> Well Tom, I have never thought about this much, but now
that you are
> making a point of it, I am very curious. I have been
waiting for someone
> to jump in and explain this, but so far no takers.
This actually has been discussed several places over the
years. My opinion was formed from contributions people made
in those discussions as well as through my own observations
and experiments over the years.
> Could this be a real justification for the use of
porcupine balls? Or
> would that just make it worse because there is more corona
with the
> balls, even though it would be located not on the elements
but close by.
We pointed directional antennas at tall or sharp objects.
They clearly were radiating noise.
For example?
The only cases of Beverage noise I have are with Beverages
near or aimed at my towers. At this location I have
virtually no noise at any time from Beverages, but my
antennas are at least 500 feet away from my towers and only
antennas over 2000 feet away point towards the towers. The
intensity of noise from those antennas is what should be
expected from coupling measurements of RF, and any small
noise that is heard comes from the direction of tall towers.
When we were looking to cure VHF noise that disrupted
communications systems with antennas on tall buildings or
towers, it was *always* the antennas that were highest that
had the most noise. As a matter of fact side mounted VHF
antennas were rarely disrupted by noise during storms or
inclement weather despite being hit by the same moisture.
Anyone who has ever been on a tall tower or building during
conditions that cause the receiver noise probably has heard
sharp points producing noises. If you have a portable
receiver you can walk right up to corona sources on building
roofs.
We greatly reduced "precipitation static" noise in a system
on one building by installing a tall flag pole with a
rounded ball (metal toilet tank ball) on top. The last
thing you'd want to do is put something that intentionally
generates streamers near a receiving antenna. My opinion is
spiny balls do nothing at best, and if they do anything they
are probably harmful since the corona they generate would
only increase site noise. Any noise reduction would come
from a protection cone effect that reduced corona from an
antenna, not by the fact we install something that
intentionally generates corona.
Personally, I've never seen a system where noise clearly
tracked the rate of charged moisture hitting antennas. I've
seen dozens or hundreds where it doesn't.
I even attempted to simulate the noise by charging a stream
of water using a system that I used for electrostatic
painting. No success.
This doesn't mean there can't ever be a case where the
charged particles don't produce noise. It does mean there
are many repeatable common cases where the noise doesn't
come from charged particles contacting the antenna.
73 Tom
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