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PRODUCT SHOWCASE Hung Chang 20MHz dual trace oscilloscope trols are three pushbutton switches to select Channel 1, Channel 2 or both channels added together (ADD). By pushing the INVERT button for channel 2, the ADD button will provide a display which represents the difference between the two channel inputs. This is not quite the same as having a scope with differential inputs but it’s a handy facili­ty. Above these controls and to the right of the screen are the Power switch, Intensity, Focus and Scale Illumination (for the screen graticule) controls. Also in this section of the panel is a screwdriver preset for trace rotation. This can be used to ensure that the traces are exactly parallel to the horizontal lines on the screen graticule. As well, there is a Calibration terminal providing a 0.5V peak-peak square wave reference signal. This is used for setting the compensation of the scope probes (ie, for optimum square wave display). Timebase & triggering This attractive oscilloscope has a 20MHz bandwidth, dual trace operation and a maximum vertical input sensitivity of 1mV/ div. Its timebase extends up to 0.1µs/div. While many electronic hobbyists might yearn for a 200MHz digital storage oscilloscope with screen save to disc capabili­ ties, a great deal of measurement work can be done with a much lower priced instrument such as this Model 6502 from Hung Chang in Korea. It is quite compact, with dimensions of 140mm high, 335mm wide and 420mm deep. The front panel manages to feature all the usual controls while appearing to be very clean and uncluttered. Even so, there are no less then 11 knob controls, 11 pushbuttons and four 3-position toggle switches. The active screen area is 10cm x 8cm and the screen phosphor is blue. To the right of the screen are the vertical attenuators. These have nine settings ranging from 5mV/cm to 5V/ cm in a 1:2:5 sequence. By pushing the x5 MAG switch, the sensitivity can be increased to a maximum of 1mV/ cm while knobs concentric with the attenuator switches give continuous variation of sensitivity. To the right of each attenuator is a 3-position toggle switch allowing AC or DC coupling and Gnd while above each atten­uator is the trace position control for the respective channel. The vertical input BNC sockets are beneath the input attenuators with an earth terminal between them. Between the vertical position con- At the far right of the panel is the Time/Division switch giving 20 sweep from 0.1µs/cm to 0.2s/cm in the usual 1:2:5 steps. Below this and to the left are two 4-position toggle switches. The first is for Trigger Mode allowing selection of Auto, Norm, TV/V and TV/H triggering, while the second switch is trigger Source. The positions provided here are Internal, Ch2, Line and External. Note that if the oscilloscope is being used in the single channel mode, either Ch1 or Ch2, then sync is provided by selecting the Int source. To the right of these switches is the Trigger Level control. Above and to the right of the time­ base switch is a timebase Variable control and two pushbutton switch­es for trigger slope (either + or -) and XY mode. When pushed in this causes the Ch1 and Ch2 inputs to be displayed as an XY Lissajous plot. Trace magnification Two more pushbutton switches provide timebase magnification (MAG x5) and ALT-MAG. November 1996  79 The first is self explanatory while the second is not. When pushed it displays an additional trace with the timebase being five times normal speed. If the scope is already in Dual mode and ALT-MAG is depressed, then four traces will be shown. This is quite an unusual feature and can be handy in a number of situations. One control missing is that for selecting Alternate or Chopped mode for dual trace operation. Instead, these functions are selected automatically as the Timebase speed is altered. Trigger sensitivity for the Model 6502 on internal sync is quoted as three divisions for DC to 20MHz bandwidth. Our sample easily exceeded this spec. Reliable sync was obtained up to 2MHz with a displayed signal of less than one division and at 20MHz with a two division signal. This is good. Another interesting point about this scope is its very high maximum sensitivity of 1mV/cm although this is not useable in some situations where the vertical input amplifiers become unstable and oscillate. This is mentioned in the instruction manual and can be cured by good grounding of the KITS-R-US RF Products FMTX1 Kit $49 Single transistor 2.5 Watt Tx free running 12v-24V DC. FM band 88-108MHz. 500mV RMS audio sensitivity. FMTX2A Kit $49 A digital stereo coder using discrete components. XTAL locked subcarrier. Compatible with all our transmitters. FMTX2B Kit $49 3 stage XTAL locked 100MHz FM band 30mW output. Aust pre-emphasis. Quality specs. Optional 50mW upgrade $5. FMTX5 Kit $98 Both a FMTX2A & FMTX2B on 1 PCB. Pwt & audio routed. FME500 Kit $499 Broadcast specs. PLL 0.5 to 1 watt output narrowcast TX kit. Frequency set with Dip Switch. 220 Linear Amp Kit $499 2-15 watt output linear amp for FM band 50mW input. Simple design uses hybrid. SG1 Kit $399 Broadcast quality FM stereo coder. Uses op amps with selectable pre-emphasis. Other linear amps and kits available for broadcasters. 80  Silicon Chip signal source as well as placing a 220Ω resistor in series with the scope probe. Sweep linearity of the instrument was good and the trace sweep times within specification of ±3%. The displayed trace was very fine, with even focus across the full screen area. In short, the Hung Chang model 6502 oscilloscope is a good performer, especially at its low price. Recommended retail price is $799 including sales tax. Dual sensitivity 80MHz probes are available for $39.95 each, tax paid. Our review instrument came from Altronics, 174 Roe Street, Perth 6000. Phone 1 800 999 007. Price reduction on Fluke graphical DMM Fluke’s 860 series Graphical Multi­ Meters have proved very popular since their release in 1995. Combining advanced multimet­er capabilities with waveform display, in-circuit component testing, trend plotting and logic activity detection in one easy to use handheld instrument, they represent good value. The Fluke 865, the mid-spec model PO Box 314 Blackwood SA 5051 Ph 0414 323099 Fax 088 270 3175 AWA FM721 FM-TX board $19 Modify them as a 1 watt op Narrowcast Tx. Lots of good RF bits on PCB. AWA FM721 FM-RX board $10 The complementary receiver for the above Tx. Full circuits provided for RX or TX. Xtals have been disabled. MAX Kit for PCs $169 Talk to the real world from a PC. 7 relays, ADC, DAC 8 TTL inputs & stepper driver with sample basic programs. ETI 1623 kit for PCs $69 24 lines as inputs or outputs DSPTH-PCB and all parts. Easy to build, low cost. ETI DIGI-200 Watt Amp Kit $39 200W/2 125W/4 70W/8 from ±33 volt supply. 27,000 built since 1987. Easy to build. ROLA Digital Audio Software Call for full information about our range of digital cart players & multitrack recorders. ALL POSTAGE $6.80 Per Order FREE Steam Boat For every order over $100 receive FREE a PUTT-PUTT steam boat kit. Available separately for $19.95, this is one of the greatest educational toys ever sold. in the family of three, is currently being offered for a limited time at the reduced price of $749.00 excluding sales tax. The 865 features a basic DC accuracy of .04%, selectable display modes, including Meter Mode, Waveform Display, TrendGraph Mode, In-Circuit Component and Logic Test Mode. It is supplied with test leads and battery eliminator and housed in a shock-absorbing protective holster. For more information, contact Obiat Pty Ltd, 129 Queen St, Beacons­field, NSW 2014. Phone (02) 9698 4111; fax (02) 9699 9170. Mini-Circuits Designer’s Guide To encourage radio amateurs to build and develop their own communications equipment, Mini-Circuits USA are offering, free of charge, their RF/IF Designer’s Guide. Mini-Circuits manufacture an extensive range of mini-modules, such as RF amplifiers, fre­q uency m ix er s, po wer splitters, filters, detectors, attenuators, etc. Circuits are available in various case style packages to suit applications from surface mount to external equipment mounts. Typical mixer frequencies range from 10kHz to 4.3GHz, making them ideal for LF to SHF work. If you would like a free copy of RF/IF Designer’s Guide, contact Mini-Circuits’ Australian representatives and stockists, Clarke & Severn Electronics, PO Box 1, Hornsby, NSW 2077 or call (02) 9482 1944. PCB POWER TRANSFORMERS Programmable multimeters Meter International has added the MIC-3130 to the 3000 series of programmable multimeters. These allow the setting of low and high levels of current, voltage or resistance. When a measurement falls within the set values, a warning tone is sound­ed. This can free an operator from referring to the display when looking for a particular measurement. The Automatic Data Hold allows the operator to concentrate on probe placement, updating the display every three seconds on valid inputs. A “beep” indicates the reading is locked in. This feature significantly reduces measurement difficulty in confined areas and increases safety when measuring dangerous voltages. A special feature of the MIC3130 is the option of connect­ing K or J-type thermocouples, with the display showing either °C or °F. The MIC-3130 can also measure capacitance from 1pF to 4µF over four ranges. A frequency counter to 4MHz is also included. The unit comes in a rugged case with pushbutton range selection. The display has large 4000 count 1VA to 25VA Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 digits with range annunciators. A bargraph is incorporated into the large 4000-count display. A standard feature is the fast display mode, which updates the display every 50ms instead of the normal 300ms peri­od. For further information, contact Computronics Corporation Ltd, 31 Kensington Street, East Perth, WA 6004. Phone (09) 221 2121; fax (09) 325 6686. ® Design low frequency loudspeaker enclos­ures fast and accurately with BassBox® software. Uses both Thiele-Small and Electro-Mechanical parameters with equal ease. Includes X. Over 2.03 passive cross­over design program. $299.00 RS-232 chips meet ESD requirements Analog Devices Inc has introduced a family of +5V, RS-232 transceivers which meets the European EMC (Electromagnetic Compa­ tibility) requirements. The ADM2xxE product line is the indus­try’s first family of robust, RS-232 and V.28 interface tran­ sceivers which provide ±15kV of ESD (ElectroStatic Discharge) and ±2kV of EFT (electrical fast transient) protection. Designed for modems, printers, lap­top and notebook comput­ers, the devices offer low EMI (electromagnetic interference) emissions in accordance with EN55022 and provide compliance with the IEC-1000-4-x immunity standards. These standards must be met for all electrical or electronic equipment carrying the “CE” (Comm­ BassBox Plus $6.00 postage. Pay by cheque, Bankcard, Mastercard, Visacard. EARTHQUAKE AUDIO PH: (02) 9948 3771 FAX: (02) 9948 8040 PO BOX 226 BALGOWLAH NSW 2093 un­aute Europeene) mark sold into the European market after January 1, 1996. Operating from a +5V supply, all five devices come with latch-up protection and immunity to high RF (radio frequency) fields to allow for operation in unshielded enclosures and electrical­ly-harsh environments. The product line offers a variety of driver/receiver combinations and all devices are available in SOIC, SSOP and TSSOP packaging The ADM2xxE family offers a pin-compatible upgrade for existing, industry-standard +5V, RS-232 transceivers. Additional features include a low power consumption of 17mW, a guaranteed high data transmission rate of 230 kbits/second, a 1µW shutdown mode and operation over a temperature range of -40°C to +85°C. For further information, contact Hartec, 205A Middleborough Road, Box Hill, Vic 3128. Phone 1 800 335 SC 623. November 1996  81