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[TowerTalk] Lightning questions.

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Subject: [TowerTalk] Lightning questions.
From: (Bill Aycock)
Date: Sat, 13 Jun 1998 20:33:50 -0500
I just read Tom Russels posting about the probability of "hits" on a
multi-tower set-up.  I am not so fortunate as my almost near neighbor, but,
at the scale I am, I  have similar results.  With a grounded antenna or
tower, you shift the locus of the potential that is going to "arc-over".

There have been several real experts on here that have repeatedly assure me
and the list that there is not enough current carrying capacity to "suck
off" the charge between the cloud and the ground enough to prevent a
strike. There is just too much energy to bleed it off without having the
result be a strike.  This, like a lot of other statements, is true, but it
answers the wrong question.

It is NOT NECCESSARY to bleed off much- just enough to change the local
potential a little, so that the place where the leaders seek each other out
is somewhere else. 

1. last January, I had a direct hit on the transformer feeding my house.
the strike was about 200 feet in front of the house. My 135 foot dipole was
grounded and had no problems. The hit apparently followed the waterline
(Plastic pipe !) for over 200 yrds, and blew two holes in it, about 15 feet
apart.  This pipe passes within about 4 feet of the pole brace (anchor) at
the pole where the transformer was hit. NO electronic devices in the house
were damaged. 

Side note- we have superb power service- the transformer was replaced and
power restored in less than an hour and a half- in a driving storm,  late
afternoon, in a rural area. 

2. about three years ago, I had a direct hit on a tree about 50 feet from
the end of a grounded Windom. There was no damage to the house (directly
under the Windom), but the Windom came down.  I just happened to be
watching out the shack window, and saw the hit, and the rope (dacron)
break. I could see the shockwave from the hit travel across the  field, by
the motion of the tall grass. there was no damage to the rope except the
break at a frayed place- I think the shock-wave jerked  the tree it was
fastened to enough to break the line.  The tree that was hit shed exploded
bark all around the area. The steam explosion in the inner bark layer makes
the stuff look like yellow styrofoam.

The most lightning damage I have ever had was from a strike over a mile
away, which followed a phone line (underground) that distance to take out
several phones, a computer, and a TV. The ground wire at the phone box at
the point where the line enters the house was found to be disconnected.
Second to that was the loss of a KPC-3 and an FT-411 used for packet to a
near hit. (Try to explain to the insurance adjuster how a radio normally
used in your hand got hit by lightning). The antenna was on the roof, and
was not disconnected or well grounded.

I will still disconnect my antennas and ground them. I think it helps. I
will probably change the point at which I ground them, though. The
grounding panel is a little too close to the rigs. 

Bill- W4BSG

Bill Aycock   W4BSG
Jackson County, AL
W4BSG is "vanity" this time, but was 
earned by exam in 1954, the first time.

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