I recently bought a Westinghouse GP-7 transmitter in the swap meet at this year’s annual West Coast Military Radio Collectors Group meeting, held in San Luis Obispo, CA at the beginning of May. This transmitter was made for use in Navy aircraft, and it requires 120 VAC 800 Hz power like other Navy radios of its era. Aircraft commonly use AC power at higher frequencies than our common 60 Hz “wall power” so that their transformers and motors can be lighter. The higher power frequencies allow transformers and motors to use less massive iron cores without magnetic saturation. 400 Hz power is now commonly used in large aircraft that require AC power supplies, but this transmitter was made before 400 Hz power became the standard. Unfortunately, it can’t simply be plugged into 60 Hz power. That would saturate the transformer cores, and then they would release their magic smoke and stop working.

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