[TowerTalk] Rain static

[Jim Lux]

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.