The DCNV-900 is a basic RF downconverter system that is designed to convert television or other wideband signals in the 902-928 MHz (33 centimeter) range to a 61.25 or 67.25 MHz IF output frequency (CH3 or CH4) to enable reception of these signals on a standard VHF TV receiver or monitor. It features a low noise RF amp feeding a mixer transistor, a tuneable LO, and a feedBack pair IF preamp stage. The RF amplifier is a low noise dual gate MESFET that is followed by a mixer stage stage using a UHF bipolar transistor. Three tuned circuits are used in the RF amplifier. These are of stripline construction for ease of reproduction. The on-board local oscillator (LO) is voltage tuned and is tuned by either an on-board potentiometer or via the coax fed DC tuning and supply voltage. All necessary circuitry for remote tuning is on-board for coax DC and IF feed. This enables the downconverter to be mast mounted to avoid feedline losses generally associated with this frequency range. No separate DC feed is necessary since the coax (RG59/U or RG6/U recommended) carries both DC power, tuning voltage and IF signal. A DC block can be used at the receiver for the purpose of separating the DC voltage supply and the tuning voltage. This allows a cable run of several hundred feet if needed. Input impedance is 50 ohms and a suitable 900 MHz antenna should be used.
For on-board tuning the potentiometer may be used. The LO is voltage tuned and is fed from a voltage regulator IC. The downconverter PC board has the same footprint as our 440 MHz and 1300 MHz models and matches our 900 MHz ATV transmitter in physical size. The power supply requirements are 11 to 20 VDC at approximately 30 milliamperes, or a variable supply from 11 to 20 volts for combined DC and IF feed on a single coaxial cable for remote tuning. Overall gain is 35-40 dB nominal with >30 MHz RF bandwidth and tuning range when set up for 902 to 928 MHz operation. This downconverter is not intended for reception of narrowband FM or SSB signals since it uses a tuneable L.O.
This downconverter can also be combined with our IF44 Video IF which will produce baseband video and line level audio output if this is preferred. Both of these units can be mounted in our NC1575 Plastic case to produce a complete video-audio receiver unit.
By using this downconverter and the ATV12-915 transmitter, a physically small 900 MHz ATV station can be constructed, since both units are each 2.50 x 4.00 inches x 1.00 high, and can be stacked together. A small PC board camera, battery pack, relay, and a pocket TV receiver can be used with these units to make a very compact portable ATV station. 900 MHz antennas can be small and lightweight. Construction is rather simple and the downconverter is aligned simply by peaking for maximum received signal with no tricky alignment procedures or specialized RF test gear necessary for good results and performance.The kit can be easily assembled in two to four evenings, depending on experience. There is some small work so suitable tools should be available. Some experience is assumed, but the average electronic hobbyist will have few if any problems. Some familiarity with RF circuitry is assumed.
Price $52.00 USD plus Shipping and handling (See Order Form)
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NORTH COUNTRY RADIO
PO Box 200, Hartford NY 12838-0200