DCNV-440 HIGH DYNAMIC RANGE
DOWNCONVERTER FOR 440 MHz

This ATV downconverter will enable reception of ATV signals in the 70 cm. 420-450 MHz amateur band, using an ordinary TV set or monitor tuned to VHF CH 3 or CH4. It uses a passive Schottky balanced mixer and is intended for applications in strong signal areas. This feature is useful in metropolitan areas where high level RF signals are present. The circuit operates from a nominal 12 volt supply (11-15VDC), negative ground, at about 27 mA. It has an overall gain of approximately 25 dB and a NF of 2 dB or less. Input impedance is 50 ohms nominal, and the output impedance is 75 ohms to match most TV sets or monitors. The circuit consists of a tuned dual gate MESFET RF stage, a double balanced schottky diode mixer, and an IF stage at 60-72 MHz (CH3 or CH4). A varactor tuned LO stage is used in conjunction with a built in tuning potentiometer for continous tuning over a 30 MHz frequency range. A zener diode regulator is used to stabilize the LO against supply voltage variations.

The use of a MESFET RF amplifier, three tuned RF circuits, and a high level Schottky diode mixer allows good strong signal performance. The downconverter is linear with up to 5-10 millivolts RF input signal. The circuit board is compact (2.5" X 4.0") and matches our 2W transmitter board sizes. The tuning potentiometer can be mounted in two different configurations, which allows flexibility in packaging. The downconverter can be used alone or in conjunction with one of our transmitters to make up a 2-way ATV station transceiver.

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.

AVAILABLE EXTRAS:

• Hardware Package All connectors (power, F, BNC), switch, wire, LED, fasteners, and spacers for mounting in typical enclosure.
• Case NC531
• IF44 Video IF
• Complete Case Package

April 24, 2008