Seventy-five years ago this month, the March 1942 issue of Popular Mechanics carried a construction article for this portable phonograph oscillator.  Mounted in the always available cigar box, the one-tube record player used a 117L7-GT tube to produce a signal that could be tuned in on any nearby radio.

The tone arm could be removed when not in use, and plugged in with two phone tip plugs to hold it in place and make the electrical connection.

Since the phono oscillator only required one tube, and didn’t need an expensive speaker or transformer, they were quite popular for playing records for those who already had a radio.

For use right next to the radio, no external antenna was required.  For a bit more range, a short piece of wire could be added.  The coil inside was wound on a one-inch piece of cardboard, and a variable condenser could be tuned to a blank spot on the dial.