This is slightly off topic but last night on PBS there was a show called
"Rough Science" that showed a bunch of attractive young scientists "stranded"
on an island off Grenada, "Survivor"-style, and their challenge was to make a
transmitter and receiver out of wire, some screws, a rusty razor blade and
lump of coke (coal) for crystals, and a car battery. Fortunately they found a
high-impedance earphone on their desert island :-)
Anyway, they were able to fashion a basic spark transmitter (overlay on the
screen said "Don't try This At Home!") and a crystal receiver using the lump
of coke. The rusty razor blade didn't work as well.
The point is that the radio signal you are receiving is probably a product of
a rectifier-radiator circuit that could be formed from just about anything. I
would doubt it's the N-teenth harmonic of a radio station unless the radio
station is really close or badly run - you would receive the harmonic fairly
clearly. With line noise present in it could be the result of some rusty old
power line hardware. I would track it down using the same techniques I'd track
down power line noise.
-Wiley KF6IIU
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