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Re: [TowerTalk] Lightning Advice

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Subject: Re: [TowerTalk] Lightning Advice
From: "Roger (K8RI)" <>
Date: Tue, 11 Sep 2007 12:33:49 -0400
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There have been some good suggestions as to grounding. A good Single Point 
Ground (SPG) is essential.
As to supressors, they can/may *help* when properly grounded and the rest of 
the house is properly grounded.
Supressors on the phone, cable, and electrical lines coming in also help, 
but are not guarantee.  There's a lot of wire in a house and a strike a mile 
away can induce as much as a 1000V per meter of wire. Even with grounding 
you can not prevent strikes from causing the voltages to rise in the house, 
but hopefully you can get them to all rise the same so the system sees no 
large differences in potential.

I would add that where lightning is concerned, nothing is absolute and each 
strike is has its own characteristics and the strength varies over many 
magnitudes from weak to the so called super strikes. Fortunately the super 
strikes, which are now believed to have brought down a couple of airliners, 
are rare.

I've said this many times here on the group, but the tower shown in has been up for 7 seasons 
now and has taken an average of 3 "visually verified" hits a year. ( 5 last 
year and none so far this year) If it makes it through the rest of the 
season this will be the first year it hasn't taken a hit. The ground system 
consists of 32 or 33,  8' ground rods CadWelded (TM) to over 600 feet of 
bare #2. The coax and control cables come in through underground conduit to 
a grounded bulkhead/SPG at the entrance.  Not all cables are 
shown in this series.  Since the ground system was completed I've had no 
damage except for some severely etched coax connectors on the remote antenna 
switch near the top of the tower. The switch is opposite the UHF TV antenna 
pointing to the left (NW).  The South pointing UHF TV antenna and the AV640 
(on the shop) are more visible in . The big white C-Band 
satellite dish has also been removed in the second photo.


Roger (K8RI) 


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