system which we will investigate in a later episode of this series. While every locomotive is fitted with a driver's cab at each end, only 39 locos are equipped as command units with LOCOTROL sending equipment. Creep control The maximum tractive effort a locomotive can exert depends on: (1). The total motor power. (2). The gear ratio from armature shaft to axle. (3). The percentage adhesion of the wheel-rail contact; which depends on the wheel and rail surfaces and the weight on each wheel. The QR 3000 class electric locomotives have about the maximum motor power and gear ratio for the weight per axle allowed by the track. Apart from applying sand to the rails, one way to maximise adhesion is to improve the wheelrail surfaces. The polished wheel OCT0BER1988 79 Other auxiliaries include cabin airconditioning, blower fan motors (for traction motor cooling), cooling oil pumps for · the main transformer, thyristor cooling and air compressors for train air brakes. These pumps and blowers are driven by 3-phase 415 volt AC induction motors. The 3-phase 415V AC supply is derived from a single phase to 3-phase converter driven by an extra secondary winding on the main single phase transformer. Comeng have used a rotary machine consisting of a phase motor driving a 3-phase alternator which is hung beneath the loco cab. The Clyde/ASEA-Walkers' locos use a solid-state 3-phase converter instead. Results Clyde/ASEA-Walkers is building 70 of the new 3500 class electric locomotives at its Maryborough works. This photo shows two partially completed bodies. surface resulting from the use of composition brake blocks tends to cause wheel slip. Over the last few years great advances have been made in minimising wheel slip in locomotives and thereby maximising tractive effort. This is called " creep control". It also has the benefit of keeping both driving wheel and rail steel surfaces in the best condition for maximum adhesion. In essence creep control is an automatic control system which makes the loco driving wheels travel up to 5 % faster than the forward speed of the train. This is referred to as "5% creep". Creep also has the effect of continually grinding the loco wheels on the rails so that the wheel contact surfaces remain clean but not polished. Such a surface ensures maximum wheelrail adhesion. Experience has shown that 5% creep is an optimum figure. If more creep is allowed the driving wheels will tend to slip, and produce less tractive effort. Naturally, when less than maximum tractive effort is required, the creep value will be less, as set by the control system. 80 SILICON CHIP To maintain creep at the critical value of 5 % , ASEA has provided radar equipment below the locomotive, to measure true ground speed. Also a tachogenerator measures axle rpm. This then gives a true comparison of wheel periphery speed and rail speed. If the wheel periphery speed is more than 5 % faster than rail speed, the traction motor armature current feedback signal is increased by the creep controller. This feedback retards the phase of the trigger signal for the GTO thyristors supplying armature current, hence reducing motor current and torque to bring the creep back to a figure of 5% . Should the creep be less than 5 % the reverse action increases motor current and speed to regain the optimum creep. Microprocessors do the control functions. Auxiliaries Essential auxiliaries such as the phase control circuits of the GTO thyristor bridges, running lights and emergency lighting are powered by a 110V DC lead-acid battery slung under the loco body. The first loco built, No.3501, rolled out of the Maryborough workshops on Thursday 29 May 1986 and was operating between Rockhampton and Gladstone by 6 September 1986. The first electrically hauled coal train ran in May 1987. The whole electrification program including the main line from Caboolture to Rockhampton and the coal lines in four stages will cost one billion dollars . This money will eventually be repaid by the achievement of faster running times with resultant greater use of wagons, increased revenue and huge savings in diesel oil. These electric locomotives a re eminently successful, with 10,000 tonne trains being hauled by six locomotives at considerably higher speeds than could be achieved by the previous diesel electric locos. Footnote While the 3000 series are the first large order of Tri-Bo locos to be ordered by an Australian railway system and one of the few Tri-Bo classes in the world, the first Australian Tri-Bo loco was the 8650 delivered to the NSW system in October 1985. This was a test bed for the triple-bogie arrangement used in the 3000 class, as built by Comeng. The rest of the 50-strong 8600 class NSW DC electric locos have conventional Co-Co bogies. ~ Silicon Chip Back Issues Issue Highlights November 1987: Car Stereo in Your Horne; 1GHz Frequency Meter; Capacitance Adapter tor DMMs. 1987: 1 00W Power Amplifier Module; Passive lntrared Sensor tor Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. December January 1988:~ 'Ci:ll11'100Wtie UHF Antenn · ly; CustolS Adapter t l!JlcGI wer Suppmger; Subcarrier M Tuners. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of · File Indicator tor Modems; Simple Door Minder; Low Ohms Adapter tor Multimeters. March 1988: Remote Switch tor Car Alarms; Telephone Line Grabber; Low Cost Function Generator; Endless Loop Tape Player. April 1988: Walkaround Throttle tor Model Railroads; pH Meter tor Swim· ming Pools; Slave Flash Trigger; Headphone Amplifier tor CD Players. May 1988: Optical Tachometer tor Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm; Restoring Vintage Radio Receivers. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Automatic Light Controller; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show; Tone Burst Source tor Amplifier Testing. 1988: Build a Plasma Display; Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. August September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; Switchmode Charger tor 12V Gel Batteries; Vader Voice. BACK ISSUES ORDER FORM Please send me a back issue tor: D November 1987 D December 1987 D February 1988 D March 1988 D August 1 988 D May 1 988 D June 1 988 D July 1 988 D April 1988 D Sept.1988 Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard Card No I~~~~~~~~~~~~~~~~~ Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_/_/_ _ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ __ _ _ _ _ _ _ _ _ _ Postcode____ D Visa Card Price: $A5.00 each (includes postage): Overseas orders add $A 1.00 per issue tor postage. NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 L - - - - - - - - - - - - - - - - - - - - - - - - -·- - - - - - - - - - - - - . . . . J OCT0BER1988 81 Our range of DATAK products has proved enormously successful: small wonder, this quality product, made in the USA, makes virtually every aspect of PCB making a breeze. Below are just some of the DATAK products - many reduced to tempt you to try them! ·Etch Resist Pen Dry Transfers DATAK PCB designing and Remember the pen we used to sell? We stopped selling it_ when we found out the resist was a deadly poison (others still sell it!). The DATAK etch resist pen is a non-nasty, highly effective way to make one-off PCB's. Cat N-5180 DATAK make some great transfers. To whet your appetite (no, Lucretia, you don't eat them) here are two. . SAMPLER ASSORTMENT, containing 17 different sheets. A 5766 ~~~rter pack. Cat N95 S ~- NOW 16 Datak Burnishing Tool: Save $3 TARGETS & REGISTERS, containing 40 different pcb & crosshair registration marks for precision alignment. Cat N-5820 ~ You'll need one of these if you're at all serious about making PCB's. Cat N-5715 NOW s4es UNIVERSAL OIL PATTERNS, allowing you to make any OIL pattern up to 40 leads. 48 in pack. Cat N-5768 s1495 Datak Contact Frame: Datak Circuit Fix It Kit: Save $13 Eventually, you'll get a PCB that's RS. Fix it with Cricuit Fix Kit. Pure Copper traces & donuts with adhesive backing, readY. to repair a PCB or modify a new one. Great for developers too. Cat N-5900 Save $6 ~~~~ii~~~~~t exclusive to Dick You've asked for them: an economic range of tapes, pads, lettering and so on for designing PCB patterns, marking panels and so on. Here they are! TITLES, LABELS, NUMBERS ETC• A great range of w~rdmg re;dy for your front panel or other marking applications Dry transfer lettering simply rub over them with a suitable burnisher (such as a ball point pen). Audio, TV & HI Fi Five sheets containing titles for the above applications plus one letter/ number sheet. Available in Black (Cat N-5753) or White (Cat N-5754) Amateur Radio & TV Similar to above, five sheets to pack, with letter/number sheet. Black (Cat N-5755) White (Cat N-5756) Test & Industrial Equipment Completing the set: 5 sheets for CRO's, meters, analysers, etc etc. Yep, you'll need one of these Also includes letter/number sheet. too. If you're serious, that is. Black (Cat N-5757) White (Cat N-5758) Beats the old sheet'o glass and 95 two books routine anytime. Cat ALL ABOVE SETS: N-5710 s8 Was$35.95 DIAL MARKINGS, SCALES, PATTERNS, PANEL & METER Marks & Switch Patterns Three sheets of assorted arrows, lines, switch graduations, numbers, etc in both Black and White. Cat N-5750 95 set s11 NEED EXTRA POWER? As we get more and more electrical products, we have less and less spare outlets. Dick Smith Electronics solves your power point problems - without going to the expense of having extra outlets installed! Click Spacesaver Double Adaptors Not like four old ones: these fit flush on the power point to _creat~. a d~~ble power point from a single. I you already have a double power point, you can fit the twin Spacesavers to make a 4-way outlet! Single Spacesaver Double Adaptor Resist These Bargains? Unlikely! DATAK quality resist products to make your PCB making a breeze. They're also refills for the DATAK PCB kit Developer Resist Filter N-5905 N-5907 N-5711 Was $11.95 Was $18.95 Was $10.95 Now $9.95 Now $15.95 Now $6.95 {SID ....,.,,, IIESHIY LIQUID ~ .:~·•;""!.,~ -==· film Processing Chemical Pack Photo-sensitive polyester film suitable for laying out PCB patterns in pos or neg format. 6 sheets 125 x 150mm. Cat N-5705 Film developer and fixer pos/ neg him, or for replacement pack for PCB kit Cat N-5909 Was $11.00 Now s995 s14 PCB Making Materials Datak precision tapes, pads and donuts perfect for commercial as well as hobbyist pcb pattern preparation. Available in various sizes as listed: TAPES - precision slit highly flexible crepe. .031in (N-5780) .080in (N-5786) .040in (N-5782) .093in (N-5788) .062in (N-5784) .125in (N-5790) ~~~~NE s395 ea ,DONUTS - precision cut donuts · to accurately match tape. 380 donuts in each pack, all .031in OD on 0.2in x 0.3in centres :~~~:~ = All one price .125in 00- N-5774 s-425 15 5775 · 0in OD - NPATTERNS - Various styles suit most applications. T0-18 Pattern (3 pin), 144 in set. Cat N-5760 84 Jg·~-m~rn (3 pin). in set. 32 set ~1 pack, in 16 Pin OIL pack, narrow pads. 32 in set Cat N-5765 •A 25 k All one Price: ... gg ~:m~ pack ~-if~ paC ""o"'w•a"'v"'a"'ila'■.'b■.'te"'a"lt"ll!'"'51!0""',es111■:--------■-•------•----- Fit to both the left and right outlets of a double power point to turn It into a 4-way outlet on the wall Ideal for stereo systems, computers, etc etc Cat P-5-'-44""4_ _ __ Fits to a single outlet or to the nght hand outlet of a double, extends to the nght hand side cat P-5442 s395 s7es ---...~~~~~:=,=!~:!;, " ~ ,:_l} ~~ea,J,,,;;;;;;,,j.JI How about a bit of protection? If you're running sensitive equipment, (computers, video & TV, etc) you should know that spikes or surges on the mains can damage or even destroy it, or destroy hours or days of work on disk! The Surgebuster series of mains suppression filters virtually eliminate these surges: in fact, they're so sure of themselves they offer $5000 FREE INSURANCE COVER against voltage spikes or power surges I Click Single Power Point Protector The Surgebuster Junior plugs into any outlet and protects any device or devices plugged into it. Don't forget the $5000 free insurance cover is included! Cat P-5617 s4ges Click Surgebuster &-Way Board The best of both worlds: a six way power board - with all oullets on that board protected against surges or spikes. It's also overload protected. And yes, it too comes with the $5000 insurance cover Cat P-6515 '5995 TIME FOR A NEW TV ANTENNA? How were the Olympics? Twenty runners in each heat? Two high-jumpers on the bar at once? You need a new antenna! Dick Smith Electronics has a huge range of antennas - there's one right for your area (ask for free, helpful advice at your nearest store). Here's just a small sample: Band IV and V Suburban VHF It's a great all-round performer for the typical suburban home (regardless of city). Easy ~o erect, good fib ratio and very good value for money. .----"Cat L-4022 S6S95 - What a performer! Covers all UHF channels, so if you've got both bands we've got you covered! Butterfly elements, · gold anodised / finish for long ,,. • long life. ,,. Cat L-4084 sgg ~ ~~~~e!r!r~~ Meter Dial Markings Four sheets with dial plate arcs & graduations to let you customise any meter movement. Suits meter radii from 25 to 125mm. Black only. Cat_N-5752 50 set taEV/! Twin Pack Spacesavers ~y~u~e~n ~!p~I~! chances are you only want channel 28 UHF. This band IV , antenna Is pertect - and It wont break the bank! Cat L-4082 '65 band V stations (which include most l~cal area translators). High gain easy to erect Cat L-4080 '5995 - Accessories, Too: Barge Board Mount: Easy way of getting the antenna up from a vertical surface. Catl-4150 Short Mount: Designed to hold vertical masts. 28cm long, with saddle clamp. Cat L-4152 Longer Mount: As above, but 69cm long to clear eves, etc. With saddle clamp. carL-4153 Mast Section: 2.4m galvanised pipe for mounting antenna. 27.5mm diam. Cat L-4156 Telescopic Mast: 4.8m galvanised telescoping mast for that extra height. Cat L-4157 Saddle Clamp: 90 degree V-block and U-bolt assembly for holding mast to mount, antenna to mast, etc. Cat L-4165 2-way Splitter: Inside splitter for running two TV's from one antenna. Suits 300 Ohm cable. s495 Cat L-4218 4-way Splitter: As above, but for running up to 4 TV's from one antenna. For high signal levels. Cat L-4220 ~~hm: Use with coax cable installations for running 2 TV's. Inside use only. 2 ~Jhm: As above, allowing 4 sets from one antenna. Suitable for strong signal levels. 4 Baluns: Used for converting 300 ohm system to 75 ohm and vice versa (eg coaxial lead to an old TV with 300 ohm antenna inputs). •2"5 Universal: Inside use only. Cat L-4456 Outside: Protected from the elements. Cat L-4465 Masthead Diplexer: Combines the signals from UHF and VHF antennas, allowing one cable ~;ft!/ t_f~J ;:dn~~:i~~:~: Used where TV set has only one antenna input but VHF and UHF antennas need to be connected. cat L-4476 TVI Filter: High-Pass filter for VHF & UHF TV, eliminates or reduces interference from CB, HF amateur, etc. Cat L-4475 • N SW• Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 6 71 7722 • Bondi Junction 38 71444 • Brookvale (Warringah Mall) 905 0441 • CampbeHtown (046)27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • MaiUand 33 7866 • Miranda 525 2722 • NewcasUe 611896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 •ACT• Fyshwick 80 4944 •VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 4281614 • Ringwood8795338 • Springvale5470522 • QLD • Brisbane City 229 9377• Buranda 3916233 • Cairns 311 515 • Chennside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide Ctly 2321200 • Bevet1ey 3471900 • St. Marya 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • FremanUe 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 811977 NOW AVAILABLE AT ALL STORES - OR CALL TOLL FREE: (008) 22 6610 FOR HOME DELIVERY! IT'S STILL OUT THERE ... Yes! You could still find a $1000 bonus ii you're the lucky customer who purchases the One Millionth Fun Way Kill At time of going to press it was still out there, somewhere on a shell in a Dick Smith Electronics store (or possibly even in DSXpress, the Mail Order Centre). No questions, no qualifications: ii you buy the lucky one millionth kit, you'll win the prize: $1000 worth of any products from your Dick Smith Electronics store. NEW! GENUINE CANNON CONNECTORS Butane "Pencil" Blowtorch Soldering, silver soldering, glass bending, heatshrinking, even small brazing - they're all easy with this superb little tool. Butane powered (standard cig lighter refills) with controllable flame down to near pin-prick. All in a tiny (200mm long x 13mm diam) hand-held torch. Cat T-1380 Why take the risk with cheap imitations? Genuine Cannon Connectors for Audio & mains use wi ll see you right - and won't let you down when the going gets tough! s1495 Mains Rated (fully approved ½ Price Superstand for mains use) AXR-LNE-12 AXR-LNE-32 AXR-LNE-31 AXR-LNE-31 LINE PLUG P-1627 $9.95 PANEL PLUG P-1629 $7 ,50 PANEL SOCKET P-1630 $7 .95 LINE SOCKET P-1631 $9.50 THE ONE MILLIONTH FUNWAY KIT WITH $1000 BONUS! s12s5 Hobbyists - repair shops - labs assembly benches - if there's one item your bench really needs, this is IT! Heavy cast base with stands for Soldering Iron (complete with spiral), solder rol AND an adjustable vice with 360 degree, rotation for holding and turning pcb s One of our most ~ o p u l a r stands - our bulk buying OJ saves you money Cat T-5700 12V Tester High Power Audio Ran!e (ideal f Or Speaker COnnectOrS, efc AXR-PDN-12W LINE PLUG P-1632 $10.50 AXR-PDN-11suNE socKETP-1634$9.95 AXR-PDN-31W PANEL SOCKET P-1636 $7.50 SAVE ON SWITCHES! Mercury Switch ~ WAS s69 96 NOW ON•'Y s3495 • L <at> 125V AC 3A. Ideal for projects or automotive Now 5 175 '119 Standard DPDT Ji yr No, not literally - only the price. When you want the best in performance/noise/weight/size ratio, you cannot go past a toroidal transfomer. And now both of these are reduced $10! Hurry - limited stocks at this price! use. Standard toggle with on/off indicator plate. Ill CatS-1215 ~ 45+45V<at> 3.3A plus 15+ 15V (ideal high power amplifiers) Was $1 95 ~ Cat M-1600 Tilt mount switch SPOT. Essentially a movement detecting switch. Low Same as above but 1!_ 1 current applications. Ideal double pole/double for bike and car alarms, throw. Cat S-1216·; ~ etc. Cat S-1935 ~ • • Was $3. 95 NOW 5295 - TOROIDAL TRANSFORMERS Standard SPST SLASHED AXR-PDN-14B PANELPLUG P-1638 $8.50 SOS: ~ Was $2.25 NOW s1 75 What a Bargain Manufacturer's Error: You reap the benefit! Quality Bit Blitzer "121" Internal Modems, fully guaranteed and in perfect working order, around $100+ less than you'd expect to pay. Cat X-3304 .. . ONLY s199 NOW IN STOCK. We've raved about these in our catalogue. We've told you how fantastic they are - now they're in stock so you cand find out for yourself! AC Voltage detectors which don't rely on contact - so they're S-A-F-E! About the size of a small marker pen, perfect for electricians, maintenance people. hobbyists, everyone! First shipment is almost sold out! Cat Q-1530 Was $79.95 NOW ONLY S69 95 35+35V<at> 2.2A plus 15+15V (ideal medium power amplifiers) Cat M-1602 Was $69.95 NOW ONLY s59 95 CHEAP CASE! Another beauty: this one's for auto cable testing. Actually pierces the insulation without removing cables, gives no go/maybe/good indication with 3 leds. Also tests HT pulses from distributoL Look at the price! Cat a-2000 795 Was $9.95 NOW S NEW! No Frills Multimeter Most hobbyists need two multimeters: their good bench meter (often a digital) and a cheapie - one that can take the rough and tumble, and doesn't cost a fortune. This one's the latter category: but for the low low pr1ce you get a great 10k/v meter with 18 ranges including 2 battery check seales. Includes probes. Cat Q-1015 s2495 Huge range of moving coil and digital multimeters from only $17.95 .· Hobbyist CRO We made thousands of these cases to suit our low cost amplifier. To many! Our loss is your gain: we've slashed the price to_ move Most hobbyists need a CRO excess stock. They make great cases for virtually any pro1ect: most don't have one. Once simply put the front panel on to suit yourself and WOW! Cat H-2900 you've used a CRO you'll how you got on without W $ 34 95 ~~ 11 wonder it! This one won't break the bank, but gives a usable o response to beyond 6.5MHz • ideal for most users. Try it: you'll like it! Cat 0-1280 as , $2795 NOW ~ ---·· ___,,,. GET INTO SCANNING! s399 175XL Mobile 1OOXL Handheld 60 Meg Probes Coloured Here's a value-packed set of Test Clips probes for CRO use. Multiple What a great hobby: no licences or qualifications required, and you can start straight away with these superb Bearcat Scanners! Hurry! Stock won't last long at this crazy price! 101 Key Keyboard The cheapest around - but there's no loss of quality! Superb "Alps" keyswitches for reliability, ideal for most IBM compatible computers. Cat X-3821 Covers all popular bands, with 16 channel memory to store your favourite frequencies. 12 volt operated, comes with AC Adaptor to use at home. Cat D-2812 S369 s149 Our most popular 16 channel memory, covers 9 bands between 66 and 512MHz. Complete with rechargeable NiCad batteries and charger! Cat D-2813 s399 MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: • NSW • Arlll411t: Sound Components 72 4981 • Ballina: Ballina Electronics 86 7022 • Bownl: F.R.H. Electrical 611861 • Broken Hill: Hobbies & Electronics 88 4098 • Cllarltslown: Newtronics 43 9600 • Cliffs H1r1lot1r: Coifs Harbour Electronics 52 5684 • Ou~bo: Chris's Hi-Fi 82 8711 • Fonler: Forster Village Electronics 54 5006 • Glen lnaes: John Sommerlad Electronics 32 3661 • Griflilh: Miatronics 62 4534 • lnvenll: Lyn Willing Electronics 221821 • Li111on: Decro Electronics Services 21 4137 • Moree: Moree Electronics 52 3458 ofll1N1111: Head ware 72 3895 • Nown: Nowra Electronics 21 4979 • Wqga: Phillips Electronics 21 6558 • VIC • Morwlll: Morwell Electronics 34 6133 • Slllpparton: Phillips Electronics Pty. Ltd. 21 9497 • W1rrn1"1bool: Marrtronics 62 9870 •OLD• BIN1111ni: Bob Elkin Electronics 72 1785 • Kinprey: Holmes Today Electronics 62 1658 • Klwana: Splitec 94 7349 • Mlcuy: Stevens tlectronics 511723 • Mlryboroqh: Keller Electronics 21 4559 •SA• M16I1111iitr: Hutchessons Communications Centre 25 0400 •WA• Allllny: Micro Electronics 41 2077 • Genldlon: Batavia Lighting & Electrical 231842 • Klrn1'1: Dave's Oscitronics 85 4836 • TAS • Dtvonport: A.I. Electronics & Hobbies 24 8322 piece set, with x1x10 switch, 60MHz bandwidth all in a handy plastic pouch. ~ Cat Q-1247 .;0 If you're birdsnesting or even doing a lot of circuit testing, these multi-coloured test clips are great. Mini size, come in a variety of colours. And they're near hall price this month! Cat W-4588 Normally 95c ea NOW ONLY 5Oceach AMATEUR RADIO By GARRY CRATT, VK2YBX How to convert a CB radio to the 28MHz amateur band It's easy to convert a CB radio to the 28MHz amateur band. Just build and fit this simple oscillator circuit for 40 channel operation on AM or SSB. One of the main problems confronting the amateur operator when it comes to multi-band operation is the cost of multiple transceivers to cover every band. In particular, transceivers for the 10-metre (28MHz) band are expensive. But there is another way convert a low-cost 2 7MHz CB transceiver to do the job. While this task may appear to be quite daunting, it's really fairly straightforward. All you have to do is fit the simple oscillator circuit described here and perform a few circuit tweaks. The converted transceiver can be used for novice operation on 10-metres or for driving a transverter (ie, a frequency converter) for operation on the VHF or UHF bands. A 40-channel CB transceiver capable of SSB operation is an ideal candidate for conversion to 28MHz operation. These transceivers were imported in vast quantities so their prices are much lower than equivalent amateur-band models. CLARIFIER AND AMISSB OFFSETS 5.12MHz 10.24MHz -101--1.-~ VCO = 16.27MHz (CH 1) TO 16.71MHz (CH 40) CHANNEL SELECT PLUS SSB OFFSETS +N = 91 (CH 1) TO 135 (CH 40) DOWNMIX INPUTS = 0.91MHz (CH 1) TO 1.35MHz (CH 40) 10.695MHz AM 10.6975MHz LSB 10.6925MHz USB Tc, AM/SSB OFFSETS Fig.1: the Uniden AX 144 uses phase locked loop (PLL) frequency synthesis to set the output frequency. To change the band of operation, the tripler is disabled and a signal from an external oscillator injected into the PLL mixer. 84 SILICON CHIP As well, they were made to meet stringent DOTC regulations, thus guaranteeing reasonable quality. For this project, we chose to convert a Uniden AX 144 SSB transceiver which retails for around $329. However, many other late-model SSB transceivers employ similar circuitry and could be modified just as easily. PLL tuning Fig.1 shows the block diagram of the transceiver. As can be seen, the unit uses phase locked loop (PLL) frequency synthesis to select a precise 40-channel segment in the 27MHz band (26 .965MHz to 27.405MHz). What we have to do is change this to a 40-channel segment of the 28MHz band. The first thing to note is that the frequency bandwidth of t he transceiver is fixed at 440kHz (ie, 27 .405MHz to 26.965MHz). This means that it's not possible to cover the full 28MHz band. A good compromise, for either 10-metre or transverter operation, is to convert the unit to operate from 28.285MHz to 28.725MHz. OK, so we've now selected the frequency segment in which we wish to operate. We now have to decide how to convert the transceiver to this higher frequency segment. What we have to do is increase the VCO frequency, as set by the PLL, by a fixed amount on each channel. Because of the way in which the PLL and the VCO operate, the easiest way to do this is to change the frequency that's normally fed RB 100{) r---......---....--'¥1~-0+BV REG. 3xBA244 OR SIM. D1 R1 3.3k CS 10pF -----111--oOUTPUT .,. B L1,L2,L3 : 12T 25 B&S ENAMELLED COPPER WIRE CLOSE WOUND ON FERRITE SLUG EOC VIEWED FROM BELOW Fig.2: the external oscillator circuit is a Colpitts type with diode switching to vary the output frequency. Either AM, LSB or USB operation can be selected by switching the corresponding input to + 8V. from the P11 to the P11 mixer via the tripler. As Fig.1 shows, the P11 generates a 5.12MHz signal by dividing the 10.240MHz reference oscillator frequency by two. This 5.12MHz signal is then externally tripled to 15.36MHz and mixed with the VCO frequency to give a control frequency for the P11. This control frequency is simply the difference between the tripler and VCO output frequencies. In normal CB mode, the VCO frequency ranges from 16.27MHz (Ch.1) to 16.71MHz (Ch.40) and so the control frequency ranges from 0.91MHz to 1.35MHz. Note that the VCO output is also fed to both the transmit and receive mixers. To change the band of operation we simply disable the 5.12MHz tripler and inject a suitable (higher) mixing frequency into the P11 mixer from an external oscillator. This oscillator must incorporate some method of frequency compensation to allow for USB and 1SB operation, as well as AM operation. Oscillator circuit Fig.2 shows the circuit of our oscillator. It is a Colpitts type employing diode switching to vary the amount of inductance in series with the crystal (Xl). The nominal frequency is set by crystal Xl but is modified according to whether 11 , 12 or 13 are switched in. The mode switching function is achieved by conveniently utilising the 8-volt output from the mode switch on the front panel of the transceiver. Thus, for 1SB operation, the mode switch connects the 1SB input of the oscillator to + 8V. This forward biases D1 and connects 11C1 to the crystal. The AM and USB modes are selected in exactly the same fashion. Crystal frequency So much for the basic oscillator circuit. We now have to calculate the crystal frequency (Xr) required to give us the desired frequency band. To do that, we use the following equation: Xr = 15.36MHz + (N x 0.44)MHz where N equals the number of 440kHz band segments above the original CB band. In this case, we have to move the frequency band up by 1.32MHz (ie, N = 3). Thus: Xr = 15.36 + 1.32 = 16.68MHz. It is necessary to add 2.5kHz to this figure to allow for USB operation. This is because the series inductors in the circuit only allow the oscillator frequency to be reduced. Thus, the final crystal frequency becomes 16.6825MHz. Construction The circuit is built on a small printed circuit board coded 06210881 and measuring 53 x 35mm. Fig.3 shows how to install the parts. You can install the parts in any order you like although the three coils are best left until last. Keep all component leads as short as possible and push the transistor all the way down onto the board before soldering its leads. The three coils are all wound using 12 turns of 25 B&S enamelled copper wire on an F14 ferrite slug. This gives an inductance of 5-l0µH, depending on the position of the ferrite slug. Clean and tin the enammelled copper wire leads before soldering the coils to the PCB. It is a good idea to check the oscillator for correct operation before fitting it to the transceiver. use-~,.,....,,_ .._, AM----:rrs:;-·,._"'_,,"-"'l " ..,, "-..,.r~= LSB +BV REG. Fig.3: keep the leads as short as possible when installing the parts on the PCB. Fig.4: you can use this full-size artwork to make your own printed circuit board. OCT0BER1988 85 PARTS LIST 1 PCB, code 06210881, 53 x 35mm 1 16.6825MHz crystal, 30pF parallel cut, Hy-Q code GE05E, OC49 holder 1 BC548 NPN transistor 3 BA244 or similar switching diodes 3 F14 ferrite slugs Capacitors 1 1 1 1 1 1 1 .01 µF ceramic 330pF ceramic 1 OOpF ceramic 82pF ceramic 39pF ceramic 18pF ceramic 1 OpF ceramic Resistors (0.25W, 5%) 2 X 22k0, 3 X 3.3k0, 1 1 x 1 kO, 1 x 1000 This view shows bow the oscillator board was mounted in the Uniden AX 144 transceiver. The AM, LSB and USB inputs are connected to the mode switch pins on the PCB at the front of the chassis (top right). L12 470uH R93 22k C96 ... .047r This is easily done by checking the output with an oscilloscope, frequency counter or HF receiver. Of course, you will have to strap the AM select input temporarily to the positive supply so that the circuit will oscillate continuously. If everything checks out OK, adjust L2 for an output frequency of 16.680MHz. The LSB and USB modes should then be selected and 86 SILICON CHIP Fig.5: to disable the tripler, you simply lift one end of C73 (marked with a cross). The output from the external oscillator is then fed into C73 and L14 adjusted to give PLL lock on the new band. Ll and L3 adjusted for output frequencies of 16.6775MHz and 16.6825MHz respectively. These adjustments will interact slightly but don't worry too much at this stage - we'll adjust the oscillator more accurately later on. Fitting the oscillator The location of the oscillator board is not critical, although care X 2.2k0, Miscellaneous Hookup wire, 25 B&S enamelled copper wire for coils. should be taken to ensure that it is clear of the speaker when the transceiver is reassembled. It can be secured by soldering a piece of heavy guage tinned copper wire from the earth foil to an adjacent metal can on the main transceiver PCB. The + 8V regulated DC rail is available on pin 11 of the PLL chip. The next step is to locate the 5.12MHz output from the PLL and disconnect it from the tripler circuit. Fig.5 shows the location on the AX-144 transceiver. In this case, the 5.12MHz output appears on pin 10 of the PLL (IC2) and is fed to the tripler circuit (113) via C72 and thence to the PLL mixer (TR19) via C73. To disconnect the tripled PLL signal, you simply lift one end of C73 (marked with a cross on Fig.3). The output from the external oscillator is then coupled to the PLL mixer (TR19) via C73. Installation can now be completed by wiring the "mode select" inputs on the oscillator to the back of the mode switch. This will automatically select the correct 2.5kHz oscillator offsets when USB and LSB are selected. Fortunately, the mode switch connections are easily accessible on the PCB runn- Table 1: Channel Frequencies Channel 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Old Frequency 26 .965 26.975 26.985 27.005 27.015 27 .025 27.035 27.055 27 .065 27.075 27 .085 27.105 27 .115 27 .125 27 .135 27 .155 27 .165 27.175 27.185 27 .205 27 .215 27.225 27 .255 27 .235 27.245 27 .265 27 .275 27 .285 27.295 27.305 27.315 27 .325 27.335 27.345 27.355 27.365 27.375 27 .385 27.395 27.405 ing along the front of the transceiver. They can be identified by checking for the presence of + 8V on each of the terminals, when the appropriate mode is selected. Adjustments A few adjustments are necessary to ensure correct operation. The first step is to adjust the VCO to give PLL lock on the new band of frequencies. This is done by monitoring the DC voltage at test point 2 (see Fig.5) and adjusting L14 for 4.5 volts when channel 40 is selected. New Frequency 28.285 28.295 28.305 28.325 28.335 28.345 28.355 28.37528.385 28.395 28.405 28.425 28.435 28.445 28.455 28 .475 28 .485 28.495 28.505 28.525 28.535 28.545 28.575 28.555 28.565. 28.585 28.595 28.605 28.615 28 .625 28 .635 28 .645 28.655 28 .665 28.675 28.685 28 .695 28 .705 28.715 28.725 Once PLL lock has been achieved, L2 on the oscillator board should be adjusted to set the CHl output frequency to 28.285MHz. To set the USB and LSB offsets, the transmitter should be modulated with a lkHz tone and L3 and Ll on the oscillator board adjusted to give 28.286MHz on USB and 28.284MHz on LSB. These adjustments may interact so it is wise to run through the alignment procedure several times. Finally, the receiver sections prior to the IF stages should be realigned for optimum performance, as should the driver and output stages of the transmitter. This is best done by referring to the service manual for the transmitter. Where to get the parts The 16.6825MHz crystal is available from Hy-Q International, 1 Rosella St, Frankston, 3199. Telephone (03) 783 9611. The cost is $25.23 post paid. Be sure to specify full details as set out in the parts list. BA244 switching diodes or similar can be obtained from Dick Smith Electronics Kit Department (PO Box 321, North Ryde, 2113), or from VSI Electronics, 16 Dickson Avenue, Artarmon 2064; phone (02) 439 8622. F14 ferrite slugs are available from Neosid Pty Ltd, 23 Percival St, Lilyfield, 2040; phone (02) 660 4566. Service manuals for the AX144 CB transceiver can be obtained from the importer, Santronic Corporation Pty Ltd, 27 Garema Crescent, Kingsgrove, 2208; Phone (02) 599 3355. 16 PRODUCT SAFETY RECALL DICK SMITH ELECTRONICS PTY. LTD. NOTICE TO ALL CUSTOMERS TEMPERATURE CONTROLLED SOLDERING STATION Cat T-2000 Sold in all states, may constitute a safety risk as the power switch in some units has been found to be incorrectly wired . The units which may be affected are fitted with a meter having a white, translucent background and bear the legend "AUST DES REG NO 86081" on the front nameplate below the temperature control. Customers are asked to return this product as a matter of urgency to the nearest Dick Sm ith Electronics Store for immediate attention to the problem. We apologise for any inconvenience caused. Further enquiries may be made by contacting Rex Callaghan, Technical Services Division on (02) 888 3200. OCT0BER1988 87 BOOKSHELF Dynamo Design & Construction The Homebuilt Dynamo, by Alfred T. Forbes. Published 1987 by ToddForbes Publishing, Oratia, Auckland, New Zealand. Hard covers, 307 x 220mm, 182 pages, with over 300 illustrations. ISBN O 95977 49 0 4. Price $85.00. Many people in remote areas are looking for alternatives to mains power from the local supply authority. Often the connection is just too expensive or they want to be completely self-sufficient. Whatever the reason, there is always a need for books on how to generate your own power, hence this book. It is a practical step-by-step guide to building a large low speed alternator. You may wonder why anybody would bother to build an alternator when automotive and truck alternators are available so · cheaply. The author explains that automotive alternators require a relatively high shaft speed before they will generate any useful power. His low speed alternator is intended for use with windmills or THE HOMEBUILT DYNAMO DYNAMO DESIGN and CONSTRUCTION WITH CERAMIC MAGNETS AN OAIG!N.6:L MOOULAR DESIGN BASED ON PRACTICAL EXPffi!ENCE byAJfred1:Fottm A P!Ctu«I Diary Of Step.by-Step C00$tructk>n ofaLD#SpeedGeneratorMdtlO'N lthasbeenpullOuse water turbines which run at low speed. He then goes to describe in great detail, with the aid of hundreds of photographs and diagrams, how ,he made an alternator with an output of about 1000 watts. However, it is not a conventional alternator. It uses high power ceramic magnets instead of rotor coils and these act against individual wound stator coils, all connected via bridge rectifiers to a common output. The resulting 28kg alternator no doubt works and the author makes claims of high attained efficiency. The only problem is that it is not a explanatory text is minimal. At the low cover price they are worth looking at. They are available from all Tandy stores. Mini Notebooks From Tandy Engineer's Mini-Notebook: Op Amp IC Circuits, 48pp, $2.69; Digital Logic Circuits, 48pp, $2.69; Communications Projects, 48pp, $2.69; Optoelectronics Circuits, 48pp, $2.69; 555 Timer IC Circuits, 32pp, $1. 79; Basic Semiconductor Circuits, 48pp, $2.69. All written by Forrest M. Mims III. Published by Radio Shack. Soft covers, 135 x 210mm. This is a handy series of six notebooks which present a small aspect of electronics in a stylised form; ie, in hand-printed form with circuits sketched rather than drafted. In this form it may seem 88 SILICON CHIP practical alternator for charging any sort of battery-powered lighting system. Because it uses ceramic magnets in the rotor, the usual method of output voltage regulation, by varying the field current, is not possible. Hence, as is normal for any uncontrolled generator or alternator, the voltage output roughly doubles for a doubling in shaft speed. Nevertheless, you must admire the grit and determination of anyone who undertakes such a project. It must have taken hundreds of hours, as just about every step was done with the aid of simple hand tools. He even describes the process of cutting ceramic magnets with a hand-powered diamond saw, as well as making a magnetiser powered by a bank of 4700µF 75V capacitors charged by handpowered dynamo. He also shows how to precisely cut thousands of stator laminations with a jig using a pair of tin-snips ! Our copy of the book came direct from the author in New Zealand. It is available via airmail for $A85.00. See the classified ad section in the back of this issue. Towers' IC Substitution Books less daunting to the beginner. Certainly, with all but one of these booklets being only 48 pages, they don't take long to read through. They can be regarded as a useful source of circuit ideas although the amount of supporting Tower's International Digital IC Selector; Towers' International Op Amp Linear IC Selector. Both priced at $29.95 from Jaycar stores. These two books were reviewed in our June 1988 issue. They were wrongly stated as being available from Dick Smith Electronics stores. They are available from Jaycar stores. We apologise to the corn- · parries concerned and to readers for any inconvenience. wpoD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C NEW COMTESTERS NOW AVAILABLE 1. 2. 3. 4. 5. 6. Tip Heater holder Filter p ipe Filtetcam idge F ilt91" removing 1..,er Suction / Hot air change lr.,er 7. Thermo sensor control 8 . Electric outlet cord 9. Cleaning pin ~ G Q:: C) IJ.. Cl C) ~ ~ :i: CJ Q:: C) IJ.. Cl C) ~ NEW DESOLDERING GUN The SC-5000 gun incorporates a motorised diaphragm pump. There are no tubes or separate compressors. A built-in thermo sensor circuit controls the 60W ceramic heater to ensure rapid warm-up. Exact temperature control prevents damage to sensitive circuitry. The gun can also be used as a hot blow tool. $399.00 ex tax ($479.50 inc tax) Optional Stand $18.00 Contact Geoff for all your semiconductor and IC requirements. Our range Is constantly expanding. Always remember to call "Wood for Chips!" HIGH QUALITY SILICONE RUBBER LEADS ~ No more pungent smells when your iron touches on a test lead. These are the best in the business from HCK. Super flexible and we now have the new 2mm sizes available. Who else offers such a comprehensive range of test leads? :i: CJ Q:: C) IJ.. _. Cl C) ~ ~ :i: CJ Q:: C) I I ~ <-· ,__,_, COMTEST CT 212 and CT225 are the basic tools for testing and troubleshooting RS-232 interfaces. They ease installation and verify the proper operation of the most widely accepted interface between computers modems etc. Small sized and self contained both can be easily used with data comms devices and computers. Both offer many features not found on other testers such as clear and logical layout of the face-plate , a unique Ground Potential Difference Test function and optional Three level bidirectional Current Loop Test, Pulse detect and battery check. FUNCTIONS • Breakout Box • Interface Signal Monitor • Signal Simulation • Ground Potential Difference Test e Cable Testing (Model CT225 only) • Parallel Interface Testing (Model CT225 only) • Pulse Trap - Optional (P.T./C.L.) • Current Loop Test - Optional(P.T/ C.L.) Price Ex Tax Inc Tax Corniest GT 212 $250.00 $285.00 Corniest CT225 $365.00 $415.00 Corniest P.T./C.L. $ 70.00 $ 80.00 Tax exe~ price& are only available where official tax ex&l'Tl>"" tion certificate giving Name. Address and Tax Nun-ber is provided at time of ordering. SILICONE LEADS TO SUIT 2mm FITTINGS HCK-MS101 2mm RED 1m 7.70 HCK-MS102 2mm BLK 2m 7.70 2mm FITTINGS HCK-8234-1 2mm RED HOOK CLIP 3.00 HCK-8234-2 2mm BLK HOOK CLIP 3.00 HCK-9217-1 2mm RED STKBL PLUG1 .85 HCK-9217-2 2mm BLK STKBL PLUG 1.85 HCK-9225-1 2mm RED TEST PROD 2. 70 HCK-9225-2 2mm BLK TEST PROD 2.70 HCK-9229-1 2mm RED TWEEZERS10.60 HCK-9229-2 2mm BLK TWEEZERS 10.60 IJ.. g ~ ~ ~ Q:: C) IJ.. Cl C) ~ ~ G Q:: C) IJ.. Cl C) ~ SILICONE LEADS TO SUIT 4mm FITTINGS HCK-9014-1 HCK-9014-2 HCK-9016-1 HCK-9016-2 HCK-9024-1 HCK-9024-2 HCK-9026-1 HCK-9026-2 HCK-9112-1 4mm RED STGHT 1m 4mm BLK STGHT 1m 4mmREDRIA1m 4mmBLKRIA 1m 4mm RED STGHT 1m 4mm BLK STGHT 1m 4mm RED RIA 1m 4mmBLKRIA 1m 4mm RED SFTY 1m 11.40 11 .40 12.10 12.10 12.25 12.25 12.80 12.80 4.75 FEATURES Breakout Switches Probe Points Probes DB25 Connectors Model Indicators Fixed Floating Weight Case 4mm BLK SFTY 1m 4.75 4mm RED SFTY RIA 1m4.75 4mm BLK SFTY RIA 1m 4.75 4mm BLK 16A 0.5m 6.85 4mm RED 16A 0.5m 6.85 4mm BLU 16A 0.5m 6.85 4mm YEL 16A 0.5m 6.85 6.85 4mm YEL 16A 0.5m 4mm VIO 16A 0.5m 6.85 4mm BLK 16A 1m 8.70 8.70 4mm RED 16A 1m 8.70 4mm BLU 16A 1m 8.70 4mm YEL 16A 1m 8.70 4mm GAN 16A 1m 8.70 4mm VIO 16A 1m 4mm BLK 16A 1.5m 10.45 4mm RED 16A 1.5m 10.45 4mm BLU 16A 1.5m 10.45 4mm YEL 16A 1.5m 10.45 4mm GRN 16A 1.5m 10.45 4mm VIO 16A 1.5m 10.45 1 1 26 52 1 9V battery 145 X 40 X 90 (Wx H x D) 240g Clamshell LED's total Power Dimensions HCK-9120-1 HCK-9120-2 HCK-9123-1 HCK-9123-2 HCK-9209-1 HCK-9209-2 HCK-921 0-1 HCK-9210-2 HCK-9206-1 HCK-9206-2 HCK-9116-1 HCK-91 16-2 HCK-91 19-1 HCK-91 19-2 HCK-91 24-1 HCK-9124-2 HCK-921 4-1 HCK-921 4-2 HCK-9132-1 HCK-9132-2 HCK-9205-1 HCK-9205-2 HCK-9203-1 4mm FITTINGS HCK-9203-2 4mm/2mm RED ADPTR 1.80 HCK-9230-1 HCK-9227-1 4mm/2mm BLK ADPTR 1.80 HCK-9230-2 HCK-9227-2 HCK-9112-2 HCK-9113-1 HCK-9113-2 HCK-S051 HCK-S052 HCK-S053 HCK-S054 HCK-S055 HCK-S056 HCK-S101 HCK-S102 HCK-S103 HCK-S104 HCK-S105 HCK-S106 HCK-S151 HCK-S152 HCK-S153 HCK-S154 HCK-S155 HCK-S156 25 50 12 terminated, length 15mm 2 one fixed , one free CT212 CT225 12 25 RD CLMP GRIP 50mm 10.60 BLK CLMP GRIP 50mm10.60 RED COUPLING XHK 1.50 BLK COUPLING XHK 1.50 RED CROCODILE 2A 2.70 BLK CROCODILE 2A 2.70 RED CROCODILE 15A 4.40 BLK CROCODILE 15A 4.40 RED HEX PROBE 3.00 4mm BLK HEX PROBE 3.00 4mm RED HOOK GRIP 9.50 4mm BLK HOOK GRIP 9.50 4mm RED JAW GRIP 14.50 4mm BLK JAW GRIP 14.50 4mm RED ADPTR XSA 3.00 4mm BLK ADPTR XSA 3.00 4mm RED PNL MT SKT 2.95 4mm BLK PNL MT SKT 2.95 4mm RED PNL TW SKT 3.50 4mm BLK PNL TW SKT 3.50 4mm RED SQ PROBE 2.70 4mm BLK SQ PROBE 2.70 4mm RED STKBL PLG 2.70 4mm BLK STKBL PLG 2. 70 4mm RED TWEEZERS10.60 4mm BLK TWEEZERS 10.60 GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road , (Corner Beatrice St. ) iNc INNsw Lane Cove West, N.S.W. P.O . Box 671, Lane Cove N .S.W. 2066 Telephone: (02) 4271676, Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $_5.00 to cover postal cha rges. Next day delivery in Sydney add $5.00. All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA , CHEQUES OR CASH CHEERFULL Y ACCEPTED ~ a .,, 0 a lJ ri :i: =;, V, I PRODUCT SHOWCASE I Escort EDM-55 digital multimeter Do you find ordinary digital multimeters. hard to use in some situations? It can be tricky to place probes on measurement points while looking at the reading. Here is a possible solution. The Escort EDM-55 is a small probe digital multimeter with a 3-1/2 digit liquid crystal display and a 6-position rotary function selector. It is auto-ranging (ie, no need to switch voltage, current or ohms ranges) and the readings can be held on the display by using the DH (data hold) button. The meter measures DC volts, AC volts, ohms, diode and continuity. DC volts can be measured in 5 ranges from 200mV to 500V. The 200mV range has 100µ V resolution with an accuracy of ± 2 % of reading plus 4 digits. The input impedance for this low range is an unbelievable lOOOMO. However, we were able to confirm that it is indeed lOOOMO. The 2V range has an accuracy of ± 0.7% of reading plus 4 digits and an input impedance of 1 lMO. The 20V, 200V and 500V ranges have accuracies of ± 1.3% of reading plus 4 digits, and lOMO input impedance. The AC function has 4 ranges from 2V to 500V. The accuracy is ± 2.3% of reading plus 8 digits with a frequency response of 40Hz to 500Hz. Input impedance is about lOMO for all ranges except for the 2V range which is 1 lMO. Resistance is measured in 6 ranges from 2000 to 20MO with accuracy of ± 2 % plus 4 digits for all ranges except for the 20MO range which is ± 10% plus 4 digits. Double layer capacitors for memory backup Where it is necessary, to power random accessory memory (RAM) while a computer is powered down, the designer essentially has two choices: a lithium or other expensive long life battery which will eventually need replacement or a high value double layer capacitor. For the latter approach, Murata have the AC 200 series of 5.5V ceramic double-layer capacitors (compatible with rµost microprocessor and TTL logic), with values ranging from 18,000µF to 100,000µF (or 0.018 to 0.1 Farad). To give an idea of their size, 90 SILICON CHIP The meter also checks diodes by displaying their forward voltage. Continuity measurement has a range of up to 2k0 and the buzzer sounds when the resistance is lower than 3000. The meter is protected against overvoltage to 700V for the DC and AC ranges and 250V for diode, resistance and continuity functions. Battery life from the two 76A camera cells is quoted at 80 hours. (A bit short; don't forget to turn it off). The batteries are included with the meter as well as an insulated long probe tip. The Escort EDM-55 is available from David Reid Electronics for $79. Phone (02) 267 1385. Single pole circuit breakers the AC 200 series O. lF measures only 12.5mm in diameter and 7mm in height. Other values are smaller, at 11 x 6.5mm, with 5mm pin spacings. For further information, contact the Australian distributor for Murata products, IRH Components, 32 Parramatta Road, Lidcombe, NSW 2141. Phone (02) 648 5455. With some equipment you just cannot help blowing fuses and it becomes expensive after a while. This can happen with power supplies or with new designs which are under development. The solution is to fit one or more of these thermal circuit breakers from Potter & Brumfield. They're Touch screens for personal computers Some people like them, others don't but they are becoming much more popular. What are we talking about? Touch screens for personal computers. In the past these have used an infrared grid or membrane immediately in front of the monitor screen. The new MicroTouch screen uses capacitive sensing. Each screen is made from a single sheet of glass with a resistive pattern bonded to its surface. This provides 1024 x 1024 touch points. The screen cannot be scratched by pens or sharp objects and is superior to plastic membrane screens in optical clarity and durability. The superior resolution of the MicroTouch screen allows the development of comprehensive menus via the supplied software. Among the programming tools are software-controlled or switch-set data formats, modes and parameter settings, and a full function intelligent auxiliary serial port. Software is available for IBM PC AT, XT and compatibles and for the Apple Macintosh. On the hardware side, there are two interface cards, an RS232C serial controller and an IBM PC bus controller. The Microtouch screen is available as a complete video monitor in kit form to be fitted to most monitors, from 23 to 68cm diagonal. Flat panel screens from 23cm to 168cm are also available. For further information on MicroTouch screens contact Paul Tenukest at Rand Walker Pty Ltd, 33/47 Neridah Street, Chatswood, NSW 2067. Phone (02) 419 2088. about the same size as a 3AG fuseholder . and clip-mount into a 16mm diameter hole. Priced at $7.80, they're available from Geoff Wood Electronics. Phone (02) 427 1676. Handy logic probe from Jaycar The HYT-07 Logic Tester is a pencil probe which is suitable for checking all logic families such as TTL, LS, CMOS etc. The unit includes a pulse/normal switch to indicate pulse or continuous signals. Three LEDs plus a small audio transducer provide the logic level indication. In the normal mode, a green LED indicates a logic LOW, a red LED indicates a logic HIGH and with both LEDs out, the probe voltage is between HIGH and LOW logic levels. The audio beeper gives a low note for a LOW and a high note for a (logical!). Pulses are indicated by a yellow LED which gives a 200ms flash for each pulse detected. The audio beeper also sounds briefly for each pulse. High or low-going pulses are indicated when the red or green HIGH LED flashes in sync with the yellow LED. The probe can detect pulse widths as narrow as 25ns and for frequencies to 20MHz. The HYT-07 Logic Tester is available from Jaycar Electronics, catalog number QT2210. OCT0BER1988 91 THE EQUIPMENT YOU NEED, AT BARGAIN PRICES! ECONOMY SOLDER SUCKER • • • • Light weight Sturdy construciion Easy to remove tip Excellent value for money ! Cat. T11271 $11.95 ECONOMY ANTISTATIC SOLDER SUCKER • • • • L=--"""""'-:j HUNG CHANG (RITRONJ 20 MHz DUAL TRACE OSCILLOSCOPE •Wide bandwidth and high sensitivity •Internal graticule rectangular bright CRT •Built in component tester •Front panel trace rotate, •TV video sync filter •Z axis (Intensity modulation) •High sensitivity X-Y mode •Very low power consumption •Regulated power supply circuit PORTASOL • Four~~Ps~~~~Po~~h. Hot Blow . Hot Knife • No Cords or batteries • Heavy duty. tip temperature adjustable up to 400°c . • Equivalent to 10-60 watts • Hard working . Average continuous use 90 mInuters • Refills in seconds • Powered by standard butane gas lighter fuel • Ran~e of easily replaceable screw tips mcluded • • Includes metal stand for the sotdenng iron when workmg • Cap features built-in flint for igniting Portasol tip • Includes snap case for storage Cat T12639 $89.95 Light weight Sturdy construction Easy to remove tip Excellent value for money! Cat. T11 281 $13.95 FREE POSTAGE FOR SILICON CHIP READERS THIS MONTH MINIMUM ORDER OF $50 APPLIES JUST QUOTE THIS ADVERTISEMENT f!l~~re ~2Y ~ 1~c~ l1~R!r ... • Sanding • Engraving • Grinding • Polishing • Cutting • Dnlling • Milling • Erasing . etc. Features : Operates on sale , low 12 volts from mains electricity via AC adaptor (s_upplied) . Light and easy to handle with touch switch and lock for ~~~~-ufgi~n~'.~~M~~:~~,r~r;mm holes In steel . 2 year guarantee Contents : • 12V Super Tool • Plugpack AC adaptor • 1 spherical milling cutter • 1 wire brush • 1 grinding wheel • 4 drill bits. 0.6, 0.8. 1.0. 1.2mm • Set of 5 chuck coHets • 6 eraser sticks • Instruction sheets Cat. Tt2300 $64.95 r.9.~~~~w ~~ufib~ PPRJ LL COMPONENT TESTER is the special circuit with which a single component or components in circui t can be easily tested. The display shows faults of components, size of a component value, and characteri stics of components. Thi s feature is ideal to troubl eshoot solid state circuits and components with no circuit power. Testing signal (AC Max 2 mA) is supplied from th e COMPONENT TEST IN termina l and the result of the test is fed back to the scope through the same test lead wire at the same time. motor, this lightweight (113gm) drill is ideal for many jobs. Perfect tor PCB work! Has a 0.8 to 1.2mm chuck and 1mm drill t}it Requires 12V 1 AMP.(usewith ~;?~~~302 ..... ~ b~ o~u9et ~or q~!ri~~unlike our opposition·s! 60/40 Resin cored Cat. No . Description Price T3t000 71mm250gm ..... $8.95 T31002 71 mm500gm .. $15.95 T3t010 .9tmm250gm ... $7.95 T310t2 91mm 500gm $14.95 T3 t 020 1.6mm 250gm .... $7 .50 T31022 1 6mm 500gm .. . $13.95 T31030 71mm 1 metre .. $1 .50 T31032 91mm 1 metre ... . $1.25 T310341 .6mmlmetre .... $1.00 RS232 BREAK OUT BOX A simple way o f monitoring RS232 mterface lead activity. Interface powered , pocket size for circuit testing, monitoring and paIchmg . 10 signal powered LED "s and 2 spares. 24 switches enables you to break out c1rcuIts or reconfigure and patch any or all the 24 acttve positions SPECIFICATIONS , Connectors : 0825 plug on 60mm ribbon cable and 0825 socket. Indicators : Tncolour LED"s tor TD . RD . RTS, CTS. DSR. CD . TC . AC . OTA. (E \TC . Jumper Wires : 20 tinned end pieces Power : Interface power. Enclosure: Black. high impact plastic. Dimensions : 85 x 95 x 30mm X15700 $94.95 $19.95 CRT CRT : s·· (150mm) Flat-faced high brightness CRT with Internal Graticule Effective d i splay area : 8 x 10 d1v (1 div 10 mm ) Acceleration potential : 2KV VERTICAL Operating Modes : CH -A. CH-8 . DUAL. ADO (CH-8 can be inverted.) Dual modes . Alter . 0.2uls- O.Sms/d1v Chop : 1ms • O.Ss1d1v CHOP frequency 200KHz approximately. Deflection factor : SmV1cllv 20V1div + 3 0:o. 12 ranges tn 1-2-5 step w11h fine con trol Bandwidth : DC : DC - 20MHz ( 3d8) AC . l OHz - 20MHz 3dBJ . Rise Time: Less than 17ns Overshoot : Less than 3 % . Input Impedance : 1M ohm t 50:o. 20pF + 3pF Ma ximum Input Voltage : 600Vp-p or 300V (DC ,1- AC Peak) Channel Isolation : Better than 60 dB at 1KHz . 3800 HORIZONTAL This instrument is a compact. ~~i &!'!~~~~2u~ii~!~1:n.d A~J;.,~20 ranges m 1-2-5 step wItn rme control Sweep Magnifier : 5 times (SX MAG ). Linearity : 3% TRIGGERING ~~~s~g~~~tETXETRE~iL~( :d1i~~~:~~l~~f:/,~~~(:;2_0~~z~;(~~;;:~~~:~~ore more Ihan 30MHz) . Source : INT. CH-A. CH-8 . LINE and EXT. ~~t~~;:ruannd Negative . continuosly variable with level control PULL 1 Coupling :AC . HF-REJ and TV TV SYNC Vertical and Horizontal Sync !~f~: ~:ii~~~rz~~~~~ye:~~~~ea;ro~~:~?~' i~~.f~i:n:Y;~~ef>v~~,1~::el)a~: switched automatically by SWEEP TIME/OIV switch . TV -V·O.Ss/d1v to 0 .lmsldiv. TV-H :50uts/div to 0 .2uts/div . X-Y OPERATIONS X-Y Operations : CH-A : Y a>Cis. CH-B: X axis Highest Sensitivity : 5mVldiv . COMPONENT TESTER Component Tester : Max AC 9V a1 the terminal with no load . Max current 2mA when the terminal is shorted . (Internal resistance is 4.7K ohm) OTHER SPECIFICATIONS Intensity Modulation : TTL LEVEL (3Vp-p) : Positive ...... brighter. BANDWIDTH : DC - 1MHz MAXIMUM INPUT VOLTAG E: SOV (DC + AC Peak) Calibration Voltage: 0.5Vp-p +/- 5%, 1KHz 1 / 5% Square wave Trace Rotation :Elec1rically ad1ustable on the fron t panel Power Requirements : AC : 100, 120. 220. 240V 20W Weight: 7kg approximately. Size: 162(H) x 294(W) x 352(D)mm . only $895 (tax exempt only $775) Bulk orders, schools, please phone (03) 543 2166 for special low pricing METEX MULTIMETER METEX 3530 MULTIMETER This instrument is a compact. • Dtode testing with I mA fixed current. • Audible Continuity Test. • Transistor hFE Test. SPECIFICATIONS Maximum Display: 1999 counts 3 ½ digit type with automatic polarity indication. Indication Method : LCD display. Measuring Method : Dual-slope in A-0 converter system. Over-range Indication: ·· 1·· Figure only in the display. Temperature Ranges : Operating OoCtC' + 40-C Power Supply : one 9 volt battery (006P or FC- 1 type al equivalent) Cat .Qg 1530 ........ Normally $109 ;ujje~g~a:~rJ~~t9:raf~rdnl~!~~~~d DC and AC voltage, DC and AC current. Resistance and Diode , Capacitance. Transistor hFE and Continuity Test. The Oual•slope A-0 Converter uses C-MOS technology for auto-zeroing, polarity selection and over-range indication . Full overload is provided. It is an ideal instrument for use in the field , laboratory. workshop, hobby and home applications. Features ... • Push-button ON/OFF power switch. • Single 30 position easy to use rotary switch for FUNCTION and RANGE selection • 112" high contrast LCD. • Automatic over-range indication wilh !he ·· 1 .. displayed . • Automatic polarity indication on DC ranges . • All ranges fully protected plus Automatic "'ZERO Mof all ranges without short circuit except 200ohm Range which shows "000 or 001 ·· . • High Surge Voltage protection 1.5 KV-3 KV. • Capacitance measurements to 1pF • Diode lesting with 1 mA fixed current. • Audible Continuity T esl. • Transistor hFE Test . SPECIFICATIONS Maximum Display: 1999 counts 3 ½ digit type with automatic polarity indication . Indication Method : LCD display. Measuring Method : Dual-slope in A-D converter system. Over-range Indication : ·· 1 ·• Figure only in the display. Temperature Ranges : Operating OoC to + 40•C Power Supply : one 9 volt battery (006P or FC-1 type of equivalent) Cat. 091540 ...... .. Normally $139 SPECIAL$79 SPECIAL $109 ;ujJe~Q~~1tl~~~~~rdrT)~~~~~,;~d DC and AC voltage , DC and AC current. Resistance and Diode . for testing Audible con11nuity and transistor hFE . The Dual-slope A-0 Converter uses C-MOS technology for auto-zeroing, polarity selectron and over-range indication . Full overload is provided. Jt is an ideal instrument for use in the field, laboratory, workshop. hobby and home applications . Features ... • Push-button ON/OFF IX)Wer switch. • Single 30 position easy to use rotary switch for FUNCTION and RANG E selection . • 1;2 '" high contrast LCD . • Automatic over-range indication wilh the '"1" displayed . • Automatic polarity indication on DC ranges. •f~,~~~j; .!~~ FfJ·'~~~?r~~~es without short circuil except 200 ohm Range which shows " 000 or 001 "' . • ~~~~~fv~oltage protection METEX 4500H MULTIMETER METEX M-3650 MULTIMETER ~~e~:;~n:i~it\~~~~:7ii{ capacitance meter and transistor tester. J~~;~~c6~~a~a~uJi~;t"1e11ow ~irr~~~~~g~ ~~i~~~(t~e2gJ~~~ts diode and transistor test. continuity (with buzzer), capacitance meter, up to 20 amp current measurement and comprehensive AC/DC voltage , current and resistance ranges. CHECK THESE FEATURES .... • Push-button ON/OFF switch. • Audible continuity test 10A, 41;, digit multimeter with digital hold, transistor tester and audible continuity tester. The Metex 4500H is perfect for the 0 ~~~~~c~~rre;~i:~r~h: ,eand~~~~tof a 41,2 digit multimeter. This meter is exceptionally accurate, Uust look at the specifications) , and yet. still retains an exceptionally low price! The Metex 4500H features digital hold which is normally only found on very expensive multimeters. This enables you take a reading and hold that reading on display even after you have removed the probes, simply by pressing the hold button . CHECK THESE FEATURES ... • Readout hold • Transistor Tester • 4 ½ digit x 1J.2'"(H) LCD • Audible continuity tester • Push-button ON/OFF switch . • Quality set of probes • ~~t~tt~~~~tcio,~i~ince~~~o and RANG E selection . • Transistor test • Diode test • Quality probes • 1;2•· High contrast LCD . • Full overload protection •20Amp • Built in lilting bail • Capacitance meter • lnstruciion manual • r~nug;: ~st\'.f~C~l~N and RANGE selection. • Built in tilting bail • Instruction manual • Full overload protection • hFE test • Battery and Spare fuse • Diode Tester • Vinyl case 091550 . Normally$ 165 Special, only $129 091560 .... Normaliy$ 175 Special, only $159 :~t~~~~ 1-9 10+ Cat. S12500 ..... ... Normally $7.95 1-9 10+ 25 + $4.95ea $4.25ea $3.95ea • -======a QUALITY 3mm LEDS RELAYS We have a great range of panel meters at great prices ! Cat.No. Description Price 010500 MU45 0-1mA 12.50 010502 MU45 50-0/SOuA 12.50 0 10504 MU45 0-1 OOuA 12.50 0105 10 MU45 O·SA 12.50 0 10518 MU450- 1A 12.50 0 10520 MU45 0-1A 12.50 010525 MU45 0·20V 12 50 010530 MU52E 0· 1A 14.50 0 10533 MU 52E 0-SA 14.50 0 10535 MU45 VU PMelre 14.95 0 10538 MU65 0-SOuA 16.95 010540 MU65 0-1mA 16.95 010550 MU65 0· 100uA 16.95 010560 MUGS 0·20V 16.95 1-9 10+ 100+ S. P.D.T. 3Aconnectors ..... S1 4060 $1.50 $1.30 $1.10 O.P.D.T. 3A connectors ..... S14061 $1.95 $1 .75 $1.30 S.P.O.T. 12V Coil 10A240V S141 14 $4.95 ECONOMY TRANSFORMERS 1-9 10+ 2155 240V 6-15V 1A Cat. M12 155 $9.95 $8.95 2156 240V 6-1SV 2A Cat M 12156 $14.95 $ 13.95 2840 240V 9V CT Cat. M12840 S5.95 $4.95 2851 240V 12-6V CT 1SOmA Cal. M1 2851 $5.95 $5.50 2860 240V 15V CT 250mA Cat. M12860 $5.95 $4.95 6672 240V 15·30V 1A lapped Cat. M16672 $14.95 S13.95 $3.95 $3. 75 Cat. No. Col. 1-9 210 140 Red $0.15 2 1014 1 Grn $0.20 210 143 Ylw $0.20 2 10 145 Ora $0.20 10+ tOO+ $0.12 $0.15 $0.15 $0.15 $0.10 $0.12 $0.12 $0.12 :p /~ U.V. TUBES ' Fits into standard 15W flou ro holder. Suitable for Scotchcal, Eprom erasing etc. As used in ETI Eprom Erasing Kit. WARNI NG : Do not look directly into UV Tubes . Cat H28600 ............ .. .. . $29.95• "If ordering by mai l please include an extra $2 for '"special '" packin~ . ' , QUALITY 5mm LEDS Cat. No. Col. 1-9 2 10150 Red $0.08 2 1015 1 Grn $0.15 2 10152 Ylw $0.15 10+ 100+ $0.07 $0.06 $0.12 $0.10 $0.12 $0.10 10TU U D POTENTIOMETER Spectrol Model 534 ¼ " shaft. Save a fortune on expensive throw away batteries with these quallty Nlcads and Rechargers! Size Desc. 1·9 10+ 100 + AA 450 mA.H $2.95 $2. 75 $2.50 C 1.2 A. H. $9.95 $9.50 $8.95 D 1.2 A.H . $9.95 $9.50 $8.95 RCA GOLD PLATED PLUGS AND SOCKETS For those who need the ulti mate in connection. Essential for laser disc players to get that fantastic sound quality. Plug Cat. P10151 $2.95 $2.25 Socket Cat. P10150 = 1 Equiv (Bourns 3540S , Beckman 7256) Dials to suit 16-1- 11 . 18-1-1 1. 21-1- 11. R14050 SO R A14100 SK A14055 100A R141 10 10K R14060 200R A14120 20K R14070 SOOR A14130 SOK A14080 1K A14140 100K A14090 2K 1·9 10 + $9.95 $9.50 NEW TRANSISTORS Rod Irving Electronics have two new transistors which will replace a multitude of common hard to get devices. The PN100 is a NPN genera.) pufP?se medium power amp and switch with continuous collector current up to 500mA. The PN200 is a PNP general purpose amp at collector currents to 1 Amp. Both are T0 -82 plastic package PN100 REPLACES : PN222t , PN2222 , PN2222A, PN3585. PN3568, PN3569, PN3643. PN5133 , 2N22 19A , 2N2222A . 2N3414. 2N341 5, 2N3416. 2N341 7. 2N3700 , 2N3704. 2N3904, 2N4123 . 2N41 24, 2N4401. 2N5088, 2N5210. PN200 REPLACES: PN2907, PN2907A. PN3638, PN3638A. PN3640, PN3644 , PN4 121 . PN4 143. PN4248. PN4249. PN4250 , PN4355. PN4916, PN4917, PN591 O. 2N2905A. 2N3467. 2N3702. 2N3906. 2N4125. 2N4 126 . 2N4291, 2N4402, 2N4403 , 2N5086, 2N5087, 2N5447 . PN100 Cat. T9000 1 PN200 Cat. T90002 1·9 10 + $0.20 $0.18 GOLD INSERT LOW PROFILE IC SOCKETS • • • • Gold machined pins Extremely high quality Anti-wicking. Ideal for professional use or where field service of components is required . Cat.No. Description 1-9 10+ P10620 8 pin $1.20 $1.10 P10624 14 pin $1 .60 S1.50 P10626 16 pin $1.90 $1.80 P10628 18 pi n $2.00 $1.80 P10630 20 pin $2.20 $2.00 P10632 22 pin $2.40 $2.20 P10634 24 pin $2 .60 S2.40 P 10640 28 pin $2.90 $2.60 P10644 40 pin $3.00 $2.70 Leakproof. long service life batteries ideal for security systems emergency lighti ng or as a computer backup power supply. etc .. Cat. S1 5029 . Normally $19.95 1-9 $13.95 ,.firirf1 , WIRE WRAP IC SOCKETS These quality 3 level wire wrap sockets are tin-plated phosphor bronze . Cat.No. Description 1-9 10-t P10579 8 pin $1 .50 $1.40 P10580 14 pin $1.85 $1.70 P10585 16 pin S1.95 $1.80 P10587 18 pin $1.95 S1 .80 P10590 20 pi n $2.95 $2.70 P10592 22 pin $2.95 $2.70 P10594 24 pin $3.95 $3.50 P10596 28 pin $3.95 $3.50 P10598 40 pin $4.95 S4.50 - 3 ?. 1,9 P10960 3 PIN LINE MALE. 10 ➔ $3.90 .. ...... .............. $3.50 P10962 3 PIN CHASIS MALE $3.00 ............ .......... $2.50 P10964 3 PIN LINE FEMALE $4.50 ...................... $3.90 P10966 3 PIN CHASIS FE MALE $4.95 .................. .... $3.95 ,.-•-.~ I 1' t \ I SPECTROL 64Y MULTI TURN TRIMPOTS Cat.No. R14700 A14710 R14720 R14730 R14740 A14750 R14760 R14770 R14780 R14790 A14800 R1481 0 R14820 R14830 R14840 R14850 Description 1-9 10R ......... $3.50 20R ... .. ... $3.50 SOR ... ...... $3.50 100R ....... $3.50 200R ..... .. $3.50 SOOR .... ... $3.50 1K ....... ... . $3.50 2K .... ....... $3.50 SK ... ....... . $3.50 10K ..... .... $3.50 20K . ...... $3.50 SOK ......... $3.50 100K . ..... $3.50 10 + $3.20 $3.20 $3.20 $3.20 $3.20 200K ..... .. $3.50 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3 .20 SOOK ....... $3.50 1M .. ........ $3.50 $3.20 $3.20 1 ,! ! ' LOW PROFILE IC SOCKETS Save a small fortune on these '·Direct Import"" low profile IC sockets! PC B mounting solder tail. Dual wipe. All tin plated phosphor bronze or berryllium and dual wipe for reliability. Cat.No. Description 1-9 10+ P10550 8 pin ... .. ... $0.20 $0.15 P10560 14 pin .......... $0.25 $0.20 P10565 16 pin ..... ..... $0.35 $0.20 P10567 18 pin ........ .. $0.40 $0.30 P10568 20 pin ........ .. $0.40 $0.30 P10569 22 pin .. ........ $0.40 $0.30 P10570 24 pin .......... $0.40 $0.30 P10572 28 pin .. ... ..... $0.50 $0.40 P10575 40 pin .......... SO.SO S0.40 MAIL ORDER HOTLINE 008 335757 • • fTOLL FREEJ LO. _L; -77 - CHROME LED BEZELS 9mm hole. available 3 colours Cat. No. Description Price S1 4030 Red ............ .... .... $1.20 S14032G reen .... ... .... ... $1.45 S14034 Yellow ... ........ . $1 .45 TYPE 1-9 10+ 100 + gp $0.60 $0.60 $0.50 $0.65 $0.65 $0.60 $0.60 $0.65 $0. 60 $0.50 $0.50 $0.40 $0.60 $0.60 $0.50 $0.50 $0.60 $0.50 9S 9C 15P 15S 15C 25P 25S 25C $0.70 $0.70 $0.60 $0.70 $0.70 $0. 70 $0.70 $0.75 $0.70 DB 25 CRIMP SPECIALS! Type 1-9 Femate $2.95 Male .... S2.95 HIGH INTENSITY RED LED BAR GRAPH Dimensions : Overall : 63mm across, 5mm high. LEDs: 10 x 5mmx: 1mm 10 + Cat .No. 1-9 $2.75 2 10180 $2.95 TAG TANTALUM CAPACITORS SPECIALS! Price 0.48 R16125 16V 10uF. 0.52 R16126 16V 15uF. 0.75 R16128 16V 22uF ..... 0.85 R16216 25V 2.2uF . 0.40 R16220 25V 4.7uF .. 0.70 R16222 25V 6.8uF . 0.70 R16224 25V 10uF . 0.60 R16228 25V 22uF .... 2.40 R16300 35V 0.1uF .. 0.30 R16302 35V 0.15uF .. 0.30 R16304 35V 0.22uF .. 0.30 R16306 35V 0.33uF .. 0.30 R16308 35V 0.47uF .. R16310 35V 0.68uF .. R16311 35V 0.82uF .. 0.35 R1631 2 35V 1.0uF. R16314 35V 1.5uF . R1631 6 35V 2.2uF .. 0.50 R1 6318 35V 3.3uF . R16320 35V 4.7uF .. R16322 35V 6.8uF . 0.80 R16324 35V10uF. R16326 35V 15uF ... ~~8 R16328 35V 22uF . 3.50 2r~~f4 fgJC Ji~~in... DB25 CONNECTOR SPECIALS! ' 000 00~ cw ....... ,, ~,,CANN CONNECTORS 10+ $2.50 100+ $1.95 $2.50 $1.95 sn 8(£]<at>] SPECTROL MULTIDIALS MODEL 15-1-11 Numberof t urns : 10 Minor Scale Division : 1/500 turn Shaft Bore: 6.35mm ( 1/4 '") Finish: Satin Chrome Body Size: 25.4 x 44.45mm (1 X 13/ 4 ") Depth: 25.4mm (1") Weight: 45.4g (1 .6oz.} Cat .R14405 .. ..... .. $45.95 SPECIAL, $35.95 MODEL 16-1 -11 Number o f turns: 15 Minor Scale Division : 1/50 turn Shaft Bore: 6.35mm ( l /4 ") Finish: Clear Anodize Body Size: 22.2mm diameter (.875" ) Depth: 22.2mm (.875" ) Weight: 19.8g (0 .7oz.) Cat.R14400 ........ . $26.95 UnencOded keypad . 10 digit keys plus two utility keys. Light grey in colour. OUTPUT ARRANGEMENT: Output Pin N°· Symbol 1 ... .. .... ..........N.A. 2 ....... .... ... .... Shield plate 3 ....... ... ....... Colum n2 4 .. .. ........... ..... Aow4 5 ................. ... .Column 3 6 .......... .... ....... Row1 7 .................... Column 1 8 .................... Row 2 9 .. ... ............... Row3 10 .......... .. ........ N.A. Cat.C 19030 1-9 10 + 100+ $2.95 $2.50 $1.95 SPECIAL, $21 .50 Cat.R1441 0 ....... .. $46.95 SPECIAL, $37.50 FREE POSTAGE FOR SILICON CHIP READERS THIS MONTH MINIMUM ORDER OF $50 APPLIES JUST QUOTE THIS A0VERTISEMENT . ~ 42mm PIEZO BUZZER S15073 .. . $7.95 MELBOURNE: 48 A ·Beckett St. Phone (03) 663 6151 NORTHCOTE: 425 High St. Phone (03) 489 8866 CLAYTON : 56 Renver Rd . Phone (03) 543 7877 SOUTH AUSTRALIA : Electronic Discounters P/L, 305 Morphett St , ADELAIDE ~g~r:~i?i~ls~~/v~~;111te rs1illP du e 10 fre1ghtcosts1 2 MAIL ORDER : Local Orders: (03) 543 7877 Interstate Orders: (008 ) 33 5757 All Inquiries : (03) 543 7877 CORRESPONDENCE : P.O. Box 620, CLA YTON 3168 Telex: AA 151938 Fax : (03) 543 2648 - . MAIL ORDER HOTLINE 008 335757 fTOLLFREEJ (S TRICTLY ORDERS ON LYJ LOCAL ORD ERS &INQUIRIES f03J 543 7877 MODEL 21 -1-11 Number of turns: 15 Minor Scale Division : 1/100 turn Shaft Bore: 6.35mm ( 1/4 ") Finish: Satin Chrome Body Size: 46.04mm diameter (1.812") Depth: 25.4mm (1" ) Weight: 85.g (3oz .) gJg ~ 8:g8 Rod Irving Electronics 0~~ ULTRASONIC TRANSDUCERS Designed to transmit at 40k Hz (L 19990) and receive at 40kHz (L 19991) with up to 2~V 1/P on the transmitter. These units can't be heard and so are ideal for.TV remote controls. water level de1ectors, burgalar alarms , motion detectors and information carriers as they can be either pulsed or used in the continuous wave mode. Full specifications below for design purposes. Maximum Input Voltage : 20V rms 0 ~~~: ~~=~~~;r!~~N= o4S ~M~~ POSTAGE RATES : S1 S9.99 S2.00 S10 S24.99 S3.00 S25 $49.99 S4.00 $50 S99.99 S5.00 $100 S199 $7 .50 $200 $499 S10.00 $500 plus S12.50 The above postage rates are ~or basic postage only . Road Frei ght . bulky and fragile items w ill be charged at different rates . All sales ta x exempt orders and wholesale inquiries to : RITRONICS WHOLESALE . 56 Renver Rd, Clayton . Ph . (03) 543 2166 (3 lines) Errors and omissions excepted Prices and spec1f1cat1ons sub1ect to change 110d8 min . Sensitivity (dB/v/ubar) min. : - 65 min . Bandwidth (kHz): Transmit: 4.0 (at 100c:IB) Receiver: 5.0 (at - 73dB) :~~:a~ ~s~J;n~;~ari~~~Tii~~~~~ M achmes · Apple 1s a ,eg1s tere-d trademark lm~=~~rsoo respect,ve ownets Receiver: 5000 Cat. L 19990 (Transmitter) Cal . L19991 (Receiver) . . ·0eno1es 1eg,s1e1ed tradm arks o11he,1 $6.95 $6.95 ■[ffil ::E Phone privacy junction box NEW PRODUCTS - CTD Regulated power supply from Oatley Electronics Bargains in power supplies are few and far between but this offering from Oatley Electronics rates a mention. They are an open chassis unit originally used in Telecom equipment. They have two outputs, 24 volts DC rated at 1.3 amps and 32 volts AC also at 1.3 amps. While these ratings are fairly modest, the Hand-held 2-metre transceiver Captain Communications is now stocking the very small learn u2A/ A, a palm sized transceiver for the 2-metre amateur band. It measures just 11. 7cm high, 5.8cm wide and 2.8cm deep. Features include 10 programmable memories, offset capability, LCD readout, 2.6 watt output and 32 built-in sub-audible codes. For further information, contact Captain Communications on (02) 633 4333. 94 STLICON CHIP transformer is a bulky fully encapsulated unit rated at 140VA. This means that it could deliver over 4 amps at 32 volts AC. Essentially then, you get the makings of a much bigger supply which could be either fixed or variable. Full circuit details are provided plus suggested modifications for making a fully-variable supply. Price is $26.95 plus $10 for freight. For further information contact Oatley Electronics on (02) 579 4985 (see advert on page 100). If you thought the Line Grabber for telephones featured in the March 1988 issue of SILICON CHIP was a useful idea but didn't fancy building it, here is an alternative. The PTl 15 Privacy Junction Box from Arista is the prototype of the Line Grabber. The difference is that the PTl 15 is fitted with US modular phone plug sockets rather than Telecom sockets. It performs exactly the same function as the Line Grabber; if you pick up the phone all other phone extensions on the line are unable to listen in. It is priced at $32.95 from all Arista outlets. Cassette salvage and repair kit I Hands up all those readers who have at least one partly destroyed cassette in their collection but which they're still loath to throw out. Maybe the case is buckled, the tape broken or tangled, or perhaps it is jamming. Now there is a solution in this handy repair kit. It comes with a spare cassette housing (handy if you have to destroy one of those housings which are glued instead of screwed together), splicing bar, razor blade and splicing tape. There is even a little rewinding knob which is much more effective than rewinding a loose tape with a pencil. The kit is good value at just $2.95 and is available from David Reid Electronics, 12 7 York Street, Sydney 2000. Phone (02) 267 1385. Hydraulic hole puncher makes metal work easy Any tradesman who has laboured over the process of cutting clean circular holes in metal panels will love this appliance. It is designed to punch holes in any sheetmetal including copper, brass, aluminium and the toughest of them all, stainless steel. Essentially it is an updated version of the screw punch and die set except that now the die is pulled through the sheet metal by a hydraulic ram. It works on the same principle as a hydraulic jack - you pump the handle to apply pressure to a larger cylinder which does the work. If you've sweated when using the old screw punch and dies you'll wonder why this wasn't invented years ago. It is available in a number of versions. Pictured is a portable unit, type HP-1, with an ability to punch round holes from 10mm to 80mm in diameter or 20 to 50mm square holes. Maximum material thickness ranges from 1.6mm in stainless "Sensational Price Offer" a: w 0 a: 0 ..I ci :I I ffi0 IC 0 ..I ci :I l ~ CONTACT CONTACT ELECTRONIC PARTS COMPUTER SPECIALS DB8 DB15 DB25 0837 PLUG PLUG PLUG PLUG 80c 70c 85c 1.85 DB8 DB15 DB25 DB37 SOCKET SOCKET SOCKET SOCKET 80c 70c 85c 2.00 DB8 DB15 DB25 DB37 BACK SHELL BACK SHELL BACKSEHLL BACKSEHLL 80c 80c 80c 1.50 CARD EDGE CONNEClORS 20 WAY IDC PLUG 34 WAY IDC PLUG 1.75 2.25 MACHINED IC SOCKETS 8 14 18 18 20 22 24 28 40 PIN PIN PIN PIN PIN PIN PIN PIN PIN 55c 70c 85c 80c 1.00 1.25 1.30 1.30 2.25 CONTACT COMPUTER SPECIALS MATH CO-PROCESSOR SWITCH BOXES 40 350 585 $750 $1250 $1900 8087 • 3 8087 • 2 80287 • 8 80287 • 10 80387 • 18MHz 80387 • 20MHZ 12 COMPUTER POWER SUPPLIERS 150W 200W 200W COMPACT r05 165 155 MOTHER BOARDS XT TURBO 8MHZ ZERO RAM AT 4 LAYER 12MHZ ZERO RAM 386 18-20MHZ ZERO RAM 1210 650 $3000 RS232 RS232 RS232 RS232 • • • • 2WAY 3WAY 4WAY X OVER CENTRONICS CENTRONICS CENTRONICS CENTRONICS • • • • 2WAY 3WAY 4WAY X OVER 48.00 53.00 58.00 85.00 58.00 81.00 65.00 75.00 ADD ON CARDS CGAfHORYi MGA PRINT R PORT) MUL I 1/0+FDC E PROM WRITER CARD 78.00 115.00 120.00 199.00 "RED HOT FAVOURITES" LED 5MM ROUND RED-GREEN-YELLOW 10c VOLT REGULATORS 1.2AMP HARD DRIVES SEAGATE ST225 20MEG $480 7805 TO 7824 7905 TO 7924 50c 50c TRANSISTORS HAND SCANNER HS2000 $480 2N3055 TIP 31 C Suite 2 - 283 Burbridge Road Brooklyn Park SOUTH AUSTRALIA 5032 PH. 08 • 234 - 0240 Fax 08 • 352 .• 1449 Mall Order Postage Less than $50 ............................... $3.50 $50 • $99 ...................................... $4.50 $100 • $250 .................................. $7.00 NxNe $250 ................................ $10.00 Heavy Items adds extra 0 BANKCARD O MASTERCARD O VISA Gard No .............................................. .. 0 ::Ill 0 m ::Ill I ,. I: i= 0 ::Ill 0 m ::Ill 1.00 50c ALL PRICES INCLUDE SALES TAX WHOLESALE ENQUIRES WELCOME PRICES VALID WHILST STOCKS LAST CONTACT INTERNATIONAL ii= EXPIRY DATE Signature: .... .... .......... .......................... ... .... ...... .. ............. . (Note: unalgned credit card mall ordera cannot be accepted) Name: ................................................. .......................... . Address: ......................................... ............................... . .. .. .. .. .. .. . .. .. .. .. .. ... .. .. . .. .. .. .. .. .. .. .. .. .. . Postcode: .................. . (Please allow 14 DAYS for normal mall and bank clearance delays) I Mailbag - continued from page 3 pointer to relevant documents put out by these organisations. I enjoy your projects, my most recent effort being the 1GHz Frequency Counter (which is a ripper!) but I think that learning to understand both the theory and the application is as important, if not more so, than the feeling of achievement. In this regard the explanations provided in the articles are usually pretty complete but in this case I feel I have missed out. A final emphasis is that while many people consider the 'rules' set by government controlling bodies to be irksome, I know that you will agree that we need the orderliness they seek to achieve. It follows that we need to be continually aware of these requirements and that in publishing construction projects you have some obligation to quote the specific provision of standards or government regulations applying to the project. P. J. Lees Jolimont, WA The Department of Transport and Communications has allocated a frequency of 304MHz in its Interim Document RB243. This covers personal safety and security radio systems. Transmitters operating on this frequency are restricted in their equivalent radiated power to less than 100 microwatts. The occupied bandwidth of emissions from the transmitter must not exceed 1D0kHz. Please see other correspondence on this project in the "Ask Silicon Chip" pages of this issue. Caution on the Discolight While noting the serious and responsible approach to electrical safety standards and practices taken by the magazine, I feel I must point out an oversight in the wiring of the "Discolight" appearing on pages 44 will and 45 of the August issue of SILICON CHIP. According to the parts list only the rear panel is of aluminium and therefore the front is plastic. On the front you show a mains switch (S6) with a metal toggle and frame; also a number of small toggle switches and two pots with aluminium knobs. All these are probably connected together and appear not to be mainsearthed. In the event of damage or failure of the mains switch the front panel may acquire mains potential. Similarly, but less likely, a failure in the internal circuitry could place mains potential on the tracks of pots and contacts of the switches, posing a risk of leakage or breakdown to their respective frames. If an aluminium front panel had been specified then it could be securely mains earthed and the unit rendered safe. I believe this is required under SAA regulations. As an alternative, the mains switch at least should be earthed or replaced with a plastic enclosed type. Hoping you can bring this matter to the attention of your readers and kit suppliers. Frankly, the likelihood of the specified heavy-duty switch breaking down is extremely remote. We have never heard of a single instance of a mains-rated switch breaking down to frame. And the likelihood of the the optocouplers breaking down and making all the circuitry live, at mains potential, is even more remote. It is also standard practice with most kitset suppliers to use screen printed plastic front panels. Still, it would be good wiring practice to earth the metal bush of the mains switch and those of the two potentiometers. ~ ~~ U~ ~ UV,,,, - C g~ r --'~ ..~au ·co •~~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 96 SILICON CHIP Wire stripper and crimper P. Allison Summer Hill, NSW ft~ 0 steel to 3mm in aluminium. A larger version, the NP-2, punch round holes from 15mm to 150mm in diameter or 20mm to 100mm square holes. Other portable models have die heads which are separate to the hand-powered section, to enable hole punching in awkward spots. For production use, there is the model EG-3 which is designed for bench mounting. For further information on this range of hydraulic hole punchers contact Stainelec Industries, 26 Boola Avenue, Yennora, NSW 2161. Phone (02) 632 6797. Some combination wire strippers and crimpers are not very effective. Perhaps they don't strip wire without nicking the conductors. Some are hopeless at the task of crimping connectors. So if you are buying one of these tools be aware that if it is very cheap, it might not be the bargain you expect. This combination wire stripper and crimper from Geoff Wood Electronics works very well indeed. It automatically adjusts its jaws to strip the insulation from almost any size of wire without nicking the conductors. It has an effective wire cutter as well as being able to cope with three sizes of crimp connectors. It is priced at $34.95 from Geoff Wood Electronics - phone (02) 427 1676. ~ ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Video distribution system has ghosts on one channel Could you please give me some advice on a video distribution system? I've shown a diagram of what I would like to achieve - ie, the VCR or off-air signals available at any of four TV sets. I would install a masthead amplifier as decribed in the July 1988 issue of SILICON CHIP because I live about 10km from the transmitter. We don't have line of sight to the transmitter because I live in a gully and have to use an anti-ghost TV antenna. The picture on the ABC is OK but on TVT-6 it is very bad with vertical bars on the screen about 10mm wide. Do you think the amplifier would improve the situation or not? Also, would the amplifier be suitable for UHF CB? (G. O'S., Rosetta, Tas). • Your method for making the TV and VCR signal available to four TV sets should be satisfactory but Enclosure design for a widerange speaker I am interested in a reflex cabinet for a British made 8-inch Richard Allen loudspeaker with a frequency range of 45Hz to 17kHz. It has a 4-inch (10cm) magnet. Would it be possible for you to give some idea of internal measurements in inches or centimetres? It could perhaps be 30 inches high and 18 inches wide with a specified depth and a vent or port to suit. Have you any suggestions? (S. N., Devonport, Tas ). • Dear, oh dear. We don't have an inch rule. What are we going to do? Seriously, without having the Thiele-Small parameters for your loudspeaker, it is probably a waste of time designing a vented enclosure for it. We don't even VCR ,--------tOUTPUT INPUT------. BEDROOMS 1 2 MAST HEAD AMPLIRER (SC JULY 88) 1----t TWO-WAY COMBINER TWO-WAY SPLITTER FOUR-WAY SPLITTER KITCHEN LOUNGE Fig.1: proposed arrangement for distributing VCR and off-air signals to four TV sets. unless you have fairly weak TV signals to begin with or the expected losses via the combiners and splitters are high, the masthead amplifier may not be necessary. It certainly will not improve the reception on TVT 6 if you have vertical bars down the screen. These are vertical sync pulse ghosts and are symptomatic of very bad reception conditions. Unless you can obtain a more directional antenna for channel 6 and/or orient the antenna so that the ghosts are placed in the null points of the antenna (for a Yagi, deep nulls are present in the sides), no improvement is possible. We assume that your antenna is on a high mast. Yes, the masthead amplifier will work on UHF CB signals but you should be aware that UHF signals are even more directional than the VHF TV signals that are presently giving you problems. If you are in a "shadow" as far as UHF signals are concerned, it is unlikely that any masthead amplifier will help you. know the free-air cone resonance although it is probably around 50Hz or so, we'd guess. It's a stab in the dark, but we'd suggest you install the loudspeaker in a sealed (ie, with no vent or port) enclosure with a capacity of around 40 litres or so. As for suitable dimensions, we suggest a cabinet with internal dimensions 580mm high, 340mm wide and 220mm deep. Use 12mm or 20mm thick particleboard or plywood and fill the enclosure with Innerbond (bonded acetate fibre) wadding. and July 1988) without the cost of an expensive rack mounting box. Would you please advise readers where they may obtain the following: (1) LM833 op amps; (2) pots with indents; (3) balance control (MN) as specified; (4) PC-mounting DPDT push-on push-off switches. To my knowledge they have never been catalogued by any of the four major suppliers. In fact, I have been informed that as far as the pots are concerned, they are not available. Your assistance in this matter would be greatly appreciated. (D. G., Julatten, Qld). • Pots with indents are a big supply problem at the moment but you can obtain suitable pots without the indents, including the balance control, from Jaycar. They can also supply the LM833s and the switches. Parts for the Studio 200 preamp As a reader of your magazine from the first issue I am currently trying to put together your Studio 200 control unit (described in June OCTOBER1988 97 2.2pf INPUT- I - - - - - - - - - - RF OSCILLATOR A.UOIO OUTPUT LOW PASS ALTER 3.3pf QUENCH OSCILLATOR Fig.2: block diagram of the front-end of the Remote Alert/Doorbell. Its operation is explained in the text. Self-oscillating detectors are intriguing I am intrigued by the detector used in the "Remote Alert/ Doorbell" described in your August 1988 issue. Can you supply any further information other than the fact that "whenever a signal is received, this stage oscillates at 304MHz" please. (J. E., Bull Creek, WA). • To paraphrase a cer tain old TV show, "you asked for it". As you have guessed, the circuit operation is a lot more complicated than our short description indicates. When you've read the description, you'll see why we gave the brief explanation. We based the circuit on one featured in an article in the IEEE Transactions on Consumer Electronics, Volume CE-33, No 3, Electronic ignition for model aircraft · As a novice electronics hobbyist, I find your down-to-earth explanations of electronic circuits and component functions most helpful. I am a radio control model aircraft enthusiast and am in the process of building your optical tachometer. The reason for this letter is to ask if you can come up with an electronic spark ignition for model aircraft engines, particularly 4-stroke models. Keep in mind that such a design would have to be as light as possible and must not interfere with the receiver. (D. De V., Toowoomba, Qld). • Your suggestion is a good one 98 SILICON CHIP .,. Fig.3: Q2 is a super-regenerative receiver which consists of both an RF oscillator and a quench oscillator. August 1987. The relevant part of the circuit is reproduced here as Fig.3. The circuitry associated with Q 2 is a ctually a super regenerative receiver which consists of both an RF oscillator and a quench oscillator. The RF oscillator comprises Q2, 1 2 and the 22pF, 3.3pF and 2.2pF capacitors. It runs at close to the transmitted centre frequency (in this case, 304MHz). The quench oscillator comprises the series inductor 13, a lkO r esistor and a .OOlµF capacitor at the emitter of Q2. The RF oscillator rapidly alter- although we don't have a lot of background info on this topic. If you or other readers have info on model aircraft ignition it would be a help in the development of a suitable circuit. New life for cassette players I read with interest the article "New Life for Old Cassette Players" in the March issue of SILICON CHIP. I feel that it was an excellent article for all young beginners just entering electronics. It will encourage many to retrieve an old tape player from a dusty shelf and get it going again. I would like to see a future series nates between an oscillatory and non-oscillatory condition at the quench frequency rate. The function of the quench oscillator is ·to ensure that continuous oscillation does not occur in the absence of an input signal. In effect, the RF oscillator "squeggs" (ie, gives very short bursts of oscillation) at a rate set by the quench oscillator. When a modulated signal is received, the fluctuating RF level of oscillation causes the DC level at the base of Q2 to vary accordingly. This signal is then fed via inductor L4 to the following amplifier stage. of service notes and techniques for servicing cassette decks, radios . and CD players similar to the fine articles which we regularly read in the Serviceman's Log column. With the above idea in mind, I would like to ask you, or one of your readers, if there is a simple solution to remedy the newly arrived problem of auto-reverse cassette players continually changing direction when a tape has been inserted. I don't mean changing the direction when a tape has come to the end of one side, but as soon as the tape has been inserted and the mechanism activated. The machine then continually clicks back and forth and will not stop. It seems after watching the machine that the mechanism is under some tension and cannot decide which direction to stabilise on. I have seen several machines which exhibit the same characteristic and hope that you can provide an answer. (R. P. , Latrobe , Tasmania). • We have not experienced this problem. Can any reader provide the answer? Power supply for . video light In the November 1987 issue of SILICON CHIP you featured a 12V power supply for a car radio which was rated for a continuous 1 amp. Can I use it to supply a 12V quartz halogen video light that runs from a 12V dry battery? The light is rated at 100 watts. (E. D., Cheltenham, Vic). • The 100 watt rating on the light is the essential clue. Dividing that figure by 12V gives a current requirement of no less than 8.3 amps. That's a very high current for any dry battery to sustain and even the average car battery would only last for a few hours at that rate. The alternative of a mainspowered 12V 8.3 amp continuously rated supply would not be a cheap item by any means; ideally it should be well regulated to ensure long life and correct colour temperature of the lamp. We have not described a suitable supply but if there is sufficient demand we would do so. As an easier alternative, why not enquire at a lighting supply store which stocks quartz halogen spot lamps? You may be able to substitute a 240V-rated lamp which would do the job without any need for a power supply. Wants information on semiconductors Is there a data book available which explains the full functions of most semiconductors? For example, with a unijunction transistor (UJT}: when the anode voltage is 0.5V above the gate, the UJT will conduct. What I am looking for is some publication which goes into some CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 tor up to 15 words plus 40 cents for each additional word ; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds , PO Box 139, Collaroy Beach , NSW 2097. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($7.40) 17 ($7.80) 18 ($820) 19 ($8.60) 20 ($900) Name ......... .... ....... .. ... ...... .. ..... ... ..... ... .. Address . Suburb/Town .. ....... .. . Enclosed is my cheque or money order for $ D Bankcard D Visa Card Card No lL --'------'- Postcode .... or please debit my L--'----'-----'-----'-- ''----'----'-----'----'--- - - ' . -'-----_j_J Signature detail on how these semiconductors will activate or de-activate. (A. M ., Browns Plains, Qld). • We can understand your problem. General Electric published a number of handbooks which were very good on explaining how devices such as unijunctions worked (eg, GE Transistor Manual, GE SCR Manual). As far as we can determine though, these books are no longer available and we are unable to nominate a suitable alternative. Actually, the device you are referring to is not a unijunction transistor (which has two bases and one emitter) but a PUT (programmable unijunction transistor). This was a device developed by General Electric as a more predictable "unijunction". A PUT is actually an "anode gate silicon controlled rectifier" (SCR} which is a variant on the more common cathode-gate SCR. The ultimate answer to this need for a data book which explains how these special semiconductors work will be provided when we get our series on Discrete Devices under way. Unfortunately, we can't make any promises on the starting date. Notes & Errata Studio 200 Stereo Control Unit, June1988: experience with the control unit when teamed with a number of power amplifiers has shown that the combination can oscillate supersonically when the Treble control is at maximum and the Volume control is at high settings. While these are abnormal control settings, if oscillation is allowed to persist it may damage the power amplifier or the speakers. To prevent the condition occurring, we suggest that an additional 270pF capacitor be connected across the 4. 7k0 feedback resistor for IC2 in each channel. In addition, a 560pF capacitor should be connected across the volume control potentiometer; ie, one 560pF capacitor across VR1a and one across VR1 b. Remote/Alert Doorbell, August 1988: when setting the transmitter frequency for Ql, do not connect pin 15 of IC1 to the + 12V supply. This can damage IC1. Instead, disconnect the 47k0 resistor from pin 15 and connect it instead to the + 12V supply to make the transmitter run continuously. OCT0BER1988 99 T CEN·1· Cash in your surplus gear. Advertise it here in Silicon Chip. PROJECT REPAIRS PROJECT REPAIRS - Having trouble getting your EA/ETI/SC kit to work? Phone (03) 7 49 3480 for estimate or send kit to K. Hunter, 5 Yatama Crescent, Werribee 3030. FOR SALE NEW 64K-256K PRINTER BUFFER design release. VER 4.0 and REV G boards now available. Double-sided PCB, EPROM and instructions: $39 .00. Optional additions include 2 by 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches, computer switches, and serial converter boards. For a free catalog sent a 37c stamp to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. RADIO/TV RESTORERS - We have a large stock of new valves . Send SAE for list or phone Shellharbour TV Service , 268 Mary St, Shellharbour, 2529. (042) 95 1175. EPROMS 2764 $4, 27256 $6, 27512 $10, 74HC374 $1, uP6800 $3, 6802 $4. All minimum quantity 100. Transistors - PNP 2N2907 A 5c, mimimum quantity 1000. Ask for Winnie on (02) 344 0173 after 6.30pm. Oatley Electronics - for exclusive and selected kits. These prices will not be repeated. Passive lnfrared Movement Detector Kit (SILICON CHIP, Dec. 1987): a PIR detector employs body heat detection and represents the most reliable type of detector currently available. This unit employs a dual pyroelectric detector and its performance is equalled by only the more expensive commercial equivalents. With the wide-angle lens fitted this unit has a view of 90 ° and a useful range of more than 1 0 metres. The narrow angle lens gives a useful ran ge of more than 25 metres! The kit include both the lenses and a scaled pattern of the lens housing. The lens housing consists of thin tin plate which 100 SILICON CHIP is easy to cut out and solder. On special until the end of this month for an incredible low price of only $44.95 including p&p (normally $57 .95). Metal box not included. Satellite Siren/Backup Siren Kit (EA, Sept. 1987): comes into action when the main alarm power is interrupted or the vehicle battery is disconnected. This unit is simple to install; it requires only two connections to your existing alarm system. What's in the kit? - 1 PCB plus kit components, 1 battery holder, 1 barrel key switch with two keys, and a suitable plastic case. All this for only $39.95 incl. p&p (normally $55.00). PCB and components kit only $16.90. UHF Remote Controlled Key Kit (EA, Jan. 1986): this multi-purpose unit is on special for only $41.95 plus $2.50 p&p. For full details see our advert in SILICON CHIP, July 1988. Stereo VU Meter Kit (EA, June 1987): the kit includes the stereo meter movement and is priced to clear at an incredible low price of only $9.95 (normally $17.95) plus $1.50 p&p. Only while they last. FM Transmitter Kit: professional quality - low noise - has pre-emphasis suits microphones, guitars, instruments etc. See EA, Sept. 1986. You can buy the complete kit which even includes the preamp for only $14.95 plus $1.50 p&p to clear stock. Want more information on a listed kit? Just send us $1 .00 and a stamp and we will send you a complete copy of the instructions. If at a later stage you decide to buy the kit, simply tell us not to include the instructions and subtract $1.00 from the kit price. Mail address: Oatley Electronics, PO Box 89, Oatley, NSW 2223. Shop address: 5 Lansdowne Parade, Oatley West, Sydney, NSW 2223. Phone (02) 579 4985. Shop hours: Mon; Wed; Thur; and Fri. between 10am and 5pm. Also Saturday between 10am and 1 pm. Telephone orders: Bankcard, Mastercard and Visa Card accepted with phone orders. Minimum order on a credit card Is $15.00 Mail orders: Bankcard, Visa Card, Mastercard, cheques and postal money orders accepted. Advertisers Index Allied Capacitors .................. 11 Altronics ....................... . 40-43 Arista Electronics .... .. ...... .. ... 39 Avtek ........ ..... ...... ......... .... IBC Bell lRH .. ...... ........ ...... ........ 19 Contact International .......... .. 95 Dauner Electronics .............. 4 7 David Reid Electronics .... ...... 13 Dick Smith Electronics .. .. . 62,63 82,83,87 Elmeasco .. ........ .. ........ ...... IFC Geoff Wood Electronics .... .. .. 89 Jaycar Electronics ...... .... 24-27 72-75 J.V. Tuners .. .. .... .... .. ...... .... . 47 Kenwood Australia ... ... .. .... OBC Marantz Australia ............ 50,51 Pre Pak Electronics .. .. .... .. .. .. 69 RCS Radio .... .... .. .. .............. 96 Rod Irving Electronics ..... 34,35 92,93 Scan Audio ........ .. .......... ..... 11 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd , 651 Forest Rd, Bexley, NSW 2207 . Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool , WA 6106. Phone (09) 350 5555 . • Marday Services, 2139 Great North Rd , Avondale, Auckland , NZ . Phone 88 5730. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines. The definitive book: "The Homebuilt Dynamo" (1987) , 182 pages, 8.5" x 12", hardback. Generator design and construction with ceramic magnets. Complete plans, 268 photographs, step-by-step construction details. $A85.00 postpaid airmail (brochure $A5.00 refundable). Todd-Forbes Publishing, 627 West Coast Road, Oratia, Auckland . NOW GET EVEN BETTER VALUE ON THESE OUTSTANDING MODEMS Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even better value when you buy. Purchase any one of our modems before November 31st and you can purchase a Cybersoft Gateway V3 High Performance Communications Software Package for ½ price <at> $75.00. Just check the features and the prices of Avtek and you'll see why it's the modem chosen by more and more PC users. MEGAMODEMS 12/123 Specifications: Ddta Standards - CCITTV.21, Bell 103, CCITTV.22, Bell 212. Data rates - 300/300, 1200/1200 (model 123 1200/75 VIATEL). FROM s375 {Including 12-month warranty) More compact and reliable than most and suitable for data transfer between PCs, on-line services, E-mail and all videotex facilities like VIATEL (Model 123 only). Available as a standalone RS232 model or as a plug-in true ½ card for IBM PCs and compatibles. A fully automatic operation, HAYES-compatible smart modem. 1 ,~E: · :~y,,;; MINIMODEM II AN IDEAL FIRST MODEM! Specifications: Data Standards - CCITTV.21 (300/300 baud full duplex). Data rates - CCITTV.23 (1200/75 baud). .. J • t ,. Ji 1 t : 1' • $199 '~'* VALUE AT {Includes 3-month warranty) I 'l't '; 'f'a f, Vt • l 1!'; • f . I ~ . HI\ \ \ T Y !:V' \\') · · •H U..a'.::.L,u:,.il.).~ A highly reliable data communicator at a budget price. The compactly designed Minimodem II is supplied complete with Telecom-approved, pushbutton phone . PHONE NOW FOR FAST DELIVERY. PH.: (02) 888 5333. MAIL ORDERS WELCOME. AVTEK, P.O. BOX 651, LANE COVE 2066. 30-DAY. NO-QUESTIONS-ASKED, MONEY-BACK GUARANTEE. All Avtek modems are sold complete with power supply, instructions and telephone connections. Designed and built in Australia, service and technical support for modems is available direct from Avtek Data communcations. fAVTEK DATA COMMUNICATIONS (A Member of the NetComm Group of Companies) r-:- - - - - - - 1 nease send me further information and detailed broGhures to: I Name _ _ _ _ _ __ II __________ _ _ _ _ _ __ Address _ _ _ _ _ _ _ _ _ _ _ _ __ II Postcode Post to Avtek Data Communications, P.O. Box 651, LANE COVE 2066. _