To answer Ray’s questions from a few days ago regarding the AT-1 (12 volt) and AT-7 (24 volt) transmitters:

• Tuning range is 1.5 – 5.0 MHz on Channel A and 5.0 – 20.0 MHz on Channel B. In addition, the transmitter originally came equipped with internal crystals for operation on 375 and 500 KHz (Channel A only). The purpose of 500 KHz is obvious; 375 KHz was used for obtaining a DF bearing. Crystal control or variable frequency control could be selected for the entire HF range.
• The AT-1 transmitter was paired with the AR-2 receiver and the AT-7 was used with the AR-6 receiver. Receiver tuning range is 140 – 400 KHz & .48 – 21.0 MHz. The receiver also included RDF and aircraft intercom circuitry.
• The transmitters have CW/MCW/AM capability. The “NOTE” switch seen on the right side of the front panel selects the audio frequency on MCW and the sidetone heard when using CW.

Both receiver and transmitter can operate under local or remote control. The transmitter has a heater in the oscillator compartment and according to one manual, “Its purpose is to remove hoarfrost .......during extremely adverse conditions of operation” .

The RCAF used these radios in a variety of aircraft, some sources have suggested they were also used as temporary installations in new aircraft being flown from North America to Britain. The fact that many have turned up in the US northeast in original transit cases would seem to support this. I would welcome any further information. At one time, the Overbrook Company in Wellesley, Massachusetts had enough of the receivers to warrant publishing a partial manual. There is also a US military manual for the receiver (T.O.No. 08-45-26) and I believe Robert Downs also has the corresponding one for the transmitter.

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