[TowerTalk] Re: static cat

[Bill Aycock]

Didier- IMHO, your first paragraph has such  fundamental errors that the 
rest cannot be supported. The charge on the earth side is NOT uniform over 
miles; the earth is not a superconductor and has finite resistance. All 
common descriptions I have seen showing the charge distributions show both 
the earth and the clouds with charge, but of opposite sign. This is 
contrary to your first statement.
Bill

At 12:07 PM 3/21/2004 -0600, you wrote:

>The problem is that the ground is not charged, the clouds are charged. 
>Think of the earth and the cloud as both plates of a capacitor, except 
>that the bottom plate is a few 10 of thousands of miles long and 
>conductive, and the top plate (the cloud) is a few thousand feet wide, and 
>basically a charged insulator (each water droplet is charged, but isolated 
>from its neighbor. The charge on the earth side is for all practical 
>purposes infinite. You cannot drain it to anywhere because it always 
>returns to earth.
>
>When charges escape the porcupine, they do not make it to the cloud. They 
>just dissipate in the air and return to ground, so they do not contribute 
>to reducing the charge in the cloud. I'll agree that they may locally 
>reduce the field in the air somewhat (as seen from a distance of a few 
>feet). The argument is whether that reduction is sufficient to reduce the 
>probability of a lightning coming from hundred or thousands of feet higher up.
>
>Think of it another way. The earth is conductive. At least until lightning 
>strikes causing great amounts of currents, before that point little 
>current flows, so the potential along the earth is not affected very much 
>by a few charges flowing out of a porcupine because the earth is 
>conductive and charges are replaced as soon as they escape. Charges may be 
>flowing out and into the air, but the earth's potential is the same, and 
>the potential difference between earth and the cloud is what causes the 
>lighting to go.
>
>The other side of the argument is whether it is actually a good thing to 
>eliminate smaller strikes, as they act as bleeders and may prevent the 
>larger strikes.
>
>I am not sure I want a lightning protection device that would reduce the 
>number of smaller strikes at the expense of greater probability of getting 
>the big one.
>
>There is a lot of anecdotic evidence that these types of devices work, but 
>no serious, objective, peer reviewed studies to support the same.
>
>The bottom line, as long as you are happy with it, and you do not cause 
>other problems doing this, why not do it? Just be aware that it may or may 
>not work, and it may even increase the probability of getting a serious hit.
>
>73,
>Didier KO4BB
>
>At 10:20 AM 3/21/2004, you wrote:
>>I think that's the key.  Their web page is misleading, but, in my own
>>belief, not entirely wrong.  Yes, there will be direct strikes to the
>>tower, even the whiskers.  But before the differential reaches the point
>>of discharge, I think the whiskers are trying hard to discharge it
>>slowly, thus preventing some of the smaller strikes.
>
>
>_______________________________________________
>
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>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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Bill Aycock - W4BSG
Woodville, Alabama