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Since I haven't done any research on Phono Oscillators, I can
only assume that they were simply used to connect phonograph players to radios. For those not wanting
to modify their radios for a direct phono input connection, this was the easy way to go.
The oscillator on this page is based on the 1939 Zenith S-7000 series, but a few additions and changes have
been made to the original "transmitter" circuit. (Both schematics are attached.)
In the late 50's and early 60's, many young boys used a similar version of this wireless broadcaster to
play DJ, and broadcast music to nearby homes. I was no different.
 The one I used was sold in kit form by Allied Radio/Knight Kit.
(Lafayette also sold one that was a very similar design.) The "radio station" was professional (?)
with dual turntables and a real microphone. I can still remember pulling the weather report from the
daily newspaper, and running upstairs to check the latest temperature.
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This radio is simple to build, and works as expected for its
intended design. It won't blast a signal around the house, but it will give good audio on nearby
receivers. Since this is a simple oscillator, it does transmit harmonics, so don't use this stock
version connected to any outside antenna. Limit your antenna wire to about 9 feet, and keep it close
to the target receiver.
I've seen three versions of the Zenith phono oscillator. Two were mounted on a wood chassis
(including mine), and one was mounted on a metal chassis. Mine was actually a shipping container for
candles. It seemed a shame to dump it in the trash when I could put it to good use. What you
don't see in the picture are three strips of wood added to the top of the box. This gives the top
some added strength and a nice inlaid look.
One word of caution. Always be aware that lethal voltages are present on tube gear. Always
unplug the radio and check for stored voltage from the power supply capacitors before attempting to service
the transmitter.
Joe
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