There seems to be a number of commercial antennas
described as H-field antennas intended for LORAN
application. Most claim improved immunity to
precipitation static. Is there a theoretical basis
for such claims?


Yes. It increases sales just like zoom zoom zoom in car advertisements.

Seriously, precipitation static is caused by corna discharge from an
antenna or object someplace near the antenna. The radiated field from
that leakage current can be almost any field impedance and will always
be a mixture of time-varying electric and magnetic fields.

What a small loop actually buys you is a compact antenna that has no
sharp protruding edges, and that decreases the chances of having corona
right from the antenna. A whip would have a sharp protruding point, and
that would encourge corona discharge and the resulting noise we call
"precipitation static".

Other than that, there is no advantage.

73 Tom

wrote:
There seems to be a number of commercial antennas
described as H-field antennas intended for LORAN
application. Most claim improved immunity to
precipitation static. Is there a theoretical basis
for such claims?


Yes. It increases sales just like zoom zoom zoom in car advertisements.

Seriously, precipitation static is caused by corna discharge from an
antenna or object someplace near the antenna. The radiated field from
that leakage current can be almost any field impedance and will always
be a mixture of time-varying electric and magnetic fields.

What a small loop actually buys you is a compact antenna that has no
sharp protruding edges, and that decreases the chances of having corona
right from the antenna. A whip would have a sharp protruding point, and
that would encourge corona discharge and the resulting noise we call
"precipitation static".

Other than that, there is no advantage.

73 Tom


I think the precipitation static talked about is
caused by the accumulation on the antenna of
charges carried by precipitation particles (e.g.,
snow). Apparently this is a common problem on
aircraft antennas, and hence the interest in LORAN
antennas with better immunity to the accumulation
of precipitation charges.

Doesn't sound like a simple antenna geometry issue
and it doesn't sound like a corona issue.

Which is not to say it isn't all hype, but
wouldn't the charge on the antenna simply
redistribute itself over the body of the aircraft
(assuming it is metal) and not accumulate on the
antenna as it would were the antenna insulated
from the aircraft body?

Chuck

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On Tue, 06 Jun 2006 20:49:54 -0400, chuck wrote:
I think the precipitation static talked about is
caused by the accumulation on the antenna of
charges carried by precipitation particles (e.g.,
snow).

Hi Chuck,

Snow, rain, dust, soot, anything airborne which in fact is the
principle carrier of current from earth to air in the current cycle
that feeds the electrostatic potential of lightning clouds (which
amounts to about 600 V/m).

wouldn't the charge on the antenna simply
redistribute itself over the body of the aircraft
(assuming it is metal) and not accumulate on the
antenna as it would were the antenna insulated
from the aircraft body?

Charge moves to the smallest radius surface, and once there, if there
is sufficient flux will break down insulators (air being one) and
arc-over (corona discharge). One solution is to reduce the number of
small radius surfaces (pin-points) and loops qualify (vastly larger
radius than a monopole tip). However, and at altitude, if the loop is
in fact a square, then the corners are prone to discharge. HCJB
antenna design tested this at altitude in Quito, Ecuador and they
solved it by moving the feed point so that the high potential fell in
mid-span, instead of at the corners. Auto manufacturers also had to
contend with the problem, they put small round caps on the ends of
their car antennas.

73's
Richard Clark, KB7QHC

Precipitation static, eg., from highly charged raindrops and fine snow
or fine sand, impinging on the antenna wire, just causes an increase
in receiver white noise level. It can be reduced but not removed by
using a very thickly insulated antenna wire, like the inner conductor
of a coaxial cable complete with its polyethylene jacket.
----
Reg.

Reg Edwards wrote:
Precipitation static, eg., from highly charged raindrops and fine snow
or fine sand, impinging on the antenna wire, just causes an increase
in receiver white noise level. It can be reduced but not removed by
using a very thickly insulated antenna wire, like the inner conductor
of a coaxial cable complete with its polyethylene jacket.
----
Reg.

I've never seen a case of precitation static occuring that way.

In every single case I've seen, whether on tall buildings, tall towers,
or antenna hear earth, it has always been corona discharges from the
antenna or objects near the antenna.

How do I know this?

1.) I had side by side "insulated" and "unisulated" Beverage antenna
wires that are otherwide identical except for being spaced a few dozen
feet apart, and the antebnna pointed towards my tall towers had precip
static and the others did not. Both were equal in noise despite the
fact they are hit by the same rain or dust.

2.) I have Yagis on towers that are identical, and the LOWER antenna
almost never has precipitation static despite the fact they are hit by
the same rain or dust.

3.) I've had dipoles at various heights, and the lower dipole always
has much less precipitation staic than the high dipole despite the fact
they get the same rain or dust.

4.) The period of the noise has nothing at all to do with the number of
droplets hitting the antenna. It increases in pitch as the charge
gradient between earth and clouds builds, then when lightning flashes
it immediatly stops without time delay.

5.) On tall buildings on dark nights in storms, we could actually hear
the same pitch noise as the repeaters rebroadcast, and walk to the
noise source and actually see the corona.

6.) Antennas in fiberglass radomes were no quieter than bare metal
dipoles on tall buildings.

7.) I even used an electrostatic sprayer to charge droplets and hit an
antenna, and could only simulate noise when the antenna element had a
sharp point and I got near the sharp point...at which time I could see
faint corona.

73 Tom

Dear Tom:
Your message may one of the most interesting and unexpected that I have
read in a long time. Some comments follow. Please note my extreme
reluctance to engage in anything but a calm exchange of experiences and
opinions. I have no interest in provoking you.

Your experience does not seem to agree with experience at remote, flat,
treeless sites here in Michigan. Please note the qualifiers in the last
sentence. Especially in the UP of Michigan, at certain times of the year,
P-noise is the major factor in limiting radio use.

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.

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.
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.

There is no doubt that an antenna experiencing P-noise will radiate and
thus noise will be received by nearby antennas. That is why successful
receiving antennas here in the flatland are placed a long distance from
metallic objects.

Most people have never heard P-noise because their site precludes same.

A paper published in August about 1961 (IEEE Vehicular Transactions) is
one of the few references that has been published that deals with means for
reducing P-noise. The article involved a fixed, not mobile, antenna. It
appears that additional work has not been published that deals significantly
with fixed antennas. (Lots of papers exist dealing with aircraft antennas.)

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.

Your #7 is especially interesting. Our EMC group has on the drawing
board just such experimentation. We will be on the lookout for "end
effects." Your note is a valuable observation.

Regards, Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
wrote in message
ups.com...

Reg Edwards wrote:
Precipitation static, eg., from highly charged raindrops and fine snow
or fine sand, impinging on the antenna wire, just causes an increase
in receiver white noise level. It can be reduced but not removed by
using a very thickly insulated antenna wire, like the inner conductor
of a coaxial cable complete with its polyethylene jacket.
----
Reg.

I've never seen a case of precitation static occuring that way.

In every single case I've seen, whether on tall buildings, tall towers,
or antenna hear earth, it has always been corona discharges from the
antenna or objects near the antenna.

How do I know this?

1.) I had side by side "insulated" and "unisulated" Beverage antenna
wires that are otherwide identical except for being spaced a few dozen
feet apart, and the antebnna pointed towards my tall towers had precip
static and the others did not. Both were equal in noise despite the
fact they are hit by the same rain or dust.

2.) I have Yagis on towers that are identical, and the LOWER antenna
almost never has precipitation static despite the fact they are hit by
the same rain or dust.

3.) I've had dipoles at various heights, and the lower dipole always
has much less precipitation staic than the high dipole despite the fact
they get the same rain or dust.

4.) The period of the noise has nothing at all to do with the number of
droplets hitting the antenna. It increases in pitch as the charge
gradient between earth and clouds builds, then when lightning flashes
it immediatly stops without time delay.

5.) On tall buildings on dark nights in storms, we could actually hear
the same pitch noise as the repeaters rebroadcast, and walk to the
noise source and actually see the corona.

6.) Antennas in fiberglass radomes were no quieter than bare metal
dipoles on tall buildings.

7.) I even used an electrostatic sprayer to charge droplets and hit an
antenna, and could only simulate noise when the antenna element had a
sharp point and I got near the sharp point...at which time I could see
faint corona.

73 Tom

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

wrote:
J. Mc Laughlin wrote:
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?

This is a well known phenomenon in Arizona. What else, besides
charged dust particles, could cause arcing at coax connectors
on a perfectly clear windy day?
--
73, Cecil http://www.qsl.net/w5dxp

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

wrote in message
ups.com...

Reg Edwards wrote:
Precipitation static, eg., from highly charged raindrops and fine
snow
or fine sand, impinging on the antenna wire, just causes an
increase
in receiver white noise level. It can be reduced but not removed
by
using a very thickly insulated antenna wire, like the inner
conductor
of a coaxial cable complete with its polyethylene jacket.
----
Reg.

I've never seen a case of precitation static occuring that way.

In every single case I've seen, whether on tall buildings, tall
towers,
or antenna hear earth, it has always been corona discharges from the
antenna or objects near the antenna.

How do I know this?

1.) I had side by side "insulated" and "unisulated" Beverage antenna
wires that are otherwide identical except for being spaced a few
dozen
feet apart, and the antebnna pointed towards my tall towers had
precip
static and the others did not. Both were equal in noise despite the
fact they are hit by the same rain or dust.

2.) I have Yagis on towers that are identical, and the LOWER antenna
almost never has precipitation static despite the fact they are hit
by
the same rain or dust.

3.) I've had dipoles at various heights, and the lower dipole always
has much less precipitation staic than the high dipole despite the
fact
they get the same rain or dust.

4.) The period of the noise has nothing at all to do with the number
of
droplets hitting the antenna. It increases in pitch as the charge
gradient between earth and clouds builds, then when lightning
flashes
it immediatly stops without time delay.

5.) On tall buildings on dark nights in storms, we could actually
hear
the same pitch noise as the repeaters rebroadcast, and walk to the
noise source and actually see the corona.

6.) Antennas in fiberglass radomes were no quieter than bare metal
dipoles on tall buildings.

7.) I even used an electrostatic sprayer to charge droplets and hit
an
antenna, and could only simulate noise when the antenna element had
a
sharp point and I got near the sharp point...at which time I could
see
faint corona.
========================================
Tom,

The description "precipitate" clearly applies to what is being
precipitated onto the antenna, eg., rain drops, hail-stones, snow
particles, sand particles in a sandstorm, etc.

When charged to a high potential, on impinging on the antenna wire,
the charge on a particle is suddenly released causing a click in the
headphones. A very rapid succession of small random clicks
constitutes white noise.

I, and everybody else in the uK, have experienced rain static dozens
of times, sometimes 10 or 20 dB above S9 on the S-meter. At the start
of a rain storm and when nearing its end, individual clicks can be
heard. As expected, when the clouds are most highly charged, the
noise is most intense when there is thunder about. It can amount to a
roar. It is loudest on the lower HF bands and at MF but that may be
due to the physically larger antennas.

What you have been suffering from is not precipitation or rain static.
You should give it a different name. If you have never experienced
rain static, perhaps you disconnect your antenna when a thunder storm
storm is approaching and before it starts to rain.
----
Reg.