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Leo Simpson and Greg Swain present ... Hifi review: Marantz' s super new CD-94 CD player Aeg1s1ered o, Ausiraha Pos; Publica11on No NBP 9047 Fluke. First Family of DMMs. When accuracy, performance and value are important, professionals the world over look to Fluke - the first family of DMMs. Reliable Fluke-quality 3½- or 4½-digit DMMs fit every need - from design engineering to industrial troubleshooting. There's the low-cost 70 Series - the most DMM you can get for the money. The tough 20 Series - totally sealed and built to survive the dirtiest, grimiest, roughest jobs. The reliable 80208 Series - made to withstand the rigors of the field service environment. The precise 8060A Series the most powerful and complete test and measurement system available in~ handheld package. And, of course, the versatile Bench/Portables that carry on the Fluke tradition for precision and durability in lab-quality bench instruments. Fluke comes in first again with the world's largest selection of quality accessories to help extend the capabilities of your DMM even further. There's no need to look anywhere else. Uncompromising Fluke design and leading edge technology are the reasons why attempts at imitation will never fool the millions of professionals that accept nothing less than a Fluke. FROM THE WORLD LEADER IN DIGITAL MULTIMETERS. IFLUKEI ® E L MEASCO Instrument/I Pty. Ltd. Dealer enquiries welcome f aik to your local Elmeasco distributor about Fluke • A&.L.. John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 • ll.S..W. 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.Di xon (049) 69 5177 • Ebson 707 2 111 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Ply Ltd 698 4776 • Petro•Ject 569 9655 • David Reid 267 1385 • Selectroparts 708 3244 • Geoff Wood 427 1676 • N.TERRITQRY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 • OgfENS~Nfs Auslec (07) 854 1661 • G.Brown Group (07) 252 3876 • Petro-Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff t:le ronics 1 55 • Nortek (Townsville) (077)79 8600 • l.E.Boughen 3691277 • Fred Hoe & Sons 277 4311 • The Electronics Shop (075) 32 3632 • T hompson Instruments (Cairns) (070)51 2404 • S AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 0391 • Petro -Ject 363 1353 • TASMAWA George Harvey (003) 31 6533 (002) 34 2233 • VICTORIA Radio 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 8222 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 • WAUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044 JANUARY 1 988 FEATURES 4 The Evolution of Electric Railways 12 32 68 86 by Bryan Maher Pt.3 - The problem of braking The 1987 CESA Hifi Awards by Leo Simpson Best amplifier, tuner, CD player & loudspeaker Marantz's Elegant New CD Player by Leo Simpson For the audio connoisseur OTC'S Automatic Seaphone Service by Leo Simpson Ship-to-shore dialling for all boat owners Digital Fundamentals, Pt.3 by Louis Frenzel Teach yourself digitial electronics WHAT WERE the best hifi products for 1987? We name the winners of the 1987 CESA Grand Prix hifi awards on page 12. PROJECTS TO BUILD 14 High-Performance UHF Antenna by Leo Simpson Uses readily available materials 24 Update the Sound of Your Telephone by John Clarke Simple circuit fits in your telephone :t 18.5V power supply by John Clarke The ideal supply for your workbench 48 1 GHz Digital Frequency Meter Pt.3 by Steve Payor Construction, calibration a nd troubleshooting 64 Subcarrier Adaptor For FM Tuners by John Clarke Listen to hidden FM transmissions 71 The Flexo Shortwave Antenna by Ed Noll Improve your shortwave reception 38 Dual Tracking IF YOU CAN do basic metalwork you can build this high-performance UHF antenna. It's a four-bay bowtie design to cut down on interference and ghosting. Details page 14. SPECIAL COLUMNS 56 Serviceman's Log by the original TV serviceman When the chips are down 76 Amateur Radio by Garry Cratt Amateur television: getting started 82 The Way I See It by Neville Williams Information has its place, but what about knowledge DEPARTMENTS 2 Publisher's Letter 3 Mailbag 10 News & Views 22 Circuit Notebook 43 Bookshelf 79 Product Showcase 94 Ask Silicon Chip 96 Market Centre HERE 'S THE ideal power suppl y for your workbench. This is a dual tracking design giving up to ± 18.5V, and features voltage metering and short circuit protection. Turn to page 57. JA NUARY 1988 1 SILICON CHIP PUBLISHER'S LE'I-IER Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, 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 ttie publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Waterloo , NSW 2017 . Printing: Macquarie Publications Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates are currently $42 per year ( 1 2 issues). Outside Australia the cost is $62 per year surface mail or $120 per year air mail. 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 B.,each , NSW 2097 . Phone (02) 982 3935 . ISSN 1030-2662 * Recommended and maximum Australian price only . 2 SILICON CHIP There's a UHF antenna in your future Some time ago we planned to publish a four-bay bow-tie UHF antenna. We thought it would be quite a popular project since more and more viewers, even in the country, are now being serviced with UHF television broadcasts. The bow-tie array we are publishing this month has a number of desirable advantages over the more familiar long Yagis used for UHF. First, it covers both UHF bands and it has better discrimination against "aircraft flutter". With those thoughts in mind, we were quite pleased to be going to press with this antenna as featured in our article. And that would probably have been the end of the story as far as our January issue was concerned. However, just as we were going to press, the Department of Transport and Communications issued stage one of a timetable for television channel changes from the VHF to the UHF bands. This is the long awaited announcement of the Department's plan to move television stations from the FM band, so that more FM stations can go on the air. Most of the displaced TV stations will have to move to the UHF (ultra high frequency) bands. The timetable will mean far reaching changes for millions of people around Australia. Whereas most people up till now have not felt a pressing need to install a UHF antenna, even though some UHF services have been available, they will now have to do so. It will be mandatory, if they wish to continue watching the same programs. Three television channels are in the FM band, 88 to 108MHz: channels 3, 4 and 5. As well, channel 5A will also be moved upwards. And a number of translator services occupying channels elsewhere in the VHF (very high frequency) bands will also move into the UHF bands to make way for some of the stations moved from the FM bands. In stage one of the timetable just released, 15 TV stations and three translators will be moved from channels 3, 4, 5 and 5A. These moves will be accomplished by late 1990. Stage 2, for channel changes after 1990, will be announced in the next few months. We'll publish full details of the changes as they become available. The changes have been decided upon after a long period of consultation with all parties in the TV broadcast industry. In the short term, they will cause some disruption while viewers slowly make the necessary adaptations. In the long run, we'll have a lot more FM stations which will be all to the good. But sooner or later, many more people will be watching UHF TV broadcasts. Which makes our UHF bow-tie array rather timely, doesn't it? Leo Simpson MAILBAG A winner I have just read the first issue of SILICON CHIP and you have an absolute winner. I cannot remember the last time I picked up an electronics magazine that had so much meaty editorial and project content. It is also pleasing to see that you have assembled a great team of contributors. It has been a long time since I actually looked forward to the next issue of an electronics magazine. Gary Johnston Managing Director Jaycar Pty Ltd Congratulations Our hearty congratulations on the birth of your great new magazine. The high standard of both features and construction projects looks a winner. A few years ago the ranks electronics enthusiasts were decimated by defections to the personal computer phenomenon. I'll bet 90 % of them have now found personal computers pretty droll. SILICON CHIP should be just the ticket to entice the hackers back to the world's most interesting hobby - electronics. Jack O'Donnell Managing Director Altronic Distributors Pty Ltd Delighted with format Congratulations on your exciting new venture. As a long time enthusiast and previous subscriber to another electronics magazine, I was delighted with the format and content of the first issue of SILICON CHIP and wish you the best of luck for its success. It was a pleasure to see some simple, cheap yet extremely useful projects which other magazines have been lacking in recent times (namely the Capacitance Adaptor for DMMs and the Off-hook Telephone Indicator, both of which I'll be building). Hope you'll keep up the excellent standard. George Mangos Maroubra, NSW Likes steam As a regular peruser of newsagents' shelves for magazines of various kinds, and a regular reader of various Australian electronics magazines, I was impressed with your first issue. It contained a good variety of articles, without the sanctimonious suggestion that everything therein (steam engines, for instance} was intrinsically tied up with "stateof-the-art" electronics. Congratulations. T. Graetz Walla Walla, NSW SIUCON CHIP, PO Box 139, Collaroy Beach 2097. Does not like steam I have just purchased and read your first copy of SILICON CHIP. On the whole it appears to be a good attempt to breathe some life back into the electronics magazine scene in Australia. My definition of an electronics magazine is one which introduces the reader, both beginner and experienced, to the technical aspects of electronics. These are to include explanations of new technologies, processes, design techniques and construction projects where possible to help reinforce the concept. I am particularly interested in getting involved in amateur radio and I hope that your section will provide a good deal of information along with projects. Too often these days, it appears to me, many magazines are overburdened with vaguely related topics. Just because its got a processor does not necessarily make it interesting. Therefore, I cannot condone your feature on electric railways or any similar articles you may have planned. An article on the devolopment and operation of electric motors would have been more relevant. How your particular publication develops will be up to yourselves and your contributors but I wish you all the best of luck on your venture. Hands up who has done that in the last two years! I have since debated this issue with electricians who genuinely understand the problem (there are very few who do} and they argue that two earths must provide better protection than one. While this may be true, it is also true that the consumer will be unaware when one of the earth connections becomes faulty. This condition could exist for several years. The real problem occurs when the other connection becomes faulty or is disconnected by a tradesman (electrican or plumber). That's when every three-conductor appliance in the premises will become live at 240V AC above earth! Worse still, if the neutral is faulty and a plumber disconnects your incoming water pipe, all your taps will be live in addition to your appliances. How often is that likely to occur you ask? I firmly believe there have been at least five deaths in Queensland alone in the past several years that were directly attributable to the above condition. Newspaper reports say the deaths were due to an electrical fault. Your article suggested that consumers could buy "clamp-on meters" and check their own installation. I do not believe people will go to this trouble, technical or not. There is a safer solution: (1} Convert all premises back to the "Direct Earth" system; and (2) Earth all neutral wires at suitable intervals at street power poles. This will give the advantages of the MEN system without the safety hazards to consumers. L. Iemi Bentley, WA M. McDonald Wynnum, Qld Safer solution to M.E.N. hazard I was very interested in your article "Your House Wiring Could Kill You" (November 1987). The MEN system has concerned me for many years, since introduction, due to the reasons outlined in your article. I wrote to a number of authorities several years ago, stressing the inherent dangers of the system, to no avail. The bottom line was: "It is the consumer's responsibility to ensure his electrical installation is maintained in a safe ·condition." Jumper lead solution I like your new magazine. It looks good and the content is excellent. Good also to see the Veroboard alternatives for projects. I don't usually buy kits and have no enthusiasm for making boards, hence usually have to do the conversion myself. I have two comments on your article entitled "Your House Wiring Could Kill You". You say the wiring can develop a dangerous fault. Actually the danger only arises when continued on page 70 JANUARY 1988 3 PART 3 - TIIE PROBLEM OF BR 'I'H E EVOLUTION OF ELECTRIC RAILWAYS While early railway development in England and America is well documented, much pioneering work was also done in Europe, particularly in Fronce, Germany and Sweden. By BRYAN MAHER Sweden did some impressive development for they were in the railway business quite early, having used horse-drawn mine railways as early as 1798. The first steam locomotive built in Sweden was named the "Forstlingen" and began service on a private line from 4 SILICON CHIP Ore bro to Nora in March 1856. The Government responded with the opening of a line from Goteborg to Jonsered and another from Malmo to Lund, the first segments of their future National Network, in December of the same year. Within six years the railway crossed their country from ,/', Stockholm to Goteborg and by 1892 they had in operation the world's first International Train Ferry, connecting Helsingborg in Sweden with Helsingor in Denmark. In 1885 to 1902 they built the fi~st railway within the ~retie Circle, the Lapland Railway, · · to transport iron ore from Kiruna to Norway's ice-free seaport Narvik. This railway was electrified in 1915. Extended to the Swedish port Lulea on the Gulf of Bothnia in 1903, the whole 490-kilometre length was fully electrified by 1922. This world-first initiative in the development of low frequency alternating current traction H· •·-· At left, a view of Sweden's Lapland Railway in mid-summer. This line runs within the Arctic Circle but ◄ carries 38 trains per day in each direction. (Bryan Maher photo). systems initially used a 15kV 15Hz supply generated specifically for traction in low speed water-driven alternators at the Porjus Power Station and transmitted via 80kV single phase power lines. The motors used are series commutator motors. The reason for the low frequency supply is that on higher frequencies like 50Hz the interpoles do not effectively cancel the armature magnetic field reaction on the main magnetic field, leading to severe arcing between commutators and brushes. The permanent summer snowline in such northern climes is a mere 1000 metres above sea level. Since about half the line's length is above 500 metres elevation, the track is only free of snow during midsummer. Therefore, the electrical designers decided to house all trackside 80kV/15kV transformers within large brick buildings for protection. But this plan came slightly unstuck when the electrical workers had the transformers temporally installed and working out in the open while the bricklayers were still at it. As winter approached, all work necessarily ceased but the transformers and electrical gear performed beautifully all winter, even in blizzard conditions. The cold air gave better cooling and allowed the transformers some overload rating so the engineers decided to leave them where they were. Keeping in mind the low frequency used, transformer cores and hence complete transformers are considerably larger than similar 50Hz types so the now unwanted brick buildings had been built to generous proportions. But what use could be made of them now? Even- tually, these strong brick structures were put to good use as the roomiest passenger waiting rooms on the system. As well as being a lesson in international cooperation, as locomotives of both countries (Sweden and Denmark) share the work, this line is unusual for Europe as ore trains of 5500 tonnes are commonly hauled by Dm class 4.8 megawatt (6400 horsepower) or Dm3 class 7.2 megawatt (9400 horsepower) locomotives. Perhaps you may find it difficult, gentle reader, to picture such an Arctic installation as a busy thoroughfare but in fact the average traffic is 38 trains per day in each direction six passenger and 32 ore trains. More than 30 million tonnes of iron ore are shifted to Narvik annually. When other Swedish lines were electrified, frequency converters were used to derive 16.666Hz single phase traction supply at 15kV from the three phase national grid 50Hz system. This method eventually replaced the 15Hz supply on the Lapland line also. By 1942 the world's longest electric train journey was in Sweden, a distance of 2022 kilometres. Braking In the 1830's it became quite apparent to the railway world that a moving train is very hard to stop and the early increases in locomotive power and train weight only increased the problem. Originally in England, hand operated brakes were fitted to each wagon and a guard was appointed to run along beside the train and set each truck's brakes as the train slowly rolled over the top of a hill. You may find it hard to believe, but this method of braking was still use on a few privately owned coal lines in the Newcastle areas as late as the 1960s. Increases in train speed in the 1840s soon put this method in the "too hard" category. American railroads responded by This two-axle electric locomotive was made by Messrs Fowler & Co, of Leeds, England at the turn of the century. It was intended for use on short lines. Electrical pickup was via trolley wheel. (Norm Marks photo). JANUARY 1988 5 turned a valve to allow some air into the "train line" and all truck brake cylinders let go partially or fully so the brakes were pulled on by the brake-springs. The nice part was that should a train coupling break and the train become parted, the hose couplings automatically uncoupled, allowing air into the lines of both parts of the train and all were brought to a safe stop. This method was used for years in Britain but trouble came when trains became heavier and faster still. Other countries experienced the same problems as they were building lines up and down mountains. There is a limit to the pull that can be exerted by a vacuum cylinder as it can only have one atmosphere pressure or about 15 psi acting on the piston. That limits the useable strength of the brakespring and hence limits the braking force that can be applied. Some way of using higher pressures was clearly needed. Westinghouse air brakes Built in 1901 by Messrs Siemens & Halske, of Berlin, Germany, this experimental loco used 50Hz three-phase AC at 10,000 volts. On board transformers stepped the voltage down to 750VAC. Just imagine the complications of the overhead wiring at points. (Norm Marks photo). fitting a walkway along the top of the roof of every wagon. At the end of each wagon's walkway was a handwheel to apply the brakes. Brakemen had to run the length of the speeding train to apply the brakes by turning each wagon's handwheel. When some handwheels were found hard to turn, each man was supplied with a heavy wooden club to assist. Tales of the Roaring West showed that these brakemen's clubs were useful in a brawl too! With longer trains up to four brakemen per train were employed, two riding in the brakevan and two riding on the engine. If two large locomotives were used doubleheaded, a train crew could be considerable, with a driver and two firemen to each loco , four brakemen and a conductor, eleven men in all. Such a headcount can only reflect the low wages and long working hours of those days. Can you appreciate their tough working 6 SILICON CHIP conditions descending the mountains in a winter snowstorm? To further assist in stopping trains the caboose (guard's van) was made large and heavy and equipped with a powerful handbrake operated by the conductor from within. Coal trains in the Newcastle area up to the 1960s still used the same idea. Vacuum brakes England, with more finesse, invented a vacuum operated brake system with vacuum pipe, hoses and hose couplings running the length of the train. Brakes on each wagon were pulled on by a spring and simultaneously held off by vacuum in a piston and cylinder. The train driver set the steamdriven vacuum pump in operation which evacuated the "train line" (ie, the pipe, hoses and all brake cylinders), pulling all truck and loco brakes off. This was the running condition. To stop his train, a driver simply That's where the Americans came into the picture. Inventive readers across the country can be heard mumbling something like "So what's the problem ? Why not just apply compressed air to the piston, any pressure you like to make it, instead of vacuum? Use 100 psi or 200 psi or whatever is necessary to pull off a more powerful brakespring?" Such an idea would give protection in case of a train coupling breaking. Furthermore, a wagon parked on a siding would perforce have its brakes on, and a handwheel and gearing could be used to pull the brakes off a parked truck when we want to move it for loading. The idea has in fact been used for short trains; you could call it a " straight air" system. But the catch comes with a long train, say a kilometre long with 100 wagons, each with its brake cylinder full of air. That's a large quantity of air to be moved a long distance to the engine before the brakes are applied, and-the brakes would be firmly "on" in the front wagons long before the air had travelled from the back of the train where the brakes are still "off" This would result in a nasty Pictured is a battery-operated loco used on the Lancashire and Yorkshire Railway. The loco weighed 22 tonnes and was capable of pulling loads up to 120 tonnes. (Norm Marks photo). "concertina" effect every time the driver uses his brake control. The Westinghouse organization of the USA patented a system wherein each wagon carries its own high pressure air reservoir and a 3-way air valve called the "triple valve". Brakes are applied by air pressure, not by spring, when the triple valve opens a path from the wagon's air reservoir to the brake cylinder. Brakes are released when the triple valve opens a path from the brake cylinder to atmosphere, letting the air escape, and simultaneously closing off the wagon ' s air reservoir. The lost air from the wagon's reservoir must be replaced for the next brake application. While brakes are not being used the triple valve opens a path from the train air pipe to the wagon's air reser- voir, allowing the air compressor on the locomotive to refill all wagon air reservoirs. This pumping-up process usually takes some time but that is acceptable if the system is used intelligently. "And just how?" you ask "does that clever triple valve know when it is supposed to change its function as aforesaid?" Yes it is a clever little valve indeed. Its function is dictated by the difference in the pressure between the wagon's reservoir and the "train line". So the loco driver controls the triple valves and thereby the brakes by letting air out of the train line or allowing his compressor to pump the line back up again. The above story is a simplified explanation but it does show that full brakes can be applied by emptying to atmosphere only the air contained in the train line pipe. This is not a great quantity of air so it can be done fairly quickly. And if coupling breaks the train, full brakes are automatically applied to all train sections. Furthermore the guard or conductor can apply emergency brakes to the whole train, including the locomotive, by opening a simple onoff valve mounted in his guard's van or caboose emptying the air out continued on page 74 Now being phased out, this is typical of the heavy caboose or guards' van used on American railroads. (Conrail-J. Hill photo). JA NUARY 1988 7 BUILD-IT-YOURS SAVE$$$$! Flip-top steel case 200W Power Supply At last! The perfect opportunity to get yourself the perfect computer ... perfect because it has in it what YOU want! All the features of the'AT': Range of pre-assembled blinding speed, expandability, compatability, and so on. cards available - graphics, But you pay much, much less because you put it together yourselfl disk controllers, ports, etc No, there's no soldering or other difficult work required. All that's already done for you. Every pcb is pre-assembled and pre-tested 'Baby AT' mother (there's even a 12 month guarantee on every component!). All you do with 8 expansio is select what you want in your computer and connect it together, using & provision for 1 the cables and connectors supplied -from the detailed instruction manuals included with each component! Yes, it's that simple! And it's guaranteed to be that simple: everything you buy is designed to fit together ... holes line up, slots are in the right place, etc etc. No more hassles with bits and pieces from various suppliers which sometimes fit, sometimes don't! WHY BUILD YOUR OWN COMPUTER? Apart from the reasons above (ie, you get what you want and you pay less - two of the best reasons ever invented!!!) there are a few other big reasons to 'do it yourself': (1) You'll learn as you go! Nothing teaches you more about how something functions than constructing it yourself. It's the best way for anyone to gain an understanding of the fundamentals of computer operation - even if you've never looked inside one before! Suddenly all those 'buzz words' you've often wondered about will start taking on meaning ... (2) Imagine being able to say 'I built it myself!' Yes, just imagine. It must be one of the ultimate projects! School & Tech students - think of how this will shape up as your major project: and think of how much value it will be to you in the future! Business People: now the computer you've always wanted at work can be the one you have. And with the money you'll save, there'll be enough left over for another one at home! Hobbyists: how long is it since you've really been able to get your teeth into a 'real' project? (3) We've made it so affordable! You don't have to outlay a large amount in one hit: this computer has been deliberately kept in 'modular' form so you can buy the individual bits and pieces when you want them - and when the pocket will allow them! 4 clock speeds from 6 to 12MHz inbuilt Keyboard lock for security BRIEF Mother Board: 80286 CPU 6, 8, 10 & 12MHz speed (selectable) Provision for 256K, 512K, 640K or 1024K RAM on board CHIPSet technology & IC's 7 Channel OMA 16 Level Interrupt Award BIOS (fully licensed) Real time clock on board (battery b/u) 8 Input/Output Slots (6 with 62 and 36 pin connector, 2 with 62 only) CMOS Memory to Maintain System Configuration IBM PC/AT compatible All LSI & RAM IC's fully socketed 80287 Co-processor socket provided ELF'AT' Buy what you want, as you want it ... Baby AT' Motherboard: Complete with 8 expansion slots, back-up battery, speaker, manual and all lC's except RAM. Catx-1000 $799 Hinged Steel Case Footprint just 430mm square, case covered In quality bone crinkle finish. Pre-drilled, slotted, etc as required, complete with front panel. Catx-1005 *175 200W Power Supply With enough capacity for full expansion, complete with whisper quiet fan, on/off switch and input/ output connectors. cat x-1010 *275 DISK CONTROLLERS: Floppy Controller:- Up to 4 36OK or 1.2Mb drives. CatX-2014 Hard/Floppy Controller: Handles 2 of each hard/flopoy. CatX-2008 *129 *399 DISK DRIVES: *269 *795 1.2Mb Floppy Disk Drive Complete with cables Cat x-2200 20Mb Hard Disk Complete with cables Cat x-2203 PLUG-IN CARDS: *129 *149 *399 *139 CGA & Parallel Printer: Cat x-2010 MGA & Parallel Printer: catX-8141 EGA card with Hercules Compatabillty: cat x-2013 Serial/Parallel/Game Port Card: Cat x-2012 KEYBOARDS 1.2Mb Floppy and/or 20Mb Hard Disk SPECIFICATIONS Hard/Floppy Disk Controller: Controls 1 or 2 hard disks Ind. standard ST-506/ST-412 Interface Up to 2048 cylinders Up to 16 read/write heads Data Transfer rate SMb/s Controls 1 or 2 floppy disk drives Interface similar to FD-SSF minifloppy Double density 320/360Kb or 1601180kb High density 1.2Mb Rated to work up to 12MHz Graphics Cards: MGA, CGA & EGA available Ports: Keyboard port on motherboard Parallel, serial & game ports on interface Monitor port on appropriate graphics card 84 Key 'IBM' Format Cat X-3820 101 Key Expanded Style: (direction keys and extra function keys) Cat X-3821 MEMORY Fast (120ns) top quality 41258 RAM chips. 9 required per 256K bank. CatZ-9313 (each): Special price tor 18 or more: (each): *129 *149 *1095 •9• 5 EXCLUSIVE TO l>CK0SMITH EL iCS PTY LTD DSEB465/RT1087 NEWS & VIEWS Radio BDR in Darwin has begun transmitting in AM stereo and is the most recent of the ABC's metropolitan stations to have this facility. We were interested to read the following in a press release on the event. "Because AM stereo is a recent innovation, only late model Pictured above is the previewed Philips CD Video player, the CD475. It can play 12cm, 20cm and 30cm video discs. Note the massive disc drawer. Just when you thought things were fairly quiet on the technological front, Philips have stirred the pot again. Late last year Philips previewed CD Video - compact discs with video. They weren't just video stills either, they were the full bit - moving colour pictures, every bit as good as from the current VHS HQ VCRs. And they have the same high quality compact disc sound. "Alright," you are saying,"that's pretty radical but I can accept it. So what?" Well, CD video discs will not just be on the familiar 12cm discs we have become used to; they will also be in 20 and 30cm versions too. The 12cm version will contain six minutes of video and music plus another 20 minutes of music only. And it can be played on any CD player, video or not. It will be known as the video "single". The 20cm version of the disc will contain about 40 minutes of music and video while the 30cm version will contain about two hours of music and video. In a throwback to the vinyl record days, they will be known as "extended play" and "long play" discs. With the disc drawer closed, the CD475 looks very much like a normal CD player. No release date has yet been set, nor is there any indication of price. 10 SILICON CHIP Have you taken all that in? The next bit is even more interesting. Philips have developed a player which plays all the CD video discs described above, plus normal compact discs, plus all optical video discs ever made. They demonstrated the machine, the Philips CD675, with a video disc released nine years ago! This means the player can be used with interactive video discs. Naturally, the machine has perfect video stills and slow motion replays. Boggle, boggle. At the time of writing, no info was available on the likely release date to the market of the discs or the players; nor was their any real indication of prices. We expect that release will probably be towards the end of this year. • Philips and Sony, the codevelopers of the compact disc, have agreed on specifications for a CD Write-Once system intended for professional use. The proposed write-once recorder will permit recording of data or audio information onto a blank write-once disc. The information can then be played back repeatedly, as for a normal compact disc or CD-ROM. Data storage capacity will be essentially the same as for the existing CD-ROM; ie, a mind-blowing 600 megabytes. Philips gives James Bond the best radio receivers are capable of receiving and reproducing AM stereo, however all AM radio sets can still receive AM stereo broadcasts. Those sets without stereo capability will simply reproduce them in mono. ABC listeners wanting stereo sound reproduction should first check that their radio sets have built-in AM stereo capability." We wonder if ABC listeners will bother. rA:nstra ·a man11fact er baml to-g:eth-ei A group of Australian hifi manufacturers have formed an association to promote their products on local and overseas markets. It sounds like a good idea to us. We hope they do a lot more than the majority of foreign-owned companies at present in the market. While some sectors of the hifi market are doing quite well, others are dying on their feet because of the lack of any promotion. There is just one drawback to this promotional scheme; it will go under the dreadful logo, Ozfi. Will anyone take a product with an "Ozfi" label seriously? Come one, come all. All amateur radio operators, their families and anyone interested in amteur radio are invited to attend the 1988 Central Coast Radio Club Field Day to be held on Sunday, 21st February at the Gosford Showground. If you're interested, put the date down in your diary. If you are a potential trade exhibitor, contact the Central Coast Amateur Radio Club, PO Box 238, Gosford, NSW 2250. Advertising has leapt to i:iew heights with the release of the latest James Bond film, "The Living Daylights". This is loaded with the usual improbable plot, improbable dialogue and improbable escapes and is a lot of fun. The most unusual feature for us was the exposure of Philips products. This wasn't glaringly obvious you understand, and you could easily miss it if you weren't aware but we noted at least 12 instances where the Philips brand name or Philips products were featured. Some of the tasks to which Philips products were put to were a little unusual to say the least. As far as we know though, James Bond's special keyring which is loaded with a number of techno-gimmicks, is not a standard Philips product. We doubt whether it would be approved for general sale. Radio service for Japanese tourists In case you didn't believe it, Australian companies are working harder to cater to tourists, particularly those from Japan. Commencing next month, there will be a special radio service aimed at Japanese tourists. Known as Travrad (Travellers' Radio), the service will be broadcast in Adelaide, Alice Springs, Brisbane, Cairns, Canberra, Darwin, Gold Coast, Melbourne, Perth and Sydney. Broadcasts will be narrowband FM on about 151MHz from 6am to 10pm every day. The broadcasts will be picked up on fixed receivers in motels and hotels and on portables which will be available for hire at hotels and other tourist destinations. The service will be operated by a new company, Fidelity Communications Corporation Ltd. It will be a Japanese language service carrying news and info about tourist activities, Australian history, customs and lifestyle, music and human interest material. Better throw another shrimp on the barbie, eh? Cordless phone import ban The Department of Transport and Communications has moved to prevent overseas travellers from bringing back cordless telephones into Australia. In a recent announcement, the Minister for Land Transport and Infrastructure, Mr Peter Duncan, said that all cordless phones brought into Australia are being impounded and must be tested before release, by the Department of Transport and Communications, by Telecom and by one of the Electricity Authorities. He noted that fees for this type of testing may exceed $1000 and there is no guarantee that any equipment will be approved for use. Better knock that item off your overseas shopping list. Approved cordless phones will continue to be on sale in Australia. Four-wheeled boats! Now that OTC's automatic Seaphone service with direct dialling ship-to-shore has been introduced (see story this issue), how many cars are likely to be fitted with marine radios? That's a question the pundits are asking themselves as they compare the pros and cons of Telecom's cellular radio with Seaphone. With the much lower initial cost of Seaphone, it is probable that quite a -few will be fitted to cars. It seems that OTC's base radios do not ask the position of boats when they call in so they have no way of knowing whether the radio is fitted to a boat or car. There has been at least one instance of a Seaphone call for road service. JANUARY 1988 11 FOR A NUMBER of years now Sony has had a reputation for very fine tuners and this year they won out with their model ST-S444ESX. Its outstanding specification includes an ultimate signal-to-noise ratio of 96dB in mono and 91db in stereo. RRP is $893. WINNER IN THE Technological Development category, the Bose Acoustimass system uses the very small stereo satellite speakers pictured above, which are only 19cm high and have magnetically shielded drivers, allowing them to placed near video monitors. The Acoustimass woofer module, pictured below, can be positioned anywhere in the room. 'IHE 1987 IIlFI AWARDS - TIIE WINNERS From a limited field of runners, this year's CESA Grand Prix hifi awards produced some interesting winners. Consistent performers like Marantz and Sony were there again, as was Yamaha, while Bose chalked up its first award. BEST AMPLIFIBR this year was the Marantz PM-64Il which has comprehensive input control facilities, including video inputs and CD-direct, which bypasses the tone controls and other preamp circuitry. Power output is 100 watts RMS per channel and up to 300 watts (IlIF music power) into 2-ohm loads. RRP is $1099.00. 12 SILICON CHIP YAMAHA HAS been one of the few Japanese loudspeaker manufacturers to really gain a reputation for its loudspeakers. This is not the first time it has won the CESA award for best loudspeaker. This very fine 3-way system, the NS-10000, uses carbon fibre technology in the woofer and beryllium for the tweeter and midrange domes. RRP is $13,000.00. By LEO SIMPSON The CESA Grand Prix hifi awards have been having a rough trot since their inception three years ago and each year has been marked by less entries as more hifi distributors retire from the field to lick their wounds and comtemplate an ever toughening market. A surpise, but no surprise really, was that there were no entries at all in the turntable category. The Japanese have virtually abandoned the field altogether to chase after the burgeoning compact disc market. This, while millions of people around the world still have billions of records they wish to play. Winner in the amplifier category was the Marantz PM-641( making it two consecutive wins for this company. The PM-64II is a keenly priced model with plenty of power and facilities. Runner up was the powerful Perreaux PM2350 with 200 watts per channel. No award was made in the receiver category, since it was only a two-horse race. Similarly, the judges decided not to make an award in the cassette deck category - it was a field of plodders but the racers of the day hadn't been entered. In spite of the large number of CD players on the market, there were only five entries in this category, from Marantz, JVC, Yamaha, Sharp and Sony. Sony was the winner, with their highly rated model CDP-555ESD. Sony also won the tuner category, with their ST-S444ESX model which has very high performance in its FM section. The other two awards, for best loudspeaker and for technological development, were interesting because the respective winners were originally not entered in their ultimate award category. The Bose Acoustimass, a sa telli te-cum-superwoof er system was entered in the loudspeaker category but won the award for technological development. And the Yamaha NSl0000, which was entered in the category for technological development, won the prize for best loudspeaker. Let's hope there are a lot more horses running next time. SONY'S top-of-the-line CDP-555ESD CD player has every feature you could think of, including remote volume control. It can also be teamed with an optional linear D-A converter, the DAS-702ES, for even higher performance. RRP of the player on its own is $2299.00. JANUARY 1988 13 14 SILICON CHIP By LEO SIMPSON & BOB FLYNN If you can do basic metalwork you can build this antenna. Your bill of materials will be around $25 and the finished antenna should give better performance than commercial UHF Yagi antennas costing up to a hundred dollars and more. In Australia, on the UHF (ultra high frequency) TV bands, the Yagi antenna is king. UHF Yagis are now very familiar on Australian rooftops. They have a long boom, up to 1.8 metres or more, with many short elements arranged along it. The Yagi design for UHF has many advantages. It is easy to mass produce, uses a modest amount of material, has relatively low windage (ie, force due to wind acting on it), good directional characteristics and good gain, depending on the number of elements. The Yagi does have a number of drawbacks though. It must be made with considerable precision if it is to perform well, so it is not so easy for the enthusiast with basic metalworking facilities to build. It is also a no-compromise design in that it is not practical to design a Yagi which will cover both UHF bands, particularly if you want a modicum of gain. You can have band IV or band V but not both. In Australia, by the way, UHF band IV covers channels 28 to 35, 526 to 582 Megahertz. UHF band V covers channels 39 to 69, 603 to 820MHz. Each channel occupies a 7MHz slot. In Europe and other parts of the world, there are common alternatives to the Yagi design. One is a Yagi with a corner reflector, another is a bow-tie with corner reflector, while a third is the most common, the bow-tie array. This is essentially a dipole (shaped like a bow tie) with a plane reflector close behind it. Higher gain is obtained .. .. .. :(l 1 REFLECTOR ELEMENTS 6mm x 1mm WALL THICKNESS ALUMINIUM TUBING 600mm LONG 17 REQUIRED Fig.1: front and side elevation of the new UHF antenna. This diagram labels all the special hardware items that you have to make except for the reflector elements. Below is a close-up view of two of the dipole bays. Thinking about building an antenna to pick up UHF TV in your area? This four-bay bow-tie array has high gain and covers UHF bands IV and V without modifications. JANUARY 1988 15 THIS ROW OF HOLES ALL 6mm DIA. r ... "'"' N :!l + .,... BILL OF MATERIALS I .... "' N -+-t-+--+- ~ ., ;;; t .,... .,... l t I I "' "' I l l FRONT t "' "' I SIDE FRONT VERTICAL BOOM 19mm SQUARE x 1.6mm WALL THICKNESS ALUMINIUM TUBING BACK SIDE REAR VERTICAL BOOM 19mm SQUARE x 1.6mm WALL THICKNESS ALUMINIUM TUBING Fig.2: cut and drill the front and rear booms exactly as shown here. 16 SILICON CHIP by stacking bow ties, in either twobay or four-bay arrays. The latter is the design we are presenting. The four-bay bow-tie array antenna has a number of advantages over typical Yagis. First, it can cover both bands IV and V without modification. Second, it has better gain than all except the highest gain Yagis which may measure up to three metres long. Third, it has good front-to-back ratio and a much narrower acceptance angle, in both the vertical and horizontal planes . (Note: the 18-element TC-18 from Hills is a combination of a long Yagi with a small corner reflector. The corner reflector gives it slightly higher gain and a narrower acceptance angle. For those who do not wish to build their own antenna, it Antenna 1 .6 metres of 1 9mm square aluminium tubing with 1.6mm wall thickness 13.8 metres of 6mm aluminium tubing, 1 mm wall thickness 1 .4 metres of 3mm dia. solid aluminium rod 270mm x 130mm x 1.6mm aluminium sheet 4 1 0mm x 50mm x 3mm thick Perspex 50 pop rivets (3mm x 6mm , aluminium mandrel); or 50 stainless steel self-tapping screws (see text) 2 U-bolts and clamps to suit mast 16 stainless steel screws, 3mm dia. x 16mm long, nuts and shakeproof washers Balun Box 1 80mm x 52mm x 30mm plastic box 1 printed circuit board, SC2-1-0188 3 6BA x 12mm screws with nuts 2 6mm spacers 3 stainless steel self-tapping screws, 1 5mm long Miscellaneous 7 50 semi-air spaced coax cable (Hills SSC32 or equivalent), plastic cable ties, silicon sealant, Delrin plugs (for square tubing) is a good choice in fringe areas. It is available in Band IV and Band V versions). The narrow acceptance angle of a four-bay bow-tie array is important, particularly if your location does not have a good line-of-sight to the transmitter and if you are often over-flown by aeroplanes. This combination of circumstances can lead to a phenomenon known as "aircraft flutter". When this occurs, the signal reflected from the aircraft to your antenna can be stronger than the more direct signal received from the transmitter. This causes very strong ghosting on the screen and a slowly fluctuating vertical bar on the screen which is the ghost of the horizontal sync pulse. The picture flutters because the plane is moving at high velocity relative to your antenna and so the path of the strong reflected signal is changing rapidly. In severe cases. aircraft flutter can cause the picture to lose horizontal synchronisation. Where the bow-tie array has a considerable advantage over the Yagi is that it has a much narrower vertical (and horizontal) acceptance. This is about half that for a Yagi of equivalent gain; ie. about 27° versus about 40°. This means that the bow-tie array will pick up much less reflected signal from high flying aeroplanes and therefore interference is much less. Well, what about the disadvantages of the bow-tie array versus the Yagi. Yes, it does have some. First, because it is a vertical rather than horizontal array, it has considerably more windage. Ser:;ond, there is probably more work in fabricating a do-it-yourself design such as this. While we did not have equipment for measuring the absolute performance of the bow-tie array featured here, we were able to make a lot of direct comparisons with commercial UHF band IV and band V Yagi designs. These were essential to optimise the performance for both band IV and band V. After a lot of trial and error, we are pleased to present a design which is very competitive with pre- The front and rear booms are fastened together using four tie plates (see Fig.6). Bend the cross-coupled harness connectors slightly so that they do not touch each other. sent commercially available Yagis and as noted above, it is notably less susceptible to "aircraft flutter". Design features Our bow-tie array is similar in appearance to a number of corn- mercial designs which are available overseas. It is constructed mainly of 6mm aluminium tubing with the two vertical structural members (booms) being 19mm square tubing. The four dipoles are effectively vestigial bow-ties, being Vees made of tubing rather than JANUARY 1988 17 tapping screws. These are strong, readily available and corrosion resistant. We do not recommend galvanised, bright zinc or cadmium plated steel screws as these do not stand the test of time. Often they will start to rust within a few days' exposure in seaside areas. They may be OK for roofing work but in combination with aluminium they rust. If you live away from the sea and decide to use these types of screw anyway, we recommend that you paint the antenna. We'll talk about that later. Don't, on any account, use brass or mild steel screws. If you use these, you will spoil the job. 207 Fig.3: the 16 dipole elements are all made from 6mm aluminium tubing. Cut the dipoles to a length of 207mm. Q "' 18 26 26 18 100 Fig.4: either 3mm thick Perspex or clear Lexan can be used for the dipole carriers (four required). Making your antenna DIPOLE MOUNTING CLll'S 1.6mm ALUMINIUM 8 REQUIRED + + Fig.5: the eight dipole clips are cut out using tin snips and then bent up in a vice. ◄ 87 triangular pieces. This cuts down on the windage while keeping the bandwidth essentially the same. The reflector is essentially a large grille about 60cm wide and 80cm high. The four dipoles are mounted on a common vertical boom which is spaced away from the vertical boom of the grille by about 50mm. The antenna is shown in front and side elevation in Fig.1. This diagram labels each special hardware item you will have to make. These are: (A) the dipole carriers, four required; (B) the dipole mounting clips, eight required; [C) the main mounting plate; (D) balun box assembly; (E) dipole elements, 16 required; (F) the boom tie plates, four required; (G) front boom; [H) rear boom; (J) o'!lter harness connectors, four required and [K) inner harness connectors, four required. Also shown on Fig.1 but not 18 SILICON CmP Fig.6: cut and drill the four aluminium tie plates as shown here. These tie the front and rear booms together. labelled as such, are the reflector elements, of which 17 are required. Fasteners After a few years' exposure to the elements, many antennas are in a poor state. Because aluminium is such an active metal, the right fasteners must be used otherwise corrosion will be very rapid, especially in seaside areas. We recommend three types of fastener for this project: (1) Aluminium pop rivets with aluminium mandrels. Those with steel mandrels are not recommended. Eventually, their mandrels will rust and while this may not harm the antenna it will cause unsightly discolouration. (2) Though often hard to get, aluminium screws are recommended although they are not available in self-tapping types and so all screw holes would have to be tapped. (3) Stainless steel self- Most enthusiasts will have the tools needed for this project. You will need a hacksaw, electric drill, vice, pop-rivet gun, blow-torch or LPG cylinder and torch. Apart from a pair of antenna clamps [U-bolts ), no special hardware or fittings are needed as we will detail how every part is made. Making and assembling this antenna is a fairly straightforward process although some steps are a little tedious. You must first obtain all the aluminium and hardware listed in the Bill of Materials, and make sure you have access to all the tools we have listed above. Having assembled together all the raw materials, you can start work by cutting all the aluminium elements with a hacksaw. Cut the two booms first, which are made of 19mm square aluminium tubing. The details are shown in Fig.2. The rear boom is 812mm, while the front boom is 720mm long. Then centre-punch and drill all the holes in both booms. Make sure that all the holes for the reflector elements in the rear boom are precisely in line and that their centres are 4.6mm from the front surface as specified on the diagram of Fig.2. Do not forget the holes for the tie plates or the holes in the back of the rear boom, for the main mounting plate. Trying to drill these after the antenna has been partially popriveted together would be a tricky task. The mounting plate is rivetted to the back of the rear boom and carries two U-bolts to mount the antenna to the mast. Next, cut all 17 reflector elements and the 16 dipole elements. These are made from 6mm aluminium tubing with a 1mm wall thickness. The dipole element dimensions are shown in Fig.3 while the reflector lengths, all 600mm, are shown in Fig.1. Assemble each reflector element into the rear boom, one at a time. The method we used was to thread one element through the boom, centre it precisely and centre-punch on the front of the boom, at the intersection of the centre-lines of the boom and the reflector element. Drill a 3mm (or 1/8-inch) hole through the front of the boom and element and then pop rivet the two together. Do this for all 17 reflector elements. Dipole plate & clips Next, make the four dipole plates, as shown in Fig.4. We used 3mm thick white Perspex but you can use clear Lexan or Perspex as they stand the weather equally well. When drilling, do not use too high a speed otherwise the Perspex will tend to melt and congeal on the drill. Now, make the eight dipole clips. We cut and bent these from a strip of 1.6mm thick aluminium, 38mm wide. Fig.5 shows the details. Each clip can be cut with tin snips, flattened with a hammer and then each side bent up in a vice. That done, you can make up the four dipole assemblies, each requiring a Perspex dipole plate, two dipole clips, four dipole elements plus four stainless steel 3mm screws, nuts and lockwashers. Next, make the four tie plates which tie the front and rear booms together. You can also make the main mounting plate at this stage, since it uses the same material, 1.6mm thick aluminium sheet. The details are shown in Fig.6 and Fig.7. Now assemble the front and rear booms together. using the four tie plates. You can use pop rivets or stainless steel self-tapping screws for this job. Fix the main mounting plate to the rear boom, using pop rivets or stainless steel self-tappers. Mount the four dipole assemblies onto the front boom. Use pop rivets or stainless steel self-tappers. Your antenna now looks the part and only lacks the harness and balun box assembly. JANUARY 1988 19 Make the inner and outer harness connectors, as shown in Fig.8. These are made from 3mm diameter aluminium rod. This is the trickiest stage in the whole process. After cutting to length, the ends of each connector must be hammered flat. To do this satisfactorily, you will have to anneal each end with a blow torch (or LPG torch). Unfortunately, there is no easy way of judging how much heat to apply but if you overheat the end it will suddenly melt and fall on the floor. The way to do it is to place each end in the flame for a few seconds and then hammer it flat. If necessary, reheat the end to finish the job. In fact, aim to do the flattening in two steps of hammering and annealing otherwise you will inevitably melt it. That done, centre-punch each end and drill 3mm holes. The eight connectors are then ready to be attached to the four dipoles but before you can do that you need to prepare the balun box assembly. Incidentally, note that when the ends of the harness connectors are hammered flat, they spread and stretch quite a bit. This accounts for the fact that the outer connectors are cut to 200mm long but when the ends are hammered flat, the hole centres for the connector screws can be drilled 199mm apart. Balun box assembly The balun box provides a correct termination for the antenna harness and terminals for 75-ohm coax cable, all sealed away from the elements for protection. It takes the form of a black plastic box with a small printed circuit board inside. This mounts the air-cored balun and the terminations. The printed circuit measures 30 x 70mm (code SCZ-1-0188) and has a very simple pattern. The balun is made of two small coils of enamelled copper wire, as shown in Fig.9 and Fig.10. Use wire with selffluxing enamel for this job. Selffluxing enamel melts easily in a solder pot or with a soldering iron and is much easier to work with than high temperature wire enamels which must be thoroughly scraped off before the wire can be tinned with solder . .20 SILICON CHIP ~ ~ • 4 -I--. • ., I ♦ • ~ -$ 15 35 0 • 15 35 116 Fig.7: drill the mounting plate to suit the Ubolts and clamps used. CE==========================~ 199 OUTER CONNECTORS 3mm DIA SOLIO ALUMINIUM 4 REQUIRED CUT PIECES 200mm LONG, ANNEAL ENDS ANO HAMMER FLAT I 75 I { ~ 130 INNER CONNECTORS 3mm DIA SOLID ALUMINIUM 4 REQUIRED CUT PIECES 132mm LONG, ANNEAL ENDS AND HAMMER FLAT BEND AS SHOWN BEFORE MARKING HOLE POSITIONS Fig.8: dimensions for the inner and outer harness connectors. Use a blow torch to anneal the ends before hammering them flat. Incidentally, do not think that the connection of the outer coil of the balun is a mistake, as shown in Fig.10. It is correct, with both ends soldered to earth. The balun printed circuit board and its accompanying box is tricky to mount. We suggest the following method. First, attach the four harness inner connectors to the printed board using stainless steel screws and nuts. The aluminium conductors must not make physical contact with the copper side of the board. You can use brass or copper plated steel for the coax cable clamp. We suggest you solder brass nuts to the copper side of the board to secure the cable clamp and the screw to terminate the inner conductor of the coax cable. Fig.11 shows the details of the balun box and how it is mounted. Use one self-tapping screw to secure the box to the front vertical boom. Use two spacers and two self tapping screws to secure the printed board to the case bottom. The latter two screws should penetrate the boom. Now attach all eight harness connectors to the dipole assemblies and the antenna is virtually finished. Do not over-tighten the dipole assembly screws otherwise the Perspex will distort and possibly crack. You will need a pair of antenna clamps or U-bolts to mount the antenna to the mast or J-pole (for barge-board mounting). We prefer the use of galvanised U-bolts and Vclamps for this job rather than the cadmium-plated and passivated types used for most antenna hardware. The latter have a gold finish and often start to rust prematurely. U-bolts and clamps for automotive exhaust systems are 0 300{) ANTENNA __ 7~{l T _,. ~ BALUN TRANSFORMER PRIMARY 12T, 0.67mm ENAMELLED COPPER WIRE CLOSE-WOUND ON A 3.2mm DIA. MANDREL SECONDARY SLIPPED OVER END OF PRIMARY AND BOTH ENDS SOLDERED TD EARTH BALUN COILS MOUNTED ON COPPER SIDE OF BOARD SECONDARY 6T, 0.67mm ENAMELLED COPPER WIRE CLOSE-WOUND ON A 4. 76mm DIA. MANDREL Fig.9: winding and termination details for the air-cored balun. Fig.10: the balun coils are mounted on the copper side of the PCB. Note that both ends of the secondary are soldered to earth. tThe completed balun board. Brass nut-s are soldered to the copper pattern to secure the screws for the cable clamp, coax cable inner conductor, and harness connectors. generally quite suitable and have good corrosion resistance. Or, if you want to be really fancy, go to a ship's chandlers and buy stainless steel U-bolts and clamps. They're costly but good. We suggest that the ends of all the reflector and dipole elements be stopped up with silicone sealant. This will stop them from whistling in the wind. You can do the same with the booms although, for a neater result, you can buy square Delrin plugs. Installing the antenna Take a lot of care when installing your antenna. There's no point doing a fine job of assembly and saving all that money if you end up in hospital because you fell off the ladder. Climbing ladders with anten- 0 PLASTIC BOX BOX CENTRE LINE 00 00 ,- II -l- 1 N 0 0 (J en This is the actual size pattern for the balun board. nas is dangerous work. The first step in installation is to decide where to mount your antenna. For best results mount it as high as possible and well clear of other antennas. It is not really practical to mount this bow-tie array on the same mast as a VHF antenna unless it is vertically separated by at least one metre. Having mounted your mast, take the antenna up and secure it with the U-bolts. Then terminate the coax cable. For minimum signal attenuation and good cable life, we recommend Hills semi-airspaced cable, type SSC32 or equivalent. At your TV set end of the cable, you will probably need a diplexer to continued on page 95 View inside the balun box assembly. It should be sealed against the weather. WIRING HARNESS (BENO HARNESS TO CLEAR '--..._ ~ - - - - - + - - - - - - / " - - , , C A B L E CLAMP) ' FRONT BOOM 0 1 ,- I COAX 6.6mm DIA. HOLE FOR COAX IN ONE ENO DNL Y Fig.11: details of the balun box assembly. It is secured to the front boom at one end using a selftapping screw and at the other end by two selftapping screws which pass through the PCB and 6mm spacers. JANUARY 1988 21 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. Sequential lamp flasher for your car S1 0--0"""", FLASHER TIMER 2 TIMER 1 + 12 V LAMP 1 10k For those people who are tired of having a single pair of lamps at the rear of their car to indiciate righthand or left-hand turns, this circuit will make your vehicle different indeed. It allows three lamps to be flashed in sequence. Lamp 1 lights first, then lamp 2 and then lamp 3. Then all the lamps extinguish and the sequence begins again, at the rate set by the car's existing flasher module. You could add the extra lamps to the rear parcel shelf or mount them externally. Either way would give you much more visible turn signals. The circuit begins to operate with switch S1 closing. This lights lamp 1 immediately and capacitor Cl begins to charge towards the positive rail. When the anode voltage of Ql exceeds the gate voltage by 0.5V, Ql switches on and ,. A A(:f} SCR1 C106Y G ~~. C1 0.47 16VW KAG SCR2 C106Y G + _ 0.47 16VW .,. .,. triggers SCR1. This lights lamp 2 and powers the second timing circuit. This operates in a similar manner to the first timing circuit and lights lamp 3. When the flasher module opens, all lamps are extinguished and the sequence recommences when the flasher module closes the circuit again. Since each SCR drives only one lamp, usually 21 watts or + thereabouts, no heatsinking will be required. The time period can be adjusted by changing the value of the 0.47 µF capacitors. Note: this circuit will not work with those flasher modules which place residual voltage across the lamp filaments during the "off" periods. This residual voltage will result in the SCRs failing to turn off and the lamps would cycle once and then flash simultaneously. High impedance op amp with input protection The circuit presented here was designed to provide a high impedance input, namely 1MO in parallel with ZOpF, input protection to at least ± 100V and bandwidth limiting to about 2MHz. The first approach is shown in (a). This shows an LF351 op amp in voltage-follower mode (output connected to inverting input) and with input clamping diodes connected to ± 10V rails. The problem with the diodes specified is that they are too leaky. This would not normally be a problem but the gain of the following stage (not shown) is 80. The effect of connecting a low impedance source to the input amplifier was a shift in its output by 250mV. When multiplied by the following stage's gain, this would be enough to overload it. 22 SILICON CHIP +10V OUTPUT (a) -10V One solution is to use low leakage diodes such as BAV45s but these cost more than the LF351. Another alternative is to use the gate-source junction of a JFET. Many of these devices exhibit the right characteristics (not switching types) but have a maximum current of only 10mA. The base-collector junction of many ordinary bipolar transistors, such as 2N3638A, is fine, with leakage currents in the picoamp region. I . used PN3653s because they also exhibit quite low junction capacitance. That then raised the concern that the variation of the input voltage might vary the capacitance of the base-collector junction and hence vary the bandwidth with input voltage. An elegant solution is presented Crowbar over-voltage protection for power supplies 2A v+-<r-...o-----SCRl C122D Most logic circuitry can be damaged if the supply voltage goes too high, even for brief periods. For this reason most power supplies for computer and logic applications have fairly complex circuits to assure good regulation. When this circuitry fails though, the usually well-regulated output goes much higher and following circuitry is usually damaged. To avoid this, crowbar circPitry is often added, to provide drastic protection in the last resort. In the event of the supply rail going high, a dead ·short circuit is placed across + 10 (a) it. This blows a fuse and renders it safe. Three crowbar protection circuits are presented. (a) is a simple circuit involving just a zener diode to sense the voltage and an SCR (silicon controlled rectifier) to provide the short circuit and blow the fuse. When the supply voltage rises slightly above the zener voltage, current is fed via the zener into the gate of the SCR to trigger it. The fuse blows within one microsecond which is fast enough to protect semiconductor circuitry. The problem with this circuit is that it is too dependent on the particular zener characteristic and on the trigger current of the SCR. (b) is a better circuit. Ql acts as a comparator, comparing a preset voltage at its base with the zener voltage at its emitter. Because of the gain of Ql, the circuit has a much more precise trigger point and it has the advantage of being adjustable with VRl. (c) is better still. The diode in series with the zener provides V+--o-2-AD-_.,__ _ _ _ _ _ _ _ _ _ __ SCRl C1220 2.2k 10 (c) (b) temperature compensation of the reference voltage. The circuit has higher gain and the differential amplifier acts as a more precise comparator. +lOV D1 1N914 Substituting electros 2x1N914 D3 D4 OUTPUT 3.9k INPUT 10pf+ 1M .,. (b) D2 1N914 -10V in (b). This shows the 1N914s strung across the input of the op amp and with further clamp diodes connected to the output. The ± 10V rails must then be able to handle the full current of the op amp when it is over-driven. This configuration eliminates the leakage problems of the 1N914s because they have virtually no voltage across them until the input is overloaded. At other times the input diodes are effectively bootstrapped out of circuit by the op amp's output. $20 to: Phil Denniss, University of Sydney. Where an electrolytic capacitor is specified in a circuit, you can always substitute a capacitor with a higher voltage rating, provided that the size of the capacitor is not a problem. You can often also substitute a capacitor with a lower voltage rating, provided the voltage across the capacitor is not likely to be exceeded. Circuit designers often standardise on capacitors with only two voltage ratings, say 16V or 25V. In many cases though, a capacitor rated for 25V may have much lower voltage impressed across it which gives the opportunity for substitution. JANUARY 1988 23 Update the sound Our phone ringer has been designed to go on a small printed circuit board which can be installed in just about any phone although we expect that most will be installed in older phones with electromechanical bells. Only six components are used in the circuit, five of them mounted on the printed circuit board (PCB). The exception is the piezoelectric transducer which actually produces the chime sound. How it works Are you tired of the sound of your telephone bells? You can change to a modern sounding chime by building this simple module. Apart from wishing for a change in the sound of your old telephone bells, there is another good reason for building this personal phone ringer. If you work in a large office with many telephone extensions, it can be very difficult to tell whether it is your phone that is ringing or not. With this little circuit wired in place of the existing bell or solid state chime, you can set the tone of your phone so that it is distinctly different from all the other phones. That way, if you are away from your desk, you won't be wondering if it is a call for you every time a phone starts to ring. Another reason for using this ringer circuit instead of your phone's existing bells may be if you or someone in your household is partially deaf. You may not want to go to the trouble and expense of having an extension bell installed if this ringer can do the job. + C2I OV0UT BRIDGE RECTIFIER AND 28V CLAMP THRESHOLD CIRCUIT WITH HY S!~R~~IS t---""" 8 12.6V OUTPUT FREQUENCY CONTROL RT PSB6520 TONE RINGER IC .,. Fig.1: block diagram of the PSB6520. Rt sets the oscillator frequency while Cs sets the rate at which the oscillator is modulated. 24 SILICON CHIP .,. The heart of the phone ringer is a Siemens PSB6520 tone ringer integrated circuit (IC) which is specifically designed for use as an electronic bell in a telephone set. The functions of the PSB6520 IC are shown in Fig.1. When a ring signal tone is sent down the telephone line, the voltage is coupled via capacitor Cl while the current is limited with series resistor Rl. An internal bridge rectifier converts the AC ring tone to a DC voltage which is clamped to a maximum of 28V. C2 at pin 7 is a filter capacitor to provide a smoothed DC voltage. When the DC voltage derived from the ring signal reaches about 18V the oscillator circuit begins to operate with switch Sl closing to the upper position. If the DC voltage falls below 8.4V, Sl will reclose to the lower position and the oscillator will cease operation. Resistor Rt at pin 4 sets the frequency of the oscillator while capacitor Cs sets the rate at which the ocillator is modulated to produce its pleasant burble tone. Naturally, the tone is audible only while the ring voltage is present, so instead of going ring ring your phone will now go chirple chirple. Fig.2 shows the final circuit. As can be seen, we have not included capacitor Cl in the circuit, since all telephones will already have a of your phone Design by JOHN CLARKE PARTS LIST PCB, code SC121 -1287 , 28 x 36mm PSB6520 tone ringer IC (Siemens) piezo transducer (Jaycar Cat. AB-3440 or equivalent) 1OµF 63VW PC electrolytic capacitor 1 0. 1µF metallised polyester capacitor 1 22k0 miniature vertical trimpot 2.2k0 0.25W resistor Miscellaneous Solder , hook-up wire . We installed the prototype in this phone by glueing it to one of the flat metal pillars which support the dial mechanism (bottom left). capacitor for the existing bell or ringer circuit. The value for Cs is O.lµF while a 22k0 trimpot is used for Rt. The 10µF capacitor at pin 7 of ICl filters the DC supply. Assembly Assembling the printed board is not an onerous task since there are not many · components. The only point to watch is the need to install the IC and the 10µF capacitor the right way around. When you have installed and soldered all components into circuit you can check the unit on a DC power supply. Feed in about 20 volts DC to the input terminals and note that you get a continuous "chirple" sound from the piezo transducer. You can adjust the frequency of the oscillator with the trimpot to suit your taste. For optimum results though, we suggest you slowly vary the trimpot until the sound from the transducer is loudest. There will be distinct setting for the trimpot which gives a much louder sound output than any other. This corresponds to the Fig.3: parts layout for the printed circuit board. .J 0 , continued on page 85 ;;1·:~~ J. L. -~-... ~~ i°/ l<'ig.4: the printed circuit board measures 28 x 36mm. ~l~!l~ili!i~g~~H o fS (U;!'"' INTERNAL TO TELEPHONE I ACROSS PHONE BELL IC1 PSB6520 :· . _,,i ;; ; 10 63VW + CS _0 1 VR1 22k PERSONAL PHONE RINGER 121-1287 Fig.2: the complete circuit diagram for our phone ringer. / I b(6)U--""'I FROM PHONE BELL !"!lo TO PIEZO TRANSDUCER ,.....,.ra--,_. , .. ,., ,, .,,. /f/ ~ ij~~ Fig.5: the circuit is so simple, it can easily be assembled on a small piece of Veroboard. Use an oversize drill bit to make the cuts in the tracks. JANUARY 198B 25 ltronics Will Deliver Any Of These Quality Products To Your Door faster Than An Other Australian Supplier (Within 24 Hours To Every Capital City and Suburbs - Allow Additonal 24 - 48 Hours For Country Areas) 111111111 ll11111111111111111 IIIII IIIIIII II lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIIll Ill IIII IIIIIll IIIIIII IIII IIIII IIIIII IIIIIIIIIIIIIIIIIIIIllll 11111111111111111111 The Power House Arrives Operatea from 12 or 24 Voll 1yItemI via Internal wiring connection, Big brother to our 300W Model this brilliant design can be internally connected for either 12 or 24Voperation . Full 600watt output- and that will power a fantastic array of appliances e.g. Lighting, Electric Motors, Electric drills, Hi Fi , TV Sets, Computer. An abaoluta muat for H°':'.11 P~w•r or for. ~h.•. Tn,c:_~,.. Jr.!l!'JOr etc. 677 f'..77 Complete Kit Fully Built & Tested New Model /RD Has Fantastic Range With Two Mode Lens Why Pay $150 or More Our Price $99ea 10 or More $90ea Operates From 12V Car Battery Just think how handy it would be to have 240 Volt AC Mains Power when camping or for your boat or Caravan. Auto Start draws power from your battery only when appliance is plugged in and "turned on" . i.e. battery can be left permanently connected if desired. Thermal Over Load. Current Regulated. Current Overload .. t Complete Kit Fully Built & Tested 99. Features: • Lens simply 'snaps' to either wide angle (range 40 feet) for normal use or Normal angle (range 80 feet plus) for corridor applications . • Snazzy integral mounting bracket allows corner 90 deg . mounting as well as normal surface mo unt.(This is a fantastic feature as these work best in corners and are visually unobtrusive} • 12V DC Powered • Built-in test lamp • Alarm output SPOT 30V 1a S 5301 professional detectors use st ate of the art circ uitry to achieve ultra operation. They are currently specified by several "Name" commercic>.I mpanies. We believe the Vector to be one of the finest and most sensitive Radar Detectors available in the World today. Approximately 4db greater sensitivity than the A 1520 Until now, GaAs diodes have onl y been used in sophisticated military radar equipment. The Microeye Vector is the first consumer electronics product equipped with this new technology. Why GaAs Diode ■ 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. Features: • Separate audio alerts for X and K Band. • Three operational switches: Power: On and Off: RSD (Radar Signal Discriminator) to minimize extraneous signals with a LO (local ) positon and a LR (Long Range) position ; FIiter Mode designed for instant computerized analysis of incoming signals with O and LA positions. Invisible from outside your car. The Vector simply clips onto your sun visor. Thus the Gendames and would be villains ar non the wiser. Counter Kit (See Silicon Chip Mag. Nov 1987 for Details) s A 1530 UV Eprom Eraser Erase your EPROMS quickly and safely. This unit is a cost effect1_ve sol~t1on_to your problems. It will erase up The Tec hnical excellence of this counter to 9 x 24 pin devices in complete safety in about 40 places it w ith Hew!"ett Pac kard and other minutes for 9 ch ips (less for less chips). world famous test equ ipment makers. •Erase up to 9 chip• at a time• Chip drawer has conductive foam pad • Mains Powered K 2515 Due Mid Dec' • High UV intensity at ch ip surface ensures thorough erase• Engineered to prevent UV exposure• Long Life UV tube• Dimensions 217 x80x68mm • Weigh t 670g . Super Bargain 1/2 Price en volumes written about the benefits of negative ions combating air rette smoke etc. can be very beneficial to Asthma suffer--3rs. Our gnat erates · · · second! Inc ludes tester. Heart disease strikes down many people in their early 40's (or even 30's). The tragedy remains that had such victims been alerted , remedial n,edical , physical and dietary action could have been prescribed to avoid illness and in many cases restore full bodily health . X 3055 Blood Pressure and Heart Rate Monitor Feature•: • Non- Microphone Measurement System • LCD Readout gs h Po uallty Virtually a~h~!XP.~~e~ol!!~!ake~~w~s~B!en~o~P~!o~!ne Cones with their drivers. The advantages are considerable• less cone flexing or "break up", improved bottom end response and reduced enclosure sizes. One of the probl~ms of course, has been the high cost of P-P drivers. Fortunately, with Altronlca direct Import prices, you can now be the owner of any ol the18 fine 1peaker1 tor I lr1cUon of what you'd expect. Note: the conservative power ratings, the massive magnets employed and high order sensitivity specifications with these fine Drivers. Brief Specifications (All 8 ohm Voice Coil Impedance) oofer 100W Mu C 3055 C 3060 Frequency Re1pon19 fo-3000Hz Resonant Frequency 36Hz Sensitivity (1 M/ 1Watt) 87 db (+ or -2db Voice Coll 25mm Nell Weight 900gm Electromagnetic Q .48 Magnet 280 gm. P 3000 P 3010 P 3020 P 3030 P 3040 P 3050 P 3090 Male 9 Pin Female 9 Pin Male PCB Rt/l Fmale PCB RVL Male PCB mnt. Fmale PCB mnt. Backshell cover 2.95 3.25 3.75 4.50 2.95 3.95 P 3100 r 3110 P 3120 P 3130 P 3140 P 3150 P 3190 Male 15 Pin Fmale 15 Pin Male PCB Rt/L Fmale PCB RVL Male PCB mnt. Fmale PCB Backshell cover 3.25 3.85 4.35 5.50 3.85 4.85 2.20 P 3200 P 3210 P 3220 P 3230 P 3240 P 3250 P 3290 Male 25 Pin Fmale 25 Pin Male PCB Rt/l Fmale PCB Rt/l Male PCB mnt. Fmale PCB mnt. Backshel I cover Frequency Re1pon19 Fo-3000Hz Re1onant . Frequency 33Hz Senaltlvlty(M/ 1 Walt) 90db (+ or-2db) Voice Coll 38mm Nett Welght2200 gm. Electromagnetic Q 4 Magnet 836 gm. • C 3070 C 3065 15 25 1.95 150W Mu 100W Mu . 15 Frequency Reaponl8 fo-3000Hz Resonant Frequency 30Hz Sen1ltlvlty (1 M/1 Wall) 92db (+ or -2db) Voice Coll 38mm Nell Weight 2650 gm Electromagnetlc Q .23 Magnet 836 gm. 29 • Frequency Reaponl8 fo-2000Hz Resonant Frequency 23Hz Sen1ltlvtty (1 M/ 1Watt) 93db ( + or -2db) Voice Coll 38mm Nell Weight 3620 gm Electromagnet Q .22 Magnet 1410 gm. II IIIIII III IIIIIIIII I111111111111111111111111111111111111111111111III IIIIIIUIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIII 115 S• ~~-~ • • The use of Super Heavy Duty Heatsinks as Rack Case sides now allows a myriad of Amplifiers, Power Supplies, Battery Chargers etc. to be built in an "Off the Shelf" rack case. 10• Fantaallc tor Stereo Ampllflers-Each Heatalnk wtll accommodate an audio output 1tage of approxlmately 120W wtth normal efficiency and dlsllpallon. A Great Cha11l1 lor Heavy Duty Power Supplies and Battery Chargers. We 1uggest the mounting of Rectifier Bridge or diodes on one Heatslnk and the Regulator devices on the other. 4.95 5.50 4.95 6.90 4.95 6.25 2.20 Order With Either Black Or Natural Anodised Front Panela Natural Anodised Front Panel Specifications: Heatalnks Altronics H 0590 Front Panel 3 unit Rack size 480mm x 132mm x 3mm Base 1.0mm steel, ventilation slots provided Top Cover 1.0mm steel, ventilation slots provided Internal Dlmen1lon1125 x 370 x 250mm External Dimensions 130 x 440 x 252U'm plus standard front panel Finish Black anodised aluminium plus powder coat black top/ base. hassls Now your preamps, Amps, Control Modules Monitor Panels etc. can look every bit as good as Technlcs Nakamlchl and other top manufacturers. Please Note: This product is a genuine Pan Brake Bender allowing you to make quite complex chassis boxes, lids, trays etc. It is made from solid steel and is not to be confused with inferior Non Pan Brake simple benders currently sold by our competitors. Make Your own Chassis and Cases and Save a Fortune Value Plus T 2400 ......... $99.95 e Su erb Micron Varlabl FEATURES: These beautifully craftea racK cabinet boxes will give your equipment.a real 1st class appearance with removable top and bottom cover panels • All dimensioning conforms to the International Standard • Netural or Black finish • Ventilated lid • Deluxe finish front panel • Individually cartoned• Supplied in Flat Pack Form - Easily assembled in minutes - Side Elevallon1:- D=254mm C (Internal Chassis Height)• B (mounting Bolt Centres). SIX NATURAL AND BLACK FINISH MODELS - The Black or Natural finish cabinets are each available in 44mm, 88mm or 132mm high models. Mountirig hole centres conform exactly to International Racking Specifications both vertically and horizontally. Cat. No. Flnlah Natural H 0401 H 0402 Natural H 0403 Natural H 0411 Black H 0412 Black H 0413 Black A 44 88 132 B 34 57 89 44 34 88 ~32 57 89 C 38 82 126 38 82 126 Were $59.95 $69.95 $85.00 $59.95 $79.95 $89.95 No more changing tips to obtain the correct working temperature - simply select any one of 5 temperature settings between 320 and 440 deg. C Temperature Readout via. LED bargraph. Temperature Stablllty to within 4% of selected mean temperature. Heat Capacity full 48 watts available for H/D work . Low Voltage Element Slllcon rubber bum re1l1tant lead Chrome plated Iron clad llpa. * * * T 2440 Be Qulckl Next Month $139 a er Own An lnphone And Your Neighbours Will Be Green With Envy Here's Why Its Completely Mobile The Go Anywhere Cordless lnphone No Installation Costs Simply Plugs Into Your Phone Socket • lnphone Is Great Around The Factory or Building Site is not tied to the wall with wires - you simply take it where you want. Never again need you spend half the night crouched around the kitchen bench or draughty hallway with those long winded calls. • Use It By The fireside fn Your Favourite Chair • Super Handy When Sunbaking By The Pool INPHONE is quite simply the finest cordless phone available . No other cordless phone has the quality , security and the features at any where near an affordable price of INPHONE. AT HOME you can keep in touch around the swimming pool. (Please note the equipment is not waterproof). In the garden . Under the car. While watching T.V. In the bathroom . In Bed . Or next door when you' re playing cards or having a Barbecue with your Microphone neighbours. IN BUSINESS a busy executive can take the INPHONE around the factory, warehouse , showroom , sales yard or construction site or into the car park, and not miss a deal! Also INPHONE is ideal for use in restaurants. IN SPORT on the field or track , the gym , around the swimming pool , Lifesavers on the beach etc . Comprehensive 6 months Warranty Brilliant Performer SIMPLY GREAT AROUND THE POOL Normally Great Value At S269 Exclusive Offer To Readers Of Silicon Chip Magazine This Month · S 199 - But You Must Mention T · When Ordering We Regret This Special Offer May Not Be Available From Altronics Dealers dvert Just lmag ne a an Hour - ys em you can na a n abou Uses No Wiring or Cables and Costs Less than $1 for the Mounting Hardware e / Fantastic UHF 305MHz Microprocessor Control Wireless Security Alarm System Commercial grade, quality alarm systems are expensive - Just phone one of the "Name" security firms and get a quote for your home-our estimate is that it will be anything up to $1,000 just for the equipment-then there 11 the ln1tallatlon-countless holes punched through walls, miles of wiring and a day or two of installers labour and that'• around $25 per hour theM day,. Hardly worth the effort 11 It? After all what h■ve you gotto looM?-Only the 'Video Player, CD Player, Camera, HI FI, TV, Jewellery and 10 onll Well all that 11 now changed-with our brllllantly englnHred Home Guard WlrlH1 Security Sy1tem Read OnApart from the flawless operation of the Home Guard System-One of the great features is its application with rented or leased premises-Lets face it, money spent on installing a wired system in your Home or Office. Factory etc. is irrevocably lost when you move on. With the Home Guard you simply take it with you . · This alarm system is a brand new design that features completely wireless connection to all accessories. even the reed switches. Think of how easy it Ideal for the lounge room, family room or is to install a "Wireless" alarm system. The benefits are endless, hallways e.g. anywhere where an intruder is e.g. arming your Flat or Townhouse with an alarm you don't need to run likely to pass through. Mounts up on the wall or wires through the roof or drill great holes through your walls. When moving house the alarm is simple to dismantle and re-install elsewhe,e. on top of bookshelves etc. Detects movement within an area of 9M by 9M by sensing intruder The system divides protected 3reas into either perimeter zone or internal body heat movement through the protected area zone, programmable by dip switches in each transmitter/ detector. Pocket Should not false trigger with the family cat or remote control can simply arm or disarm your house perimeter from your curtain movement etc. - as is the case with the bedside when retiring etc. this allows essential protection while cancelling cheaper Ultrasonic alarms. internal zone as desired. Each transmitter/ detector unit can be programmed into interior or perimeter zone. Zones can be programmed S 5280 1 9 for instant or delayed trip . The system has a built-in ear piercing siren for •• · • ' ••· •· •••' •• intrusion and panic alarm signals. It also has another dry relay output with normally closed, normally open contacts for connecting to other alarm reporting devices such as telephone dialer, additic;,nal outdoor siren etc. System Is Comprised Of : This unit is an optional line carrier receiver. Receives signal through 'AC' line i.e. it would ideally be located in, say, the roof space and plugged into mains power . S 5290 peclal Package Price Comprl1lng: One S 5265 Main Controller One S 5270 Reed Switch One S 5280 Passive I/R Detector One S 5285. Wall control unit. Including Batteries Sy1tem Cat.No. S 5260 .... . . Accessories • Wireless reception of external or internal sensors or detectors . • Selectable home or away modes for selecting internal and external arming or just external to allow movement inside the building • Built in Piezoelectric siren gives different signals to indicate different functions. • Sends signal down power line to activate one or more remote sirens. • Programmable Arm/ Disarm switch buttons. The main control receiver runs on 240V AC with a 12V 1.2AH battery for emergency backup. All other units with the exception of the line carrier, run on a 9V battery each . The average life expectancy is approximately one year. System works around the 305MHz frequency where there is less chance of false alarm. The range of the unit is normally 80 metres in open space. Alarm and Indication Sound ■ Intrusion Alarm - Panic Alarm - Arm Tone - Disarm Tone - Exit Click Tone - Monitor Tone - Tampering Alarm . qeed Switch) Suitable for Window, and Doore This consists of an enclosed reed switch and compact UHF transmitter and a removable enclosed magnet. The unit is at rest when magnet and reed are side by side (within 25mm or 1 inch). When the magnet is moved away more than approximately 1 inch the alarm signals to the Main Control Receiver and the alarm is sounded. In practise the Reed/ Transmitter is mounted on the door or window frame with the magnet on the moving door or window . Note: For larger installations your system may well require several Reed switches, movement detectors and 2 or more sirens . Also the remote door , controller and or pocket remote controls could be very worth while accessories. The fantastic thing about the Altronic system is you simply add more detectors as you discover the need - no wiring, no e:<pensive technicians. no modifications to equipment. A real joy to use - keep it at the bedside table allows you to, say, alarm the house perimeters when retiring or you can take it with you when you go out, arming your system after you lock the door. Unit is a function control transmitterto send 4 different signals. 011 - To disarm the system before entering . Home - To instantly arm the system with 'Perimeter' detection only. Away - To arm complete system after a given exit delay time of about 40 seconds. Panic - To start an emergency signal whenever needed, in any mode. S 5275 nt Door Keypad This handy accessory virtually duplicates the function of the Master Controller unit but at a more convenient location i.e. just inside your entry door etc. System can thus be armed or disarmed without the need to go to Master unit. Especially handy for larger homes or offices. S 5285 ................................ . rs for Long Range, ro uction Altronics proudly release the Eleco System - Used Worldwide by Entertainers i.e. Rolling Stones, Dire Straites, Tina Turner and 1000's more! Superb Microphone Reproduction Compares with Shure,Beyer and AKG Unique Microphone design completely Eliminates "Dangling" Antenna Breathtaking performance without signal drop-out or noise interference. The Eleco Wireless Microphone System Is virtually the ultimate in an Entertainers Microphone system (or for any roving microphone application for that matter!) All the annoying wireless microphone characteristics such as "drop out", static and noise are completely eliminated by use of auto 1wltchlng dual diversity recelvere. The output of each receiver is continually monitored, with the strongest and clearest signal always selected. Dynamic Range exceeding 100 db is obtained by employment-of a Patented special Parabola level compressor and Dynamic expander. The operating range 11 a minimum of 50 metres (often this can be extended to 200 metres and more in normal circumstances). Several Frequencle1 are available to aleviate cross interference when two or more systems are used in proximity. Brief Specifications Frequency 202.1, 202.9, 203.7 MHz (Please specify if you have a preference) Mlc Carrier Power i;omW (Max) Mlc Antenna built-in Dynamic Range over 100db S/N Ratio better than 90db Frequency Re1pon1e 20Hz to 16KHz + or - 3db Mlc Battery 4 x AA cells Battery Life over 24 hours continuous operation. RecelverSen ■ltlvlty 12db/microvoltfor60db S/N ratio Preemphaol ■/De emphaol■ sous. Receiver output unbalanced 6.3mm phone jack and balanced 3 pin cannon type. Output Level (adjustable) Unbalanced 0-2.SV Balanced Oto+ or - .3V into 600 ohms. Receiver Power Supply 200 - 260VAC. Prices (A) Dual Diversity Receiver $729.00 (B) Entertainment Microphone (hand held type) (C) Lavalier Type Microphone $349.00 • Fr• ue C 0111 C 0113 C 0115 C 0121 C 0123 C 0125 C 0131 C 0133 C 0135 $349.00 ecelver and J •• 999 Please Note 3 different operating frequencies are available (you will need to specifically nominate desired frequency only if the equipment is being used in proximity with other Eleco Systems on the 200MHz band. • Dual Diversity Receiver Dual Diversity Receiver Dual Diversity Receiver Entertainment Microphone Entertainment Microphone Entertainment Microphone Lavalier Microphone Lavalier Microphone Lavalier Microphone 202.1MHz 202.9MHz 203.7MHz 202.1MHz 202.9MHz 203.7MHz 202.1MHz 202.9MHz 203.7MHz $729 $729 $729 $349 $349 $349 $349 $349 $349 IIIIIIIIIIIIIIIIIIIIIIIII IIIIIIII IIIIIll IIll II IIIIIIIIIIIIIIIIIIIII IIIIIIIIIII1111111111111111111111111 Wide Range Weatherproof Extension Speakers For Your Stereo System G a F r The Back Patio, wlmmlng Pool, Games Room , Den Pool Ro m E g I y Weather Proof Speakers ed ord • Rugged extruded aluminium construction • Superb powdercoat industrial paint finish • Engineered in Australia • Excellent reproduction • Superior to imports - Yet just a fraction of the price! Altronics proudly announce the release of the superb Redford Weatherproof Speaker and Sound Column Range. Imagine a wide range speaker system which is highly directional and with efficiency approaching that of reflex horns! Redford is the solution for high quality sound reproduction outdoors. The Five Models to choose from '.'FIii the Bill" from applications on boats to high grade paging and music entertainment installations. D 11 OhM M Using a dual doped cone driver these fantastic weatherproof speakers are of quite surprising performance. The 4 Ohm models are intended for use as main speakers i.e. for car sound systems/ graphic equalisers on your boat or Four Wheel drive etc. The 16 Ohm versions are intended for use with higher power systems. 16 ohms is employed to give a generally correct volume balance when used as extension speakers to the main speaker system - An added bonus is your amplifier load is kept to respectable limits! Great for back patio, den etc. C 0932 White 4 Ohm C 0938 White 16 Ohm C 0,934 Black 4 Ohm C 0940 Black 16 Ohm All $99 each or $190 per Pair u These vibration free enclosures are constructed from die extruded heavy gauge aluminium and finished with incredibly durable industrial powdercoat enamel. The speaker ends are sealed via gaskets and tough moulded "LU RAN S" U / resistant end caps. The end result iS "Good Looks" together with assured rugged durabilitv for the Australian environment. The drivers have been chosen for wide range.low distortion, mid range "pr_esence" (essential for high grade vocal work) and high efficiency in general. Power Capacity for short term use, the drivers will safely handle 150% of rated power. Acoustic wadding is used to dampen Bass resonance. Weather Proof Con ■trucllon and uae of "Doped Cone1" Foam plastic and cloth is sandwiched between Baffle and Front Grill to prevent water ingress. A first for Redford is the use of a patented cone moisture repellant process for all models. Dimensions 260mm wide x 170mm high x 150mm D. (Mounting brackets are included) 20 I Oltm (Ml 30 Watt) ■t Use 2 special dual doped cone drivers for those wanting a bit more umph! C 0943 C 0944 f Black White 100 Volt L $139ea $139ea o A $260 per pair $260 per pair II F UN Ith Prof Mualc Sy tem PA Using a "Doped" wide range drivers and fitted with grain oriented steel line transformer Output cable allows connection to 10W/SW/2.SW with 10 watt models, 20W/10W/5W with 20 watt models and 40W/20W/10W with the 40 watt versions. C C C C C C _ 0941 10W/100V line Black $119ea $220 per pair 0942 10W/100V line White $119ea $220 per pair 0945 20W/100V line Black $169ea $299 per pair 0946 20W/100V line White $169ea $299 per pair 0950 40W/100V line Black $225ea $399 per pair 0955 40W/100V line White $225ea $399 per pair :4 •• (. L. ~- .. . -1 •• I " • $17.50 ( " NO NEED TO Low-Cost Unit UNSOLDER Checks Values from 1pF -1 00uF SUSPECT TRANSISTORS " FEATURES: * Output 3 to 30V at 1A * Short circuit The readout consists of a bright 4-digit LED display and the full scale readings for each range are 9999.9nF and 99.99uF. No adjustments are necessary when taking a reading . You simply connect the capacitor to the • Tests both NPN and PNP trans istors 1n test terminals and select the appropriate range. The circuit can accurately circuit at the touch of a switch • Tests measure capacitance down to one picofarad (1 pF). This is made possible Diodes and SCRS as well • No need to by the internal nulling circuit which cancels any stray capacitance switch between NPN and PNP- its automatic. Two LED indicators are used to between the test terminals or test leads . So when you measure a 5pF show condition of device being tested . capacitor, the unit will display 5pF. Altronlc1 Kit Feature - " ABS" jiffy box and test leads supplied. Cat. K 2530 K 2522 .. . ............................. . protec ted* Load switchi n g* Current lim iting . Dual sc ale meter • Housed in o ur Deluxe " ABS " instrument case . FEATURES: SPECIFICATIONS: * Output Voltage - 3 to 30V * Output Curren t - O to l amp (full y variable ) • Load Regulation - Better than 0 .2% from Oto ful l load* Output Ripple-Less tha n 2mV RM S. Cat . K 3210 This Ultrasonic Movement Detector provides added protection against illegal entry via. an open window etc . Connects d irectly to an alarm with a normally open input. Detects Dead easy to build and (even better ) there ara only 3 electrical connections required to the car wiring system . This alarm drives off would be thieves with an ear splitting modulated tone. Once activated it is near impossible to stay within the confines of the car. Featuret: Entry Delay• Exit Delay• Alarm Timer • Lamp Flasher • Three second soft alarm reminder. Piezo siren produces any movement up to 3 metres within an angle of 30 degrees. Will operate directly oft 12V i.e. Car Battery etc . 4400 29.50 modulated tone of 110dbat 1 metre. Simple to build and install. Two Sensor Inputs Sharpens up your picture when Copying Video to Video Here's a ■ lmple but effective video enhancer that is super eHy to bulld at a fraction of the cost of commercial mod~ls. Unit sharpens picture detail , and can .actually improve the quality of a copy by amplyfy,ng the top end of the video signal K 5825 174 Roe St. Perth W.A. 6000 Perth Metro & After Hours (09) 328 1599 P.O. Box 8350 Perth Mail Exchange W.A.6000 . - We process your order the day received and despatch via. Australia Post. Allow approx 7 days from day you post ord er to when you receive goods. Weight limited 1 Kgs. . - We process your order the day received and despatch v1.a. Overnight Jetservlce Courier for delivery next day Country areas please allow addItIonal 24-48 hours . Weight limit 3Kgs. days for delivery - For deliveries exceeding 3Kgs and less than 10Kgs - allow 7 - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. . . - As with virtually _every oth~r Au~tra~ ian 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" . - Bank~ard Holde rs can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnlg_ht Jet■ervlce we deliver next day. ALTRONICS RESELLERS Cha~ces are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. Please Note: Resellers have to pay the cost of freight and insuran?e and therefor~ the prices charged by individual Dealers may vary slightly f~om_ ~his Catalogu~ - in many cases, however, Dealer prices will still represent a srgn,f1cant cost saving from pnces charged by Altronics Competitors. Don't forget our Expreu Mall and Phone Order Service • tor the cost of a local call Bankcard, Visa or Ma■tercard holders can phone order for ■ame day de■patch. ' If you have a Retail Shop, you could increase significantly by becoming an Altronics Dealer, Fobister (09) 328 2199 for Details. COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K.B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronics 854836 MANDURAH Lance Rock Retravision 351246 NEWMAN Watronics 751734 WYALKATCHEM D & J Pease 811132 ALICE SPRINGS Ascom Electronics 521713 Farmer Electronics 522967 CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 CITY Active Wholesale ■ 6023499 All Electronic Components 6623506 SUBURBAN ASPENDALE Giltronics 5809839 CHELTENHAM Talking Electronics 5502386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 SWAN Hill Cornish Radio Services 321427 CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 523762 Fred Hoe & Sons Electronics 2774311 PADDINGTON SLACKS CREEK David Hall Electronics 2088808 TOOWONG Techniparts 6710879 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 NAMBOUR Nambour Electronics 411604 PALM BEACH The Electronic Centre 341248 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 Purely Electronics (Shopping Fair) 280100 Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 CITY Electronic Comp & Equip . 2125999 Force Electronic ■ 2122672 SUBURBAN BRIGHTON Brighton Electronics ■ 2963531 CHRISTIES BEACH Force Electronics ■ 3823368 ENFIELD Force Electronics ■ 3496340 PROSPECT Jensen Electronics ■ 2694744 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 HOBART George Harvey ■ 342233 LAUNCESTON Advanced Electronics 315688 George Harvey ■ 316533 Nichols Radio . TV 316171 CITY David Reid Electronics ■ 2671385 SUBURBAN BLACKTOWN Wavetront Electronics 8311908 CARINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY ALBURY Webb's Electronics ■ 254066 COFFS HARBOUR Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 ORANGE RAYMOND TERRACE Alback Electronics 873419 TENTERFIELD Nllthan Ross Electronics 362204 WINDSOR M & E Electronics ■ Communications 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 Blue Ribbon Dealers are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item tor you. HIFIREVIEW arantz's elegant compact disc la er Marantz is moving up market. That's the very strong conclusion we came to after looking at their latest CD player, the CD-94. This machine leaves previous models for dead in terms of operating refinement, sound quality and, most of all, finish. Reviewed by LEO SIMPSON In the last few years Marantz has gone through its vicissitudes but now it has a new direction and commitment to the highest audio fidelity. This new direction has been mostly due to its chief audio designer Ken Ishiwata, a Japaneseborn engineer operating at Marantz headquarters in Eindhoven, Holland. His hand was clearly demonstrated in Marantz's award winning PM94 stereo amplifier and one can see that a great effort has been made to achieve the same standards with the CD-94. Let's face it. There are many cheap compact disc players on the market and as far as most people are concerned these do a perfectly satisfactory job; they play the music and they do it to a far higher standard than their delighted owners were probably used to with 32 SILICON CHIP their disc-based equipment. But there is more to the compact disc than just the basic CD players. There are a substantial number of people who want quite a lot more than the basic machines offer. And up till now, there have not been many machines catering to their needs. There probably never will be but this new machine from Marantz is certainly a contender for the very top of the market. Unfortunately, mere photos do not do the Marantz CD-94 justice. They can't show the very fine finish. They can't show the glasslike texture of the timber end panels, the subtle colouring of control panel illumination and major control lights. Nor do they show the solidity of the machine, or the action of its controls. We'll attempt to tell you something of the physical attributes of the machine but you really need to have it demonstrated "in the flesh" to fully appreciate it. At first it does not look all that different from other CD players. It is largish but not overly so and since so many CD players are black these days it does not really stand out as being really different; quite the opposite in fact. It is unobtrusive. It has very few controls visible on its front panel. Turn it on though and it starts to look more the part. Its display panel lights in a very subtle blue (it's a vacuum fluorescent display) with a large pair of digits for track number and then smaller digits to show index numbering and elapsed time in minutes and seconds. There is also a line of very small digits which show the number of tracks on a disc (up to 24) and those that have been played. What we like about this display is that it is bright enough without being at all gaudy. Press a very discreet open/close button and the disc drawer slides out quickly and smoothly. So many CD players give a poor impression at this stage. The drawer either makes graunching noises, or is too slow or is jerky. None of that with the CD-94. Once the disc is dropped onto the Inside the rigid diecast aluminium chassis of the CD94: note the generous transformer and all the capacitors which are specially made for Marantz. The player is particularly immune to shock and vibration, a legacy of the comprehensive error correction circuitry and the rigid construction. platform, you can either nudge the drawer to make it withdraw or you can push the open/close button to achieve the same result. Good. This is a most desirable feature since not a few players can be jammed or damaged if the CD drawer is physically pushed home. The only other controls visible on the front panel are the two large buttons to the right of the display panel for play/replay and pause/stop, and three small buttons below the display for FTS (favourite track selection) and track selection (forward/reverse). That may not seem like enough until you lightly press the lower part of the front panel. It then drops open smoothly (damped by a dashpot) to reveal a whole array of controls to enable you to make the machine do just about anything. Paradoxically though, most users will probably never use these controls because, as far as we were able to determine, it can all be done with the infrared remote control. Playing features The CD-94 has all the playing features of most compact disc machines and a lot more besides. One of these is shuffle play. Instead of playing the disc through from start to finish, you can press "shuffle" and have the tracks played in random order. This can be a pleasant change when playing anything except classical music. Another unusual facility on the CD-94 is "FTS" which stands for favourite track selection. This enables you to program the machine to play selected tracks on a compact disc and omit the others. Once you have programmed the machine for a particular disc it will always remember it. Thereafter, as soon as you feed the disc into the machine, it shows FTS on the display and you can then play the programmed selections by pushing the FTS button on the front panel or on the remote control. Depending on how you use it, the Marantz can store a hundred or more compact disc 'favourite track selections'. For example, 155 discs can be programmed to play an average of five tracks each. In some ways, we would prefer to think of this facility as the "disliked track non-selection" - you can program the machine to omit those tracks you hate. Good idea? The CD-94 also has "Index" play whereby you can program or select musical passages to be played by JANUARY 1988 33 The lower part of the front panel drops down to reveal an impressive array of control buttons for programming. There is also a headphone socket with its own level control. A nice touch is the gold plating on the ten track selection buttons. their index number. These are generally not used on pop music discs but are frequently used to identify movements within classical pieces. Another facility is "AMS" or automatic music selection. This goes through and plays the first ten seconds of every track. Repeat play is also featured, a common facility on CD players, but the Marantz also gives a similar facility with the Play/Replay. More often than not, pushing the Play button while play is in progress makes the machine move to the next track. On the CD-94 though, pushing the Play button makes it restart the same track and it does it almost instantaneously. Response times on the CD-94 are particularly fast. It can usually access and start playing any track on a disc within two or three seconds, and often much less. The worst case, going from the first track to the last of a 25-track disc, takes four seconds flat! Another feature which sets this machine apart from others is the provision of digital and optical fibre outputs on the rear panel. This is principally to allow it to be used with Marantz's special CDA-94 Digital-to-Analog Converter. This latter is a high precision multipurpose unit which automatically adjusts its sampling frequency to suit the selected input: 44. lkHz for compact disc, 48kHz for the new DAT (digital audio tape) machines, and 32kHz for the anticipated satellite broadcast audio. Removing the highly polished timber end pieces and the heavy aluminium lid of the case reveals another big difference with the CD-94 machine. At a time when other machines are going to all plastic construction and weighing only about 5 or 6kg, the Marantz has a very rigid diecast aluminium chassis and a diecast chassis for the player mechanism too. All up weight is 10.3kg. The internal circuitry is beautifully laid out and uses analog componentry unique to Marantz. This includes the large Elna electrolytic capacitors with ceramic filling and the damped copper styrol (polystyrene) capacitors in the Bessel output filter stages. The capacitor leads are also tinned oxygen-free copper instead of the usual tinned mild steel leads, a feature which Ken Ishiwata claims is important to sound quality. A relatively large mains transformer is used, considering the low nominal power consumption of 30 watts. The machine is double-insulated and we are glad to report that the mains wiring is of a much higher standard than a lot of equipment which sports the "double insulation" symbol. A sheathed two-core mains flex is used, which is as it should be. 16-bit dual D-A converters Marantz uses the new Philips dual 16-bit D-A (digital-to-analog) converters with four times oversampling. The beauty of this system, apart from much improved linearity, signal-to-noise ratio, separation and all that, is that it allows a digital filter to remove the 176.4kHz digital residual left over The CD-94 has digital and optical outputs as well as the normal analog outputs. There are two additional sockets for use with the Marantz bus system. 34 SILICON CHIP after conversion. A third order (18dB/octave) Bessel filter takes care of the remainder of the audio filtering. This is better than typical machines which use a very sharp "brick wall" filter to remove the residual digital artefacts which inevitably results in ripples (ie, small deviations) in the audio passband. Three better from the Best. Testing Our first objective tests of the CD-94 involved its tracking performance and error correction. We used the Philips No 4A defect disc and naturally it passed all tests without so much as a murmur. Then we fed it a badly scratched disc which many players refuse to load let alone play. Here the Marantz did very well and probably better than any other player we have come across. It played all but two tracks and even with these two, which are probably unplayable by any machine, it made a fair attempt before the laser pickup was thrown completely out and the machine came to a stop. The machine was commendably immune to shocks and vibration. Short of pounding on it with your fist, it is very difficult to make it mistrack. Without doubt though, the most impressive test results involved measurement of the frequency response. Marantz claim a frequency response from 2Hz to 20kHz within ± 0.0ldB. When I first read this spec I did not believe it. It would be an unprecedented degree of precision for any piece of electronic equipment, audio or otherwise. Subsequent checking proved that the spec is genuine although I still find it hard to believe. Up till this time, the tightest tolerance we have seen for any piece of electronic equipment has been ± 0.ldB. We knew darn well that there was no piece of measuring gear currently available (maybe in Standard labs there are) which would verify the spec. But we went ahead and measured the frequency response anyhow. It was uncanny, watching the millivoltmeter pointer come up to exactly the same reference point for every frequency between 20Hz The remote control duplicates all the facilities on the player. Very fast response times are a feature of the machine. and 20kHz. Clearly, the CD94 was far better than the millivoltmeter. Marantz quote similarly ambitious figures for signal-to-noise ratio, separation between channels and total harmonic distortion. S/N ratio is quoted as better than 104dB, channel separation at better than lO0dB and harmonic distortion as better than .0015% at lkHz and 0dB. These are truly excellent figures. Unfortunately, we were not able to verify them as we presently lack a suitable filter to remove residual 44. lkHz signal. In the CD-94, residual 44. lkHz is at a level of about - 70dB and this masks signals which are much lower in level. This is a consequence of not using a "brickwall" filter, as we mentioned above. Based on the performance te.sts we were able to carry out, we have no reason at all to doubt the machine easily complies with its specifications. I would go further than that. Of all the machines I have tested or used so far, I would have to rate the Marantz CD-94 as the best overall. It is a delightful machine to use and to listen to. I'd love to own it. For such a top-rating machine, it is something of a bargain. Recommended retail price is $1699.00. For further information, contact Marantz (Australia) Pty Ltd on (02) 742 8322. ~ For decades, Ortofon has been recognised as being without peer in the development and manufacture of sound reproduction cartridges. Today, the legend moves the leading edge a significant step further. You are invited to hear the introduction of the three latest Ortofon Moving Coil Cartridges each with 3 unique features: 1. Unsurpassed quality of the moving coil principle. 2. High output (2mVl directly into a . standard phono input, totally elimin~ting the need for a step-up transformer. 3. Trade-in and trade-up options at point of purchase. Ortofon MC X-1 Elliptical diamond. Ortofon MC X-3 Fineline diamond. Ortofon MC X-5 Van den Hui diamond. These 3 cartridges have been so well received by the hi-fi press that we will let them complete this advertisement: "It was one of the smoothest, silkiest, and leasHoloured cartridges we can recall using. The Ortofon XJMC is a delightful cartridge, the kind that can be enjoyed tor hours without creating an urge to listen to something else. And the price is right!" Stereo Review, March 1987. " ... overall we consider the X3-MC a very clean, uncoloured cartridge and among the most handsome sonically of the movingcoil models we·ve tested." High Fidelity, January 1987. "Whatthecartridgessharesonicallyaresweet,nonagressive behaviour, freedom from vinyl whoosh, and an openess ideal tor portrayal of atmosphere and ambience ... the X3 will do justice tosystemscostingwaybeyonditspricecategory." Stereophile, Vol. 10 No. 1. "Colouration was very, verylow,vinyl'whoosh' and tracing noisevirtuallynon-e,istent,andambiencewaswell-conveyedby both IMC-Xl and MC-X3) ... it has to be regarded as an ideal introduction to the joys of the MC ownership." Hi-Fi News & Record Review, January 1987. For full details and free brochures, contact the Sole Australian Distributor, SCAN AUDIO or your nearest ORTOFDN specialist. SCAN AUDIO Pty. Ltd., 52 Crown Street, Richmond, Victoria 3121. Telephone: (03) 429 2199. ortofon accuracy in sound S& T SA 5042 JANUARY 1988 35 Heathkit® SELLOUT! The chance of a lifetimel We're clearing out our remaining stocks of famous Heathkit products ... many WAY BELOW COSTI Hurry - Limited stocks only! Hero Jr. Robot.. BELOW COST! The robot of the future is here today. It's Hero Jr - from Heathkit, of course. More than just a robot, Hero Jr will become a real member of your family. He (she?) is pre-programmed: Hero Jr will wake you up (even listen to make sure you're awake!), remember dates and anniversaries, walk, talk ... protect you and your home (it can even activate the optional Health Security Centre) and much more. You can program Hero Jr to perform a myriad of tasks for you - with either its own keypad or with your own home computer (using the optional RS232C link, BASIC cartridge, terminal emulation software and cartridge adapton. Of course, Hero Jr is battery operated (rechargeable) and comes with a recharger (240 to 115V stepdown transformer required). How much for all this wizardry? Cat G-1005 s595 9£; Buitt up version: was $1995 Now sg95 fii ~ In ktt fonn: Was $1395 Now cartridge adaptor: (for plug-in command cartridged) Cat G-1050 BELOW COST! s79 ~ t.t.\.~ Was $179 Now Computerized Weather Station . \ A,!,1. ~~ '-~ --.,- From the most respected kit builders in the world, comes the most advanced computer weather station! Features digital clock/4 year calendar, 4 digit accuracy, barometer, thermometer, wind vector, memory and more! WAS NOW '999 *395 WAS NOW 199 *149 CatG-2000 ~!b!=.!~~ian you won't find better quality! Modulated and unmodulated signals from 310kHz to 110MHz with calibrated harmonics to 220MHz. Cat G-4005 1 Audio Signal Generator An economical piece of test gear that you'll find essential for audio and WAS digital circuits. 10Hz to 100kHz frequency range with both sine and square 1 159'8 wave output. Battery operated (2 x 9V batteries, not inc.) Cat G-4010 Signal Tracer Kit Save a heap of time on repairs! The signal tracer kit will check RF, IF, even WAS audio circuitry quickly and easily. Ideal for any workbench! Cat G-4015 1 189'8 Hobbyisfs R-L-C Bridge can Sava your money! Your junkbox is probably choka with unmarked components. Don't throw them out - or buy new ones: Check them with this R-L-C Bridge. Put it together in about 4 hours - and start saving! Resistance: 10 ohms to 10M. Capacitance: 10pF to 10uF. Inductance: 10uH to 10H. Cat G-4025 NOW *149 NOW *129 WAS NOW ' 199 *169 DICKe SMITH c~'itaTIi~LJCf~ ELECTRON ° ICS ONLY AVAILABLE THROUGH DSXpress Sydney (02) area cal 888 2105 PTY LTD Build this low cost Dual tracking ±18.5V po"7er supply Take a squiz at this: a dual tracking power supply of modest cost giving up to + 18.5 volts DC. It has voltage metering, a LED dropout indicator and short circuit protection. By JOHN CLARKE & LEO SIMPSON Sooner or later, every electronics enthusiast needs a DC power supply. They used to get by with a variable supply giving up to 15 volts or so at around 500 milliamps but today's circuits using op amps, memory and logic devices need a lot more than that. For op amps you need balanced positive and negative supplies of ± 15V while some memory chips such as EPROMs need ± 5V. The problem with designing a power supply for the enthusiast or technican is that it is easy to get carried away with fancy features that are seldom used. The end result is an expensive supply that no one can afford. So we at SILICON CHIP have put our heads together on this project to produce a supply which has good performance and features while keeping the cost within bounds. What are the big cost items in a power supply? That was the question we asked ourselves as we set out to design this supply. The big cost items are the transformer, meter, case, filter capacitors and printed circuit board. We could not eliminate any of these components in a self-contained power supply so we selected them very carefully to optimise the performance versus price ratio. For example, we selected a transformer with a centre-tapped 30V winding rated at one amp. This was much cheaper than a centretapped 44V 1.5-amp transformer that we would have selected as first choice if price was not so important. But we had to admit that the times when enthusiasts want high currents are fairly rare. By picking the smaller transformer, we greatly cut down the power dissipation in the circuit and thereby reduced the heatsinking requirements, the size of the case and the cost of the filter capacitors and regulatprs, all for very little reduction in overall utility of the supply. We also saved money by using a smaller meter, smaller rectifier diodes and so on. The end result is a compact power supply which will serve the needs of the vast majority of electronic enthusiasts and technicians. It will become another in a growing list of SILICON CHIP test equipment. JANUARY 1988 37 D7 1N4002 POWER LOAD S2a 0--0+ E • 2.7k 2200 + 25VW _ 100 + 25VW D10 1N4002 -14V 47k 1200 LOAD OUT S2b o-o- 2.7k 08 2.2M LED2 DROPDUT D11 DUAL TRACKING POWER SUPPLY D41-188 ... ..,. 4x1N4148 Fig.2: the circuit uses a 30V 1A transformer to drive a bridge rectifier and two adjustable 3-terminal regulators. ICl inverts the control voltage provided by VR1 to drive the LM337. IC2 monitors the output ripple to provide drop-out indication. The SILICON CHIP power supply has tracking positive and negative DC outputs adjustable from ± 1.2V to ± 18.5V. Both supply rails are protected against short circuits and 2.Dr x~ - - - . - - - - . - - - - . -- --, ~ ::E 5. ... ~ 1.011--f'----+--- = :::, c., -+-----+----t c:, ; D._._ _...,__ __.__ __.__ _ D 1.2 Fip, 1 10 ~ 15 SUPPLY VOLTAGE (VOLTS) Fig.1: this graph plots the maximum output current for voltage settings between ± 1.2V and ± 18V. 38 SILICON CHIP 20 voltages generated by external loads. Maximum load current is 1. 7A between ± 3V and ± 10V. When the supply stops regulating, a LED indicator lights. You can use the power supply in the conventional way to provide balanced positive and negative rails, or you can take the output from between the positive and negative output teminals and thereby get more than 36 volts DC output. The circuit is fully floating (ie, not tied to mains earth) and so the output can be referenced to earth via the positive, negative or 0V rail. What will it do? Fig.1 shows the maximum output current available for voltage settings between ± 1. 2 volts and ± 18 volts DC with the positive and negative rails loaded. Up to 1. 7 amps is available for settings between ± 3 and ± 10V. Above 10V the available current reduces, to 200 milliamps at ± 18 volts. Remember that this performance applies with both the positive and negative rails loaded, so that by taking the output between the positive and negative rails, you get get up to 1. 7 amps at 20 volts and up to 200 milliamps at 36 volts. Line regulation is within ± 5mV of a given output voltage setting for mains input variation between 220V AC and 260VAC. Load regulation at 1.7 amps is within 100mV at a setting of 9 volts; ie, close to 1 % . Ripple output (ie, 100Hz hum and noise superimposed on the DC rails) is less than lmV peak-to-peak for load currents up to one amp. These are excellent figures. Dinkum. Note that the actual maximum The supply is very easy to wire but you should take extra care with the mains wiring. Use a cord-grip grommet to secure the mains cord. available current from the power supply will depend on the temperature of the heatsink and the amount of power being dissipated in the regulator(s) for a given output setting. Circuit details Fig.2 shows the complete circuit. As already noted, it is based on a 30V centre-tapped 1A power transformer, Arlec 6672A or equivalent. Diodes Dl to D4 are connected as a bridge rectifier which, combined with the two 22001,lF filter capacitors, give plus and minus DC rails of about 21 volts. These unregulated DC rails are fed to LM317 and LM337 3-terminal regulators to provide the adjustable plus and minus supply outputs respectively. We'll briefly explain how these regulators work before going on with the rest of the circuit description. · The regulators are designed to give 1.25V between their output and adjust terminals. With this in mind, and the fact that the current flowing out of their ADJ (stands for ADJust) terminal is negligible, it is easy to design a variable regulated Fig.3: operating principle of the LM317 3-terminal regulator. Rt and R2 set the output voltage (see text). · supply. The circuit of Fig.3 demonstrates their operating principle. Two resistors are used to set the output voltage in the circuit of Fig.3. Rl is fixed while R2 is variable. Since the voltage be~ween the OUT and ADJ terminals is fixed at 1.25V, the current through Rl and R2 is also fixed. This gives a simple formula for the output voltage as follows: Vout = 1.25(1 + R2/R1) In our circuit Rl is 1200 while R2 is made up of of a 2.7k0 resistor in parallel with VRl, a 5k0 potentiometer. The maximum effective value of R2 is thus 1.75k0 and the theoretical output voltage range is therefore between 1.25 volts and 19.5 volts. However, the unregulated DC voltage fed into the regulators is normally not quite high enough to enable 19.5 volts output to be delivered. That explains the circuit as far as the positive regulator (LM317) is concerned but what about the negative regulator'? It has an operational amplifier connected to its ADJ terminal instead of a variable resistor. What giveth'? The idea of the op amp is to provide a mirror of the voltage at the ADJ terminal of the positive regulator. So if the ADJ voltage at the positive regulator is + 10 volts, the op amp will produce an output of - 10 volts by virtue of the fact that it is connected as a unity gain inverting amplifier. So ICl ensures that the negative regulator always tracks with the positive regulator. The 1200 resistor between the ADJ terminal and output of the LM337 is there for two reasons: first, to give the required minimum load for the regulator, and second to set a load current flow into ICl. This load current of 10.4 milliamps impresses a voltage drop of 10.4V across the lkO resistor at the output of ICl. This allows the op amp to drive the ADJ terminal of the LM3 3 7 regulator to - 17. 3 volts in spite of the fact that the negative supply rail to ICl is only - 14 volts. The supply rails for ICl are provided by zener diodes D5 for the positive line and D6 in series with LED 1 for the negative line. Diodes D7, DB, D9 and DlO protect the regulators from reverse voltages which may be generated by capacitive or inductive loads connected across the outputs. Drop-out indicator When the regulators are working as designed, the ripple voltage superimposed on the DC rails will be very low. However, if the current drain is higher than the regulator can supply while still maintaining about 2 volts between its input and output terminals, the ripple voltage will suddenly become quite high. The output voltage will fall rapidly if even more current is called for and the ripple will go even higher. When this condition is beginning to occur you may have no idea that it is happening. You need a visible JANUARY 1988 39 PARTS LIST 1 plastic instrument case, 205 x 159 x 68mm 1 PCB, code SC041-188, 112 x 92mm 1 . Scotchcal front panel, 1 90 x 60mm 1 meter scale display, 52 x • 43mm 1 6672 30V, 1 A transformer 1 single-pole pushbutton mains switch 1 DPDT mini toggle . switch 4 banana panel terminals (blue, white, red and green) 1 5k0 potentiometer 1 knob 1 mains cord and plug 1 cord clamp grommet 2 solder lugs 1 aluminium panel, 196 x 64mm x 1.5mm 2 T0-220 insulating kits (mica washer and bush) 1 MU45 panel meter, 0-1mA movement Semiconductors 1 LM31 7T positive adjustable 3-terminal regulator 1 LM337T negative adjustable 3-terminal regulator 1 TL071, LF351 FETinputop amp 1 741 op amp 9 1N4002 or equivalent 1A diodes 6 1N914, 1N4148 small signal diodes 1 12V 1W zener 1 15V 1W zener 2 5mm red LEDs Capacitors 2 2200µF 25VW PC electrolytic 2 1 OOµF 25VW PC electrolytic 4 1µF 25VW PC electrolytic 1 0.1 µF metallised polyester Resistors (5%, 0.25W) 1 x 2.2MO, 2 x 47k0, 1 x.39k0, 1 X X 22k0, 3 X 2.7k0, 3 X 1k0, 1 2200, 1 X 1800, 2 X 1200 Miscellaneous Solder, hookup wire, insulating sleeving, screws, nuts, selftapping screws etc. Putting it together Close-up view showing how the 3-terminal regulators are mounted (see also Fig.5). Use your multimeter to check that the metal tabs are isolated from chassis. indicator. Hence, we have designed a drop-out indicator using IC2. ICZ is connected as an inverting amplifier with a gain of about 800. It monitors both the positive and negative regulators via 2.7k0 resistors and a O.lµF capacitor. Diodes Dl 1 and Dl 2 limit any noise or ripple signal level to a maximum of ± 0.7V. The amplified ripple at the output of IC2 is fed to a full wave rectifier 40 SILICON CHIP consisting of D13 to D16 via a lkO limiting resistor, to feed a light emitting diode, LED 2. The LED begins to glow when the ripple at one of the regulator outputs becomes greater than about 4mV peak-to-peak. At about 19mV p-p ripple the LED is fully alight. A lmA meter monitors the output voltage via the lkn and 39k0 resistors. This gives it a full-scale reading of 20 volts. The supply is housed in a standard plastic instrument case measuring 205 x 159 x 68mm (Altronics Cat. No. H-0480 or equivalent). All the circuit with the exception of LEDs, switches and the pot, is accommodated on a printed circuit board measuring 112 x 92mm (coded SC041-188). Both 3-terminal regulators are bolted to the rear metal panel of the case for hea tsinking. You can start assembly by checking the copper pattern of the board for any breaks or shorts in the tracks. Compare it with the pattern published in this article. With that done, you can install all the small parts on the printed board. These include the resistors, diodes, links, small capacitors and the two op amps. Make sure that the ICs and diodes are correctly oriented before soldering them into place. Note that the two ICs face in the same direction. Use the wiring diagram of Fig. 4 to check each stage of assembly. Next, install the two 2500µF capacitors and the two 3-terminal regulators. The regulators should be mounted so that their bodies are about 10mm clear of the board, to allow them to be easily bolted to the back panel of the case. We recommend the use of PC pins for all external wiring from the POWER TRANSFORMER CLAMP GROMMET \ MAINS CORD Fig.4: follow this wiring diagram carefully and your supply should work first time. Use medium-duty 24 x 0.2mm cable for connections between the PCB and transformer, and to the output terminals and Load switch (see text). board. They simplify connecting it up and give easy test points when checking voltages. The completed printed board is supported on four of the integral plastic standoffs on the base of the case and secured with self-tapping screws. The transformer must be mounted directly onto the base of the case. To do this, two of the standoffs will have to be removed or drilled out and holes drilled for 3mm roundhead or countersunk screws. Use lockwashers under the two nuts. Note that the mains earth wire is terminated to a solder lug on the rear metal panel of the case and thence to a solder lug secured by one of the transformer mounting screws. The earth wire also goes to the green GND terminal on the front panel. When the printed board has been installed, slide the metal rear panel into the case and mark the mounINSULATING BUSH \ ~ Ml .I WASHER iI SCREW Deburr de burrs HEATSINK (REAR OF CASE) NUT ting hole positions for the two regulators. The mounting holes should be drilled for 2.5mm screws. Fig.5 shows the mounting details for the two regulators. Note that a mica washer and insulating bush must be used to isolate each device from the metal panel. / T0220 DEVICE Fig.5: mounting details for the two 3-terminal regulators. Before securing the regulators, make sure that the mounting holes are free of burrs. Lightly smear heatsink compound on the regulator heatsink surfaces and the mating areas on the metal panel. Then screw the two regulators to the panel as shown in Fig.5. You should then switch your multimeter to a low Ohms range and use it to check that the metal JANUARY 1988 41 tabs of regulators are both isolated from the metal panel. You can then work on the front panel. Kitset buyers can expect that they will be supplied with a screen-printed precut panel but if you're working from scratch you will probably have to make or purchase a Scotchcal panel. The artwork can be used as a drilling template for the front panel. The meter is supplied with its own template for the four mounting screws and 46mm diameter cutout. This latter hole can be made by drilling a series of small holes just inside the circumference of the marked circle and then filing the resulting cutout to a smooth circle. Having drilled all the holes, you can affix the artwork to the front panel. The material covering the holes is then removed using a Stanley utility knife. Now the front panel hardware can be mounted. In complete kits, a new scale should be supplied for the meter. This is easily fitted. Just unclip the meter bezel, undo two screws, remove the old panel and replace it with the new and then reassemble. Alternatively, you can remove the existing scale, erase the numbering and re-do it with Letraset. Complete the wiring by following What's a dual supply? "Wotsa dual tracking power supply anyhow and why would I want one?" we hear you ask, in your ardent quest for knowledge. The word dual refers to the fact that this power supply has two supply rails , one positive and the other negative. The word tracking refers to the fact that when you adjust the positive supply, the negative supply automatically follows so that it has the same absolute value. So if you set the positive output to plus 1 0 volts DC, the negative rail will be very close to minus 10 volts. That's what you'd expect, isn't it? Fig.4. Connecting wires to the potentiometer, the two LEDs and the meter can be light-duty hook-up wire but the remaining wiring should use heavier wire, such as 24 x 0.2mm insulated cable. The 3-core mains cable should have its outer insulation layer removed for a length of about 10cm so that the active lead can reach the mains switch on the front panel. The mains cord can then be secured to the rear panel using a cord-grip grommet. The neutral lead is terminated directly at the transformer, as is the other lead from the mains switch. Both the mains termination on the transformer and the mains switch itself should be sleeved with plastic tubing to avoid the possibility of accidental shock. When all the wiring is complete you should check your work carefully against Fig.4 and Fig.2 (the circuit diagram}. With that done, you can apply power and check the voltages. The unregulated voltages to the input of the two regulators should be about ± 21 volts, while supplies to the two op amps should be + 15V at pin 7 and - 14V at pin 4. Now check that the positive and negative supply rails can be varied over the range from below 1.5V to above 18V and that the two supplies track each other within ± lOOmV. The dropout indicator can be checked for correct operation by connecting a 220 resistor across either the positive or negative supply. Now, when the output voltage is wound up above 15 volts, the LED should light. All that remains is to secure the lid of the case and your power supply is ready for work. lb ~ _, _ .i. CLASS-2.5 • MU -45 • Fig.7: this full-size artwork should be used to replace the existing meter scale. The old artwork is removed by unclipping the meter bezel and undoing two small screws. Fig.6 (left): this full-size reproduction of the PC pattern can be copied and used to etch your own PC board. 42 SILICON CHIP BOOKSHELF Comprehensive text on power supplies Switching and Linear Power Supply, Power Converter Design, by Abraham I. Pressman. Published 1977 by Hayden Book Co, Inc, Hasbrouck Heights, NJ. Hard covers, 160 x 235mm, 372 pages ISBN O 8104 5847 0. These days switching power supplies are becoming ever more widespread throughout electronics as efficiency, compactness and low heat dissipation become more desirable. For this reason alone the book is of considerable interest but it would be a mistake to regard it as just on switching power supplies. As the title suggests, there are also major portions devoted to the design of linear power supplies and power cqnverters. A brief explanation of these terms is in order before going on to review this text. Switching power supplies vary and maintain their output by rapidly switching on and off their main control element which these days is a high power transistor or transistors. A linear power supply is one in which the output voltage is varied or maintained by continuously adjusting the main control element which again is a power transistor or group of transistors. Lastly, power converters are circuits which step up or down from a DC input voltage to provide one or more DC outputs. They usually consist of a high frequency transformer driven by switching transistors. And now to our review: as far as the subject matter is concerned, this book is old. Published in 1977 and possibly written a year or two before that, it naturally misses out on all the developments in power supplies and electronics generally, that have taken place in the last twelve years or so. That means that such things as 3-terminal regulators, gate turn-off thyristors, power Mosfets, CMOS logic circuits and Fet-input op amps don't get a mention. Nor is there any discussion at all on power control using silicon controlled rectifiers (SCRs) or Triacs and hardly a mention of 3-phase circuits. Be that as it may, it is still a very worthwhile book, now in its seventh printing. I would regard it as one of the best overall texts on the subject of power supply design that I have come across. There are nine chapters in all, starting with a chapter on basic voltage regulators and power converters. This has a good section on the design of zener diode and emitter follower regulators. An understanding of this topic is essential to anyone involved in power supply design. Chapter two is basic square wave power converters and regulators while chapter three is on compound regulators. Chapter four is an excellent dissertation on the subject of thermal design which is applicable to power amplifier design as well as power supplies. It discusses forced air cooling too. Chapter five is another on fundamentals, this time on rectifier design using capacitive filters. This also contains a useful section on voltage multipliers, using diodes and filter capacitors. Chapter six goes into the nitty- gritty on series pass regulators and includes sections on foldback current protection and crowbar overvoltage protection. Chapter seven is on integrated circuit voltage regulators, mainly on the Fairchild µA723 although the National Semiconductor LM105 and Motorola MC1560/1561 are also covered. Finally, chapter eight covers DC/DC converters while chapter nine covers switching regulators, both in considerable detail. In summary, it's an oldie but a goodie. Our copy came from Jaycar Electronics. Active filter design Active Filter Design, by Carson Chen. Published 1982 by the Hayden Book Co, Inc, Hasbrouck Heights, NJ. Soft covers, 152 x 228mm, 133 pages. ISBN O 8104 0959 3. This small text is aimed at the engineer who wants a quick reference on the subject of active filters. It makes con$iderable use of mathematics to support the text, particularly S-parameters. There are essentially six chapters, as follows: (1) Transfer Functions, Decibels and the Quality Factor; (2) Magnitude, Phase, Poles and Zeros; (3) Some Basic Transfer Functions; (4) Basic Filter Topologies; (5) Mathematical Approximations: Butterworth, Chebychev, Elliptic and Bessel; (6) Cascading, Normalisation, Frequency Transformation and Impedance Scaling. It is by no means an easy text to read. For example, the sections on poles, zeros, normalisation and impedance scaling are unlikely to be understood by anyone who has not previously come up against these concepts. In summary then, it is OK for the engineer or engineering student but anybody else can probably forget it. Out copy came from the publisher. JANUARY 1988 43 •• - · •. • - ·. -· • • • - · • • - · ••• - · • • -· • . • - · • • - · •• • - · • • - · •• , ., • • • - · " • _, • , ..... , •• , " ' , , ...,, . , , .... , • ...,,, . . t ... , . t >J, .. , ... ,, , ...... , .. ,\.,,.,. I ...,,.,. , ,.,,.,. , Vr"\11 un I V/"\l l ""'"' I Vl"'\n VM I Vl"'\n ,JM TVMn .JM T VMn ,Jl-\lVAN JATVAN JAY l, 1 AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJ AYCAR JAYCARJAYC AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYC ARJAYCARJAYCARJAYCARJAYCARJAY.CARJAYCAR JAYCARJAYC, AYCAR . AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR •WCAR AYCAR AYCAR I\YCAR I\YCAR A.YCAR AYCAR A.YCAR I\YCAR I\YCAR WCAR A.YCAR WCAR WCAR A.YCAR WCAR WCAR WCAR A.YCAR WCAR WCAR WCAR A.YCAR WCAR WCAR WCAR I\YCAR WCAR I\YCAR I\YCAR WCAR WCAR WCAR AYCAR AYCAR WCAR WCAR WCAR I\YCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR Ref: Silicon Chip Jan '88 Ref: Silicon Chip Jan '88 WCAR New generation door opener WCAR Usten tD hidden transmissions on FM broadcasts. alarm. WCAR PC board and components. Cat. KC-5020 WCAR Cat. KC•5014 WCAR SUB CARRIER ADAPTORS FOR FM TUNERS WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR WCAR \YCAR \YCAR IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR \YCAR IYCAR IYCAR IYCAR IYCAR 1YCAR 1YCAR 1YCAR ,YCAR ,YCAR ,YCAR ...... ,YCAR /C: .VCAR // ,YCAR /'=' ANNUNCIATO $37.50 $22.95 9V power supply Cat. MP-3010 $18.50 1.25 tD 18.5V DC, voltage metering. LED dropout !ndlcatDr, short circuit protected. Full kit. Cat. KC-5022 DUAL TRACKING POWER SUPPLY ULTIMATE CAR BURGLAR ALARM Ref: Sllcon Chip Jan '88 Includes flashing light switch, back-up battety factllty and lgnltlon killer. Cat. KC-5021 $79.50 •• $99.95 • • • • ,. ' ~ ,· ·~· ·., ·•. .>: ,._· •..:. ✓,,... 4., - 50 & 100 WATT AMPLIFIER MODULES Extras · Siren Hom Cat. LA.·5700 $26.50 Screamer Plezo Cat. LA-5255 $17.95 Back-up batlety Cat. SB-2480 $22.50 Ref: Silicon Chip lf you are tired of phone, tty this kl phone · Includes Cat. KC-5015 $19.9 :~g:~ : :i,: :,l " - - - - - - - - - - - - - - - - - - - - - - - - - - - -41111 Ref: Silicon Chip Dec '87 Kits Include PCB all parts and heat stnk bracket. O'hermtstors not supplied). SOWA'IT Cat. KC-5018 $32.95 ThermtstDr RDE115 Cat. RN-3415 $8.95 lOOWATI Cat. KC-5019 $38.95 ThermtstDr RDE245A Cat. RN-3418 $10.95 ,YCAR ,YCAR \ : .VCAR ·C···'· ,YCAR ,YCAR JAY.CAR JAYCAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAYC, ,YCAR JAYC AR JAY.CAR JAYCAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAY.CAR JAYCAR JAY.CAR JAYCAR JAY.CAR JAY.CAR JAY.CAR JAYCAR JAYCAR JAYC1 ,YCAR JAYCAR JAYCAR JAY.CAR JAY.CAR JAY.CAR JAYCAR JAYCAR JAY.CAR JAY.CAR JAYCAR JAYCAR JAYCAR JAYCAR JAY.CAR JAYCAR JAY.CAR JAYCAR JAY.CAR JAY.CAR JAYCAR JAYC, .YCAB..J.A_YCARJAVCAR JAVCAR IAVCAR JAVCAR JAVCAR IAYCAR IAVCAR IAYCAR IAVCAR IAVCAR~R lAYCAR lAYCAR lAYCAR lAYCOR IAY"AA .JAYC.A.R..JAY.CAA .1&vr,.0A .JA.,,,-, . 12" GUITAR SPEAKER 8" WHITE CONE WOOFER NEW MODEL Finally available, our updated guitar speaker with extended frequency response. Especially suited for not only Bass guitar buy Rythm & Lead as well. Specifications Resonant Frequency 60Hz (was 80Hz) Impedance 8 ohms Freq. Response 60 • 5000Hz (was 80 · 4000) Power Handling 100 watts RMS Magnet Weight 40 oz Net Weight 3610 grams (was 3520g) Sensitivity 102dB But the best news 1s the prtce • NO INCREASE Cal CG-2380 STILL ONLY $89.50 LESS 15% $76.07 Best looking and sounding 8" woofer we've seen for the prtce. White cone, large magnet 10oz, roll surround. Spees Power Handling . Resonant Freq. FIreq.dResponse mpe ance Sensitivity MOTOROLA Model KSN 1038 Over 100 watts rms, frequency 4·30kHz. No crossover required. Especially suited to H1 Fi. Cat. CT-1914 ONLY $26.95 · · ·-.· .:·· · MOTOROLA Model KSN 1016 50x 125mm This exponential horn has a full 90" hortzontal dispersion angle. With harmonic distortion of less than 1%, this unit is Ideal for HI Fi use. Frequency response 3 • 30kHz ±3dB, maximum input 25V rms, no crossover required. Cal CT-2026 • MOTOROLA Model KSN 1135 NEW MODEL Same to look at as Model 1005A (CT-1910) but handles 75 watts. SPL 96dB. Cal CT-1908 ONLY $14.95 LESS 15% $12.70 60 x 150mm Rectangular Widest frequency range of the plezo horns, otherwise similar to the CT-2026. No crossover required. Cat. CT-1912 WAS $34.50 NOW $29.95 LESS 15% $25.46 SAVE $9.04 HE ORIGINAL ADEL NIBBLING TOOL BACK AGAIN .E/G68 MOTOROLA ~ Model KSN 1089A NEW MODEL MOTOROLA Model KSN 1025A ONLY $29.95 LESS 15% $25.46 ·.. • ·• WAS $26.50 NOW $22.95 LESS 15% $19.50 WAS $26.50 NOW $19.95 LESS 15%. $16.96 SAVE $9.54 BORN IN THE USA How things change. You can now purchase from Jaycar the ortgtnal Amertcan Adel nibbling tool. Due to prtce rtses from Asian countrtes we've been bale to direct Import the ot1g1nal tool (which we sold 10 years ago) and sell It at the same prtcc as the Asian copy. • Cuts holes · any shape over 7 / 16'' • Notches clearance for plugs and w1I1ng • Trtms underslze holes to flt parts • Suitable for steel up to 18 gauge, Aluminium 16 gauge, plastic and copper Cat. TH-1765 1 5 up $24.50 LESS 15% $20.82 Why buy a Taiwanese P!ezo Tweeter when Jaycar can offer you the best for no more. MOTOROLA Model 1005A · • · ..• , ·• LESS 15% $22.90 GENUINE MOTOROLA PIEZO TWEETERS AT TAIWANESE PRICE 90mm SUPER HORN Perfect for use where Jong throw Is needed. PA's and musical instrument use. Frequency response 3.8-28kHz ±3dB, maximum Input 25V rms ( IO0W amp power), no crossover required. Cat. CT-1910 8 96dB ., 1 ;:;;{{ 5 or more $79.50 LESS 15% $67.58 WAS $24.00 NOW $18.95 LESS 15% $16.10 SAVE $7.90 _. ohms 3." Direct Radiating Tweeter Looks like a normal 3" cone tweeter. Great for car sound and H1 Fi. Cal CT-1906 ONLY $9.95 LESS 15% $8.46 •••••••••••••••••••••••••••••••• • SLIDER POT PACK JAYCARJ AYCARJAYCARJAYCARJAYCARJ AYCARJ AYCAR JAYCARJ AYCARJAYCARJ AYCARJAYCAR JAYCARJAYC ARJ AYCARJAYCARJAYCAR JAYCAR JAYCARJAYCAR JAYCARJ AYC, JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYC, JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYC, JAYCAR JAYCAR JAYCAR ~.2J2··_J JAYCAR JAYCAR "Y ~cf. - I '"~'"' I JAYC AR JAYCAR JAYCAR These are basically a 5mm LED mounted tn .232•• + JAYCAR 15 9 a plastic housing spectftcally designed for · mm' JAYCAR PCB mounting. Available In the 4 standard colours. JAYCAR JAYCAR Red Cat. ZD-1780 JAYCAR Cat. ZD-1781 Green JAYCAR Yellow Cat. ZD-1782 JAYCAR Orahge Cat. ZD-1783 JAYCAR 10mm LEDs - NOW AT AFFORDABLE PRICES JAYCAR .os~· 10.smm1 Red Cat. ZD-1956 JAYCAR Green Cat. ZD-1957 ~ = i , - l 1 5 m ml JAYCAR Yellow Cat. ZD-1958 JAYCAR I I I I Orange Cat. ZD-1959 (NEW) JAYCAR .100" !5.0mm<-.0.Smml 12.54mm) 10 up 42<: LESS 15% 36<: JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Jaycar has Introduced this great LED array JAYCAR for our 1988 new product line-up. It has 7 JAYCAR green and 3 red rectangular 5mm x 2.5mm 10 up $1.30 ea JAYCAR LEDs mounted In a black housing. Ideal for JAYCAR LESS 115% $1.11 VU metres or where any easy Visual clipping JAYCAR level Is required. JAYCAR JAYCAR Cat. ZD-1702 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR DIRECT IMPORT SAVES YOU MONEY JAYCAR JAYCAR (ALLRED) JAYCAR WAS JAYCAR The STD Bar for your telephone will be available 200mCd Cat. ZD-1790 99t JAYCAR sometime In Janua,y. It appeared In our JAYCAR catalogue but we were afraid to JAYCAR 10 up 70<: Less 15% release It due to to the safety 10up90t JAYCAR aspect of 000 emergency N EW"'f-sS JAYCAR Cat. ZD-1792 IS00mCd $3.75 $2.50 number. We have solved JAYCAR LESS 15% $2.12 JAYCAR this problem, and the new JAYCAR 10up$3.50 10 up $2.30 Less 115% model will allow emergency calls through JAYCAR on the 000 number, but will stop standard JAYCAR Cat. ZD-1793 l000mCd $7.95 $4.915 STD calls (except Tasmania). Cat. YT-6540 JAYCAR LESS 15% $4.20 JAYCAR JAYCAR 10 up $4.50 Less 15% JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR LED and HOLDER 'N~,,.;: FOR PCB MOUNTING 10mm ~,'I - -"'I I I DIRECT IMPORT SAVES YOU MONEY ALL THE SAME PRICE 48~ ea LESS 15% 41~ U ~ 1t1 -iL,,u WAS $1.95 ea NOW $1.50 ea LESS 15% $1.28 LOWER PRICES ON ULTRA BRIGHT LEDS $4.25 LESS 15% $3.61 STD BAR - FINALLY RELEASED rl1fl $34.95 LESS 15% $29.70 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR j~~g~~ BISHOP GRAPHICS - LESS 15% OFF ALL PRICES As demand for greater PCB density Increases so does the need for a more professional approach to PCB design. To help In this regard, Jaycar stocks a comprehensive range of PCB artwork materials from BISHOP GRAPHICS of the USA. This material Is both dimensionally stable and accurate which, enables you to produce complex layouts with greater accuracy. (Vexy necessaty for LSI, for example). Once your artwork has been produced you can make your own board. 111111 PRE-SPACED HG-9906 0.100" d!aPADS 1.58mm 240 pads $5.60 HG-99070.100" dla 1.91mm 140pads $5.60 HG-9908 0.156" dia 2.54mm 150 pad $5.60 PRESSURE SENSITIVE COPPER TAPE OOOOO0 DIL PATTERNS HG-990914 PIN 32 symbols HG-9910 16 PIN 32 symbols HG-9911 18 PIN 28 symbols HG-9912 24 PIN 12 symbols HG-9913 28 PIN 12 symbols HG-991440 PIN 8 symbols $5.60 $5.60 $5.60 . $5.60 $5.60 $5.60 DIL PATTERNS · NARROW CUT HG-9918 14 PIN 32 symbols HG-9919 16 PIN 32 symbols HG-9920 40 PIN 8 symbols $5.60 $5.60 $5.60 BLACK AR1WORK TAPE HG-9930 0.026" wide HG-99310.031" wide HG-9932 0.040" wide HG-9933 0.050" wide HG -9934 0.062" wide HG-9935 0.080" wide HG-9936 0.093" wide HG-9937 0. 100" wide HG-9938 0 . 125" wide HG-9939 0.200" wide HG-9940 0.250" wide x 20 yards x 20yards x 20 yards x 20 yards x 20 yards x 20 yards x 20 yards x 20 yards x 20 yards x 20 yards x 20 yards $3.95 $4.25 $4 .25 $4.25 $4.30 $4.30 $4.30 $4.30 $4.30 $4.30 $5.75 0.031" ID 0.031" ID 0.031" ID 0.031" ID 0.031" ID 0.031" ID $4.30 $4.30 $4.30 $4.30 $4.30 $4.30 DONUT PADS HG-99410.080" HG-9942 0.100' HG-9944 0.125" HG-99450.156'' HG-9947 0.200' HG-9948 0.250" OD x OD x OD x OD x OD x OD x AR1WORK ACCESSORIES HG-9955X-Acto knife HG-9956 5 trim pack blades HG-9957 5 art pack blades $4.65 $3.95 $3.95 • • • • 1111111 1111111 IIIIIII IIIIIII -i,8 • Ideal for repairing damaged or broken semiconductor traces on a PCB. Use to modify circuitry on existing PCB's. HG-9901 0.031" wide x 6ft HG-9902 0.050'' wide x 6ft HG-9903 0.100' wide x 6ft <;:,>.'()) ~ $4.30 $4.30 $5.35 AR1WORK FILMS POLYESTER Always use a background grtd during printed circuit artwork and layout preparation to ensure maximum accuracy on the final PCB. 10 x 10 grtd, matt on one side - 0.003" thick. This Is the material you lay your pattern on. HG-9959 8.5 x 11" pack of2 HG-9960 I I x 17' pack of 2 $4.25 $7.50 ULTRAVIOLET EPROM ERASER If you need to regularly erase the contents ofEPROM's then this Is your most cost-effective solution. It will erase up to 9 x 24 pin devices In complete safety to your eyes and your chips, In around 40 minutes for 9 chips Oess for less chips). • Erase up to 9 chips at a time • Chip drawer has conductive foam pad • Mains powered • High UV Intensity at chip surface ensures thorough erase • Engineered to prevent UV exposure • Long UV tube life Specifications 240V50Hz Operating Voltage 8 watts Power Consumption Cat. XE-4950 9 to 24 pins Capacity UV Source Wavelength 253.7nm 6.4mW/cm' UV Intensity 3000hours Tube Life 21.7 X 8 X 6.8cm Dimensions Weight 670grams $99.50 LESS 15% $84.58 --~;filiiil:l!ll!iliiii!!!!!!!!!!'!!!!!!!l!!!I!!!!!!!!!!!!!!!!!~~----------_::======================::..,, ~fflt::;r JAYCAR ·JAYCAR JAYCARJAYCARJAYCARJAYCARJ AYCAR JAYCARJAYCAR JAYCARJ AYCARJAYCARJAYCAR JAYCAR JAYCARJ AYCAR JAYCAR JAYCAR JAYCA RJ AYCAR JAYCARJAYC AR JAYCARJA Yl JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JA '✓' JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JA-. 24 TO 12V CONVERTER Ref: Silicon Chip Dec '87 Well suited to nm 12 volt appliances from 24 volt. Can deliver up to 5 amps. Complete kit Cat. KC-5017 $59.00 LESS 15% $50.15 We have managed to purchase a second batch. They are slightly more expensive but st111 represent an absolute_bargain. You guessed It, another Jaycar buy far, far below manufacturers cost where you buy at a normally sllly prlce because other people have lost heavily. This time Its a VERY HIGH QUALITY cassette deck mechanism that cost over $35 US tn 1000 lots! This JAPANESE MADE mechanism Is deck only - I.e. a door Is not fitted nor are there buttons. The deck Is not operated by mechanical buttons and all control ls by electric signals, therefore the deck could easily be software con trolled. The deck also features an air damper cylinder for soft eject, massive capstan flywheel, HI FI head and excellent specs. (see below) . This deck Is Ideal as either a fast high capacity PC memory storage or as a retrofit lo an existing cassette deck to Improve performance. Worth at least $80, grab one for ONLY SOLAR GENERATOR Ref: ETI Dec '87 This Is a cheap, no fuss way to trickle charge a 12V car battery. PC board and parts. Cat, KE-4730 $12.95 LESS 15% $11.00 HIGH IMPEDANCE AC/DC MILLIVOLTMETER $29.95 LESS 15% ONLY $25.45 Ref: EA Dec '87 This kit will measure AC and DC signals down to a couple ofmllllvolts, with negligible circuit loading. Complete kit with case and meter. Cat. KA-1695 Cat. AC-1590 SPECS: • 4 track, 2 channel Phillps compact cassette deck • Tape speed 4. 75cm/sec • Wow and flutter <0.12% RMS • Wtndlng time 110 sec FF & REW C-60 • Working volts 9 - 15V • Supplied with 12 page comprehensive manual lnclucllng circuit diagram, truth table, etc. $46.50 LESS 15% $39.53 UNIVERSAL SPEED CONTROL & LAMP DIMMER Ref: Silicon Chip Dec '87 Use for control of dnlls, fans, electric blankets, soldering Irons or a dimmer. Complete kit with box, matns leads, etc. Cat. KC-5016 $18.95 LESS 15% $16.11 JAVCAR No1 FOR KITS OCTAVE EQUALISER MODULE Ref: AEM Dec '87 This one octave EQ module Is suited for PA and professional use. Klt supplied with all components, pots, PCB. No box or hardware. Cat. KM- 3064 . $49.95 LESS 150/o $42.46 TURN YOUR SURPLUS STOCK INTO CASHII Jaycar will purchase your surplus stocks of components and equipment. We are conttnually on the lookout for sources of prlme quality merchandise. CALL GARY JOHNSTON OR BRUCE ROUTLEY NOW ON (02) 747 2022 Build this superb 1GHz Digital Frequency Meter This month, we complete construction of the 1GHz DFM and describe the calibration procedure. There's also a useful troubleshooting guide - just in case you strike trouble. By STEVE PAYOR Last month, we left off after describing the assembly of the two main printed circuit boards. The next step is to solder the two boards together at right angles. To so this, carefully align the two boards, using the arrows at each end of the display PCB as a guide, and solder tack them in several places. Now inspect the assembly carefully and make any adjustments that may be necessary. When everything ls correct, solder all the matching pads together to create a permanent assembly. Finally, check that there are no solder bridges between adjacent pads. The meter is now ready for its first test. Temporarily install an insulated This close up view shows the mounting details for the two BNC sockets. Note that two earth links are soldered to the 500 input socket. 48 SILICON CHIP link across the switch connections to the mains terminal block (the mains switch is installed later), then slot the counter module into the front of the case. Connect the power supply leads to the board with a multimeter set to measure DC current in the + 5V lead. Plug in, switch on and verify that the current is between 300 and 500mA (depending on how many digits are lit). If all is well, try pressing the front panel buttons. On power up, the display should read .000kHz and the second Function LED should be lit (frequency to 10MHz). When the Range buttons are pressed, the leading zero on the display should be directly above the selected button, and the decimal point should be immediately to the left or right of the leading zero, depending on the setting of the Function pushbuttons. The function indicator LEDs and the µsec and kHz light bars should change with the Function pushbuttons. If you strike problems here, switch off immediately and check for wiring errors. Assuming the power consumption of the counter module is within the specified limits, you can now go ahead and make the + 5V supply permanent. Twist the supply leads together and trim them so that they are just long enough to reach the counter PCB. The µsec and kHz transparencies can now be glued to the light bars. Use only water-based PVA glue (eg, Selleys "Aquadhere"). Only a tiny bead around the outside edge is re- , Se 12,8 1·. Above: the new 1GHz DFM is shown here displaying the frequency generated by the SAB6456 prescaler IC (see text). quired. If you make a mess, clean up with a damp cotton bud and try again. Testing the counter module The counter module should rest comfortably in the second PCB slot from the front, leaving a 10mm clearance between the display PCB and the front panel. At this stage, you will find that the lkO multiturn trimpot will be resting on one of the PCB guide rails, so carefully cut away the plastic at that point. Do not drill a hole right through the plastic case, as this trimpot is not meant to be adjusted from the outside. With the counter module and rear panel module in place, slip on the top half of the case, then turn the whole unit upside down. The bottom half of the case can now be removed to expose the underside of the counter and display PCBs. Next, solder a shorting link across the lMO input pads on the display PCB and plug a 1. 7V red LED into the Molex pins at the test point. The anode of the LED should be connected to the + 5V track, which is the thicker of the two. Switch on - with no signal input, the LED will either be on or off, depending on the state of the Schmitt trigger (IC2a). If the LED is off, turn VRl 1,28 ,128 QUENCV METER Hints on Drilling the Perspex Panel The greatest hazard when drilling thin perspex sheet is the possibility that the drill will take one bite and shatter the panel. To avoid this problem, the drill should be as sharp as possible, for a clean finish, but the cutting edge should have no rake . Specifically , the leading edge should be at 90 ° to the cutting direction as shown below. It only takes a minute to convert a normal drill bit, using a grinder or pocket stone. The other problem often encountered is a poor finish, caused by the drill overheating and melting the surrounding plastic. Again, keep the drill sharp. There are two other styles of drill grinding which are useful when building a project like this. The Wshaped bit is for cutting clean, perfectly round holes in sheet metal. This drill actually punches out a thin disc at the end of the cut, leaving no burr on the far side. It is perfect for drilling ventilation holes in aluminium or thin sheet steel and will even cut a clean 1 2mm hole in clockwise until it just comes on, or vice versa. Tapping VRl with a metal screwdriver will inject enough noise to trip the Schmitt trigger, so keep the blade in steady contact (or use a plastic screwdriver). NORMAL DRILL FOR SHEET PERSPEX METAL SPOTFACING tinplate. Using a normal drill for this job would leave you with a mess. The spotfacing drill is similar, but the "wings" are straight instead of W-shaped, and less rake is used on the leading edge. This type of drill will soon get rid of any unwanted plastic pillars, cutting them flush with the inside of the case. Having found one of the trip points, slowly turn VRl in the opposite direction, half a turn at a time, counting as you go. When the Schmitt trigger changes state again, you have found the other trigger point. On the prototype, the JANUARY 1988 49 The 100MHz preamplifier circuitry is adjusted with a 1. 7V red LED plugged into two Molex pins on the back of the display PCB. range was five full turns. This is a convenient way of checking the DC gain of the amplifier circuitry each turn is approximately lmV. Check the trip points once more, then set VRl exactly half-way between them for maximum sensitivity. Once VRl has been set, remove the input short and the LED. Slip on the bottom of the case and turn the instrument right way up again. The instrument is now ready for its first frequency measurement. Select a lMQ resistor and clip one lead short. Switch on and touch this lead to the 0.047 µ,F input capacitor while holding the other lead in your fingers. The DFM should show a steady reading of .050kHz. Note: the lMQ resistor, in conjunction with the input capacitance, acts as a low-pass filter for the 50Hz signal picked up by your body capacitance from the mains wiring. The 7 10 prescaler can now be checked by pressing the F3 button. The display should change to 0.05kHz (ls gating time]. Now switch to period mode. You should get a fluctuating reading of around 20,000µ,s (20ms). The reading will be constantly changing because the short-term stability of the mains is nowhere near as good as that of the crystal. Removing the signal source in Period mode will freeze the reading since the 7216A counter chip will be waiting for the required number of input cycles to 50 SILICON CHIP be completed before it updates the display. Checking the 1GHz range is easy. Press the F4 button and select the minimum gating time (R4). You should now have a rapidly updating reading of around 1.2GHz. This is because the SAB6456 prescaler oscillates at this frequency when no signal is present. Now press the R2 button and wait 12 .8 seconds until the display updates. The leading "1" will now be in the overflow position, with the rest of the digits much the same as before. The above procedure checks out virtually all of the functions of the DFM. If your unit passes all the above tests, you can be sure it's fully operational. The front panel The front panel artwork shows the drilling pattern for the panel. Red perspex is the material of choice and the colour to ask for is "Red 502". This is a deep ruby red colour which looks quite dark but transmits the wavelength of the red LEDs extremely well. The thickness of the panel should be 2mm, with 1.6mm as the second choice. Unfortunately, these thicknesses are not universally available, although 3mm sheet is quite common and can be pressed into service if you have no other choice. The 3mm sheet will fit in the wide gap between the front panel slot and the first PCB slot. The PCB should be moved to the third rearmost slot (don't forget to cut the relief for VRl ). Provided none of the components are higher than the height of the 7-segment displays, everything will still fit. If you go for this option, note that you will have to trim an extra 1mm from the top and bottom of the panel. The width remains the same. Once the panel has been cut to size, the holes can be drilled to accept the switches and input sockets. This can be done by first taping the front panel artwork (or a copy) to the panel, then marking out the holes with a sharp scriber. Pilot drill all holes with a small PCB drill to start with, then progressively enlarge the holes, checking the centring as you go . The final hole sizes are 9.5mm for the BNC sockets and 10-1 lmm for the pushbutton switches. You 1.0~--~~--~~--~ 0.9 0.8 I·e o., i 0.6 TIME (mi nutes from switch-on) Fig.12: this graph plots the warm-up drift of one of the prototypes. The total drift is better than 1ppm. POWER • cycles counted 1000 gating time, sec 10 10 128 100 1 1 12.8 10 .1 .1 1.28 1 .01 .01 .128 I 10MHz 100MHz 1GHz PER~ENCl 1Mn/10pF \llfl \llfl 50n DIGITAL FREQUENCY METER 0 C041-1187 Here are actual size artworks for the front panel, printed circuit boards, and kHz and µ,sec indicators. may wish to ream the last mm or so of the pushbutton holes, particularly if the drill is not cutting evenly. Drilling thin Perspex is not an easy task, so we have included a panel on hints for drill sharpening for those readers who are not used to working with this material. Because the inside edges of the pushbutton holes are visible, you may wish to polish them. Alter- natively, blacken them with a marking pen. Front panel assembly Affix the Scotchcal label to the front panel, then cut out the three holes for the power switch and input sockets using a sharp utility knife. A light touch with a reamer will improve the appearance of the hole for the mains switch. I!& JANUARY 1988 51 Troubleshooting the 1GHz DFM Don't rush out and replace all the semiconductors if the counter module fails to work first go. The problem is almost certain to lie elsewhere unless you've done something silly, such as installing an IC or transistor back to front. The first thing to check is that all the parts are in their correct positions and are correctly oriented. For example, the switches will not work if they are rotated 90 °. Next, check the copper side of the PCBs for soldering faults, such as bridges between the closelyspaced tracks around the IC pads. Another thing to look for is open circuit tracks, and these are most likely to occur where too large a hole has been drilled through an IC pad. One area where soldering faults are both common and easily detected is in the multiplexed display. A short between segments is easily recognised from its effect on the display, as is an open circuit along one of the segment tracks. Some constructors of previous Mount the two BNC sockets and orient them so that the solder tags will fit between the parts on the display PCB. The 500 input socket should ,have its tag at 3 o'clock (viewed from the back), while the other tag should be between 7 and 8 o'clock. Bend the tags up by 90° after the nuts are tightened. Next, solder two short lengths of tinned copper wire to the 500 socket and one to the lMO socket (the two connections to the 500 socket minimise the series inductance). This done, solder two short lengths of tinned copper wire into the central hollow pins of the connectors. Remove the counter module from the case and test the fit of the front panel over the switches. Bend the earth links from the BNC sockets to engage the PCB holes, then slide the module and panel together into the case. The leads from the input sockets can now be soldered to the 52 SILICON CHIP DFM projects have experienced trouble in getting the 7216A's oscillator to start up. The symptoms are no display at all, or only one digit lit and very briefly at that. The problem usually occurs with very cheap crystals which have a large equivalent series resistance. Calculations based on the minimum guaranteed gain of the CMOS inverter show that the oscillator will only work with a crystal having a series resistance of less than 800 and 20pF shunt capacitance, or 350 and 30pF nominal shunt capacitance. If you are unlucky enough to have a crystal with excessive series resistance, the cure is fairly simple: use less capacitance to the +5V rail at pins 25 and 26 and maintain the correct shunt capacitance by installing a capacitor across the crystal. For example, removing the 39pF capacitor and 40pF trimmer leaves the crystal with a shunt capacitance of about 3pF, so adding a 27pF capacitor between pins 25 and 26 will bring a 30pF crystal back to the correct frequency. The circuit will now tolerate a series resistance as high as 1200 although the stability will no longer be quite as good. display PCB. Finally, the wiring between the mains switch and the terminal block can be installed. Be sure to use mains-rated cable for this job, and cover the switch terminals with spaghetti insulation or heatshrink tubing to prevent accidental electric shock. For good measure, we also covered the entire switch body and part of the leads with additional heatshrink tubing. Don't forget to remove the link installed across the terminal block in place of the mains switch earlier on. sharpening). This will quickly cut the pillar right down flush with the surrounding plastic. We drilled four rows of holes in the front left-hand area of the case bottom, and another two rows on the other side of the ribbed section. The ribbed section was left undrilled (see photos pages 39 and 43, November 1987). This allows cool air to flow up under the main counter chip and around the 10MHz crystal. A small hole must also be drilled in the lid of the case, directly above the 40pF trimmer capacitor. This hole allows external adjustment of the trimmer during calibration. It is located 26mm back from the rearmost PCB guide rail, and 47mm in from the inside edge of the case (note: if the display PCB occupies the third PCB slot, read 29mm instead of 26mm). Drill a small hole first, then ream it out to accept one of those little plastic plugs that Ventilation It is important to ventilate the case correctly if you want the best possible frequency stability. Before drilling the bottom of the case, you will have to remove some of the plastic pillars that are in the way. This is best done with a spotfacing drill (see panel on drill Signal tracing A pair of headphones and a multimeter are the best de-bugging aids you can have for this project. Assuming the 1 0MHz oscillator is running , the 7216A should be putting out 500Hz signals on the digit and segment driver lines. You can verify this with the headphones. Use a 1k0-1 OkO resistor as a probe (to avoid loading the circuit and to protect the headphones), and listen to one of the digit driver outputs. A "spiky" 500Hz tone should be instantly recognisable, and all the digit drivers should sound the same. The segment drivers will have the same pitch but a different timbre as the numbers on the display change. Check that a similar 500Hz signal is also reaching the clock inputs of the 4024 and the 401 7s. As a matter of interest, follow the signal through the 4024 binary divider's seven stages . The 7 .8125Hz signal (at the output of the sixth stage) will sound like a series of fast clicks. To check the passage of the 500Hz signals through any of the 4016 analog switches , connect the headphones across the switch, using two resistors as probes. It is easy to tell when a particular analog switch is closed - it should be almost silent when its corresponding controlling Range or Function button is pressed. Faults in the signal path selection logic can be quickly tracked down using DC voltage measurements. The logic levels at the ECL gates are described in the panel on ECL logic but note that some of the DC control inputs have a logic O level less than +3.4V which is OK since any voltage between +3 .4V and ground will do for a "O" input. You can use headphones to trace a 50Hz test signal through the ECL preamplifier, Schmitt trigger, and the +5 and +2 counters (but see note below) . cover the screws on 240V wall outlets. Finally, fit four rubber feet to the bottom of the case. Construction in now complete. Calibration Before attempting calibration, you should allow a warm-up time of at least 15 minutes with the lid on. This will give the instrument time to stabilise and will ensure the best possible accuracy. To properly calibrate the instrument you will need a signal source of known frequency, with a stability better than one part per million. For most of us, this boils down to one of two choices: either local colour TV transmissions or the 10MHz standard transmissions from WWV Colorado or WWH Hawaii. The latter is preferred by the author because it has the same frequency as the crystal oscillator. All you need is a domestic shortwave The logic levels throughout the ECL signal path will be +4.3V (high) and +3.4V (low) , and the first two differential amplifiers will be biased in between at +3.8V. A special note of caution here: any external connection to the signal path will make the 100MHz preamplifier oscillate. This is why we chose to use a LED to monitor the Schmitt trigger output during the setting up procedure. You can minimise your chances of disturbing the circuitry by using a resistor as a probe for your multimeter. A value of 1 Ok0-1 OOkO is suitable for 1 OMO digital or FET analog multimeters, however you must cut the "probing" end quite short. Even a centimetre of lead will upset the sensitive wideband circuitry. If you are using a low-resistance multimeter, switch to a low voltage range and choose a resistor which wil l provide a convenient "multiplier" for the reading. The resistor acts as a low-pass filter, preventing feedback between the multimeter leads and the ECL circuitry at high frequencies . receiver and seven metres of hookup wire as an antenna. Wait until evening, when the ionosphere over the Pacific Ocean will reflect a fairly good signal, and position the DFM near the antenna so that its radiated 10MHz clock signal is about the same strength as the incoming signal. Adjust the 40pF trimmer with a plastic screwdriver until you have a zero beat. If the shortwave receiver has a tuning meter, you can watch the -beats when the frequency is too low to be audible. Adjustment to within 1Hz is often possible. Most colour TV transmissions are synchronised to atomic clock standards and the 4.43361875MHz colour subcarrier oscillator in your TV receiver is phase-locked to these transmissions. The easiest place to gain access to this signal is right at the 4.43MHz crystal. Use a probe made from a 10MO resistor shunted by a small capacitor of between lpF and 3.3pF, depending on the capacitance of the shielded cable you are using. You can tell whether the subcarrier frequency has been disturbed or not by keeping an eye on the colours in the picture. The 15.625kHz line scanning frequency is also derived from the same accurate standard and you may be able to pick this up from the stray radiation around the line output stage, without making an actual connection to the TV. Unfortunately, there are less digits to play with in this case so, to obtain the highest accuracy, switch to Period mode and adjust the trimmer for a reading of 64.0000µsec. If you decide not to calibrate the instrument, just set the 40pF capacitor to about 10% less than full mesh. This places a nominal 20pF across the crystal and the frequency will be within 10 or 20ppm, depending on the crystal tolerance. Note: some 10MHz crystals will require a nominal shunt capacitance of 30pF. You can easily tell if this is the case because you will not get a zero beat, even with the 40pF trimmer fully meshed. The cure is to add some additional capacitance across the trimmer and the existing 39pF capacitor. A pair of 15pF or 18pF capacitors should be sufficient. These are best soldered to the underside of the PCB with very short leads. If this still doesn't trim the crystal to the correct frequency, then you may have been supplied with a series-resonant crystal by mistake. All capacitors used around the crystal oscillator should be high quality types; eg, polystyrene or Philips NPO miniature ceramic plate. Fig.12 shows the warm-up drift of one of the prototypes which used a cheap 10MHz crystal and an imported power transformer which ran quite hot. Surprisingly, the drift was less than lppm. Better quality components will give even better stability. Your new 1GHz Digital Frequency Meter is now ready for work. We hope that you find it a useful addition to your range of test equipment. ~ JANUARY 1988 53 KITS Musicolor IV Flasher The Musicolor Mk IV is four chase patterns plus auto chase and reverse chase AND four channel colour organ with built-in microphone means you're ready to start a lightshow! 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Aci~ Clri.. : (732RTV) 75g tube NNtral Clrill: (738RTV) 85g tube s4as s12as Cat N-1225 Cat N-1226 STORE LOCATIONS NIW Swin & Young SIS. T55 Terrace Level Shop 1, 65-75 Main St 613 Princess Hwy Oxlord & Adelaide SIS Shop 2, 1B Cross St, W&rringah Mall Campbelltown Mall Queen St Albury BankstownSq Blacktown Blakehurst Bondi Junction Shop 235, Archer St Entrance 147 Hume Hwy 164 Pacific Hwy 99 Donniston St 4 Fl0<enca St Ellzabelh Dr & Bathurst St 450 High Street 621-627 The Kingsway 173 Maitland Rd, Tlghes Hill Lane Cove & Waterloo Rds George & Smith Sts The Clateway High & Henry SIS 818 George St 125 York St Treloar's Bldg, Brisbane St 263 Keira St Brookvale Campbelttown Chatswood Chase Chullora Gore HIii Gosford Hornsby Liverpool Maitland Miranda Newcastle North Ryde Parramatta Penrith Railway Square Sydney City (02)707 4888 (02)671 7722 (02)546 7744 (02)387 1444 (02)93 0441 (046)27 2199 (02)4111955 (02)6,42 8922 (02)439 5311 (043)25 0235 (02>477 6633 (02)600 9888 (049)33 7866 (02)525 2722 (049)61 1896 (02)88 3855 (02)689 2188 (047)32 3400 (02)211 3777 (02)267 9111 (067)68 1711 (042)28 3800 Tamworth Wollongong (062)80 4944 ACT 96 Gladstone SI Fyshwick (060)21 8399 VIC Creswick Rd & Webster St 145 McCrae St Shop 46,Box Hill Central.Main St 260 Sydney Rd Shop 1, 176 Lonsdale St Hawthorn Rd & Nepean Hwy Ballarat Bendigo Box HIii Coburg Dandenong East Brighton 1150 Mt Alexander Ad Essendon Shop 11/13 Footscray Plaza Nepean Hwy & Ross Smith Ave Shop 9 110, High St 291-293 Elizabelh St Bridge Rd & The Boulevarde Shop 2, 141 Maroondah Hwy Sprlngvale & Dandenong Rds OLD 157-159 Elizabelh St 166 Logan Rd Footscray Frankston Geelong Melbourne City Richmond Ringwood Sprlngvale 42-44 Florence St Cairns Brisbane City Buranda Gympie & Hamilton Ads Chermslde 2nd Level Western Entrance Redbank Shopping Plaza Redbank Queen Elizabelh Dr & Bernard St Rockhampton (053)31 5433 (054 )43 0388 (03)890 0699 (03)383 4455 (03)794 9377 (03)592 2386 (03)379 7444 (03)689 2055 (03)783 9144 (052)43 8804 (03)670 9834 (03)428 1614 (03)879 5338 (03)547 0522 (07)229 9377 (07)391 6233 (070)311 515 (07)359 6255 Gold Coesl Hwy & Welch St Bowen & Rulhven SIS Kings Rd & Woolcock St Cnr PacHic Hwy & Kingston Rd SA 77 Grenfell St 668 Pori Road Main South & Flagstaff Rds Shop T25, Elizabeth Ci1y Centre Main Norlh Rd & Dariington St WA Wharf St & Albany Hwy 66Adelaide St William St & Robinson Ave Raine Square, 125 William St TAS Shop 40A, Lower Level· Cat' & Fiddle Arcade NT 20StuanHwy Southport Toowoomba Townsville Underwood (075)32 9863 (076)36 4300 (077)72 5722 (07)341 0844 Adelaide Beverley Darlington Elizabeth Enfield (08)232 1200 (08)347 1900 (08)298 8977 (08)255 6099 (06)260 8088 Cannington Fremantle Nor1h Perth Perth City (09)451 8666 (09)335 9733 (09)328 6944 (09)481 3261 Hobart (002)31 0800 Stuart Park (089)81 1977 (07)288 5599 (079)27 9644 Dear Customers, Quite often, the products we advertise are so popular they rur. out wrthin a few days, or unforseen circumstances might hold up shipments so that advertised lines are not in the stores by lhe time the advert appears. And very occasionally, an error might slip through our checks and appear in lhe advert (after all, we're human too!) Please don't blame the store manager or staff: they cannot solve a dock strike on the other side of the world, nor fix an error that's appea,ed in print. ,t you're aboutto drive across town to pick up an advertised line, why not play it safe and give them a call first... just in case! Thanks. Diet< Smith Electronics. MAJOR DICK SMITH ELECTRONICS AUTHORISED RESELLERS • NSW•Armldate: Sound Components, 244 Beardy St, 724981 •Balttna:Sellina Electronics, 102a A1"'8rSt, 86 7022• Bowral: F.R.H. Electrical, 28 Station St,611861 •BrokenHUt: Hobbies& Electronics, 31 OxideSt,884098• Ch«leltown: Newtronlcs, 131 Pacific Hwy, 43 9600•CoffsHarbour: Coffs HarbotJr Electronics, Shop 3 O>fts-HaOOur Mall, Park Ave, 52 5684• Denillquin: Deni Electronics, 220Cressy St. 813672•0ubbo: Chris's Hi-R, 1/100 TalbragarStreet. 828711 • Forster. Forster Photo Sound, Shop 36, Forster Shopping Village, Breese Pde, 54 5006 •Glen Innes: John SOmmerlad Bectronics. Shops 5& 6 Mackenzie Mall. 323661 •Grtfflth: Mlatronlcs, 166-1708annaAve. 624534•1nverel: Lyn Willing Electronics, 32LawronceSt, 221821 •Kernpaey. Drummond Home Entertainment, 38 ForlhS!Teet, 626265•Leeton: Leeton Record Centre, 121 Pine A,., 53 2081 •LlghtnlngR!dge:Lighlning Ridge Newsagency,40eMorilklSt 290579•1.Jomore, Decro, 12 Cerrlngton St, 21 4137 • Uthgow: Douroy Photographies, 183 Main Street, 51 3173 •Moree: Moree Electron!cs, 26 Balo St, 52 3458 • Parkes: Strad Music Centre, 279-281 Clarinda Street, 623366• Port Mac:quarle: Hall of Electronics, The Horton Centre, 124 Hort:in St, 83 7440 • Orange: Fyfe Electronics, 296 Summer St, 62 6491 • Sprlngwood: 'Nellington's Electrical Discounts, 132 Macquarie Rd, 51 4888 • Taree: Brad's Ek!ctronlcs, Shop 6, Civic Cinema Centre, Pulteney St, 52 6603 • Tumut Tumut Electronics, 62 Russell St. 47 1631 • Uiladulla: Pau~ Electronic& Hobby Toys, Shop 1, 10 Wescn St, 55 2454 • Wagga: Phillips Electronics, 60 For,yth St, 21 6558 • WOlllngton: Wellington Electrical Service, 110 Lee St, 45 Zl25 •Young: Keith Donges Electronics, 186 Boorowa St, 82 1279 • VIC•Colac: Colao Electronics, 215 Murrary St, 31 2847 •0unotry: Finders Pfy. Ltd., 90 Broadway St, 68 1333• Moe: The Moe Store, 56 Geo~ St, 27 2155• Morweh: Morwell m~ic:~d~~E1~~~~rt~t i~y~~ ;1~5.l'.3,=~~1J:~b~i~:~a~· ~:p= ~~~BE,~~~~t: ~oi~~~ :t~~~S~p°s~ 6e=~~tt~~2~~h~t1'fs~r!K~::~n~w1~c,;~irc:.1st~~:~°r:sal~~~~~.\~~~t.,~~=I~~ ~::2se:.i~:=:~~:.s:3~1 1 ~~~~d=:":t,~?kl;~=n~!~=~~h~~~2~ 1:1~!~ rn~=~~~ 58 Certwright Cente, Nicklin 'Way, 94 7349 •Mackay.Stevens Electronlcs, 42 Victoria St, 51 1723 • Ma,yborough: Keller-Electronics, 218 Adelaide St, 21 45.59 • Mt Isa; Outback El~onlcs, Shop 71, Bandy Hwy, 43 3475 • Nambour: Nambour Electronics, Shop 4, Lowen House, Ann St, 41 1604 • Noosa Heads: Sunshine Phone Systems, Shop 6, Sunsnine Bazaar, Sunshine Beach Rd, 47 4444 •SA• Mt Gambter. Hutchessons communications centre, 5 Elizabeth St, 25 0400 :J~~n~:c::::::·~::- ·ii=i~r~ m i ELECTRONICS ~MUd:Z :a1,129e,1 POST • PACKING CHARGES Order Value Charge Order Value Charge $5.oo - $9.99 $10.00 - $24.99 $25.00 - $49.99 $2.00 $3.50 $4.50 $50.00 - $75.oo $75.00 or more ■ $Ns_.Aso. ~:=c~~es-:::= AGC: 10 Pulteney Sl Adelaide through 0~ ===----=-------P•TY--LT-D=----------------=- VIS4 P.O..Box 321, North Ryde N.S.W. 2113 Tel: 888 3200 When the chips are down I didn't have much trouble deciding which story to relate this month. It was a case of Murphy at his best. Start at one end of the circuit and it will be at the other end; start in the middle and you'll move towards the wrong end. Either way, you can't win. The story concerns an AW AMitsubishi 63cm colour set, model 6346, one of several models based on the ML series chassis. This is a very recent model and, in fact, the particular set was still under warranty, the owner having purchased it three months earlier. He was a new customer, having recently moved into the district, and apparently had been directed to me as the nearest serviceman authorised to provide warranty service for AW A sets. The first contact was by phone, initially to confirm that I could provide the service and then to find out what was involved. I confirmed that I could provide the service, but explained that it would be his responsibility to bring the set to me. Warranty agreements do not cover •house calls, or the cost of transport to or from the service department. The · customer accepted this situation philosophically enough: "No problem - I'll borrer me mate's ute." Those points clarified I made some attempt to determine the nature of the fault; loss of picture, loss of colour, loss of sound or what? "Aw no - the picture's gone all funny; kind of collapsed, if y'know what I mean." I wasn't sure whether I did or not. The best guess was frame collapse, although the implication was that there was still some kind of a picture to be seen. Perhaps it was only a partial collapse. There was 56 SILICON CHIP obviously no point in probing further; I would just have to wait and see. And so it was that the "mate's ute" eventually turned up with the set on board, and we carried it into the workshop. I took the opportunity to connect an antenna and switch it on, just in case there were any points to clarify while the owner was still there. I suppose I can hardly blame the owner for his "all funny" description. The first 75mm at the top of the screen was blank, the next 100mm showed a reasonably linear picture, from there to within 50mm or so of the bottom was grossly expanded, and the rest of the picture compressed into that last 50mm. It was, literally, not a pretty picture. Other commitments prevented me from delving any deeper at that stage and I put the set aside for a day or so. When I did get around to it I fished out the circuit and concentrated on the vertical section (Fig.1 ). Special Notice These notes are being contributed by the author who, from 1950 until July this year, wrote 'The Serviceman" in another magazine . . We feel sure that regular readers of that series will welcome the opportunity to continue following his adventures in SILICON CHIP. LP..Si KNOWN f>\CT1JR.€: OF \V\UR.?l-1'-i, ASou,- . TO BE: HI, B\.f A FALLING Sf\rE. Wl·\ll-'ST D'ROWN\t-JG l N A FL.ASH FL.00t> O~ AC It> RAIN ON '11'\ NV\..\...A.!!.01< t>L.A.INu •.. e:. Jungle IC In fact, there wasn't a great deal to be seen. Most of the functions were performed inside a 48-pin jungle type chip (IC201, MC1310AP), including the vertical sync separator, vertical oscillator, ramp generator, and an amplifier which delivered a signal at pin 16, which was applied directly to a vertical output pair, Q451 and 452. And that seemed to be all there was to it. I concentrated on the output stage for a start. I checked the various minor components, including two diodes, D451 and 452, but found nothing suspicious. Similarly, a voltage check around the two transistors produced figures very close to those shown on the circuit. The next logical step seemed to be to get the CRO going and check appropriata waveforms. The circuit shows two vertical waveforms, one at the vertical oscillator pin of the IC (pin 20, waveform 8), and one at the vertical output pin (pin 16, waveform 7). I checked waveform 8 first, and this came up virtually identical with the photograph on the circuit. But waveform 7 was another matter. Even the photograph on the circuit suggests that there is some "mush" on the pattern and this appeared to be even more so on my CRO. But this aside, the shape was nothing like that on the circuit, although the amplitude was approximately the same. So what was happening? Was the chip at fault and delivering a faulty waveform to the output stage, or was the output stage at fault and somehow loading the chip and distorting the waveform? Since I had already checked the output stage fairly thoroughly I hesitated to blame it. On the other hand, as I have remarked before, I am less inclined these days to suspect an IC until all other possibilities have seemingly been exhausted. And there could still be something funny about one or other of those output transistors, which didn't show up on my voltage check. The transistors are each mounted on a U-shaped aluminium heatsink, the "U" being inverted so that the heatsink sils above the main board. The ends of the vertical sections are cut to provide narrow tongues which fit into slots in the board, then bent slightly to hold them in place. It was necessary to remove the heatsinks from the board in order to gain access to the transistors, but this was not particularly difficult. Unfortunately, the effort seemed to be wasted. Both transistors tested OK, as did the two diodes, which I tested a second time while the transistors were out of circuit. I also double checked the minor components (resistors and capacitors), and the height and linearity controls, until I finally convinced myself that there was nothing in that part of the circuit which I hadn't cleared. Which seemed to put suspicion squarely back on the chip. But still I hesitated, trying to think of anything I might have overlooked. I drew a blank and was rapidly reaching the conclusion that the chip would have to be replaced, if only to prove the point one way or the other. After all, I could easily spend several hours searching vainly for some external fault, which may not actually exist, and finally be forced to change the chip anyway. On the other hand, if I changed the chip now, that point would be settled once and for all. Granted, I'd be down the cost of a chip if I was wrong (but one chip up in my stock) and down by the time needed to change the chip. Now I don't pretend to like changing chips, particularly 48-pin monsters - I don't suppose anybody does - but I've developed a pretty good routine and a fair amount of skill over the years, and can usually do the job in about 15 minutes. That's no record, and I know some blokes who can do it quicker, but it's time well spent to prove a point. Sydney or the bush A more practical snag was that I didn't have such a chip in stock, so one had to be ordered, which at least gave me time to think while I was awaiting delivery. In fact, this didn't help much; I had not thought of any other possibility by the time the IC arrived so, muttering something about "Sydney or the bush", I set to with solderwick, solder sucker and a good hot iron, and pulled out the suspect chip. The whole operation went smoothly enough and I subsequently fitted the new IC, tidied everything up, and switched on hopefully. I don't suppose I need spell it out; it wouldn't have been worth writing about if it had been as easy as all that. Suffice it to say that the set behaved exactly as before. I was back to square one. So what now? Up to this pointJ had convinced myself that I had thought of everything before I changed the chip. Quite obviously I hadn't, but I was at a loss to think of some new line of attack. I went over the circuit again. I had proved, the hard way, that the chip was not at fault. I was also convinced that there were no faulty components in the output stage. So what did that leave? It was more of a growing suspicion than a sudden inspiration but I found myself thinking more and more about the scan coils and any minor associated components. Faults in scan coils are extremely rare, but I have seen the effect of a shorted turn, and it does some weird things to the picture. In any case, there was not much else left to suspect. Tracing out the circuit from the vertical output stage to the scan coils revealed the existence of several auxiliary components, apart from the scan coils, and I ..,..,.., .... JA NUA RY 1988 57 ,RHJb , Ill 15K , IW !Ha) nsv Deflection Yoke ' C9 11 33µ 160 V 12 V 1 4 02 3 < 1 V "~ Y3 2 H Fig.1 portion of the AWA 6346 circuit showing the scan coils and associated circuitry. The pincushion correction circuit is on PCB-PCC. made a mental note that these would have to be checked. But first the coils themselves. I fished out a shorted turns tester that I had not had occasion to use for a long time, unplugged the scan coils, and checked for shorted turns. Result: a clean bill of health; there was nothing wrong there. That left only a few auxiliary components, the main ones being on a small printed circuit board bolted to the side of the cabinet and connected to the scan coil circuit via flying leads and plugs and sockets. The relevant portion of the circuit is reproduced here to assist readers to follow the story. The board is designated PCB-PCC, the "PCC" standing for Pin Cushion Correction. It consists of a transformer, T571, resistors R575 and 576, and capacitor C575. Connection to the scan coils is via two plug and socket sets; PV (Plug Vertical) and PH (Plug Horizontal). The vertical scan coils are connected to the vertical output stage via pin 4 on the deflection yoke diagram and eventually find their way back to chassis from pin 3, via the pincushion network, and a pair of 8.20 resistors in parallel between "PV1" and chassis. These resistors appear to be part of a feedback network, and are not shown here by reason of their remote location. 58 SILICON CHIP I had left the set running while I visually checked out this section and related it to the circuit, which meant that the set had been running for about 15 minutes, much longer than I had run it so far, since I had previously turned it on only long enough to check a few voltages or whether the replacement chip had achieved anything. In any case, I had not been observing the circuitry associated with the scan coils. But now my attention was drawn to R569, a 2200, 1W wirewound resistor, mounted on the main board, but effectively connected between pin 3 (vertical scan coil) and the 12V rail. I don't know what function it serves, but I noticed it for the simple reason that it was running stinking hot - literally. So hot, in fact, that it had melted the solder connecting its pigtails to the board. Well, it seemed that at last I was onto something, even if exactly what was not clear. Looking at the circuit again I suspected that, for some reason, the circuit from pin 3 to chassis was incomplete, forcing the scan current to seek a path through R569 and the 12V rail. And the most likely cause of this would be failure of the two 8.20 0.25W resistors (R462 and 464) already mentioned. So these were located and check- ed - only to draw a blank; they were spot on value and completely free from any signs of stress. So much for that theory. But I still had the idea that there was a fault somewhere in this chassis return path and a check with the ohmmeter from pin 3 of the scan coil to chassis confirmed that there was a resistance of several hundred ohms; much higher than seemed logical. So began a rather laborious process of checking individual connections involving the printed board PCC and the associated plugs, sockets and leads. In detail, PV is a female plug, on a flying lead, which mates with male pins, 1 and 2, on the board. The flying leads are crimped into the plug contacts and I suspected that there could be trouble here. Checking this wasn't easy because of the difficulty of ensuring that one was making an effective connection with the contact inside the plug. But, after several attempts, I finally gave them a tentative all clear. But what about the board itself, and particularly the pins. The pins are hollow and are mounted by inserting them in a hole in the board, then expanding them with a flaring tool to make a moderately strong mechanical joint. Then, when the board goes through the solder bath, the flared end of the pin is soldered to the surrounding copper pattern. I pulled the board out and examined it closely, using a magnifying glass. As far as I could see, all four pins were soldered perfectly to the copper pattern. But the ohmmeter told a different story. Measuring from pin 1 of PCC to the surrounding copper pattern showed virtually zero resistance, but not so pin 2. Here there was a varying resistance of around several hundred ohms. Significantly, even though I knew there was a fault there, I could not pick it visually. But a few moments work with a hot iron, and a somewhat lavish application of solder and flux, removed any doubt. In fact, I treated all four pins, because I could no longer trust a visual check. TETIA CORNER Blaupunkt (Bridge Rectifier Chassis) Symptom: Fuse S1242 blows repeatedly. If the fuse is replaced often enough, the set will eventually fail completely with a clattering noise coming from the chassis. Cure: D1245 (TAG 3-400) SCA shorted or breaking down under load. An emergency repair can be effected by removing diodes D1242 and D1 244 from the bridge board. This reverts the set to its original half-wave rectifier design, in which state it seems to run quite happily. This information supplied by The Electronics Technicians' Institute of Australia (Tasmanian branch). Relief and frustration Then I switched the set on and up came a perfect picture. I viewed the end result with mixed feelings; relief that I had finally cured the fault, but also a certain amount of anger at the frustration I had experienced, and the time I had wasted, all because of one miserable dry joint. Only someone else who has been through it all will know how I felt. Still, that's what the game is all about; one has to take the rough with the smooth and, in the ultimate, measure success by the end result. On that basis this job had been a complete success, even if it had been less than satisfactory financially. And I am still puzzled as to how that joint could look so good yet be so poor. ~tb.2. ANl:> 46~ FR.ON\ AN'-f 5\G,~S Of course, I had destroyed any evidence in proving the point, and there wasn't much help for that. As I saw the joint, the solder had flowed into the hollow pin and right out to, and over, the edge of the flared end. It had also flowed quite freely over the copper pattern which ran under the flared section, and it looked as though these two runs of solder had mated into one. Quite obviously they hadn't but, short of using an electron microscope that looks around corners, I am at a loss to suggest how it might have been better checked. The only real answer, I suppose, is if in doubt, resolder it. Which I did of course, but the "doubt" was a long time a-coming. And now, for a change of pace, c..oMr>LE:'1""<=-L.'-f r~ee- Or s~~ss.. _. here is a story from one of my regular contributors, Mr J.L. of Tasmania. It is an intriguing story involving both technical problems and the ingenuity in solving them, and the frustration caused by the replacement parts problem. This is his story, for which he has nominated the following appropriate title: Sharp shooting One thing about television servicing that appeals to me is the uncertainty principle. When a dead set comes into the workshop I never know what killed it, and finding out involves a series of tests and guesses that will, hopefully, point to the faulty part. This was never more clearly shown than with a Sharp CX2020 that came in recently. Tracking down the fault took both practical and theoretical knowledge, plus experience, suitable test equipment and a pile of patience. The customer remarked that the set failed to start up when switched on at 7pm, although it had been working perfectly at 5pm. There had been no sparks or smoke, just a total refusal to show any sign of life. He tried the set on a known good power point, just in case, but it was totally dead. As is the way with so many customers, he felt sure that the picture tube was done for. He wasn't really convinced when I tried to explain that if it was the tube, he should still have sound. When I switched it on in the workshop, I heard the degaussing coils go "boing" which indicated that part of the set was working. That characteristic degaussing sound meant that the power lead, mains switch and mains fuses were all intact. I could tell this much without even taking the back off. But that's as far as I could go with the back on. Next it was inside to check the DC power supply. Specifically, there should be about 300V on the collector of the chopper transistor (Q701) and, in this set, 115V on its emitter. The 300V was there, but not the 115V. Quite obviously the chopper was not running. This set uses a self-oscillating JANUARY 1988 59 TTINO I - ® C635 10µ(16VJ I DX0048CE I V R50 3 I I ,-'II-------+--+----------+., 10 ·SIZE - ----, )Li~~ • ~:a:, • (Fl. R60I 27K R- 82K C l1,1( + C608 471,1 . 039 - (16V) (ML):; C609 SW60I R6l0 5.6K(3W) [F-"°__cJ_N.I) Fig.2: horizontal oscillator (IC501) and line output stage of the Sharp CX2020. Note the protective diode incorporated in Q602. chopper which should self-start, then come into sync with the line frequency as the line output stage gets going. The pulse from the line stage (Fig.2) is not essential to run the chopper but, as well as its synchronising function, it is used by the protection network to indicate the presence of faults on the line output. No line pulse may mean a fault and so the chopper is shut down. So where should I start to look for a fault in a roundabout network of this kind. My first line of attack is to determine if the chopper is trying to selfstart. I do this by looking at the emitter of the chopper transistor with the 'scope. If I'm lucky I will see a brief flick of the trace which indicates that the transistor is being turned on, if only for one or two cycles. The output voltage appearing on the emitter is immediately reflected to the protection circuit, and if all is not right, the base drive to the chopper is very promptly terminated. In this case, the flicker of the scope trace, when it did appear, was so brief as to be almost unnoticeable. Still, it was enough to say that the chopper was trying, and at this point I had to make an 60 SILICON CHIP educated guess as to where the troubl-e lay. It could be either a fault in the supply itself, or a fault in the set proper. It's a "heads or tails" situation, but experience helps a little. Line output stage faults are more common than power supply faults. In fact, faulty line output transistors are so often the cause of stoppages that most servicemen check that component first of all. It's usually simple to reach the collector and measure its resistance to chassis. If the meter shows zero ohms, then the transistor is like the Christmas turkey. In this case there was no such indication and the transistor (Q602) checked out perfectly. Well, sort of perfectly, because the base-emitter junction is difficult to check in circuit, normally showing as a short through the line drive transformer. Still, if collectoremitter shows no sign of leakage then it's a safe bet that the base emitter junction is OK. Or so one might think. My next move was to connect the CRO to the base of the line output transistor to see if there was any drive reaching this point. Again, this was inconclusive because the trace merely flickered, without any evidence of a drive waveform. I transferred the probe to the collector of the transistor, hoping to see a similar flicker there. I already knew that the 115V rail appeared briefly, so if the line output transistor was being driven at all, there should be some signs on the collector side. But there wasn't a sausage. Unusual failure Up to this point I hadn't switched on the soldering iron, but the time had come and in a couple of minutes I had the 2SD869 line output transistor lying naked on the bench. And now I could really detect the cause of the trouble. The base emitter junction was as short a short as any short I have ever seen. It is an unusual failure for a power transistor because the basecollector junction seemed undamaged, and there was no trace of leakage between collector and emitter. So now I had the problem of replacing a 2SD869. This transistor is one of those odd animals with a built in protection diode, used in a number of recent vintage Japanese sets. Replacing these can be quite a VOOD FOR Cl-I/PS ... WOOD FOR Cl-I/PS ... WOOD FOR Cl-I/PS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS:.. WOOD FOR C SCOOP PURCHASE ~~;~~ !~: (s ilicon Chips of LM7912CT LM7915CT LM79L05ACZ LM79L12Acz s1.oo $1.40 SO.BO so.90 course!) This month we're listing a few of our ~~:9;~~c:EFE~;~Es LM1 13H s19_10 LM313H s11.oo Doni Forget - it's still WOOD Geoff has managed to get hold of a limited CHIPS quantity of genuine PA PST fans. They're the 75mm type for 220V operation. While they last you can have one for just$25.95 IC SPECIALS 27C64 200nS 8kx 8 CMOS EPROM 12.5.VPP. These are stock items in the ~~~~~~ linear range. !;~~ LM3290Z s1.1s prime quality, not factory seconds or floor sweepings! Whatever your requirement give Geoff a call And they're only $5.99 each CD4503/80C97 Hex tor CMOS VOLTAGE REGULATORS AVAILABLE AT LAST PORTASOL PROFESSIONAL (it's the complete kit!) It's a gas knife .. . it's a soldering iron ... it's hot blow. And a blow torch ... it's a hot it comes in a neat carry kit complete with a bit wiper. No cords or batteries yet it gives the equivalent of a 1 O to 60W iron. You can get up to 90 minutes average continuous use from a single fill. And you refill it in seconds using a standard butane gas lighter refill. · Tip temperatures as high as 400°C can be set. The kit includes one soldering tip, a hot kntte, blow torch and hot blow. The cap contains a flint lighter. The complete kit comes in a handy case (with stand for the iron) which just about fits Porta-Sol Professional is $81.00. PORTASOL STANDARD SOLDERING IRON in your pocket. Geoff has sold hundreds of 'em to servicemen and technicians. Complete and ready to use like the Professional but you only get the iron and bit $39.95. P.ORTASOL TIPS Expand the capability of your Portasol Iron with spare tips available for standard iron in 1 mm, 2.4mm, 3.2mm, 4.8mm and hot knife tip. Professional tips come in same sizes plus hot blow and blow torch. Tips are JlQl interchangeable between irons, so specify Standard or Professional when ordering. Tips are all $12.95 each. IBM and Compatible PC Users! Save a power point - Get a rewireable IEC plug from Geoff. It's so easy -on the back of your PC you'll fi_n d an IEC outlet which is controlled by the power switch on the computer. So cbop the mains plug off your monitor and connect the L2298 and hey presto you 'll never forget to switch your monitor off again! Qu_ality Belling Lee (Geoff has a full range of IEC connectors) Ask for !e t Q: 0 II.. Cl 0 i LM304H $6.05 LM305AH $5.85 LM3051-1 $1.75 LM309H $5.45 LM309K-STEEL $5.90 LM317H $7.30 LM317HVH $10.85 LM317HVK-STEEL $10.85 LM317K-STEEL $6.60 LM3 17KC $5.20 LM317MP $1.85 LM317T $1.05 LM320H-5.0 $9.65 LM320K-12 $7.70 LM320K-15 $7.70 LM320K-5.0 $7.70 LM320MP-12 $3.25 LM320MP-15 $3.25 LM320MP-5.0 $3.25 LM320T-12 $3.70 LM323K-STEEL $5.50 LM325N $10.75 LM326H $11.75 LM326N $10.75 LM330T-5.0 $1.75 LM333K-STEEL $14.35 LM333T $6. 70 LM337H $7.95 LM337HVH $13.90 LM337HVK-STEEL $17.45 LM337K -STEEL $9.15 LM337LZ $1.40 LM337T $2.55 LM338K-STEEL $13.25 LM340K -15 $5.90 LM340KC-12 $2.30 LM340KC-15 $2.50 LM340KC-5.0 $2.25 LM340T-12 SO.BO LM340T-15 S0.75 LM340T-5.0 SO.BO LM341P-12 $1.35 LM341P-15 $1.35 $1 .35 LM341P-5.0 LM342P-12 $1.20 LM342P -15 $1.20 LM342P-5.0 $1.20 LM350K-STEEL $9.65 LM376N S0.90 LM396K-STEEL $31.90 LM723CN SO.BO LM2925T $4.60 $1.75 LM29:l>T-8.0 LM2931CT $3.05 LM2935T $4.80 LM2940CT-5.0 $2.80 LM3524N $3.65 LM76601N $3.10 LM78L12ACH $2.05 LM7BL12ACZ S0.60 LM78L15ACZ so.so LM7905CK $4.15 LM7912CK $2.55 ~~~~~- 2 5 LM336Z-5.o LM368H-5.o LM385Z-1.2 LM385Z-2.5 LM399H LM3999Z LM349N :~: s1 .90 s 11 .90 $2.40 $2.40 $6.15 $4.75 $16.85 $1.85 $1.20 $2.65 $2.80 S0.60 $7.95 $7.95 $4.80 $1 .25 $1.05 $1.55 $2.40 $1 .20 AUDIO AMPLIFIERS LM380N LM380N-B LM381AN LM38 1N LM382N LM383A T LM384N LM386N-1 LM387N LM388N-1 LM389N LM390N LM1875T $1.90 $1.90 $6.40 $3.95 $3.05 $4.'30 $3.50 $1.65 $2.80 $2.40 $2.40 $1.95 $8.00 INSTRUMElfTA nON AMPLIFIERS LM3630 LM363H-10 LM363H-500 LM725CH $38.00 $24.00 $24.00 $9.20 OPERAnONAL AMPLIFIERS LM10CLH LM10CLN LM10CN LM1 1CH LM11CLH LM11CLN LM11CN LM301AH LM301AN LM307H LM308AH LM308AN LM308H LM308N LM310H LM310N LM312H LM316H LM318N LM321AH LM321H LM324AN LM324N LM344H LM346N LM348N $8.30 $5.95 $9.30 $9.75 $6.70 $3.30 $3.50 $1.30 S0.70 $1.95 $6.95 $5.10 $2.45 $1.00 $4.20 $4.25 $6.00 $11.20 $2.20 $28.05 $10.15 $4.70 SO.BO $11.20 $4.75 $1.90 $2.20 SO.SO $3.10 $1.25 $2.45 $1.05 $0.80 $0.50 $0.30 $1.60 $1.10 $1.90 $2.80 $0.55 $1.40 $0.90 $2.30 $2.25 $2.25 $2.25 TRANSISTOR ARRAYS VOLTAGE COMPARATORS LM306H LM311H LM311N LM319N LM339AN LM339N LM360N LM360N- 14 LM361 N LM392N LM393N LM710CH LM1414N LM3302N LM358N LM359N LM709CN LM733CH LM733CN LM74 1CH LM 741CN LM741CN-SGS LM747CH LM747CN LM833N LM1458H LM1458N LM:l>BON LM3900N LM4250CN LM13080N LM13600N LM13700N LM394CH LM394CN LM394H LM395T LM3046N LM:ll86N LM3146N $5.40 $5.40 $7.40 $3.85 $1 .50 $1.15 $2.15 TEMPERATURE SENSORS LM3351-1 LM335Z LM35CAH LM35CH LM 35DZ LM3911H-46 LM3911N $3.15 $2.40 $12.95 $13.95 $2.60 $5.05 $2.65 SPEOAL FUNCn0N BLOCKS LM331AN LM331H LM331N LMC669CCN LM1812N LM18:l>N LM1889M LM1893N LM2907N LM2907N-8 LM291 7N LM2917N -8 LM 3909N LM3915N LM3916N $9.85 $13.20 $7.60 $11 .05 $6.20 $4 .40 $5.60 $19.85 $2.35 $4.25 $4.40 $4.20 $ 1.85 $4 .25 $4 .65 COMMI.INICA nONS ORCUITS LM565CH LM567CN LMC567CN LM 1496H LM1496N LM 1886N LM:ll89N LM3189N LM3820N $5.25 $1 .40 $2.35 $5.05 $2.05 $8.05 $3.95 $5.15 $3.20 nMERS LM322N LM555CN LMCSSSCN LM556CN LM3905N $3.05 S0.50 $1.00 $1 .10 $2.35 EXAR PRODUCTS XR-2201 CP XR-2202CP XR-2200CP XR-2204CP XR-2206CP XR-2209CP XR -2211CP XR-2240CP XR-2243CP XR-5533AP XR -5534ACP XR-558CP XR -8038ACP $1 .65 $1 .65 $1.65 $1 .65 $9.40 $5.20 $7.50 $3.45 $4.20 $4.15 $3.90 $3.30 $7.30 L2298 at only $4.75 8.30 to 5 Monday to Friday, 8.30 to 12 Sat. Mail Orders add $5.00 to cover postal charges. GEOFF WOOD ELECTRONICS P/L All prices INCLUDE sales tax. (02) 427 16 76 Tax exemption certificates accepted if line value exceeds $10.00. p~~==~[ ;:::: e:::====; 229 BURNS BAY RD. (CORNER BEATRICE ST.) J~" ; BANKCARD, MASTERCARD, VISA , CHEQUES LANE COVE WEST N.SW. IN C IN NSW TWX71996 P.O. BOX 671 LANE COVE N.SW. 2066 8RI~ OR CASH CHEERFULLY ACCEPTED specialising in electronic components for the professional and hobbyist. pain as each manufacturer seems to have his own design and none seem to be compatible. Here in Tasmania we have a real spare parts problem as all manufacturers have withdrawn their spare parts services to centres in Melbourne or Sydney. So our Tasmanian customers are now faced with 10 to 20 day delays while we order the part, then wait for the invoice, then send the cheque, then finally get the part. (I know - some firms do have faster services, but most do not and our gripe is with the latter ones). The only alternative for independent servicemen like myself is to cultivate our friendships with the manufacturers' service agents. If they have what I require, and my face is welcome in their workshops, then I might be able to get the parts needed to put my customers' sets back into working order in a reasonable time. So my immediate need for a 2SD869 led me to the local Sharp agent. When I asked his receptionist about the availability of 2SD869's, a voice from deep within the workshop declaimed "Yer don't need wunna them! A 2SD350 is OK in that set." The voice was soon joined to the jovial face of their technician who volunteered the information that the 2SD869 was only a 1000V transistor, and the diode was included to catch any spikes over that level. On the other hand, a 2SD350 was a 1500V device and to his knowledge, none had ever failed in these sets. He wouldn't tell me the price of the 2SD869, but as the 2SD350 is about as cheap as any power transistor can be, I decided then and there to use one in this repair. So I soon had a 2SD350 in the chassis, in place of the original transistor. Pressing the power switch produced not the expected burst of sound, but quite the opposite - absolutely nothing. This was a real disappointment because I was convinced that the transistor had been the only faulty part in the set. So I had to start troubleshooting all over again. This time the CRO on the chopper base showed a quarter second burst of drive waveform. The 115V rail also showed a change 62 SILICON CHIP - the 'scope trace at the emitter leapt up the screen, then quickly dropped back to the zero line. This was a much more positive response than the earlier flicker, but it was no closer to restoring full operation. Continuing my investigations, I found that the line output transistor now showed more enthusiasm at switch-on, but couldn't be resolved into actual drive. It just flickered into some kind of action, them died. So what now? It could be (a) a faulty line oscillator chip (IC501), (b) a dud line driver transistor (Q601), (c) a bad line driver transformer (T601), etc, etc. With a chain of doubts like this, it is perhaps best to start at the beginning. My 'scope was not able to resolve any trace of line drive from the oscillator chip at switch on, but then a quarter of a second or less is not very long to resolve anything. What I had to do was power up the chip and see if it produced the right waveform. I used a 9V battery fitted with leads and alligator clips to apply Vee to the chip. The set uses a 12V rail at this point, but 9V is enough to see if things will work at all. In this case, 9V produced a solid train of square waves and proved the chip to be 100 % . While the battery was connected I was able to trace the signal up to the base of the line driver transistor. They went no further because the collector is powered from the 115V rail and this wasn't working yet. So I had to devise a way to get voltage onto this rail. One of the most useful pieces of equipment in my workshop is a Variac, a continuously variable autotransformer. I have also built up a simple DC power supply using an old TV transformer, a couple of diodes and a 350V electrolytic capacitor. When fed from the Variac, this supply can deliver from about 20V up to something over 200V. (It's rather crude, but I haven't had either the time or the money to build a better high voltage power supply). For this Sharp job, I connected the DC supply to the 115V rail and slowly cranked up the Variac. The 9V battery was still connected, and the IC was delivering drive pulses to the line driver transistor. The voltmeter monitoring the 115V rail at first indicated a rising voltage, but it stabilised at about 5V and went no higher. Even 100V AC into the DC supply could produce no more than 5V out, and the Variac was humming ominously. The story is nearly finished! I took no time at all to find that the 115V rail was shorted almost down to chassis. Examination of the schematic showed two components as the likely culprits. One was C713, a l00µF 160V electrolytic capacitor, and the other was ZD702, a zener diode , type EX0074CE, connected between the rail and chassis. Roast dinner The more I thought about that zener the more dubious it looked. Then in the parts list I found that it was a 130V type, twice as high a voltage as any zener I've ever seen. I'd bet a dud fuse to a roast dinner that it was the villain. And so it was. Not quite a dead short, about 10 ohms, but near enough to stop the set dead in its tracks. The zener is only in the set as a protection device and the set works quite happily without it. But it is there for safety reasons and had to be replaced. So now came the second spare parts trauma with this set - where do you get a 130V zener if not from the set's maker? Fortunately, the zener value is not critical and I was able to replace the faulty item with two 62V zeners in series. The set is now, if anything, a little safer than it was. Getting back to the philosophy expressed at the beginning of this story, I find television servicing an occupation that is intellectually stimulating and full of interest. It is never boring and the smile on the face 'of the customer when he learns that it wasn't the picture tube after all is all the job satisfaction that I could ask for. Alternative transistors Thank you J.L. for a most interesting story and an insight into the problems faced by our colleagues in more remote areas. I have no doubt that there may be those who would question the wisdom of substituting the unprotected 2SD350 in place of the original 2SD869, in spite of the higher rating of the former . In fact, when I showed this story to a colleague he immediately rattled of a list of protected output transistors, which he felt could at least be considered. These included the 2SD870, 871, 899, 900, 951, 952, 953 and 954. However, neither he nor I would be prepared to stick our necks out and claim that all of these would be compatible with the Sharp circuit. (Incidentally, most transistors of this general type, with built in protection diodes, also have an in-built resistor between base and emitter. This is not always shown on the circuit symbol and could be mistaken for leakage. Typical value is about 400. More to the point, of course, is the essentially practical problem faced by J.L. and others who live in places remote from the manufacturers ' distributors. And even then the expression "on back order" crops up all too frequently. Obviously, all is not cider and skittles in the Apple Isle, at least as far as spare parts are concerned. This being so, people like J.L. have to do the best they can with what is available. And at least the substitution was recommended by the manufacturer's agent who, in turn, appeared to be basing the recommendation on practical experience. And I'm sure that no one would have been happier than J.L. had he been able to fit the correct replacement but, if it's not available and a long wait is involved what should one do? What would you do? More to the point, perhaps, what would I do? See you next month? it l F ,-r 'S NOT A\JA\l.A~l.£, W~Prt' 8~0ULt> ONE 'OO? W~AT WOUl.t> '<OU 'Do? VJHAT \NOUl.t> ~EV t>O? '<~, W\o\Ai ~HOUt..t> WE t>o? 8. ~110:.~ >WAAT MlGHT' SHE. oo? ALll\OVGH, WMAT WOUL.t) IT 'Do? Su, Tl-\EN W~AT WOUl...t> Tu.JO OR MOR6 l)O~~E 10 ME POINT, W'°'~••. ~ ~-=? )) JANUARY 1988 63 , Listen to hidden FM transmissions Subcarrier adaptor for FM tuners This simple adaptor circuit fits in your FM tuner and lets you tap into hidden FM transmissions .. By JOHN CLARKE Just recently the Department of Transport & Communications announced that it is ready to authorise subcarrier transmissions on FM broadcasts. Testing of these transmissions is going on right now and you can listen to them by building this simple adaptor circuit. In America, subcarrier transmissions on FM broadcasts have been used for years. The Americans refer to these services as Subsidiary Communications Authorisation or SCA. It is based on a 67kHz subcarrier which is placed on the main FM carrier. In Australia the same system is being used but it will be known as & LEO SIMPSON Supplementary Monophonic Transmission (SMT) which will be generally recognised as an Ancillary Communications Service (ACS). Not a very inspiring name, is it? Australian tests have been on single sub-carrier transmissions at 67kHz but developments in the USA provide for multiple sub-carriers, some carrying digital data and others carrying audio. Now 67kHz sub-carrier transmissions are about to be authorised as regular services in Australia. To coincide with this, we have designed a suitable adaptor which can be hooked into most FM tuners with a This the ACS adaptor board, shown about 30% larger than actual size. All the parts are readily available. 64 SILICON CHIP mm1mum of fuss. Low in cost, it uses just a few readily available integrated circuits. Before we describe the circuit of the adaptor, let's briefly talk about FM subcarrier transmissions. They will have no effect on standard FM mono and stereo radios. Also, they will be fully compatible with all existing FM radios, whether stereo or mono. In fact, unbeknown to the great mass of FM listeners, test transmissions have been going on for some time. But while all FM radios are presently unaffected they are able to pick up the sub-carrier transmissions and, with the addition of an adaptor such as the one we describe here, able to detect the audio signals which will generally be music. While we were developing this adaptor circuit, the ABC in Sydney was running ACS test transmissions on 2ABC-FM. The audio modulation was the program simultaneously being broadcast by AM station 2BL. In the near future, ACS broadcasts are likely to be background music suitable for offices and factories . SILICON CHIP'S ACS Adaptor is built on a compact printed circuit board (PCB) accommodating three low cost op amps - a phase lock loop IC, a 3-terminal regulator and a handful of resistors and capacitors. ,-----.. . -------~---~-----------.----A TWIN -TEE Fil TER 220pF 10k 1.1k 11k <>-11-.w.,,,.......>;,N,,~--w,;.,,---+--4-__.,.......- 4 _ - , DEMODULATED FM INPUT VR1 10k 10 >"......W,,,,......aj21N 5600 1.1k 3 ~W,,-..::jlN IC2 LM565 DEMO OUT VCO +6V MP 5 4.7 16VW 10k 't'--~-ll-"""""'~,-.'IN,f,r+-"M"'""'9--=j P, RE -+ 1 .001 +-__.....____,.__.____.,__-+_ __;r--.......,__--- G N D 0 - - - - - - - . _ _ . , _ __ _ _ _ _ __ .__--4_ _ .,. L------------------ll-------o PLL DEMODULATOR 67kHz BAND-PASS FILTER 18d8/0CTAVE LOW PASS FILTER GAIN= -1 IN r + 1 5 V-30V 1 + 35VWI .., 0. 22 AUDIO > " - - ~ ~ OUTPUT ---------------vGNO ACS ADAPTOR FOR FM TUNERS 61-1287 12dB/OCTAVE 6kHz LOW PASS FILTER GAIN = -10 Fig.2: the circuit for the ACS adaptor is essentially just a phase lock loop with input and output filtering stages. Note that TL081 op amps may be substituted for the TL071s. 67kHz INPUT FROM FM DEMODULATOR 67kHz BAND PASS FILTER PLL OEMOOULATOR 18d8/0CTAVE 6kHz LOW PASS FILTER GAIN = -1 12dB/OCTA VE 6kHz LOW PASS Fil TER GAIN = -10 AUDIO OUTPUT Fig. 1 Fig.1: this block diagram shows the four circuit functions of the ACS Adaptor. The corresponding functions are also marked on the circuit diagram (Fig.2). How it works Fig.1 shows a block diagram of our circuit. The 67kHz signal present at the output of the FM detector (in the radio to be modified) is first fed to a 67kHz bandpass filter and then to a phase-lock loop (PLL) which recovers the audio modulation on the 67kHz sub-carrier. The audio output of the PLL is then passed through a low pass filter which attenuates frequencies above 6kHz at the rate of 18dB/octave. Another 12dB/octave lowpass filter stage completes the conditioning of the signal before it is passed to an external audio amplifier. Fig.2 shows the complete circuit. Op amp !Cl and associated components provide the 6 7kHz bandpass filter. A twin-T network comprising four 1. lkO resistors and associated 0.0022µF capacitors is connected in the feedback network of the op amp. This gives some gain at 67kHz and heavy attenuation for frequencies above and below this frequency. An additional passive filter at the input to the twin-T network (220pF and 10k0) provides some additional rolloff for frequencies below 67kHz. In practice, the bandpass action covers a frequency range of about 10kHz above and below the 6 7kHz centre frequency. VRl sets the gain of the bandpass filter stage. IC2 is a Signetics NE565 phaselock loop which demodulates the 67kHz frequency modulated (FM) signal from !Cl. The NE565 PLL consists of a voltage controlled oscillator (VCO) set to 67kHz and a comparator which compares the incoming frequency modulated 67kHz signal at pin 2 with the VCO signal fed into pin 5. The output of the comparator represents the phase difference between the incoming signal and the VCO signal and is therefore the audio modulation of the subcarrier. Treble de-emphasis (150µs) is provided by a 0.033µF capacitor (pin 7). The free-running VCO frequency is determined by the 0.00lµF capacitor at pin 9 and the resistance between the positive rail and pin 8 (lkO in series with VRZ). VRZ adjusts the oscillator frequency (also known as the "centre frequency") so that the incoming JANUARY 1988 65 signal is within the lock range of the PLL. To minimise noise in the demodulated output, it is important to reduce the lock range of the PLL to a minimum. This is achieved by shorting pins 6 and 7 together. To a lesser extent, the lock range and therefore the noise output becomes smaller for lower input signals so we keep the input signal reasonably low without prejudicing the PLL's operation. Following IC2 is the 18dB/octave filter employing IC3 which has a gain of one for wanted signal frequencies. This filter is followed by the final filter stage IC4 which has a gain of ten. The adaptor is ideally powered from the tuner or receiver it is built into so we had to make its input voltage requirements non-critical. The solution is to use a 12V 3-terminal regulator which enables the circuit to be powered from any unregulated DC rail from + 15 to + 30 volts. The three op amp ICs and the PLL ICIOI LA\231 16 FM IF' AMP, AF AMP FM OET I TPI FM OISCRI NULL CHECK Rll3 Rll2 18k 66 SILICON CHIP C!I ! 33p Cll3 0.01 are all biased to half the supply voltage by a voltage divider consisting of two 10k0 resistors which is decoupled by a 4.7µ,F capacitor. The centre-point of this voltage divider is connected to pin 3 of each op amp and the PLL. PCB assembly This photo shows the ACS adaptor installed in an older AM/FM stereo receiver, the Harman Kardon hk570i. We used two brackets to suspend the Adaptor above the tuner board of the receiver. 56k The PCB for this project measures just 5 7 x 89mm and is easily assembled. No special points need to be watched when installing the parts on the PCB except that component polarities must be correct. Note also that ICl has a different orientation to IC2, 3 and 4. When assembly and soldering are finished, check your work carefully and then connect a DC supply of between 15 and 30 volts. Now check the voltage at the output of the 3-terminal regulator, at pin 7 of the TL071 op amps, and at pin 10 of the PLL. In each case the reading should be close to 12V. The voltage at pin 3 of each IC should be close PARTS LIST IC201 LA3401 MPX 1 PCB, code SC061-1287, 57 x 89mm 3 TL071, LF351 FETinputop amps 1 NE565 phase lock loop 1 7812 3-terminal 12V regulator Capacitors R211 56k R213 47k + C209 22 16V R221 KJOk 1161 Fig.3: this is a portion of a typical FM/AM tuner (Sony ST-JX220A) showing where the ACS adaptor is tapped in, across C111, between the FM detector and the multiplex decoder. 1 1 1 1 2 1 1 1 1 4 3 1 1 4. 7 µF 1 6VW PC electrolytic 2.2µF 16VW PC electrolytic 1µF 35VW PC electrolytic 1 µF 1 6VW PC electrolytic 0.22µF metallised polyester .033µF metallised polyester .022µF metallised polyester .0068µF metallised polyester .0056µF metallised polyester .0022µF metallised polyester .001 µF metallised polyester 560pF polystyrene 220pF ceramic Resistors (0.25W, 5%) GND 1 X 20kf! 2%, 1 X 18kf!, 6 X 10kf!, 2 x 1.8kf!, 4 x 1.1kf! 2%, 1 x 1kf!, 2 X 56011, 1 .x 10kf! miniature vertical trimpot, 1 x 5kf! miniature vertical trimpot + 15V-30V GND INPUT Miscellaneous Hookup wire, audio leads, solder etc. Fig.4: take care when assembling the board. Note that IC1 is oriented differently from IC3 and IC4. to 6V and so should the voltage at pin 6 of each TL071. If everything is okey dokey, you are ready to install the adaptor in your FM tuner or stereo receiver. Finding the signal This is the tricky part. Ideally, you need access to the circuit diagram of your tuner or receiver. You need to identify a positive DC supply rail of between + 15 and + 30 volts. Then you need to find the output of the FM demodulator. In a stereo tuner this comes before the multiplex decoder and treble de-emphasis networks. In a mono tuner, you must identify the demodulator output before deemphasis. After de-emphasis, the 67kHz signal will be non-existent. We have shown part of a typical FM tuner circuit (Sony ST-JX220A) as an example of where the 67kHz signal must be picked off. As with most medium priced tuners, it uses two ICs to do most of its FM processing. These are the IF amp and detector IC and the following multiplex (MPX) decoder IC. The most convenient point to pick off the 67kHz signal is at the input to the MPX decoder. Setting up Having found the signal and made the necessary connections from the adaptor to your tuner, the continued on page 95 Full size PC artwork for the ACS Adaptor. Design by John Clarke. Luvverly, innit? JANUARY 1988 61 By LEO SIMPSON Most people will be familiar with Telecom's new cellular phone service which is becoming very popular with business people who spend much of their day in their cars and trucks. Now OTC's automatic Seaphone service is doing for boats what the cellullar phone service has done for cars but at much lower cost. OTC's VHF Seaphone service has been operating since 1976 and has been gradually expanding over the years to the point where even relatively minor coastal population centres now have it. Early this year though, OTC decided to substantially upgrade the service so that people on the waterways and as far away as 68 SILICON CHIP 100km out to sea could have direct phone dialling, ship-to-shore. Local electronics company Heyden-Spike Ltd won the tender to develop the system and has now produced a computerised system which will radically alter communications on the water. The problem of automation OTC (standing for Australia's Overseas Telecommunications Commission] could foresee a large obstacle in introducing an automated Seaphone service: cost to the boat-owners. OTC recognised that if the new Seaphone service was to be really popular the cost of upgrading to it for each boat-owner would have to be low. That meant that all existing VHF marine radios would have to be usable and the cost of any fancy dialling facility would also have to be lower than the cost of a new radio. This meant that the new equipment on the boat would have to be kept relatively simple while all the "intelligence" would have to be installed at OTC radio bases on shore. And that is what has happened. Heyden-Spike Ltd has developed a microphone which, in addition, to the usual press-to-talk switch, has 12 pushbuttons for phone dialling. The microphone can be fitted to any existing VHF marine radio although it cannot be simply plugged in. The radio must first be modified to sup- Thursday Island OTC VHF COVERAGE AREAS VII Chambers Bay Point Quobba Ch Ch Ch Ch Long Point Yanchep Ch Ch Ch Ch 16 67 23 26 Perth ■ VIP Esperance * ~<-J VIE • l Ch 16 Ch 67 Ch 16 Ch 67 Ch 16 Ch 16 67 23 26 Ch 16 ~~ ~~ Ch 26 Ch 02 )7 Existing Seaphone/Solas Stations Ho b art * Ch )G ~ Ch2l New Solas Stations C~:e~ouga,nville Sou * Daytime hours only p Ch 16 Ch 67 This map shows the regions on Australia's coastline covered by OTC's Seaphone service. The relevant VHF channels are 23, 26 and 27, corresponding to 157.1 5, 157.3 and 157.35MHz on transmit and 161.75, 161.9 and 161.95MHz on receive. Soon, virtually all of the eastern seaboard will be accessible by Sea phone. ply 12 volts to the microphone circuitry. Inside the microphone housing are two printed circuit boards, one for the keyboard and the other for the 44-pin dedicated Motorola microprocessor which has its own inbuilt memory (RAM and EPROM). The processor provides the DTMF (dual tone multi frequency) tones for dialling and the code which identifies every Seaphone licence holder. Each Seaphone licence holder will be allocated a subscriber number but, for security, the code stored in the microphone electronics will be known only to the OTC computers. Note that all the existing OTC Seaphone services will be available to marine radio users but the new automatic service will only be usable with those radios which have been modified with the new microphone. Features of the service The automatic Seaphone service will be used as follows. The user switches the VHF marine radio to a free channel (eg Ch 02, 23, 26 or 27) and listens to ensure that no calls are in progress. The phone number can then be dialled, preceded by the STD number for Australian calls or by the country code for international calls. The user then presses the "*" button to transmit the stored user 's auto-Seaphone identifier to OTC's computerised radio base station. The user 's code number is then validated by the computer which checks to see that the code is valid and that bills have been paid. A brief voice announcement will then state that "your call is being connected" . Normal ring tone will be heard and when the called party answers, call charges are recorded by the computer. While the call is in progress, the user operates the press-to-talk button in the normal way. When the call is finished, the customer presses the " #" button to reset the system. If a call can't be connected, a voice announcement tells the user JANUARY 1988 69 automated voice announcement will respond to the call and if there are messages, the system will automatically connect and bill the Seaphone call to the shore telephone subscriber who booked the call earlier. That's a nifty arrangement which must have taken a lot of thought to develop. Dial 999 for emergency Mr Kerry Stratton demonstrates the new push-button microphone which is the upgrade for VHF marine radios using OTC's direct-dial Seaphone service. Heyden-Spike Ltd (Brookvale, NSW) developed the new service and the microphone. that message and if the code is not valid or recent accounts have not been paid, the user is connected to a (human) operator at the radio base to sort out the problem. Naturally, calls can be made from shore to ship but they have to be made via the OTC base radio. This means that a telephone user calls base radio and asks to contact a person on the water. Whether or not the call makes immediate contact depends on whether the marine radio is turned on and tuned to the calling channel, and is within range. Mailbag continued from page 3 there are two faults, a broken earth and a defective neutral. The problem is that there is no indication of either of these faults until both of them occur. I know a plumber who carries a set of automotive jumper leads and he uses them to bridge the gap when breaking a run of pipe. With MEN, any green-wire fault currents should return to neutral if the water pipe is broken, with no significant voltage being developed above earth. It wouldn't be a problem and hence plumbers would not be aware of it unless there was a faulty neutral, so perhaps faulty neutrals are not un70 On the existing Seaphone service this situation is taken care of by the message system. Callers leave messages with the base radio and when the boat-owner calls in, the base radio operator can place calls. As can be imagined, this process can be quite time consuming, both for the radio operator and boat owner. In the new automatic Seaphone service, the boat owner merely presses the "*" button on the microphone at any time to interrogate the OTC system for "any Seaphone calls on hand". An SJLICON CHIP common in the system. Maybe plumbers detect them more often than the County Council people. A. Lackey Collaroy Plateau, NSW Extra earth lead Thanks very much for your article on electrical safety [November 1987). All my life I have been concerned about electrical safety, not so much for myself but for others, particularly those nearest and dearest to me. You should write some more on the subject. I too am super-cautious. Thirty years ago I fitted an additional earth In a distress situation, it is normal practice to use Channel 16 with voice contact to the base radio or a nearby vessel. With the automated Seaphone service though there is a quicker way to draw attention to an emergency situation. By dialling 999 on any OTC Seaphone channel, an immediate alarm will be activated and the computerised system will automatically display the vessel's name, call sign, type and the owner's name and address on the screen at radio base. The emergency 999 function will override any Seaphone call in progress on the selected channel. Cost of the new service The new service is not expensive, particularly as far as the initial setup costs are concerned. The cost of the new microphone plus fitting to a marine radio is $249. Phone charges are $1.30 per minute. At the time of writing OTC was considering the introduction of a 6-second normal tariff charge. On the face of it, this new automatic Seaphone service from OTC must be a winner. It is convenient, easy to use, and reasonably priced. ~ from our washing machine to the cold water pipe. You have my support and best wishes. N. Walker Como, NSW An excellent magazine Yours is an excellent magazine. I had almost given up buying electronics magazines but I will take a subscription to yours. I hope the standard of your first issue is reflected in the future. Being a mechanic by trade and a hobbyist only in electronics, I find your articles well written and understandable. A. Glover Cootamundra, NSW Build this shortwave e a Try this antenna switching arrangement and improve your shortwave reception. By ED NOLL If you've ever had difficulty in capturing those frequencies on the fringe of the shortwave spectrum, you probably know what a blessing it would be to have more than one antenna at your disposal. Now you can - well not really, but the Flexo SWL Aerial can make it seem as if you do. The Flexo SWL Aerial is an antenna/antennaswitching system that improves reception by adding flexibility to a single antenna installation, making it seem as if you have more than one antenna. Flexo's extended performance better accommodates the extraordinary frequency span occupied by the many shortwave broadcast bands. In effect, you have more than one choice in dealing with the variables of antenna length, line length, angle-of-signal arrival, and propagation conditions. With the Flexo, sensitivity is made more uniform over the entire shortwave spectrum. It provides more than one choice in finding an optimum signal-to-noise (S/N) or signal-to-interference ratio when attempting to pull in a specific station. If you listen only to strong signals, the Flexo won't do much for your receiver's performance because of the high-sensitivity, high -- --8) PLUG 1 TO - - - LY RECEIVER (a) Slb Flg. 1 selectivity, and automatic-gain characteristics of the latest receivers. However, if difficult receiving conditions and weak-signal identification are your bag, give it a try. When a signal is weak, despite the high sensitivity of the receiver, even a couple of dB of extra input signal may help you obtain an ID. Even the strong signals are subject to brief fades, so a more solid lock is attractive to the music-loving enthusiast. Since the needs of shortwave listeners tend to vary, we'll describe both a simple two-wire Flexo and a really different three-wire version. The two-wire Flexo A complete Flexo antenna and switching arrangement is given in Fig, 1. Basically, as shown in Fig. la, the antenna is cut as a dipole on the 60-metre band. A coaxial transmission line feeds the signal to the Flexo switch and another short piece of coax (not shown) then feeds the switch output to the receiver. Note that one antenna wire is angled by 45 degrees in the horizontal plane from the more usual straight line position. (b) Fig.1 - the two-wire Flexo SWL Aerial gives you four possible combinations. When S1 selects position 1, the left-hand element is connected directly to the centre conductor, which feeds the signal to the receiver. Position 2 connects the element that's offset at a 45-degree angle. In position 3, both elements connect to the centre conductor. Position 4 gives a dipole configuration with one element connected to the centre conductor and the other connected to the braided shield. JANUARY 1988 71 14.33m PARTS LIST FOR THE FLEXO SWL AERIAL J 1 - Insulated phono jack S1 - 2-pole, 4 or 6-position switch (see text) Antenna elements - bare copper wire, AWG #16 or #14 Antenna mast - PVC pipe (see text) Down lead - coax cable or insulated wire (see text) Metal box, guys, nuts, bolts, etc, 120 ' 120' ..~'J,'!,I'> As shown in Fig.1 b, the two antenna elements can be angled also by as much as 30 degrees in the horizontal plane from their usual positions. Thus, they can be positioned to accommodate the mounting space in your back yard. In tests, it has been found that more reception flexibility is obtained with one element angled rather than straight. The antenna performs pretty much as a dipole on the 41 to 60-metre bands. On the remaining higher-frequency bands, other switch settings were often preferable to the dipole connection. Remember that the antenna wires become longer in terms of wavelength at the higher frequencies and, therefore, often perform more like a long wire. The antenna mast was made of telescoped sections of PVC piping (as shown in the photos). The coaxial transmission line is fed to the top of the PVC mast by cutting a hole in the mast at about chest-height. Fig.1 shows how the inner conductor and conducting braid (outer conductor) of the coaxial line are conneoted at the top of the mast. Two bolts serve as the antenna terminals. It is to those terminals that the antenna wires were attached using solder rings. The elements were then stretched out in an inverted-V fashion and brought down to two metal fence posts at ground level. In effect, you are constructing a 60-metre inverted THREE WIRES, -:::::: LOOSELY LOOPED - PLUG 1 S1a - - - - - ~ E R ----CJ' S1b 30 20 Fig. 2 Fig.2 - The three-element Flexo installation provides greater flexibility over the two wire type by allowing six combinations. dipole, but one with the antenna wires not necessarily in line. There are four possible ways to use the two conductors at the receiver end of the coaxial transmission line. You can use the two separate conductors individually (an either-or arrangement), or connected in parallel. The fourth arrangement is to The coax cable is fed through a hole, drilled about chest-high in the PVC piping, to the top of the mast. This view of the top of the PVC piping shows that the coax cable terminates in large crimp-on lugs, which are then secured to the mast using nuts and bolts. The antenna wires are then connected to the bolts. 72 SILICON CHIP use them in dipole fashion. The four possible choices are made available by a four-position, two-pole switch. The two switch sections are shown as Sla and Slb in Fig.la . In switch position 1, the braid of the coaxial line from the antenna is connected to the inner conductor of the short section of coax line that runs to the receiver input. In effect, the coaxial braid and one of the 14.3-metre antenna wires are being used as a single~ wire feed antenna. Notice that the braid does not connect to the centre conductor of the coax line. On position 2 of the switch, the centre conductor of the coax line and its associated antenna element serve as a single-wire antenna. In position 3, the braid and the centre conductor of the coaxial feed line coming from the antenna are connected to the inner conductor of the short section coax line that channels the input signal to the receiver. Thus, both antenna wires are connected to the receiver in a single-wire feed arrangement. On position 4, the centre conductor and braid of the antenna coax are respectively connected to the centre conductor and braid of the receiver coax. Thus, when position 4 is selected, the antenna operates as a true dipole. In putting the Flexo switching arrangement together, you must make certain that the braid of the transmission line from the antenna is not connected directly to ground in the switching box. The only time that the braid is connected to ground is when S1 is in position 4. In the author·s switching arrangement, the switch was built into a small metal box measuring 80 x 55 x 100mm. On the rear of the box, the author mounted two isolated terminals (as shown in the photos) to which the coaxial line from the antenna is PVC MAST CONSTRUCTION An antenna mast can be easily built from telescoping setions of PVC tubing and a few nuts and screws to hold the structure together. A 1 .5-metre metal fence ROSt, embedded in the ground, is used as a foundation for the mast. Two 3-metre sections of PVC tubing can be used to cqnstruct a mast about 5 .4 -metres high. Begin with a 5cm diameter section of PVC tubing and insert a second 3 .8cm diameter section of tubing, to a depth of 60cm, into one end . Drill holes through the overlapping sections of tubing and bolt them together. Insert and connect the signal carrying cables as needed. Connect the wires that will Ii JI THROUGHBOLTS '---..... GROUNO LEVEL - - - ~ - - 11 11 11 II jJ In the three-element installation, the down leads are run down the outside of the PVC piping through screw-eyes, and are connected to the feed-in by bolts installed through the mast. act as the RF (radio frequency) pick-up elements . If guys are to be used, cc;onnect them now . Use nylon stranded rope - the smallest diameter you can buy. Drop the mast 0ver the fence post and secure with bolts. Finally, secure the guys. Taller masts can be built by using ionger or additional lengths of PVC tubing. If a taller mast is desired , simply add to the length by joining two 5em diameter sections of PVC tubing , using a 1-metre length of 3.8cm tubing as a joint support. Insert the joint support about 60cm into the lower section of the mast. Drill holes and bolt the two sections together. Secure the upper section in the same manner, with the two outer lengths of tubing forming as tight a joint as possible . Finish up by adding the RF pick-up elements , signalcarrying cables , etc. as needed. JA NUA RY 1988 73 connected. To the left of these is a shielded phono jack to which the coaxial line feeding the receiver is connected. If you have trouble finding a two-pole, four position rotary switch, a two-pole, six-position switch may be substituted. The three-wire Flexo Another Flexo aerial uses three antenna wires and a three-conductor transmission line as shown in Fig.2. In that arrangement, the three antenna wires are spaced 120 degrees in the horizontal plane. It, too, is erected in the inverted-V fashion. The ends are dropped down to three metal fence posts near ground level. A view of that configuration is shown in one of the photos. The three transmission line wires run down the outside of the PVC mast through screw eyes to three terminals that are mounted in the PVC piping at chest level. From there, a three-wire transmission line enters the radio room and connects to the Flexo switcher. When there are three wires that are part of the transmission line, there are as many as twelve individual combinations that can be switched in. However, the six combinations provided by the arrangement shown in Fig.2 give good results, and little improvement can be obtained with additional combinations. The switching arrangement shown can select any individual wire for use as a long-wire antenna. The remaining three positions use the antenna wires in three separate dipole configurations. As a result, the Flexo has some limited directivity when operating as a switched dipole configuration on the lower-frequency bands. On the higher-frequency bands, the single-wire combinations also display directivity. However, the main advantage is that it gives you six combinations to choose from in obtaining the best reception possible for difficult propagation and interference conditions. Don't expect it to be a cure-all; some additional ·• The switch box is simply an inexpensive metal cabinet that carries the selector switch, two screw terminals and a phono jack. options may be necessary under difficult conditions. The switch is a two-pole, six-position type as recommended previously. Note that Sla selects one of the individual antenna wires when in positions 1, 2 and 3. Those same positions on Slb are left unconnected. Thus, you are operating with a singlewire feed for the first three positions and true coaxial feed for the latter three positions. The last three positions (4, 5 and 6) of switch Slb connect the wires in pairs to give a dipole configuration. In the 4, 5 and 6 positions, an appropriate antenna wire is connected to the braid of the small section of coaxial line that connects the output of the switcher to the receiver. In checking out your results, it may be advantageous to wire the switcher in terms of the physical positioning of each antenna wire. In wiring the Flexo switch, be certain to mount three insulated terminals on the box for connecting the wires from the antenna. You can use the same size box as for the previous antenna. ~ Evolution of Electric Railways: ctd from p.7 of the train line pipe, commonly known as "pulling the train's tail". By 1950 the railway world was changing fast. Diesel electric locomotives had been increasing in numbers since the war years and superseding many steam locos. The first advantages claimed for the diesels were quicker starting and longer times between overhauls. As for running cost measured in dollars per ton-mile of train hauled, on some American railroads the diesel electric could do no better than existing steam locomotives. In many countries , including Australia, running costs of old worn-out steam plant serviced in ancient loco sheds did exceed the expense of servicing and refuelling 74 SILICON CHIP new diesel electric machines in brand-spanking new service shops. A few United States railroads did show clearly that a large ·modern steam locomotive could be serviced and refuelled in a well-equipped running shop at a cost less than or equal to the equivalent expense for diesel electric units of the same power. The Norfolk & Western Railway was one such line which built its last steamer in 1953 and continued to use steam locomotives economically right up to April 4th, 1960. Even then, economy was not the reason for the death of steam. The problem was that they were just about the only railroad left using steam and new parts and plant became virtually unobtainable. It is interesting that the major manufacturers Alco, Baldwin and Lima in America built their last steam locomotive in 1947, 1949 and 1949 respectively, while in Australia the last steam locomotive to enter service, in January 1957, was a 269 tonne giant, the articulated Garratt built by Beyer, Peacock & Co Ltd, of Manchester England. So ended the amazing 160 year steam era, with the diesel-electric locomotive now ruling the world's lines. But let us not forget the other contender, the electric locomotive which is widely used around the world, expecially in Europe. Next month when we will delve into Australia ' s part in this fascinating saga. ~ I Buy any of the three new PC500 + systems from Dick Smith Electronics ... and we'll give you the monitor FREE! PC-500+ SERIES - Power, Performance and a FREEMonitor Outstanding performance, high power, dual clock speeds, high compatibility and LOW price are just some of the features which make the Acer PC-500+ Series the obvious choice for the home user. With up to 640K RAM, singIe or double 360K floppy disk drives (or 20Mb hard drive) depending on the model, serial and parallel ports, selectable 4.77/ 8MHz clock speeds, MGA card, Microsoft MS.DOS software, 12 Months Service and FREE 12" Mono Monitor (Cat X-2400) - no wonder it's popular! Optical Mouse Virtually maintenance free! PC Optical Mouse, with no movmg parts is, faster, more controllable and more accurate than the conventional mouse! Comes with software. 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ONLYS299 - - NSW • Broolnrale 93 0441 • Chullora 642 8922 • Gore Hill 439 5311 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parnlmatla 689 2188 • Tamworth 66 1711 • Wollongong 28 3800• York S12679111 •ACT• Canberra804944 • VIC• Elizabeth S1670 9834 • Spri"9Yale 5470522 • OLD • BrialianeCity 229 93n• Buranda 397 6233 •SA• Adelalde2321200 • WA • Perth 481 3261 •NT• Darwin 81 1977 • TAS • Hobart 31 0800 Order by phone Toll Free (008) 22 6610 for DSXpress 24 hour Guaranteed Despatch B506/GU 1, II AMATEUR RADIO By GARRY CHATT, VK2YBX Amateur television: getting started This month, we take a brief look at amateur television and the equipment needed to get started. As well, there's a handy list of amateur TV repeaters and ATV groups. One of the most technically challenging aspects of amateur radio is the transmission and reception of television signals, on the amateur bands. Old timers and newcomers alike find this medium most satisfying, as most of the equipment used is "home brewed" , and program material is mostly of a technical nature. There are many types of amateur television, ranging from "slow scan" TV (SSTV) which utilises a channel width of only 3kHz, and sequential scanning at an audio rate, to "fast scan" TV (FSTV) which utilises a channel width of 7MHz and transmits 25 pictures per second. As SSTV allows a greater concentration of energy in a smaller portion of the spectrum, the distances over which communica- tions can be achieved are much greater than when using FSTV. Nevertheless, distances exceeding 400km have been achieved using fast scan TV. Reception It comes as no surprise to discover that the majority of ATV (amateur TV) activity occurs on the UHF bands, primarily due to the overlap between commercial UHF television and the 570MHz ATV band. This greatly simplifies the equipment required for reception. In fact many operators use a standard band 4 UHF TV antenna and a UHF television receiver for ATV reception. Naturally a dedicated antenna for UHF channel 35, low loss feedline, and a GasFet preamp will Fig.2: test patterns similar to this one from VK2YBX are often used during ATV test transmissions. provide superior performance, but it can be seen that very little outlay is required to receive ATV. Just as an enormous number of repeaters serve the VHF and UHF FM nets, so too do a number of ATV repeaters. In fact most activity in capital cities is via the local ATV repeater (see Table 1). As can be seen from the repeater listing, the majority have their output on UHF channel 35 (575-582MHz), so that once a suitable antenna has been obtained, it is simply a matter of determining the location of the nearest repeater, tuning your UHF television to channel 35, and waiting for a signal to appear. Many ATV repeaters are sponsored and maintained by the relevant state branch of the Wireless Institute of Australia (WIA). The WIA transmits a weekly 30-minute news broadcast, normally on Sunday mornings. These broadcasts are ideal for tuning receivers and adjusting antennae. Transmission Fig.1: some amateurs prefer to build rather than buy equipment. This photo shows a typical home-made amateur TV station. 76 SILICON CHIP As with commercial television broadcasts, the vision transmission Table 1: ATV Repeaters in Australia Location Callsign Vision 1/P Sound 1/P Vision O/P SoundO/P Canberra Wagga Wagga Sydney Springwood Newcastle Central Coast Bendigo Melbourne Brisbane Brisbane Central North Central North Adelaide Adelaide · Hockham Perth Perth Devon port North West VK1RTV V.K2RTW VK2RTV VK2RTS VK2RTN VK2RTG VK3RMZ VK3RTV VK4RAT VK4RTV VK5RCN VK5RCN VK5RTV VK5RTV VK5RWH VK6ROD VK6RUF VK7RAE VK7RTV 426.25 444.25 426.25 444.25 426.25 426 .25 426 .25 444 .25 444.25 426.25 426.25 579 .25 426.25 444.25 444 .25 426.25 426.25 444 .25 444.25 431.75 449.75 431.75 449 .75 431.75 431.75 431.75 449. 75 449. 75 431 .75 431.75 584. 75 431.75 449.75 449.75 431.75 431 .75 449.75 449.75 579.25 579 .25 579.25 579 .25 579.25 579 .25 579 .25 579.25 579 .25 579.25 579 .25 444.25 579.25 579.25 1246.25 579.25 579 .25 579.25 426.25 584.75 584.75 584.75 584.75 584.75 584 .75 584.75 584.75 584 .75 584.75 584.75 449 .75 584.75 584.75 1251 .75 584.75 584.75 584.75 431.75 sidebands and a sound carrier, the channel spacing approaches 12MHz. This sort of channel width would severely limit the number of available television channels, so a system for reducing the required channel width was developed for commercial TV stations, which is also used by ATV operators. The Vestigial Sideband (VSB) system, also sometimes known as Asymmetric Sideband (ASB) system, involves filtering out the majority of the upper sideband of the vision signal, reducing the channel width to around 5MHz. By careful compensation in the receiver, the video distortion that would normally result from the removal of most of one sideband can be reduced to negligible proportions. Sound transmission is FM, and although the techniques are similar to those used for NBFM, the deviation is much greater (50kHz). Because of the exclusive nature of ATV and the resultant lower level of activity, there are few commercial suppliers of suitable ATV equipment. The South Australian ATV Group, part of the SA branch of the WIA, has a number of Fig.4: superior results can be obtained by using a resonant antenna. This 580MHz Yagi gives BdB of gain and is available from Dick Smith Electronics. Fig.3: a portable colour or b/w camera is suitable for amateur TV. The composite video output from the camera is fed directly to the transmitter. is amplitude modulated (AM), whilst the sound is FM. Normally the sound transmitter runs about one tenth the output power of the vision transmitter, where two separate transmitters are used. However, some operators mix the FM sound at the vision transmitter output stage and consequently run even less audio power to minimise intermodulation products. The standard spacing of 5.5MHz between vision and sound carriers is used to maintain compatibility with domestic receivers. The channel bandwidth is 7MHz. Wide channel spacing is required if good linearity and adequate video bandwidth is to be obtained. With a standard AM transmission of 625 lines (25 frames per second) with two Fig.5: this is the test pattern from VK2RTS at Springwood in NSW. JA NUA RY 1988 77 Fig.6: 1W amateur TV transceiver from PC Electronics, USA. Table 2: Active ATV Groups • Gladesville Amateur Radio Club TV Group (PO Box 48, Gladesville, 2111 , NSW) . This club conducts test transmissions on UHF channel 35 on Wednesday evenings 7 .30pm-10.30pm, Friday evenings 7.00pm-1 0.00pm, and Saturday and Sunday evenings at various times. The viewing audience extends from 1 00km south of Sydney to the northern suburbs. The VK2RTV transmitter runs 20W output into a 9dB omnidirectional antenna. Contact Keith VK2ZZO for further information. • Sydney ATV Group (SATV Group, PO Box 84, Hazlewood, 2779, NSW) . This group operates repeater VK2RTS (output UHF CH35) . Operation by touch tone. Liason net operates on 14 7 .3M Hz simplex every Tuesday evening. VK2RTS re-transmits material from the VK2RTV test transmissions on Saturday at 7 .30pm. • South East Queensland ATV Group (SEATV Group, PO Box 3 , Chermside, 4032, Qld) . VK4RTV repeater input is via valid television signal. 70cm liason frequency is 438.025MHz. 2-metre liason frequency is 14 7 .3M Hz. Repeater receive antenna can be rotated by touch tone operation. • Wireless Institute of Australia. Most divisions have an active ATV group. Many state divisions stock ATV publications. See your local phone book under WIA. • South Australian ATV Gro,up (GPO Box 1234, Adelaide, SA 5001 ). The VK5RTV repeater has been licensed for 1 2 years. The present repeater is a 20W microprocessor-controlled unit located at O'Halloran Hill , south of Adelaide . Access is via a valid TV signal. The repeater has over 250 touch tone control commands, and is one of the most versatile in Australia. Regular transmissions are made on Wednesday evenings 8pm to 10.30pm, and Sunday mornings from 9am to 10.30am. A "sister" repeater to VK5RTV, VK5RCN, is located at Clare, and is powered solely by batteries, charged by a wind generator. This repeater can be cross linked with VK5RTV to provide enhanced ATV coverage form Adelaide to Whyalla and other outlying areas. • Victorian Division WIA - ATV Group (3/ 105 Hawthorn Rd , Caulfield North, Vic. 3161 ). VK3RTV operates from Mt. Dandenong and runs 1 OW into a directional antenna aimed at Geelong and Melbourne. Repeater input is via a video modulated carrier. Touch tone operation is required to activate a colour bar test pattern, and several pages of repeater information. The repeater is solid state and microprocessor controlled, and has a unique " received signal report" function. 78 SILICON CHIP transmitter, preamplifier, and receiver kits available, and it is known that the Victorian division of the WIA also had kits available some time ago. One supplier in the USA, PC Electronics (2522 Paxson Lane, Arcadia, California 91006) regularly advertises a 70cm ATV transceiver, Model TC70-1, which has met with good success in Australia. This company also has a downconverter suitable for the 420-450MHz ATV simplex (and repeater input) band which contains an inbuilt GasFet pr eamp, Model TVC-4G. One of the higher bands w hich is presently being used for FM A TV experimentation, both here and in Europe , is the 2 3cm band (1240-1300MHz). There are a number of suitable " building blocks'' which make ATV reception r elatively simple in this band. These include satellite TV downconverters which convert the 950-1250MHz and 950-1750MHz bands to 70MHz. Wyman Research (PO Box 95 , Waldron, Indiana 46182) in the USA caters for this type of A TV equipment. Recommended reading: (1). UHF/VHF Manual; G.R. Jessop (available from most amateur radio stockists). (2). The 1987 ARRL Handbook; published by the ARRL. (3.) Radio and Television Broadcast Stations 1986; Australian Government Publishing Service. .~ Bench/portable multimeter from Fluke Most technicians and enthusiasts will already be familiar with the popular Fluke 70-series digital multimeters and their rugged-20 series for use in areas where dirt and grime is problem. Complementing that range is the Fluke 37 bench/portable DMM which offers additional facilities to the former meters. As with the 70 and 20-series, the Fluke 37 is auto-ranging, has 3200 count offering greater resolution than standard multimeters, and it has the bargraph feature which is handy for nulling and peaking since it responds faster than the digital display. Naturally, it can be used with all standard Fluke probes and accessories. The 37 model offers minimax recording whereby it will store the highest and lowest digital readings, over long intervals, as much as several days. This can be very handy in servicing and design work. It also offers Relative Mode, which shows the change between a stored reading and any following reading. This can also be useful for nulling test lead resistance. All these features are incorported in an attractive bench style Cute pedal accessories from Cutec Arista has a range of eight audio accessories for guitarists. All are housed in a sturdy plastic box with heavy pedal operated switch and powered by a 9V battery (Eveready 216 or equivalent). No power switch is fitted as this function is performed when a jack is placed into the input socket. We had a look at three of the units in the range and can confirm that they are ruggedly built, well finished and quite suited to being stomped on with a size 12 boot. Typical of the range is the Stereo Chorus which uses bucket brigade devices to produce the time delay necessary to simulate two voices. The Over Drive is a distortion circuit giving a similar effect to an over-driven amplifier fuzz box case which has a tilting foot and a built-in compartment for test lead and accessory storage. The model 37 is priced at $490 plus 20% sales tax where applicable. Enquiries should be directed to Obiat Pty Ltd, PO Box 37, Beaconsfield, NSW. Phone (02} 698 4776. (for echo and reverb effects), Graphic Equaliser and Parametric Equaliser. All units have simulated stereo outputs by the way. The Cutec range is marketed by Arista and is widely available from hifi dealers and electronic parts suppliers. Wet-dry head cleaner for VCRs while the Stereo Phaser is a dynamic phase shifter which gives effects from tremolo to a jet sound. Other units in the Cutec range are a Flanger, Stereo Analog Delay While there is a certain amount of controversy over head cleaning tapes just about all VCR manufacturers distribute their own brands of cleaning tapes. This one from Arista can be used as a wet or dry cleaner and is recommended for use, by the manufacturer, for every 20 to 30 hours of operation. The cleaning tape is not abrasive but consists of a fabric ribbon. The cleaning fluid is applied by squeezing the bottle to apply five or six JA NUARY 1988 79 pliances, model train or model car motors or whatever? We certainly have. Now you can have clean compressed air for just these tasks without having to spend several hundred dollars on an air compressor or having to go to the bother of hiring a cylinder of compressed air. Smoke detector has optical sensor drops into the appropriate hole in the cassette. Arista warn that if the tape is used in this latter mode, it may trigger the dew point sensor on some VCRs. For these machines they recommend that the tape be used dry. The cleaning tapes are available from all Arista outlets. Handy 400g containers of ammonium persulphate Electrolube Air Duster is the answer. It's an aerosol-powered 550g container of irtert gas (we guess it's probably nitrogen) which comes with a small plastic hose to enable the air to be directed where you want it. It gives a good finely focussed blast and is surprisingly effective. Pardon the pun, but it's a bottler. Priced at $11.95 from Jaycar. For those who like to etch their own small printed circuit boards, Jaycar has made available this handy 400g container of ammonium persulphate. Etching instructions are on the label. According to Jaycar, the contents are sufficient to etch typical boards up to 500 sq cm in area. It is available from all Jaycar stores. Electrolube Air Duster How often have you wished you had a small air compressor to blow out carburettor jets, small ap80 SILICON CHIP Some years ago smoke detectors with a radioactive element sensor were on the market but they were withdrawn because of public fears about radiation. This new smoke detector from Arista Electronics Pty Ltd has an optical sensor comprising an infrared light emitting diode and photodiode. When the light path between the two is interrupted by smoke, the alarm is tripped. It runs from an external supply or its own 9V battery and has its own piezoelectric alarm. It may also be linked to other smoke alarms in a security system or home burglar alarm via two wires. Protruding through the grille of the unit is a test pushbutton and a LED which glows when the unit is tripped. We found it an effective unit. It is available from all Arista retail outlets. .,.•~.r..1;~.,;~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ETl and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE High per£ormance headphone amplifier for CDs REPLACEMENT TIPS Professional Porta sol gas powered soldering iron Last month we briefly reviewed the standard model Portasol iron and recommended it as a very effective unit for all sorts of situations. Now there is a new version called Professional Portasol. This blue coloured unit comes in a neat plastic case which incorporates a small dish with a piece of foam in it (for wiping the iron's tip), a small wire stand and four accessory tips. One was a standard soldering tip while the other three comprised a hot knife, a hot blower and a mini blow torch. While the latter accessories are novel they are certainly effective although the unit must be full of butane for best results. If you have the occasional need for a small blowtorch as well as a gas-powered soldering iron, this Professional Portasol is a bargain. It is available for $81 from Geoff Wood Electronics. Phone (02) 427 1676. Electromark have a high performance stereo headphone amplifier, the ILP HY67, which would be ideal for use with CD players which do not already have a stereo headphone output. Fully encapsulated, the unit has a signal-to-noise ratio of lOOdB, separation between channels of 60dB and total harmonic distortion of less than .01 %. The HY67 can drive typical stereo headphones with impedance from 80 to 2kQ and can be powered from supply rails up to ± 25V DC to obtain a generous output level. As well as being used with domestic compact disc players, the headphone amplifier would be ideal for use with a disco console for cueing. For further information, contact Electromark Pty Ltd, 40 Barry Ave, Mortdale NSW. Phone (02) 533 4896. two outlet LF-2 is $99 while the four oulet model LF-4 is $269. They are available from Jaycar stores. Back copies of Silicon Chip Squeeky clean mains filters Sooner or later anybody who has a computer system will want a mains suppressor. Transient voltages superimposed on the mains can cause system crashes and data loss. This can be frustrating, time- consuming and expensive. These filters are made in Australia by KCC and are fully approved by the Energy Authorities. They can be recommended as a source of clean mains power. The Those readers who missed the first two issues of SILICON CHIP can purchase mint copies from our offices . The highlights of the first issue included the first article on our Digital Frequency Meter, a Capacitance Adaptor for DMMs and an Off-hook Indicator for Telephones. Highlights of the second issue included a fully protected 100 watt power amp module, a 24V to 12V converter for trucks and a passive IR sensor for burglar alarms. For details on how to order, see page 92. JANUA RY 1988 81 THE WAY I SEE IT By NEVILLE WILLIAMS Information has its place what about knowledge? It's possible to assemble any amount of routine information about such things as the steam age, the gramophone era or the birth of radio and hifi in Australia but, sadly and in the normal course of events, many of us carry to the grave a wealth of first-hand knowledge of how things really were, when it was all happening. You may quibble about my choice of the two key words in the above heading and introduction but by "information" I mean routine references to dates, people, facts and situations which can be found in books, journals, newspapers and documents, much prized by those who delight in researching and reconstructing history - accurately or otherwise. By "knowledge", on the other hand, I am referring to an innate familiarity based on actual personal experience, or acquired or communicated at that level. It is important, as I see it, to differentiate between the two, not just in the context of history but of the present and future as well. Let's think about it. I'm becoming increasingly aware of the distinction, as there seems to be more than usual interest in the past at the moment. You've probably noticed the recurring historic themes on television, the emphasis on restored buildings, the proliferation of antique dealers in country towns, and so on. Doubtless, some of this can be put down to nostalgia, fond 82 SILICON CHIP memories of times and situations where people may have felt better able to cope. But, beyond that, the past has its own unique interest, and its own unique value as a reference with which to compare the present and the future. ABC's "Talking History" For me, the matter was brought into focus when I was contacted by Stephen Rapley, presenter for the ABC's Social History Unit. Their program series "Talking History" is currently being broadcast over ABC Radio National and by satellite to regional centres each Saturday after the 1.30pm news (1.00pm in South Australia). The series covers a whole range of subjects of social historical interest, but Stephen Rapley has most recently been researching for a future presentation on "Radio and Telecommunications" in Australia. At least that is the formal subject title in the ABC's "Talking History" brochure. In a news item published in the September IREE "Monitor", interest was expressed in topics such as the contribution of Australia's pioneer wireless but amateurs and engineers, the emergence of broadcast stations in the early '20s, local receiver manufacture from the same period, the Royal Flying Doctor Service, the School of the Air, the vital role of telecommunications in Australia's development, the impact of television, the FM story and so on. When he subsequently called to see me, Stephen Rapley explained the philosophy behind the series in more detail. Dates and facts have their rightful place, he said, but on their own they're pretty dry fare, especially for broadcasting. The idea behind ''Talking History" or oral history, if you like, is to record for posterity the voices and the impressions of people who were actually involved in or lived through the relevant periods. Their stories and their first-hand account of events and situations can breathe life into regular but often dry documented information. Putting his theories into action over morning tea, Stephen encouraged me to reminisce about my life as a lad in a small country town, dependent for amusement and information in those days on purely local sources. We had no telephone, no gramophone, no wireless and only irregular, shared newspapers. Talking "historians"? How did we occupy our time in the evenings? As kids, I said, we did our chores and played with other kids until dark during the summer, sat around shivering during the winter and went off to bed with a No runaround - when it was most needed! The first two articles in this series carried stories of people who had received the runaround instead of prompt electronic service. This story has a different slant. It concerns a disabled pensioner lady who wanted a "runaround" and couldn't get it. The runaround in question is an electric motorised wheelchair on which she depends for mobility outside the house. With its help, she can do shopping or attend the occasional social gathering. But recently, in the middle of such an outing, the drive system went dead and she and her chair had to be brought back home in a neighbour's panel van. Rather nervous about the cost of getting it fixed , she rang the local agent, who suggested that the fault was probably iii the speed control system . It was concentrated on an easily removeable component board and it might be possible to have it removed by warm iron wrapped up in a towel at our feet! When did I first hear a wireless set? On headphones or a loudspeaker? What was it like when we got a set of our own? What were those early receivers like? How did a country boy come to get involved in radio as a career? What was it like, working in a '30s style radio factory? And so on. None of this was actually recorded. As I talked, Stephen Rapley scribbled industriously in his note pad and fired back more prompts and more questions. He was identifying possible subject themes to be pursued and developed in the weeks that followed. Finally, what about other people with whom I had shared the wireless, radio, hifi and TV scene during my working life? And here I must confess to "dabbing in" a few associates from past days cautiously, because I was not in all cases aware of their present circumstances. But some, I knew, had a story to tell. For example: • Winston Muscio, ex STC & BSR, someone on the spot and sent in for checking. This she was about to arrange. When the board was duly removed, it was draped with the exploded remains of what had apparently been an electrolytic capacitor but there was no way of telling whether this had been the cause of the breakdown or the result of it. Sufficient to say, the board was despatched to the agent forthwith for what he had tipped to be a couple of hours' work. However, when she rang a few days later to inquire about progress, she was told that it had been sent interstate to their central service centre. When she had still heard nothing a couple of weeks later, she wrote direct to the service centre, who phoned her back to say that the unit had been extensively damaged by someone having reversed the connections to the battery this, despite her insistence that the chair had been operating normally author of "Australian Radio - the Technical Story"? "I already have some source material from him on tape", said Stephen R. • Neville Thiele, of vented enclosure fame, prominent EMI engineer, more recently retired from the ABC? "Initial contact had already been made''. • Ernest Benson, former AW A engineer/editor, writer and lecturer and pioneer electronic organ enthusiast? "How do I get in touch?" • Reg Boyle, retired PMG senior engineer, who saw broadcasting and telecommunications from the inside? "I've already made contact with him through the IREE". There were other long-time acquaintances who came to mind as we chatted and doubtless, still others who will respond positively to the news item in the IREE " Monitor". If you want to follow it up, Stephen Rapley can be contacted at the Social History Unit, ABC Radio, GPO Box 9994, Sydney, NSW 2001 (Phone 02 339 0211, Ext 2683). for months and that the breakdown had occurred quite spontaneously. As far as they ,could tell from their paperwork, the board had been repaired and despatched; it must have gone astray somewhere. They'd have to check around and let her know in due course. Where they looked and where they found the board they never admitted but the local agent did ultimately ring to say that it had just been despatched. In the meantime, she'd been sitting around for five full weeks waiting for someone to do a two-hour job! It could just be that there's a bright side to the story: she's had the runaround now for two weeks or more, without any sign of the bill. "Maybe they've also mislaid the paperwork", she said, "or they may feel bad enough about it not to charge me for replacing the little gadget" . Time will tell! Typical recording session In my case, Stephen Rapley's intention had been to record a more structured but still informal chat in my own home but intermittent traffic noise put paid to that. We ended up in an ABC studio in William St, Sydney, for the best part of three hours while I responded to questions and prompts, some from the interviewer's notes, others quite spontaneous, arising from what had just been said. I found myself having to explain the uncertainty about the time of day in the pre-wireless era. How domestic mantel clocks would vary with the temperature and whether or not they had been inadvertently under-wound or over-wound. How they could be 10-15 minutes out and we wouldn't know, unless somebody noticed the clock in the stationmaster's office on the way home and worked out that ours just had to be wrong. The chiming town clock? The nearest one would have been eleven miles (18km) of rutted road away! Wireless solved that proJANUA RY 1988 83 Problems? ... and you don't have our 112 page catalogue ... you've got real problems! ARISTA ... your one-stop problem solver. Audio leads ... Batteries ... Chargers ... Battery holders ... Cables ... Car accessories ... CD accessories ... Converters ... "Cutec" ... Earphones .. . Fuses ... Headphones ... Intercoms ... Knobs .. . Microphones and accessories ... Mixers ... Multimeters ... Plugs/Sockets, etc ... Plug adaptors ... Power packs and leads ... PA ... Disc and Tape care ... Security equipment ... Signal modifiers ... Solderless terminals ... Storage boxes ... Switches ... Telephone and TV accessories ... Tools and Technical aids .. . Video accessories ... Wiring accessories ... You name it and we're bound to have it ... Try us ... NOW! Get your catalogue ... it'II solve a whole lot of your problems! Just send $2 + 50c p&h and your return address to: ARIST~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 84 SILICON CHIP blem, as well as providing up-todate (though not always accurate) weather reports. I recalled searching the scrub with my father for a couple of tall saplings to support the mandatory 30ft (10m) high aerial; contriving an effective earth in parched ground and adding a lightning arrester vital in an area prone to thunderstorms and virtually devoid of other overhead wires. Oh yes, and the need to ration family listening to one or two broadcasts a day. Why? To conserve batteries - because in those days a set of new batteries, railed from the city, could make an awful mess of a week's wages! Mention of a week's wages prompted further recollection of the dismay when the primary winding of one of the interstage transformers in the family Colmovox burned out. What did my father do but carefully dismantle the whole thing, unwinding thousands of turns of hair-fine wire until he had located and repaired the break. Then he successfully rewound it, entirely by hand - a feat at which I still boggle. Reliving these and many other such situations, it became abundantly evident how far removed the ABC's "talking history" was from the documented information that broadcasting stations commenced operation at certain times and places, allowing battery-powered receivers of the period to bring news, weather reports and entertainment to hitherto isolated listeners. How much of the recorded material gets to air, or in what form, is not for me to say. The present intention is to edit selected segments into suitably instructive and hopefully entertaining sessions, after which the master tapes will be passed over to the national archives. Contrast that with the following. Are computers addictive? While involved in this and other historically oriented projects, I've had reason to chase through sundry references in an effort to pinpoint particular events and dates. You know how it is: you're certain you have the information somewhere; you remember having seen it when looking for something else; now you can't find it! Wouldn't it be great to have it on computer? You could simply put it up on screen, scan through it yourself or, easier still, request the computer to find this, that or the other for you - which it can do in seconds flat! So, one wet and lazy day, I reached down my copy of the Macquarie "Book of Events" and abridged the contents of the chapter on "Radio & Television" into a series of one line entries into the computer. It looked promising, even in that very abridged form and, since then, I've dropped in quite a few more dates and events as I came across them. Providing I don't decide to do it some other way, the list seems all set to grow like the proverbial Topsy. The main reason why it hasn't already reached maturity is that I've had to give priority to other, more urgent tasks. But I'm conscious that the embryo list has a certain on-going fascination (did I say addiction?); a compulsion to generate an original personalised chronological listing, almost as an end in itself. This, despite the fact that a long list of dates and abridged information on a computer screen is deadly dull! A comprehensive list would undoubtedly prove very useful but, in the process of its compilation, I personally would become little the wiser. By its use, I might even become the poorer for not having occasionally to search through the literature and be reminded of other things in the process. The way I see it, instant access to computerised information must be seen as an efficient tool in the execution of certain tasks. In no sense is it a substitute for assimilated knowledge or innate knowledge of the kind possessed by people who have "been there and done that"! My own embryo dates/events list could be regarded as a miniature version of a much wider scene. Any number of computer databases already exist out there, with the largest collection of information stored in a publicly accessible computer, in Australia, being that in "CSX", maintained by the CSIRO. The overall system is reputedly so large and diverse that the people who have access to it are said to understand only the part which they actually use. It is doubtful whether anyone is aware of its total contents. I gather that much the same applies to other larger databases around the world for the same basic reason: like CSX, they have simply grown over a period of time, without sufficient attention having been given to the problem of gaining easy access to all the information that has accumulated. For most private computer users though, databases are still something that they read about. But massive changes in the recording and dissemination of information are already visible on the horizon. Huge quantities of reference information can now be stored on derivatives of the compact disc - typically more than 500 gigabytes per disc, equivalent to 150,000 pages of printed A4 text or a complete set of a large encyclopaedia. Grolier's American Academic Encyclopaedia has already been transferred to a single disc (words only) while the UK-based Commonwealth Agricultural Bureau has been making its database abstracts available on CD-ROM on a 2-year subscription basis although currently a rather expensive option. It will only be a matter of time though, before these databases become available at a price within reach of most people with access to a suitably specified CD player and personal computer. About then, we will have entered the era of what Gareth Powell, computer feature writer for the Sydney Morning Herald , has variously described as hyperlearning , hyperteaching, h yperwriting, hyper-reading, or hyperfiling. Oddly, and according to my dictionary, the prefix " hyper" means "over" , implying excess or exaggeration. That aside, I'll go along with the terms hyperwriting and hyperfiling, because they imply a staggering concentration of information. That it certainly would be, or is. But these terms get back to my earlier objection. Access to a huge amount of information may be both practical and useful to those who need it for specific reasons, but it has no 1:1 connection with acquisition, as implied by reading, teaching or learning; in short, with acquired knowledge. In case you feel that I am expressing a purely personal view, let me quote a systems manager with whom I discussed the generalities of computer databases: "It is important to realise that they are simply capacious data files ... sources of information ... nothing more." How many families already display in their living rooms a nice1y bound multi-volume en- Personal Phone Ringer natural resonance of the transducer. You can also vary the frequency of modulation of the oscillator by using different values for Cs although we assume that most constructors will stick with the value of O.lµF which we have nominated. Installation Installing your new phone ringer is easy. Just identify the connections to the bell ringer coil(s) and substitute the two leads to the phone ringer instead. Before you make the connections though, you should work out where and how to mount both the printed circuit ctd from p.25 board and the piezo transducer. This will take some ingenuity in some cases because even though there is usually quite a lot of waste space inside most phones, much of it is unusable. On the Telecom BOO-series telephones which are installed in most homes, the bell ringer coil is connected between terminals Pl and GS5. To disable the internal bell, we suggest you connect both ringer coil leads to Pl and then wire the new ringer circuit between Pl and GS5. Doing it this way makes it easy to restore the phone to original condition if necessary. We installed our prototype in an cyclopaedia, containing a wealth of information? It could be the source of considerable knowledge but may not, in fact, be consulted from one year to the next. Is there any reason then why electronic encyclopaedias and databases should be any different, whether on disc or at the end of an incoming fibre optic cable? I'm not averse to encyclopaedias and databases on chips or discs but please, don't let's confuse mere access to information with knowledge, however acquired. Is there any real basis for such apprehension? Is there any indication of data being substituted for knowledge? I believe there is, right here in our own industry. Electronic "Living History", 1987 style, can still call on people who, in their day, shared at first hand in the application of basic technology; who were involved in the design and production of everything from small components, through consumer equipment to the largest transmitters; who enjoyed an easy rapport with their peers from overseas. Next time around, another Stephen Rapley may be less fortunate . The old timers may remember the trends, components and user manuals imported from overseas but, apart from a few isolated high-tech areas, innate knowledge will be a rare commodity. That's the way I see it! It: BOO series phone by glueing the board to one of the flat metal pillars which support the dial mechanism, The piezo ringer was then glued edge-on to the base plate close by. Five-minute epoxy was the adhesive used. Tricky, huh? Incidentally, glueing the transducer edge-on renders it louder than if it is secured on the flat. The end result was quite a bit louder than the original bells so we detuned it a little by adjusting the trimpot. As a final note, this circuit can be used as an alarm wherever a DC voltage of 20 to 30 volts is available. It is loud, arresting but not unpleasant and its current consumption is low, at around lmA. ~ JAN UARY 1988 85 DIGITAL F In this chapter, we look at the circuits· that make up the various logic elements and discuss · their operation. We also look at the various logic families; and ·we .test your knowledge. LESSON 3: DIGITAL CIRCUITS By Louis E. Frenzel, Jr. In the previous lesson, we introduced the basic digital logic elements, such as the inverter, AND gate, OR gate, and NAND and NOR gates. These are the basic logic elements that process binary signals in digital equipment. We discussed their operation in terms of the logic functions they perform and the operation of each was expressed in Boolean algebra, truth tables, and timing diagrams. Only logic symbols were used to illustrate those devices. In this lesson though, we want to take a look inside the logic symbols. There are two basic methods of implementing digital circuits: discrete and integrated. Discrete component circuits are those made up of individual transistors, resistors, diodes, capacitors and other components wired together on a printed circuit board. The integrated circuit has all the components together on a tiny chip of silicon. Today, most digital circuits you will encounter will be of the integrated circuit form. Occasionally, however, you will run across a discrete component circuit in an older piece of equipment or in one requiring some special or simple function. We will discuss both ICs and discrete component circuits in this lesson. Inverters Let's begin our discussion with the circuit used to make a logic inverter. We will talk about simple discrete-component circuits first and that knowledge will easily translate to integrated circuits. For our discussion here, zero volts or ground represents a binary O and + 5V DC represents a binary 1. The main element in an inverter circuit is a switch as shown in Fig. la. The switch is connected in series with a resistor to the supply voltage. A binary input 86 SILICON CHIP +5V ,_:~ INJ!UT---l\ ~ /OUTPUT ✓ " -- R1 OUTPUT (a) Fig.1: a logic inverter operates like a shunt switch (a) in parallel with the output. A transistor (b) operated at cut-off and saturation functions in the same manner. signal controls the operation of the switch and the binary output appears across the switch. When the input is binary 0, the switch is open. The output, therefore, is + 5V or binary 1. If the input is binary 1, the switch is closed. Current flows through the switch and resistor Rl. The output is 0 volts or binary 0, because the resistance of the switch is near zero. A common bipolar transistor can be used as the switch to form a simple inverter as shown in Fig.1 b. A transistor works well in this application because it can be turned off so that no current flows through it, or it can be turned on to let current flow through it. Recall that there are three basic operational states of a bipolar transistor: cut off or non-conducting, conducting in the linear region, and saturation. Those states are achieved by biasing (see Review of Diode and Transistor Biasing). When the transistor is cut off, it is non-conducting and acts as an open circuit. With the proper bias on the transistor, it conducts d. Fig.2: a MOSFET inverter (Qt) using a MOSFET (Q2) as a load in place of a power-consuming resistor. flJ•--.::.1•1,-:.m INPIIT .. in the linear region. This means that the collector current is directly proportional to variations in the base current. That permits a small base current to control a large collector current and thus cause amplification to take place. The linear conducting mode is not generally used in digital electronics. If sufficiently high bias current is applied to the base of the transistor it will conduct hard and act as a very low resistance. During that time both the emitterbase and base-collector junctions are forward biased. The voltage drop between the collector and emitter at that time is extremely low; therefore, the transistor appears to be a virtual short circuit. When in saturation, the transistor acts as a closed switch. Using those principles, the operation of the inverter is easy to understand. If the input to the inverter in Fig.1 b is 0V or ground, the base-emitter junction of the transistor will not be forward biased. No current will flow through Rl or the transistor. The transistor thus appears to be an open circuit. Therefore the output is + 5V or binary 1 as seen through Rl. When a binary 1 or + 5V signal is applied to the input, the base-emitter junction is forward biased. The value of resistor R2 is made low enough so that the base current is high enough for the transistor to saturate. During this time, the transistor acts as a very low resistance. A typical output voltage between collector and emitter might be 100 millivolts (100mV). This is sufficiently low so as to represent a binary o. Metal oxide semiconductor field-effect transistors (MOSFETs) can also be used to form an inverter as shown in Fig.2. Here N-channel enhancement mode MOSFETs are used. Ql is the inverter switch while Q2 acts as the load resistor. This technique is widely used in N-channel MOS (metal oxide semiconductor) integrated circuits. Transistor loads are easy to make in integrated circuit form and also take up much less space than an integrated resistor. An enhancement mode MOSFET may also act as a switch. When its gate voltage is below some threshold voltage (about + 1.5 volts in common N-channel MOSFETs), the transistor is cut off. It acts as an open switch. When a positive logic signal above the threshold value is applied to the gate, the transistor conducts; therefore it acts as a closed switch. The operation of the inverter in Fig.2 is simple. When the input voltage is binary 0 (near 0V), transistor Ql does not conduct. Q2, however, is conducting because it is biased on. The output voltage is, therefore, + 5V as seen through Q2. When the input voltage is a binary 1 level or approximately + 5V, Ql conducts. It acts as a very low resistance; therefore, little voltage is dropped across it. The output voltage is near 0V or binary 0. AND and OR Gates AND and OR gates can be constructed with diodes and resistors. For example, a simple OR gate is illustrated in Fig.3. If both inputs to the OR gate are binary 0 or ground, neither diode conducts and no current flows through resistor Rl. The output, therefore, is at 0V or ground as seen through Rl. If both inputs are binary 1, both diodes D1 and D2 conduct. Current flows through resistor Rl. The output, therefore, is a binary 1. Most of the voltage applied to the inputs will appear across Rl except approximately 0.7V which is dropped across each diode. With a + 5V input, the output would be approximately +4.3V. If one input is binary 0 and the other binary 1, the output will also be binary 1. For example, if input A is + 5V and input Bis 0V, diode D1 in Fig.3 will conduct. The output will be approximately + 4.3V. That will cause diode D2 to be reverse biased and it will be cut off. A simple discrete-component AND gate is shown in Fig.4. If both inputs are binary 0 or ground, both diodes D1 and D2 conduct. Current flows through Rl. The output voltage at that point is the voltage drop across the diodes. For a typical silicon diode, the voltage drop will be approximately 0.7V. That is a lowlevel voltage and represents a binary 0. If one input is binary O and the other is binary 1, the output will also be binary 0. For example, if input A is binary 0 and input Bis binary 1 or + 5V, diode D1 conducts. The output will be approximately + 0.7V. This means that diode D2 will be reverse biased and, therefore, cut off. If both inputs are binary 1 or + 5V, both diodes conduct. The output will be + 5V less the voltage drop D1 e--------c INPUTS 02 A B OUTPUT R1 C ,, ,, ,,, 0 0 0 0 0 ... Fig.3: simple diode OR gate and its truth table. +12V R1 01 A 8 A INPUTS C OUTPUT 02 r... B Fig.4: diode AND C ,, ,, , 0 0 0 0 0 0 0 gate and its truth table. JANUARY 1988 87 across the diodes. If the inputs are + 5V, then the output will be + 4.3V or binary 1. If both circuits are as shown in Figs.3 and 4, additional diodes may be added to accommodate more inputs as needed. Furthermore, those simple circuits can be combined with inverters to implement almost any logic function. However, discrete component circuits take up a lot of space and are inconvenient to construct. Their performance is also generally poor. For that reason, they are used only where simple noncritical circuits are needed. +5V INPUTS OUTPUT C = A.ii 00 Digital Integrated Circuits Virtually all pieces of digital equipment are built these days using integrated circuits. An integrated circuit is one in which all the components - including transistors, diodes, resistors and capacitors - are fully formed and interconnected on a tiny silicon chip. Many inverters, logic gates, flipflops, and other logic and linear circuits can be contained within a small area. A typical silicon chip is roughly square, with sides of approximately 2.5 to 6mm. The smaller chips contain several gates or inverters while the larger chips might contain a complex circuit such as a microprocessor. The chip is encapsulated in a special package with leads that can be plugged into a socket or soldered to a printed circuit board. The most popular form of package is the dual-in-line package, or · DIP (see Fig.5), which may have 8 to 64 pins. Digital integrated circuits are generally divided into four basic categories: SSI, MSI, LSI and VLSI. Those designations, described in Table 1, show how digital Fig.5: dual in-line package (DIP) for integrated circuits. OUTPUT :::::[3o---c ~ = TI NANO TRUTH TABLE A B C 0 0 D 1 1 1 0 1 1 1 1 D ~ Fig.6: simplified TTL NAND gate circuit (a), and its schematic symbol (b) and truth table. !Cs are classified according to size, density and function. Digital !Cs are also classified by the type of transistors used in their circuitry. The two basic types are bipolar and MOSFET. IC manufacturers have developed a wide range of digital IC families using both types of transistors. Typical bipolar families include resistor-transistor logic (RTL), diode-transistor logic (DTL), transistor-transistor logic (TTL), emittercoupled logic (EGL), integrated-injection logic (I2L) and several others. RTL and DTL aren't used any more in new designs, but you may occasionally find them in older equipment. TTL and EGL are widely used today while I2L circuits are common in LSI and VLSI designs. MOS logic families include P-channel and Nchannel MOS and complementary MOS (CMOS). Because bipolar circuits are larger and consume more power, they take up more space on a silicon chip and, therefore, are used primarily for SSI and MSI circuits. Most LSI and VLSI circuits are MOS or CMOS. In this lesson we are going to talk about the most popular forms of logic today, TTL and CMOS. Transistor/Transistor Logic TABLE 1 LEVEL OF ICs BASED ON CIRCUIT DENSITY SSI MSI LSI VLSI 88 Small-Scale Integration: Chips containing 12 or less gates, inverters, flipflops etc. Medium-Scale Integration: Chips containing 12 to 100 gates, inverters, tliptlops etc, usually connected as functional circuits that do something such as counters, registers, decoders, multiplexers, and many others. Large-Scale Integration: Chips with 100+ gates, tliptlops etc, often forming complete circuits such as microprocessors, pro.gram and control circuits, and many others. Very Large-Scale Integration: Chips with 1000+ gates, flipflops and other circuits such as 32-bit microprocessors, data acquisition systems, gate arrays and much more. SILICON CHIP Probably the most popular form of SSI and MSI digitial ICs is transistor/transistor logic (TTL). TTL is used in everything from personal computers to the most advanced avionics equipment. TTL circuits use bipolar transistors and operate on a power supply voltage of + 5V DC. The basic TTL logic circuit is illustrated in Fig.6. That particular circuit performs the positive logic NAND function. However, other versions are available to perform the AND, OR and NOR functions . A single input version of the circuit is used as an inverter. The circuit has three parts: a multiple emitter-input transistor fQl), a phase splitter transistor (Q2), and the output stage (Q3 and Q4}. Refer to Fig.6a. Transistor Qt and Rt function as a simple diode AND gate where the emitter-base junctions of Qt are diodes. The main purpose of phase splitter Q2 is to furnish complementary logic signals to the two output transistors Q3 and Q4. Q4 is the output switching transistor and performs the function of an inverter while Q3, along with Dl and R4, forms an active pull-up stage. It is similar in operation to the MOSFET load resistor described earlier. Some TTL circuits are available without the active pull-up stage. Q3, Dl and R4 are eliminated and the collector of Q4 is brought out to one of the DIP pins. An external load must be connected. Open collector circuits are useful for driving components such as LED indicators, relays and other external circuits. In most cases the active pull-up circuit is preferred, because it represents a very low impedance when the output of the gate is binary 1. That permits the circuit to quickly charge any external capacitance, thereby greatly reducing the rise time and speeding up the circuit. The logic levels for the typical TTL circuit are 0V to + 0.8V for binary 0 and + 2.4V to + 5V for binary 1. Now let's see how the TTL circuit functions. Remember that it is a NAND circuit. You can refresh your memory about how it works by referring to the truth table in Fig.6b. Assume that either or both inputs A and Bare at ground or binary 0. The corresponding emitter-base junctions of Ql then conduct through Rl. When Qi is conducting, it pulls the base of Q2 to almost 0V and so Q2 is cut off. As a result, base current is supplied through R2 to Q3 which conducts. Transistor Q4 is cut off at that time. The output voltage will be + 5V less the voltages dropped across R4, Q3 and Dl. This output voltage is typically in the + 2.4V to + 3.6V range. If both inputs are binary 1, the base-emitter junctions of Ql do not conduct. However, the basecollector junction of Ql does conduct and provides base current to Q2 and through Q4. Transistor Q4 saturates and effectively brings the output to near ground level. The most popular form of TTL is the 7400 series which provides of all of the commonly used logic functions. The individual ICs are usually labelled with the manufacturer's logo, the device type number, and a REVIEW OF DIODE AND TRANSISTOR BIASING Diodes and bipolar transistors are made by combining N- and P-type semiconductor materials (silicon, germanium, gallium arsenide) to form junctions . A PN junction creates a diode. CATHODE ® If the base-emitter junction is forward biased and the base-collector junction is reverse biased, the transistor conducts. This is the normal condition for a transistor operating in the linear region for amplification. In logic and switching applications, the bias arrangements shown below are used . Here the transistor is used as a switch to turn on an incandescent bulb. ANODE The diode symbol (above) is used in schematic diagrams. The current flowing in a diode depends on its bias, an externally applied voltage. The circuits show the two ways to bias a diode. 01 n + T T I I ....L. 'I .J.. 'T' I I Rl ....L. REVERSE BIAS (NO CURRENT FLOW) FORWARD BIAS (CURRENT FLOWS) C )l (a) ""T"" I I Rl .L + (b) (a) If the cathode (N-type material) is made negative with respect to the anode as shown at A, the diode is forward biased and it conducts. The amount of current flowing is controlled by the resistive value of R1 . If the cathode is made positive with respect to the anode as shown in B above, the diode is reverse biased. No curr-ent flows in the circuit. Transistor biasing follows similar rules . An NPN transistor is illustrated below. EMITTER C BASE (8) I ! ) ~---tt-·----111 ~---1 + (b) ... If the input is grounded as in A, the base-emitter junction is not forward biased. Therefore , the transistor does not conduct and the bulb does not light. If the base is made positive as shown in B, the base-emitter junction is forward biased . The base-collector junction is reverse biased so the transistor conducts and the bulb lights. If the base current is made high as determined by Rb, the transistor will conduct hard. Its collector-to-emitter resistance will be very low and only a small voltage will appear between the collector and emitter. The collector may only be +0 .1 V with respect to the emitter at ground . With the base-emitter junction forward biased and conducting , the voltage across it will be the same as a conducting diode or about +o. 7V. If the base is +0. 7V with respect to the emitter or ground and the emitter is +0.1 V, then the base is positive with respect to the collector. This means that the base-collector junction is forward biased also. This condition is caused by high base drive. When both junctions are forward biased, the transistor is said to be saturated. Saturated operation is typical in bipolar transistor logic circuits . JANUARY1988 89 date code. Each of the TTL manufacturers such as TI, Fairchild, Signetics, National Semiconductor, and others, has its own special company symbol. The part number designates the specific device. For example, a 7430 is a single 8-input NAND gate. INPUTS OUTPUT A ~ A+B B~ INPUTS NOR TRUTH TABLE Propagation delay A B C Propagation delay is the time that it takes a logic change at the input to propagate through the device and appear as a logic-level change at the output (see Fig. 7). For TTL circuits the propagation delays are generally in the 2 to 30 nanosecond range and operating frequencies up to 125MHz are possible. 0 0 1 1 0 1 0 1 1 0 0 0 INPUT---- Ip Fig.7: propagation delay is defined as the time offset between input and output logic level transitions. Power dissipation is another important parameter. The lower the power consumption, the better. However, the faster the circuit, the more power it consumes. Most common TTL circuits have a power consumption in the 1-25 milliwatt (mW) range per gate. Going faster Some TTL circuits use Schottky diodes to speed up circuits while reducing power consumption. Essentially, each transistor in the circuit has a Schottky diode connected between the base and collector as shown in Fig.B. OR Fig.8: schematic diagram of a Schottky transistor. When saturated transistors are used in an IC, it takes a finite amount of time for the circuit to turn off. That condition, known as charge-storage puts a limit on the speed of operation. However, if a Schottky diode is used, saturation does not occur and there is no charge storage problem. As a result, switching speeds are faster and propagation delays are lower. However, standard Schottky TTL circuits have relatively high power consumption. The most popular TTL circuits today are the socalled low-power Schottky devices that have propagation delays as low as two nanoseconds. Those ICs are designated by an LS in their part number (ie, 74LS20). 90 SILICON CHIP W 00 Fig.9: schematic diagram of a CMOS NOR gate (a), and its schematic symbol (b) and truth table. Complementary MOS Ip DIOOE PREVENTS SATURATION S = SOURCE G = GATE D = DRAIN Another popular family of SSI and MSI logic circuits is complementary MOS or CMOS. CMOS circuits use both P-channel and N-channel MOSFETs, thus the prefix C for complementary. The power supply voltage is typically + 5V, although most CMOS circuits can operate reliably with supply voltages in the + 3V to + 18V range. Fig.9a shows the basic CMOS logic gate which performs the NOR function as indicated by the symbol and truth table in Fig.9b. Note that Qt and Q2 are Pchannel MOSFETs while Q3 and Q4 are N-channel MOSFETs. All four transistors are enhancement-mode MOSFETs meaning that the transistor is normally off until the threshold gate voltage is exceeded with a logic input signal. Now let's see how that CMOS NOR circuit operates. Assume logic levels of 0V and + 5V for binary 0 and binary 1, respectively. Keep in mind that in order for an N-channel MOSFET to conduct, its gate voltage must be positive with respect to its source. Usually the threshold value is approximately + 1.5V. Any input voltage greater than that will cause the transistor to conduct. Otherwise, the transistor will be off. In P-channel MOSFETs, the gate must be made negative with respect to the source. Again, the threshold value must be observed. Referring to Fig.9a, assume that both inputs A and B are at 0V or at ground potential. Since ground is more negative than + 5V, the gates are negative with respect to the sources so both Qt and Q2 conduct. Q3 and Q4 will be cut off at that time, because their gates are at 0V and below the threshold level. As a result, the output will be + 5V as seen through Qt and Q2. If either input A or B is binary 0 while the other is + 5V or binary 1, then either one but not both transistors Qt and Q2 will conduct. For example, if input A is 0V and input Bis + 5V, Ql will conduct but Q2 will be cut off. If input Bis binary 1, Q2 will be cut off but Q4 will conduct. With Q4 conducting, the output will be binary 0. With both inputs binary 1, both Ql and Q2 are cut off. However, both Q3 and Q4 will conduct, keeping the output at binary 0. The truth table sums up all possible conditions of inputs and outputs of the NOR gate. Naturally, additional inputs and transistors may +5V +5V +5V 1k IN (b) (a) Fig.11: using a 7401 open-collector 2-input NANO integrated circuit as a NANO (a), and as an inverter LED driver (b). (b) .,. (al Fig.to: schematic diagram of a TTL quad 2-input NANO gate (a) and a logic circuit made from the quad sections of a 7400 IC (b). be added to create gates with 3, 4 or 8 inputs. CMOS ICs are very popular because of their very low power consumption. The only time current really flows in the circuit is while the output switches from one state to the another. The power dissipation of a typical gate is in the 10-nanowatt range. This is very low power consumption and makes power supplies simpler and cheaper, and heat dissipation from the IC practically non-existent. Even though low power consumption is the primary virtue of CMOS circuits, that does not mean that they are necessarily slow. They are typically slower than TTL circuits, but fast enough for many applications. Typical propagation delays are in the 10 to 50 nanosecond range. Another advantage of CMOS circuits is their high noise immunity. That means they essentially ignore any extraneous signal, pulse, glitch or undesirable input. As a result, CMOS is excellent for use in industrial and automotive applications where high noise is common. The two most popular lines of CMOS circuits are the RCA 4000 series and the Motorola 14000 series. Both have a wide variety of gates, flipflops, inverters and functional logic circuits such as counters, registers, multiplexers, decoders and others. Using Logic Gates Fig.10 shows how TTL gates are used. Fig.10a illustrates a common TTL IC, the popular 7400 quad SHORT QUIZ ON DIGIT AL FUNDAMENTALS - LESSON 3 7. Logic circuits using both N-channel and P1 . In logic circuits, the transistor is used as a: a. resistor c. switch b. diode d. capacitor 2. When both junctions of a bipolar transistor are forward biased, the transistor is said to be._ _ __ channel MOSFETs are called _ _ __ _ MOS. 8. An enhancement mode N-channel MOSFET has a threshold of + 1 .5V. The gate voltage is +0. 7V with respect to the source. The MOSFET is: a. cut off b. conducting 3 . To save space on an integrated-circuit chip, a ____________ is used as a pull-up or load in a MOS inverter. 9. The most popular form of TTL has high values of circuit resistors and uses diodes between the base and collectors of the transistors to prevent saturation . This kind of TTL is called _ _ _ . 4. The basic TTL gate performs which logic function: b. NANO a. AND 10. The primary advantage of CMOS is: a. low cost b. low propagation c . low noise margin delay d. low power consumption c. OR d. NOR 5. The inputs to a 7 400 TTL gate are +0 .1 and +3.8V. The output will be: a. binary O b. binary 1 c. no change d. not enough information 6. Which of the following is not a type of bipolar logic? b . ECL a. NMOS d . DTL c . RTL 11 . TTL is slower than CMOS. a. True b. False AJBU!q ·q ·g as1ei ·q · ~ ~ UO!tdwnsuoo J8MOd MO( ·p ·0 ~ A}IHOlfOS J8MOd MO( .6 JJO lOO '8 AJBlU8W8fdWOO .L SOv'JN ·e ·g ON\fN ·q ·v (JOlS!SUBJl l08ij8 Pl8!! JOlOriP,UOO!W8S ap1xo 1etaw) 1 3.:ISOv'J ·8 pateJntes · c 40l!MS ·O . ~ S~3MSN'1 JA N UA RY 1988 91 2-input NAND while Fig. lOb shows a typical logic circuit using it. Note that unused inputs should be connected together and to the supply voltage via a resistor to avoid extraneous input signals. Fig.11 shows another IC circuit application, using a 7401. This is similar to the 7400 in that it is a quad 2-input NANO. However, the outputs are all open collector, meaning that they require an external load or pull-up resistor. The pull-up resistor is shown in Fig.lla. Fig.llb shows how the gate is used as an inverter and LED driver. The output load is a LED with a resistor to set the current value. When the input is low (binary 0), the output is high and the LED is off. If the input is high (binary 1), the output is low and the LED turns on. A CMOS circuit application using a 4001 quad 2-input gate is shown in Fig.12. With two of its inputs wired together a gate becomes an inverter (Fig.12b). Two gates wired as inverters can be connected to form a simple astable multivibrator, usually called a clock circuit (Fig.12c). The output is a continuous rectangular pulse train with frequency determined by the values of resistance and capacitance in the circuit. With the values shown, the output frequency is F = Did you • llllSS +5V ~=~ 2 (b) JUUUl f = 1/2.2RC (C) (a) Fig.12: a CMOS 2-input quad NOR integrated circuit is shown in (a). With the two inputs tied together (b) the gate becomes a simple inverter that can be used for the pulse generator shown in (c).The numbers indicate the pin termination in (a). 1/2.2RC, where R = lOk0, and C = l000pF, and the frequency is 45,454Hz or 45.454kHz. ~ Reproduced from Hands-On Electronics by arrangement. Gernsback Publications, USA. © these issues? LIMITED NUMBERS OF BACK ISSUES ARE AVAILABLE SO DON'T DELAY ISSUE HIGHLIGHTS ~---------I I I I I I I I I I I ........_ ·.:',: ... -------, Please send me a back issue for D November 1987 □ December 1987 Enclosed is my cheque or money order for $ .... .... or please debit my □ Bankcard □ Visa Name .... ... ...... ... .. ..... .......... ... ... ..... ... ... .......... .... .... ....... ......... ....... . . Address ........ ....... ... ....... .. .. ... .. .... ......... ..... .. ... ...... ............... .. ....., .. Suburb/town .. .... .... ..... ........ ..... ............ ..... ..... .. Postcode ......... ...... . Card No ... ...... ... ... ..... ....... ......... ....... .... .. ........ ....... .... .. .... ..... .. .... .. . Signature .... .. .... .. .... .. ...... ........ ........ .Card expiry date ....... / ....... /... ... . I I November 1987: Your House Wiring Could Kill You; 1GHz Digital Frequency Meter; Car Stereo in Your Home; Capacitance Adapter for DMMs December 1 98 7: High-Power Amplifier Module; Building an AT-Compatible Kit Computer; Passive lnfrared Sensor for Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V Converter. Price: $5.00 each (incl. p&p). Fill out the coupon at left and send to: s,ucoN CHIP, PO Box 139, Collaroy Beach, 2097. I----------------- - ------------------ 92 SILICON CHIP THE ELECTRONICS MAGAZINE FOR THE ENTHUSIAST WE INvITE You To BECOME A SUPPORTER Because we strongly believe that many more people should come to know about and enjoy electronics, we decided to form a new magazine devoted to electronics enthusiasts. We have called it SILICON CHIP, a name which encapsulates the driving force behind all of today's electronics technology. SILICON CHIP is starting off as an independent magazine, founded by Leo Simpson and Greg Swain. We have a very small team of devoted staff including our full-time electronics engineer, John Clarke and our very experienced draughtsman, Bob Flynn. We have started as a completely independent magazine, free from the influence of any existing publishing company, because we wanted to establish the highest possible standards for accuracy and attention to detail. We also wanted complete editorial freedom. Every article you see in this magazine has been carefully selected and prepared by us to establish this high standard right from the outset. Similarly, our circuit and wiring diagrams have been very carefully laid out by our draughtsman Bob Flynn to make them as logical and as easy to understand as possible. Regular Features * Constructional Projects For The Enthusiast * HiFi Review * Digital Electronics Course * The Serviceman's Log * Cratt, Amateur Radio, by Garry VK2YBX * The Way I See It, by Neville Williams Junk mail Most magazines sell their subscriber lists to mail order companies, to earn extra income. We will not do this. We will lose some money by adopting this policy but we believe that your privacy is paramount. You can help us establish a high standard for our publication by becoming a supporter. The more subscribers we get, the more resources we can devote to improving the quality of our magazine and to the promotion of the understanding of electronics. -----------------------~--FREEPOST SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097, Australia. NO POSTAGE STAMP REQUIRED IN AUSTRALIA NAME ........................................................................................................ . 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Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Noisy transformer in amplifier I have recently completed an amplifier kit whose design I am sure you are familiar with. Unfortunately, the substituted dual Ccore transformer radiates a magnetic field which I presume is responsible for an audible hum through the loudspeakers, slightly louder on the left than on the right, and constant regardless of advancing the volume, treble or bass controls. The hum is present with and without inputs plugged in. Is there a safe way of shielding the transformer and would this be responsible for the noise? [G.M., Maroubra 2035). • We know of only one amplifier currently being supplied with a Ccore transformer. Strictly speaking though, it has only one core which consists of two C-cores held together by a Utilux hose clamp. The transformer in question should be very quiet and it is highly likely that it is not at fault at all. The most common problem in today's low noise amplifier designs is earth loops. There should be only one connection from the amplifier circuit to the chassis. If there is an additional earth connection which may be caused by a short from the outer connection of the RCA phono socket to the chassis, there will be a constant low level hum which is independent of control settings. Apart from a careful visual inspection, the way to check for the presence of an earth loop is to disconnect the main earth from the amplifier circuitry to its chassis. Then switch your multimeter to a low Ohms range and check for continuity between the amplifier circuit and chassis. There should be none. From then on it is a matter of visual detective work to see where the short is occurring. If the above checks still bring no joy and the amplifier still hums, you can still check whether the transformer is the cause. All you have to do is to remove the transformer from the chassis while still leaving it connected. You may have to extend some of the leads to enable the transformer to be positioned outside the chassis. Now turn on the power and listen carefully to the hum to see if it varies with orientation of the transformer. You may find that there is a null in the hum output with the transformer mounted at Wants Leak circuit diagram Some time ago, I was given some quality valve audio equipment. It was being taken to the local tip and a friend thought it may be of interest. It turned out to be a Leak amplifier. So now I am the proud owner of a Leak "Stereo 20" plus the "Varislope Stereo" preamplifier to go with it. As it turned out, replacing ~he various coupling and filter capacitors gave me a perfectly functional unit. This brings me to my problem. I am trying to find a source of the circuit information on this equip94 SILICON CHIP ment, particularly of the preamplifier. Could you suggest anyone with this information? I know the gear was imported into Australia from England around 1960 by Simon Gray Pty Ltd. However the company doesn't exist any longer. [J.Sweet, 91 Anne Street, Aitkenvale, Qld 4814). • Alas, we know of no source of the circuit information you require. We have printed your name and address in the hope that one of our readers can help you. right angles to its present orientation. As far as your question about shielding is concerned, it would be difficult to shield the whole transformer. However, it might be practical to install a copper strap over the winding assembly to reduce any stray leakage flux. Once again though, we don't think the transformer would be the problem. We suspect an earth loop. Wants timer with remote display I hope you can help me with my problem. I am attempting this project for a local sporting club. It revolves around a three-decade programmable timer. I am fairly confident I can design the timer myself but I also need a remote display some 30 to 40 metres away from the counter itself. How do I keep the cable stranding to a minimum? What problems will affect the digital signal over such a long run? Should I have a separate 5V supply at the remote display? What is the cheapest and simplest way? I have tried to find books and articles on the subject of data transmission but most of it applies to computers and such with transmission distances of no more than 5 to 10 metres. I thought of trying multiplexers, D-A and A-D converters or maybe UARTs. I hope you can help me. [R.O'G., Rockhampton, Qld). • Had you asked about a 3-digit timer without the need for presetting we would have said that it would be easier to have an additional remote timer so that only three leads would be necessary in the long cable; ie, + 5V, clock signal and 0V. Since you need presetta ble counters [this letter was accompanied by a suggested schematic involving three 4029s, three 4511s Ribbon or coax: which is best? All of the information I have read about UHF antennas in Australia recommends the use of 75-ohm coax cable and most of the installations I have seen in this country have used coax. But I have been overseas to the US and Japan on a number of occasions and there they seem to use ribbon cable frequently. Why is tha~? Why is there such a preference in Australia for coax? I can't believe that our reception conditions for UHF would be any more difficult than in cities in Japan and the US. • We doubt whether UHF reception conditions are any more difficult in Australian cities than overseas. Based on typical attenuations figures at UHF for ribbon cable and coax cable, you might think that ribbon would be the more desirable. After all, most coax cables have losses of 10dB/30m or more at UHF which is considerably more than the nominal losses of la.dder-type ribbon cable but we would not recommend ribbon cable on that basis. It is possible that in some situations, 300-ohm ribbon cable might give comparable reception and three 7-segment displays), you will need to run 12 separate data lines plus the supply lines. That makes it messy. We don't think UARTs (Universal Asynchronous Receiver/Transmitter) would be practical or cheap since you would need two 8-bit UARTs to send and another two to receive, plus all the timing circuitry required. Nor would A-D and D-A conversion be practical or cheap because that also implies quite a lot of supporting circuitry. The only practical way seems to be to send all 12 data lines via RS232 receivers and transmitters. We suggest you use the Motorola MC1488 quad line driver and MC1489 quad line receivers, both of which are quite cheap. You would need three to transmit and quality to 75-ohm coax but you could only justify its use in areas away from the sea which don't have high rainfall. Once ribbon cable becomes wet or coated with a salt film, it starts to produce much higher losses. It deteriorates quickly too and is subject to signal pickup on the cable itself, producing leading ghosts and smeary pictures. As far as we are aware, coax cable is universally used throughout Europe for UHF reception and the same can now be said for the USA and Japan. It is also true that many if not most installations in apartment buildings overeases would not feed UHF signals via distribution system to each tenant. The signal losses, particularly in older installations using inferior cables, would make it impractical. Rather, it is standard practice to feed the UHF signals to a down-converter so that the signals are distributed at VHF. The message is: forget ribbon for UHF. If coax cable losses are .likely to be a problem, you should use a masthead amplifier to boost the signal before it is distributed. three to receive. You will also need ± 12V supplies for the transmitters in addition to 5V for the remote display. We admit that our suggested solution does not look simple, but it is probably the cheapest way. Corrections Digital Fundamentals, Dec. 1987: Fig.6 on page 92 has been reproduced incorrectly. The type down the left-hand edge of the diagram should read INPUT A, INPUT B, INPUT C and OUTPUT D. In addition, the second last paragraph on page 92 should read as follows: At times t 1 through ta the three inputs are never high at the same time. However, beginning at time ta and ending at time t 9 the three inputs are all high so that output D goes high. Subcarrier Adaptor continued from page 67 setting up procedure is relatively simple. First, make sure that VR1 is set so that its wiper is turned toward the LM565. This will provide maximum signal level. Now adjust VR2 so that there is audio signal. Find the extreme settings of VR2 where the audio signal drops out, then set VR2 halfway between the two extremes. VR1 is used to minimise noise from the audio signal when the FM signal level is poor. Adjust the trimmer until the sound becomes distorted and then back off the adjustment until distortion is no longer audible. If you have a strong FM signal, adjustment of VR1 will have no effect on the noise level and so it should be left at its maximum resistance setting. UHF Antenna continued from page 21 enable you to terminate cables from your VHF and UHF antennas. A single cable goes from the diplexer to your TV set. Alternatively, the diplexer output may be fed to a splitter and then to various TV wall plates around your home. Tune your TV to the local UHF station(s) and then orient the antenna for best reception. Secure the cable to the mast with plastic cable ties to prevent the cable from flapping in the wind. Seal the balun box with silicone sealant to weatherproof it. Painting Depending on where you live, painting the antenna cart be worthwhile, particularly in seaside areas or near industrial areas where there may be a lot of fallout. In these cases, we suggest painting the antenna with an etch primer and then finishing with an aluminium loaded paint such as British Paints "Silvar". As a final comment, if you are building the antenna to receive stations right at the top of band V, say between channels 59 and 69, a small improvement can be gained by shortening the dipole elements by 5%. JANUARY 1988 95 CENf Cash in your surplus gear. Advertise it here in Silicon Chip. plete kit featuring a dual mechanical VU meter. Easy to assemble; the meter is soldered directly to the printed circuit board. Any audio signal can drive it since its sensitivity is adjustable from volts right down to 3mV! Can double as a microphone preamplifier. Features optional backlighting ; incandescent lamps provided in kit. This unit is inexpensive at its normal price of $1 7. 90, however during January you can buy it for only $9-95 (p&p included)- Yes it is a bargain; at this price you can afford to build one into every piece of audio equipment you own . UHF Remote Controlled Key (Jan. 86 EA). A proven and reliable wireless remote switch; 1 000s sold! Has more than 13,000 possible code combinations. Multiple outputs and an on-board off-on indicator enable this unit to remotely switch car burglar alarms, car central locking systems, home burglar alarms, etc. The small transmitter also has provision for a key ring . Our special January package includes 1 x transmitter PCB kit, 1 x transmitter plastic case with battery clips and pushbutton switch, 1 x miniature 12V alkaline (lighter) battery, and the complete receiver PCB kit for only $39.95 including pack and post. Yes, FOR SALE 0.25W RESISTORS: only 1 .5c each! Values from 4 .7n to 2 .2MQ (E12 range) . $1.00 postage. Send for free samples! Steven Fox, PO Box 4, South Bexley, NSW 2207 . NEARLY 1500 printer buffer kits now sold. Prices start at $39 for a 256K short form kit. All items advertised are in stock. Dealer enquiries welcome. Bulk discounts. Schools, Govt. Depts. orders accepted . Oh yes !!, IBM compatible . Austral ian designed and manufactured. Ideal project for user groups or students. For a free catalog send a 37c stamp to: Don McKenzie, 29 Ellesmere Cres., Tullamarine 3043. ELECTRONIC components cheap . Example : 100 5mm LEDs - 34 Red, 33 green, 33 yellow - $12.00. Free post and pack. LMF Products, PO Box 384, Cootamundra, NSW 2590 . OATLEY ELECTRONICS - for exclusive and selected kits. Here we present our January specials: Stereo VU Meter (June 87 EA) . Com- Advertising rates for this page: Classified ads - $7 .00 for 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 ru n your own classified ad, put one word on each of the lines below and send th is 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) 19 ($8 .60) 20 ($9.00) 18 ($8.20) Name ········ ·•··· ···· ··· ········· ······ ······ ··•·· ····· ·· ····· · Address ···· ··· ········· ··· ·· Suburb/Town Enclosed is my cheque or money order for $ ........ ..... ..... ..... . Bankcard D Visa D Card No. Signature .. ... . 96 SILICON CHIP Postcode . . . . . or please debit my that's everything you need and yes, it's dirt cheap! Satellite Siren (Sept. 87 EA). Add the protection of this complete second alarm system into your existing alarm system. Automatically gain the benefit of back-up battery operation and a complete and remotely placed second alarm system! This unit is simple to install; it requires only two connections to your existing alarm system. Unit is activated when the main alarm is vandalised, the main alarm power is interrupted, or the vehicle battery is disconnected. We now offer a short form kit for the "Satellite Siren" . What's in this kit? - 1 x PCB and components kit, 1 x battery holder, 1 x barrel keyswitch with two keys, and a plastic case. All this for only $29.00 including pack and post. So what else will you need later to complete the unit? - 4 x AA nicad batteries at $3 .00 each and 1 x 12V piezo siren at $16 each. Yes , all these prices are unbeatable! In the New Year our shop will re-open on Monday 18/ 1 /88 (gone fishing) and we will process our mail backlog on the same day! Happy New Year! Mail address: Oatley Electronics, PO Box 89, Oatley, NSW 2223. Shop address: 5 Lansdowne Pde, Oatley West, Sydney, NSW 2223. Phone (02) 579 4985. To obtain a list of our kits and ready made products send us a selfaddressed envelope (8cm x 21 cm) or ask us to include it with your purchase. Advertisers Index Our advertisers are vital to the success of SILICON CHIP. Please give them your support. . 26-31 Altronics . . Arista Electronics . . . 84 Australian Geographic ..... IBC Dick Smith Electronics . ... 8,9 , 36,54 ,55,75 IFC Elmeasco . 61 Geoff Wood Electronics . .. 44-47 Jaycar Electronics .. . . 96 Oatley Electronics . .. 81 RCS Radio . . . . 35 Scan Audio Pty Ltd . ~~~ ~; ··::,,? i:-..'7' MEMBERSHIP CERTIFICATE To: Australian Geographic Subscriptions Freepost 3, P.O. Box 321, Turrey Hills, NSW 2084, Australia NO POSTAGE STAMP REQUIRED WITHIN AUSTRALIA Please enter an AUSTRALIAN GEOGRAPHIC subscription in my name for (tick box): □ 1 year □ 18 months □ 2 years NAME _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ ADDRESS _ _ _ _ _ _ _ _ _ __ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ SUBURB/TOWN _ __ _ __ _ _ _ _ _ _ _ POSTCODE _ _ _ _ _ _ _ COUNTRY _ _ _ _ _ _ _ _ _ __ __ _ _ _ __ _ __ _ _ _ _ _ _ _ Enclosed is my cheque or money order for $_ _ _ _ _ _ _ __ or please debit tltis amount w my □ B=kcanl □ v;sa C«d D MasmC«d ~ Card Number s NOP SIGNATURE Subscription costs for: Within Australia Overseas Surface Mail O verseas Air Mail R 1 year 14 issues ) tJ $A28 D $A40 D $A62 18 months (6 issues) □ $A42 D $A60 D $A93 2 years (8 issues) D $A56 D $A80 D $Al24 Ut