When I first saw this ad from the Popular Electronics issue from 50 years ago this month, July 1966, I was amazed that they had achieved such a level of miniaturization, until I looked closer.  This is an ad for the Model MO-23 CB radio from International Crystal, which was so compact that it could hide under the dash, in the console, or in the glove compartment. As you can see, the radio isn’t much larger than the microphone.

Closer examination reveals that only the control head is inside the car. As with most two-way radio equipment of the 40’s through 60’s, the guts of the radio was in the trunk. The ad notes that “technically speaking, the MO-23 combines the best advantages of tubes and silicon transistors,” since the control head and power supply were transistorized, but the actual transmitter and receiver used tubes.

At least one example of this radio made it to market, since I did find this e-bay listing for one.  It shows the trunk unit, with at least nine tubes. Three transistors mounted at the back are probably part of the power supply to convert the car’s voltage to the B+ required by the tubes.

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