RadioBanter - View Single Post

June 16th 06, 02:19 PM posted to rec.radio.amateur.antenna

wrote:
Corona comes from a charge difference between two things.

No, that's not complete. A charge difference is necessary
*but not sufficient* to cause corona. Corona comes from a charge
difference between two things that causes ionization of the air
around/between the two things. Corona, in the electrical sense
that we are using the word here, doesn't exist and cannot exist
without ionization. For this definition of the word, "corona",
my unabridged dictionary says, "7. Electrical: see corona
discharge".

In the web reference I posted yesterday, two charged spheres
arced before any corona was possible. Corona never existed
in that experiment even though arcing took place.

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.

Certainly white cars exist. That doesn't mean that all cars
are white.

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

Certainly corona exists. That doesn't mean the entire universe
is ruled by some Corona God.

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

For it to be defined as corona, it must ionize the air. How do
you prove that the air has indeed been ionized? At night, a
glow invariably accompanies corona ionization. Do your antennas
glow at night? Mine usually don't.

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.

"It" being corona, not clear-sky, dry-air, charged-particle
problems. Everyone agrees that corona exists, Tom. We just
disagree with you that corona is all that can cause a charge.
Is the 10 volt charge on a capacitor caused by corona?

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.

Most of the time doesn't cut it, Tom. All it takes is one
example to the contrary to prove your all-inclusive assertions
to be false. Not all cars are white just because you have never
seen a colored car.

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.

That may be true, but the question is: Do charged particles
hitting an antenna ever cause static discharge problems. If
it has ever occurred even once in history of this planet,
your assertions are wrong. It occurred in my antenna system
multiple times while I was living in the Arizona desert. There
was not a cloud in the entire state at some of those times.

According to the web source I posted yesterday, arcing can
completely eliminate corona because the arcing occurs *before*
the corona can possibly occur. The example given was between
two spherical electrodes. The corona example involved a
pointed electrode which caused corona to occur before the
arc.

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

I think you should stop worshiping the Corona God, go
out to Queen Creek, AZ and perform your experiments.
Please prove that every dust particle carries a charge
identical to the charge on every antenna.

You remind me of the host of scientists who believed that
the earth was never bombarded by meteors and comets
because they couldn't see more than a handful of impact
craters.

You can run the experiment for yourself, Tom. Set up an
inverted-V dipole and discharge a capacitor at one end
between one element and a ground plane. Guaranteed, you
will hear the noise in an RF receiver when there's no
sign of corona anywhere.
--
73, Cecil http://www.qsl.net/w5dxp