|To:||"david jordan" <email@example.com>, <firstname.lastname@example.org>|
|Subject:||[TowerTalk] Why Rain static is worse on the top antenna. [was Quadvs SteppIR]|
|From:||"Guy Olinger, K2AV" <email@example.com>|
|Date:||Mon, 30 Aug 2004 22:48:20 -0400|
----- Original Message ----- From: "david jordan" <firstname.lastname@example.org>
Noise from point source such as a tower or building and percepitation static created when dropplets of rain or snow flakes that are charged come in contact with the elements of a bare wire or beam antenna.
I would respectfully disagree.
It is more likely that less charged raindrops come in contact with the highly charged antenna or wire.
A. It is well known that a substantial opposite charge on the ground follows the charge in the clouds overhead.
B. It is also well known that a capacitor consisting of two plates will collect the highest density of charge on the surfaces of the two plates facing one another.
C. A yagi at the top of the tower will intercept a lot less than one percent of the rain falling through it's turning radius.
D. The yagi below it will get just as wet, since the yagi above is about as effective a rain shield as an umbrella that's lost all its fabric. Or stated another way, which one of you runs out to the tower under the yagis to get out of the rain.
Given C. and D., if the rain was charged and both yagis were neutral, connected to ground, the lower yagi should be just as noisy as the yagi above. But that can't be true, since the "shield effect" is well documented.
Try the charge on the ground, from A., and the rain quite less charged (more neutral).
Since the tower and the yagi's are connected to ground, the tower complex assumes at least the ground charge. From B., the top yagi functions like the surface of the capacitor plate, assuming nearly all of the ground charge available to the tower, because it's closer to the clouds.
The neutral rain hits the high charge top yagi and the movement of the charge making the drop equal to the yagi causes the noise.
The neutral rain hitting the neutral lower yagi does nothing.
Exaggerated, of course, but you get the point.
The difficulty in seeing the ground/tower as highly charged, is that the AREA or NEIGHBORHOOD is at an elevated charge underneath the charged clouds overhead.
In thinking about what might be noisy or quiet in a tower/antenna complex, consider whether 1) there is some thing extensive and grounded above it, or if to the side a bit, is there an upward moving path from the TOP of something to something else substantial and higher yet.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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