On Nov 27, 1:30*am, Tim Wescott wrote:
I don't have a lot of reference material to look at, but I don't think
that using a crystal's overtones to generate RF really picked up until
the 50's (it was probably done during WW-II, but I only see it put forth
as a common method starting with my '50's ARRL handbooks).

In 1930's QST's it's not too uncommon to see neophytes warned that
crystals will often oscillate on something other than their marked
frequency. They didn't call this overtone operation, though.

BC-604's (WWII era) start with a ridiculously low crystal (400ish kHz)
frequency and multiply up but I think the reason for this is more to
do with FM deviation than anything else. ("Armstrong method"?) For
many decades, broadcast FM stations similarly started with low crystal
frequencies and multiplied up.

Tim.