One reason that high antennas might have a worse problem than low ones (and
why airplanes have really bad problems) has to do with the charging rate.
The charging rate is strongly affected by how many particles hit the object
in a unit of time. The higher antenna is subjected to more wind, so more
particles hit in a given unit of time (because the antenna "sweeps" a
larger volume of the air containing the particles). An airplane is not
only moving a LOT faster, but it's big and solid, so has much more cross
section to do the intercepting.
There IS another factor in the works too.. Part of the field that will tend
to cause the breakdowns will be from the earth's E field. The corona occurs
when the field at the surface gets above 3MV/meter. For a small diameter
point, say 1mm in diameter, this is only a few kV voltage, and some of that
voltage might come from "induction".
The other aspect is that it might not be the antenna that's doing the
discharging, but the tower next to the antenna, and the antenna is just
picking up the noise. When I've heard audible corona buzz, both in HV
systems and in lightning, there haven't been any antennas near.
So, whether the antenna is grounded or not might not make any difference
(or it might.. it all depends on where the discharges are taking place).
What to my ears is a several hundred hertz buzz, after filtering through a
narrow band audio chain (i.e your receiver) might be much more musical,
especially if it were, for instance, at more than 1kHz, so the harmonics
are out of band.
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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