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Thursday, 06 May 2010


The audio processor uses high gain, high impedance circuitry. It must be mounted in a shielded enclosure to avaiod hum pickup.

  • The mounting holes in the PCB are spaced to fit the base of Astatic D-104 microphones.
  • Alternately the processor can be mounted in a 2" X 4" diecast aluminum box.

The processor requires 8 to 15 volts DC at 20 mA. This is supplied by the class D transmitter or a battery can be used. The supply is connected between terminals +V and G on the PCB.

The audio output is designed to drive a load impedance of 600 ohms or higher. It can be plugged directly into the microphone input of most transmitters and even modern transceivers.

The input is high impedance (6.8 megohm) and can be connected directly to crystal or ceramic elements. The schematic diagram shows how to adapt the unit for use with electret elements.

If using the processor with a vintage transmitter, it is best to leave the transmitters mic gain control at it's normal setting and adjust the mod level control, in the base of the microphone, for full modulation. This will make A/B comparisons easier.


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