Drake TR-22C

aka Trio / Kenwood TR-2200.

WB4HFN has the User Manual for download.

It's a fairly simple circuit. One of 12 crystals is selected to generate the carrier frequency at around 12 MHz. This carrier is phase modulated by a dedicated microphone amplifier and doubled, tripled and doubled again to get 1 W at 144 MHz. There is an RF sniffer to measure forward but strangely not reflected RF power.

Similarly the receive crystal is selected and the carrier frequency is tripled and injected into the mixer 10.7 MHz lower than the desired frequency. The first IF is mixed with a 10.245 MHz signal to get to the second IF at 455 kHz. A ratio detector is used to extract the audio which is amplified after some more filtering.

The receive chain has some bells and whistles hanging off it -- there's an S-meter rectifier in the middle of the 455 kHz amplification path and squelch is extracted from just after the ratio detector, amplified by two transistors, rectified and used to mute/unmute the audio stage.

Rx frequency = Rx crystal * 3 + 10.7
Tx frequency = Tx crystal * 12

[Image] Hit Count hits since 2015-01-02.

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