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Old June 28th 06, 08:34 PM posted to rec.radio.amateur.antenna
chuck
 
Posts: n/a
Default Noise level between two ant types

Cecil Moore wrote:
Gene Fuller wrote:
OK, energy exists, and it is even conserved.
Do you feel better now?


That's a good first step. Now where does the energy come
from that supports corona under fairweather conditions?


If the antenna is a vertical,
ungrounded, uncharged wire, it is a
conductor in an electric field (the
fairweather field).

The free charges in the antenna will
move so as to cancel the fairweather
field inside the antenna wire.

At the top of the antenna, there will be
a concentration of negative charge. If a
single strand of wire sticks out, that
concentration could be sufficient to
ionize the air and cause corona.

If the corona starting voltage is
typically 30 kV/cm radius, then a tiny
wire could ionize the air at only
300volts or so for a 0.01 cm radius.

http://home.earthlink.net/~jimlux/hv/corona.htm
Corona

Based on that, it would seem the
fairweather field can support corona
formation by itself.

If a charged particle now strikes the
uncharged antenna, free charges will
redistribute themselves to maintain no
net electric field inside the conductor.

The antenna's charge will increase until
it exceeds some breakdown threshold.
This process seems functionally similar
to that due to the existence of the
fairweather field, although either could
exist independently.

The question then seems to be whether
the redistribution of charges that
occurs when charged particles strike the
antenna causes a current in the antenna
which is detected by the receiver as
noise. I believe this is the question
Cecil has been posing.

It occurs to me that the current due to
charge redistribution could be rather
significant if numerous particles are
striking the antenna in a short time
interval. Even a corona discharge will
cause a redistribution of free charges
that may show up as a detectable current
at the receiver. This would be a
different effect from the noise
generating property of the corona itself.

Any thoughts?

Chuck

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