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Old June 16th 06, 01:23 PM posted to rec.radio.amateur.antenna
 
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Default Noise level between two ant types


Tom Ring wrote:
The earth is one terminal, the air and things in the air (like clouds)
have a charge difference.


So this is an inverse form of corona? Where it comes from the
surrounding charged air and particles (whatever type they are)? Because
it's not the form I'm familiar with where the end of the antenna has a
high voltage on it.


I don't understand that Tom.

What is "inverse corona"?

Corona comes from a charge difference between two things. In this case
it is NOT a charge difference between the earth and the antenna that
you could eliminate by shorting the antenna to the earth, it is a
difference between the air around the antenna and the earth and things
connected to earth. The corona is leaping off into space around the
antenna, not back towards earth. Tying it to earth will only make it
worse, not better.

I am genuinely asking a question here. If this is the way that noise
occurs, I'd like to know the physical method involved.


In every case I have looked at, and I have looked at dozens very
carefully, it has been corna off the elements. That corna (and the
resulting noise) occurs when there are particles, when there aren't,
and at a rate different than the rate of particles hitting the antenna.

It occurs with radomes and insulated elements and without, it occurs
with grounded elements and without.

It increases with increasing height, especially compared to surrounding
objects. It is worse with protruding sharp points on the elements.

It is worse when the charge difference between earth and sky is
greatest, and less when the charge difference is less. It is terrible
when lightning is almost ready to strike. It often vanishes totally for
a brief period after a ground to cloud lightning strike.

Of course a book, especially a handbook, might say it is something
else. But then what they say should fit what occurs most of the time if
what they say is mostly true.

In my experience, and I probably have much more than most people with
this after changing dozens of antennas to try to eliminate this
problem, the idea the noise comes from an element "charging" or from
particles hitting the antenna is largely incorrect.

I think that idea comes from reading and believing wive's tales and
rumors, and not thinking and experimenting for oneself.

73 Tom

 
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