Jim Kelley wrote:
Hi Cecil -
Just a small bit of elaboration on your point - the arc is the result of
the accumulation of a sufficient amount of charge to facilitate an
electrical discharge in air. Static is heard in the receiver as the
charge is being acquired, but an AGC limited pop would be heard when an
arc occurs. (And sometimes nothing at all after the latter :-)



Has anybody experienced this first hand? I was driving during a storm
listening to talk radio and could distinctly hear a static rush build up
from the radio 1 to 2 seconds before a lighting strike. The louder it
was, the closer the strike was going to be.

A little off topic. I know this was not antenna static build up, but
found it interesting that you could listen to a charge building before a
discharge.

Chris KC8FRJ

Christopher Cox wrote:
Has anybody experienced this first hand? I was driving during a storm
listening to talk radio and could distinctly hear a static rush build up
from the radio 1 to 2 seconds before a lighting strike. The louder it
was, the closer the strike was going to be.

I have heard it to the point where the radio was desensed
just before the lightning strike. This happened with AM
radio in a fringe area.

A little off topic. I know this was not antenna static build up, but
found it interesting that you could listen to a charge building before a
discharge.

Here's some information on the subject. The electrons that
discharge into the earth during a thunderstorm return to
the atmosphere as fair weather current.

http://www.auf.asn.au/meteorology/section11.html
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Wes wrote:
Hmm. I've lived in AZ for over 60 years (almost 50 of them as a ham)
and am well familiar with dust storms and static build up on antennas
but I've never heard of it being called precipitation static.

Here's the definition of precipitation static.

http://www.atis.org/tg2k/_precipitation_static.html
--


I don't give a damn what they call it, here's a definition of
precipitation:

precipitation n. a: a deposit on the earth of hail, mist, rain, sleet
or snow: also: the quantity of water deposited.

I don't see anything about dirt.



Wes N7WS

On Tue, 19 Dec 2006 18:11:27 GMT, "B29" wrote:

Thanks for the suggestion. I have decided to make my own. There are
suggestions on the web that radio shack makes some good twin lead.

www.thewireman.com is a good place to buy twinlead and stuff.

However,
I still would like to put up a balun. What would be the best balun for me? I
intend to operate on 75 meters.

I admit to being a ham since 1956. However, I have not been very active and
now that I am retired would like to get on low band. I am not very
knowledgeable on all the types of antennas. I do know how to make a random
wire work but do not want that type of antenna again.

Also, to keep the twin lead insulated, do I need to coat the ends where they
are shorted?

I do appreciate the successful reports of using this type of antenna. What
might happen if I put an antenna tuner on the transmitter end and tried to
operate a folded dipole for 75 meters on 40 meters?

I cannot safely use my trees until they are thawed. I cannot climb them
myself and I would not pay someone to do this until it is safer.

You could attach a weight to a piece of rope or cord, throw it over a
limb, and then hoist the end of the antenna up. Beats climbing, ice or
not, and to adjust the antenna, you just loosen the rope, and let the
antenna down.

Bob
k5qwg



Michael

"Denny" wrote in message
roups.com...
Michael, please do not spend good money for something you can build
yourself for a fraction of the cost, and learn good things in the
process...
An 8X10 piece of plexiglass storm window from the hardware store will
supply strips for the end and center insulators... A chunk of 300 ohm
TV twin lead will supply the folded dipole material... A roll of coax,
some solder, and a pieces of small rope, and you are in business... A
hack saw will cut the plexi (so will a skill saw or table saw)...
Why not make one for 10 meters as a starter until spring comes... This
can be hung between two trees or whatever so it is at least head high
and will give you some fun when the band opens here and there..... You
can check the formula for length versus resonant frequency...

denny / k8do

Wes wrote:
I don't give a damn what they call it, here's a definition of
precipitation:

precipitation n. a: a deposit on the earth of hail, mist, rain, sleet
or snow: also: the quantity of water deposited.

I don't see anything about dirt.

As you know, words often have a different technical
meaning than their common Webster's dictionary meaning.
The adjective "precipitation" modifying "static" or
"noise" has been extended to dust as well as rain or
snow, just as the p-static definition indicates.

Airplanes flying through rain, snow, and dust exhibit
the same physical phenomena so dust has been included
as one of the causes of precipitation static. A web
search will prove that to be true. Example quotes:

************************************************** *****************

Volume 2, Issue 4 (December 1945)
Journal of the Atmospheric Sciences

Article: pp. 205–213 | PDF (801K)
METEOROLOGICAL ASPECTS OF PRECIPITATION STATIC

Robert C. Edwards, Lieutenant U.S.N.R. and George W. Brock,
Captain U. S. A. A. F.

ABSTRACT

*Precipitation static*, a result of electrification of aircraft
in flight, can cause loss of radio communication for long periods
of time. Electrification may consist of either of two types,
“autogenous” or “exogenous” electrification; autogenous electrification
occurs when snow, *dust* or rain strike the surface of the aircraft,
while exogenous electrification results from an aircraft being placed in
a pre-existing atmospheric electric field. Serious autogenous
electrification occurs only in snow and *dust* storms; ...

************************************************** ***********

Please note the date. Precipitation static from dust has been
recognized for more than half a century. There are many more
references available. One advertisement asks the following
question:

************************************************** ***********

Ads by GoooooogleMicro Air *Dust* Collectors
Tired of cleaning electrostatic *precipitator* cells?
www.microaironline.com

************************************************** ************

SAE Technical Papers
Title: *Precipitation-Static* (P-Static) Overview of Composite
Aircraft, Document Number: 2001-01-2933

Author(s):
Jerry W. Thornell - The Boeing Co.

Abstract:
Aircraft charging due to *p-static* results from two atmospheric
conditions: 1) the vehicle's presence in a thunderstorm, and 2)
the triboelectric charging (frictional) caused by neutral snow,
rain, or *dust* particle bombardment of the vehicle frontal surface.

************************************************** ******************

Development of Transparent Materials Which Reduce Effects of
*Precipitation Static* in Aircraft
Authors: M. U. Cohen; George A. Dalin; BALCO RESEARCH LABS NEWARK NJ

Abstract: Methods of laying a transparent electrically conductive
film on plastic airplane canopies are discussed. The purpose of
such films is to conduct to the aircraft frame the static charges
developed on the canopies by friction with air, *dust*, snow, etc.,
during flight.

************************************************** ******************

From: http://www.faa.gov/ATpubs/AIM/Chap7/aim0705.html

7-5-11. Precipitation Static

a. *Precipitation static* is caused by aircraft in flight coming in
contact with uncharged particles. These particles can be rain, snow,
fog, sleet, hail, volcanic ash, *dust*; any solid or liquid particles.
--
73, Cecil http://www.w5dxp.com

Thank you Cecil for your patience and service to ham radio humanity in
opening eyes and minds of many of us regardless of being shot at by some of
the all-knowing.

73 and Merry Christmas to all!

Yuri, K3BU


"Cecil Moore" wrote in message
...
Wes wrote:
I don't give a damn what they call it, here's a definition of
precipitation:

precipitation n. a: a deposit on the earth of hail, mist, rain, sleet
or snow: also: the quantity of water deposited.

I don't see anything about dirt.

As you know, words often have a different technical
meaning than their common Webster's dictionary meaning.
The adjective "precipitation" modifying "static" or
"noise" has been extended to dust as well as rain or
snow, just as the p-static definition indicates.

Airplanes flying through rain, snow, and dust exhibit
the same physical phenomena so dust has been included
as one of the causes of precipitation static. A web
search will prove that to be true. Example quotes:

************************************************** *****************

Volume 2, Issue 4 (December 1945)
Journal of the Atmospheric Sciences

Article: pp. 205–213 | PDF (801K)
METEOROLOGICAL ASPECTS OF PRECIPITATION STATIC

Robert C. Edwards, Lieutenant U.S.N.R. and George W. Brock,
Captain U. S. A. A. F.

ABSTRACT

*Precipitation static*, a result of electrification of aircraft
in flight, can cause loss of radio communication for long periods
of time. Electrification may consist of either of two types,
“autogenous” or “exogenous” electrification; autogenous electrification
occurs when snow, *dust* or rain strike the surface of the aircraft,
while exogenous electrification results from an aircraft being placed in
a pre-existing atmospheric electric field. Serious autogenous
electrification occurs only in snow and *dust* storms; ...

************************************************** ***********

Please note the date. Precipitation static from dust has been
recognized for more than half a century. There are many more
references available. One advertisement asks the following
question:

************************************************** ***********

Ads by GoooooogleMicro Air *Dust* Collectors
Tired of cleaning electrostatic *precipitator* cells?
www.microaironline.com

************************************************** ************

SAE Technical Papers
Title: *Precipitation-Static* (P-Static) Overview of Composite
Aircraft, Document Number: 2001-01-2933

Author(s):
Jerry W. Thornell - The Boeing Co.

Abstract:
Aircraft charging due to *p-static* results from two atmospheric
conditions: 1) the vehicle's presence in a thunderstorm, and 2)
the triboelectric charging (frictional) caused by neutral snow,
rain, or *dust* particle bombardment of the vehicle frontal surface.

************************************************** ******************

Development of Transparent Materials Which Reduce Effects of
*Precipitation Static* in Aircraft
Authors: M. U. Cohen; George A. Dalin; BALCO RESEARCH LABS NEWARK NJ

Abstract: Methods of laying a transparent electrically conductive
film on plastic airplane canopies are discussed. The purpose of
such films is to conduct to the aircraft frame the static charges
developed on the canopies by friction with air, *dust*, snow, etc.,
during flight.

************************************************** ******************

From: http://www.faa.gov/ATpubs/AIM/Chap7/aim0705.html

7-5-11. Precipitation Static

a. *Precipitation static* is caused by aircraft in flight coming in
contact with uncharged particles. These particles can be rain, snow,
fog, sleet, hail, volcanic ash, *dust*; any solid or liquid particles.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

The antenna is still just as likely to produce precipitation static
noise however.


It is unlikely that dissimilar antennas will
produce identical responses to anything including
static.

Sorry if I gave that impression. I simply meant that a folded dipole
is just as likely to produce precipitation static noise as a dipole
antenna.

Merry Christmas de AC6XG

Jim Kelley wrote:


Hi Cecil -
Just a small bit of elaboration on your point - the arc is the result of
the accumulation of a sufficient amount of charge to facilitate an
electrical discharge in air. Static is heard in the receiver as the
charge is being acquired,

Hi Jim,

Can you elaborate further on your understanding of just how an
ungrounded antenna wire that receives an increment of charge causes a
response in the receiver as the charge is being acquired?

If dust particles are charged as raindrops are (mixed polarity and
magnitude) a typical incremental charge is on the order of 8
picocoulomb. Do we have an understanding of how much power would be
transmitted to the 50 ohm input impedance of the receiver by such an
incremental charge and the mechanism by which that transmission takes
place? Based on anecdotal info, it is not unusual for these impulses to
appear at an average level of several S-units.

Thanks for any insights you can share.

Chuck, NT3G

but an AGC limited pop would be heard when an
arc occurs. (And sometimes nothing at all after the latter :-)

Putting up a 40m folded dipole caused
the arcing to cease.

That's right. The accumulated electrostatic charge would be distributed
uniformly along the length of such an antenna. Both ends of the antenna
would therefore be at the same potential, so there is no propensity to
arc across them. If at least one of the antenna terminals on the rig is
grounded, the likelihood that the antenna will accumulate a significant
amount of charge is greatly reduced. The antenna is still just as
likely to produce precipitation static noise however. If the receiver
input was strictly differential, then it would indeed be completely
insensitive to common mode signals and noise.

73, ac6xg


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chuck wrote:
Hi Jim,

Can you elaborate further on your understanding of just how an
ungrounded antenna wire that receives an increment of charge causes a
response in the receiver as the charge is being acquired?

Hi Chuck - given a large enough increment of charge it's pretty
straightforward. Best example I can think of is a capacitor. Take a
high gain amplifier with an input coupling capacitor and start daubing
clumps of charge onto the unconnected input lead. When the amount of
charge is big enough, you'll hear the pop that results from the
instantaneous change in charge. Thousands of those per second and
pretty soon we're talking some real noise. ;-)

If dust particles are charged as raindrops are (mixed polarity and
magnitude) a typical incremental charge is on the order of 8
picocoulomb. Do we have an understanding of how much power would be
transmitted to the 50 ohm input impedance of the receiver by such an
incremental charge and the mechanism by which that transmission takes
place? Based on anecdotal info, it is not unusual for these impulses to
appear at an average level of several S-units.

Thanks for any insights you can share.

Chuck, NT3G

I've never worked these numbers before, but given your typical charge
per particle of 8 picocoulombs, and a 16uV signal from a 50 ohm
antenna (converted to uamps), I get about 4x10^4 of those particles
per second. Given the density of air, that's a pretty low number I
think. If I'm wrong, please don't blast me. The back of my envelope
here is pretty messy and hard to read. :-)

73, Jim, AC6XG

Jim Kelley wrote:
I simply meant that a folded dipole
is just as likely to produce precipitation static noise as a dipole
antenna.

Probably not true for a bare-wire dipole Vs a ladder-line folded
dipole. Insulation is one well accepted method of reducing
precipitation static on airplane antennas. In any case, the two
wires in the folded dipole make it different from the single wire
in the dipole.

I'm away from my computer for the moment but consider your capacitor
suggestion. Let's say we have a perfect ground plane and are testing
a dipole Vs a folded dipole. They are in inverted-V configurations so
we can discharge a capacitor between the end of the antenna and
ground. For the dipole, there is only one path to ground through the
receiver. For the folded dipole, there are two paths to ground, one
through the receiver and one to ground. Why won't the charge
applied to the folded dipole divide and take both paths?
--
73, Cecil, w5dxp.com