The Universal Communications Mhz Downconverter Kits

Coffee cans, snow scooters, and stop-sign-shaped PC boards In every direction. That was the general situation when a group of friends and I recently purchased a number of the 2100-MHz downconverter kits from Universal Communications. These MDS, or pay-TV, converter kits were advertised in 73, and they seemed like an ideal way to try the rapidly growing frontier of microwave TV. We were not sure exactly what we were getting into, but the enticement of unique movies was definitely an incentive!

! won't elaborate on our phone-order difficulties, but it soon became apparent that we were in a plleup with the rest of the U.S. in trying to place our order. Fortunately, we got through on the third day of trying, 'he downconverter kits an rived COD three days later. Fasti The Universal Communications kit consists of the PC board, all associated board parts, a short length of hardline coax which is used for the antenna, and very good instructions/information on microwave techniques.

Construction began (immediately'} by winding three rf chokes on supplied resistors, then mounting all the components on the PC board. The board was then tack-soldered onto the back {bottom) of a one-pound coffee can, with the hardline coax routed through a small hole into a whip antenna. This arrangement provided an approximate 11-dB gain over the basic whip, and perfectly mated the PC board to the coffee can. This one particular trademark, we later teamed, is what sets Universal Communlcafions' boards apart from its com-petttors1.

Finally, the local oscillator's stripline was trimmed to the desired frequency range (a cutting chart was included) and a coax output cable was connected. fThis single line feeds dc voltage to the converter white also feeding converter output to the TV set. Varying the voltage remote-controls downconverter tuning.) Alt six of us sequentially used a borrowed 0-to-16-volt power supply for checkout, and five converters worked the first time. The sixth unit was cleared soon thereafter, with simple soldering techniques being at fault. Each of us then modified existing 12-voit regulated power supplies using Information supplied in the Universal Communications packet,

A day later, we were into studying rmcrowave systems, components, and gain-improving techniques for fringe-area setups. Several nearby residents mysteriously lost their shiny, new garbage can lids around this lime, then we found a tocal source of "snow scooters" and gain flourished. The "snow scooter." or "snow coaster," is an approximately three-foot, paraboiicly-shaped dish which, when fitted with struts to support the coffee-can setup, provides approximately 18 dB of gain—and relatively good picture reception compared to the basic coffee-can or garbage-can-1 id setup. Our personal observations revealed that previous pictures with sustantial snow were improved to almost snow-free quality, and each additional improvement of approximately one dB made further substantially noticeable improvements.

Gain improvement at these microwave frequencies, however, is slow in happening: A larger dish heips; a higher-gain rf amplifier also heips. (Universal Communications also sells these transistors for $15, and they are definitely worth it, unless one can wrangle a very high-gain/low-noise 50- or 75-dollar equivalent.) We also found that adding extra lengths of parallel conductors to the Universal Communications PC board capacitors and using low-noise microwave diodes provid-

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Sabtronics 8000b

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Three selectable gate times provide the measurement speed you need — and greater resolution. Fl he resolution is further enhanced by our counter's 9-digit display.

Like the 8000B, Sabtronics1 8610B is a high-quality precision frequency counter. It features only 4 ICs, and offers a frequency range up to 600 Megahertz.

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Frequencv Range: 10 Hz to 1 GHz

(Model 8Ö00B), 10 Hz to 600 MHz (Model 8610B); Timebase: Frequency: 10MHzt Stability: ± 1 ppm (20 to 40C°.), Aging Rate: < 1 ppm/vear; Sensitivity (adjustable): Input A< 15 mV to 100 MHz, Input B < 30 mV, 100 MHz to 1 GHz (Model 8000B), < 30mV, 100 MHz to 600 MHz (Model 8610B); Gate Times: .1 sec, 1 sec., 10 sec.; Resolution: 0.1 Hz to 10MHz, 1 Hz to 100 MHz, 10 Hz to 1 GHz; Display: 9-digit LED 0.4"; Power Requirements: 4.5 to 6.5 VDC (4 C-cells) or optional AC adapter; Dimensions: 8" wide X 6.5" deep X 3" high (203 X 165 X 76 mm), 1.3 pounds (590 g) excluding battery.

Making Performance Affordable

Making Performance Affordable



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