Drake TR-22

The Drake TR-22 is the exact same radio as the Trio / Kenwood TR-2200. It's a 1W FM-only VHF (144-148 MHz) portable transceiver with six crystal-controlled channels and a pull-out whip antenna, introduced in 1974.

I don't think there was ever a TR-22B but there is a TR-22C, which has 12 channels and seems to be similar if not identical to the Trio / Kenwood TR-2200G.

It's a fairly simple circuit. One of 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 an 11.115 MHz signal (the TR-22C uses 10.245 MHz here) 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.

The only to me interesting thing in this rig is that it has a built-in transformer to charge the batteries from mains (most rigs would use an external 12V supply or something similar). The only problem is that as far as I can see it will be either a 220V transformer or a 110V transformer -- there's no line voltage switch. So it's wise to check which is which with a rig of unknown provenance.

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

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