Dear Tom:

It appears that two noise mechanisms exist. The two are P-noise and
corona noise. A receiver will experience close to white noise in both
cases. However, corona noise tends to be accompanied by sudden stops and
starts and P-noise starts with a sequence of perceptibly time spaced pops
that increase in rate.

If there is corona off of the top of a structure then it is reasonable
to expect the antennas most close to the corona will "hear" more noise than
the antennas that are farther away (such as below).

It is also to be expected that moving charged particles that are higher
above the ground will carry more charge on the average than charged
particles that are moving near the ground. Depending on the wind and
gradient, I expect that there is a height below which few charged particles
are found when higher above ground charged particles are common.

In short: If one can see corona, it will be the dominate noise source.
If the gradient with altitude is not sufficient for corona, and weather
conditions are such that moving charged particles exist, then out in the
open the higher antennas are expected to have more discharges from moving
charged particles per second and more noise than experienced by lower
antennas.

I have offered an alternative explanation for why, absent corona, higher
antennas might well experience more noise.

Actual precipitation (rain, snow, hail) is not needed for P-noise.
Moving dust particles can carry charge and become charged. The noise does
follow the "pattern of the particle rate." However, as you understand from
other work, when the rate becomes high enough compared to the bandwidth of
the receiver the result is essentially indistinguishable from white noise.
Even with a 400 Hz bandwidth, the onset of P-noise is unique and comprises a
sequence of pops that either die away or increase in rate to produce
prodigious amounts of noise. I have used a time blanking circuit - noise
clipper - and find that it is effective at lower rates. Corona noise does
not seem to have the same temporal characteristics.

A moving charged particle is able to discharge into an insulated
conductor with aplomb. It is the very-close-to-the-antenna sudden
accelerations of charge that produce noise (radio waves). What has shown
promise is the use of slightly conductive coverings. The theory is that the
amplitude of the pop will be reduced because the rate of charge transfer
will be slowed. UV resistant materials that are easy to apply and that are
not expensive seem not to exist. Obviously, too much conductivity would be
ineffective.

Absent actual corona, a noise mechanism is contended that comprises the
sudden transfer of some or all of the charge on a moving charged particle
(that occurs naturally) into an antenna's structure, support or even into
insulation around same.

A near optimum, HF, DX, low-noise receiving antenna is a small,
horizontal, unturned loop antenna with an amplifier that is mounted on a
wood pole having no metal inserts. The pole is some 200 meters from any
exposed metal. The coax that runs up the pole to the amplifier is encased
in conductive, plastic conduit as is the loop's wire. This antenna has
close to a null at the zenith and is omnidirectional in azimuth.


It is contended that what I have observed is not in conflict with what
you have observed with corona discharges. 73 Mac N8TT

P.S. Some months ago you asked about V antennas for low HF or MF use
involving a 300 foot tower. I found that an interesting topic and did some
analysis, which I tried to sent to you. Unfortunately, the E-mail address
did not work. My conclusion, was, as well as I am able to remember, the
same as yours: at the low frequencies involved, the effort did not have a
reasonable pay-back.
--
J. Mc Laughlin; Michigan U.S.A.
Home:
wrote in message
oups.com...
J. Mc Laughlin wrote:

P-noise is not found on an antenna imbedded in a clump of trees when
an
antenna out in the open (many wavelengths from the first antenna) has
P-noise. The follow-on is that since most sites are urban or suburban,
few
radio amateurs will experience P-noise.

That does not disagree with anything I said. A lower antenna surrounded
by taller objects is not subject to the same high voltage gradient as
an antenna out in a flat clear field.

P-noise is observed when there is no rain nor thunderstorms, but
plenty
of wind. This is suggestive of moving charge discharging into the
antenna.

So how does it get there? How does it build up? Where is the spark arc
or sizzle?

Of course, one could define this action as being "corona." Of course,
if
one places enough charge on a piece of metal eventually there will be
"corona." Many antennas have a conductive path to earth that makes such
an
accumulation of charge unlikely.

The fact is grounded or ungrounded antennas all behave the very same
way. Ask anyone who has yagis on towers. It is a potential difference
between earth and the atmosphere around the antenna. It isn't the
antenna charging up so much differently than earth. It is the
difference in potential between the antenna and the space around the
antenna.

Remember those old tall mast wooden sailing ships soaked with sal****er
and the fire off the yardarms at night?

Your #6 is interesting. Unfortunately, there is so much radiation
from
what else is on a tall building that it is difficult to sort out where
excess noise is coming from. An antenna inside of a slightly conductive
radome that is placed a long distance from anything that could radiate
might
be different.

You can walk right up to the noise source, and even see the corona at
night. It's very easy to take a FSM with audio monitor or AM receiver
with S meter and walk the roof for strongest noise, and it will
generally take you right to the tallest sharpest object (grounded or
not) on the roof.

The last place you want to be is the tallest antenna on the building.
Get high winds or inclement weather and you will be destined for
noise....grounded antenna or not.

We serviced dozens of repeaters and a few STL or Remote links in the
70's, it was a pattern that repeated.

I have a suggestion. Go to a forum where there are many people with
antennas at various heights, like a contesting reflector. Ask people
who have similar or identical antennas at various heights on a single
tall tower what they observe during high winds, nasty weather, or rain.
The very same wind and the very same moisture is impacting all of the
antennas, but without fail they will tell you the lower antennas are
always much better and the taller antennas are the first to go.

If the P-staic is actually coming from the particles or moisture in air
striking the antenna, and if the same basic sample of weather is at all
the antennas, why are the upper antennas affected more?

If it is the conductor charging, why do plumber's delight antennas or
folded elements with grounded centers have the same noise as insulated
elements?

If it is moisture or particles striking the antenna causing the
problem, why is an insulated antenna with a single sharp protrusion
just as noisey as a bare antenna? Why doesn't the noise follow the
pattern of the particle rate, and why does it occur (as you even seemed
to say) when there is no actual precipitation?

Since I've always had towers taller than 100 feet, and since I've
worked on VHF and UHF systems that had to stay up during storms, I've
spent a lot of time looking at this. I've not found anything that
points to the antenna charging differently than earth or being struck
by charged particles.

73 Tom