: For a while I was thinking it could be lightning, but lightning bursts
: are much longer and don't continue into the higher frequencies.
I have a mobile RFI setup and monitor pole noise from 300-520 Mhz in AM on a
Yaesu FT-7900. Many times this Summer I have seen the strike and heard the
noise across this range. Most recently was during a demonstration of
finding
power poles producing RFI on a road in the hills. Strikes could be seen,
and heard, around 520 MHz across the valley below, a distance of about
fifteen miles.
You mention a range of several hundred feet. You might notice a lightning
strike every few seconds within that distance so I'd feel pretty safe ruling
that one out.
Hard to tell this one by the description, electric fences are more
consistent time-wise, although, there's no telling how a charger may react
with grass or branches on the wire. Could be a thermal switch on a device,
a water
heater, electric blanket, tank heater, water-bed heater or door bell
transformer. I've heard a couple of stories about battery conditioners
causing erratically timed wideband noise every few seconds depending on
battery condition but have yet to have one in my hand to verify.
Kurt
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