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Re: [TowerTalk] Does prevailing grounding scheme promote large ground lo

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Does prevailing grounding scheme promote large ground loop
From: Dick Blumenstein <rcblumen@centurylink.net>
Reply-to: rcblumen@centurylink.net
Date: Tue, 26 Jul 2016 12:36:56 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Steve-

May the force be with you... (or should I say, it appears the force is with you TOO MUCH!).
(Sigh... when man makes plans, G-d laughs.)

Sorry for all your troubles.

I have no idea what I'll be facing here in the western foothills of NC. I'll find out, though; I'm sure.
PS - If you move to Oregon, then all your connections and equipment 
might corrode/rust!
Dick, K0CAT

======================


Steve London wrote on 7/26/2016 9:37 AM:
K9YC wrote:

The problem with this (and any) analysis of a lightning event is that it is FAR more >complicated than anything we can compute, simply because the voltages and currents induced >in any system (stuff wired together) will be different in each conductor depending on >WHERE the strike is, the physical geometry of the conductors that make up that system, how >energy from the strike gets to the earth, etc.
I can attest to that ! In 13 years of living on a dry, New Mexico 
hilltop, I have learned a lot about mitigating lightning damage. 
Frankly, the cost and effort of doing lightning protection "perfectly 
right" is prohibitive. The approach I have settled on is simple 
disconnection to keep the bulk of the lightning energy out of the 
house. All RF and control cables to/from the towers (I have 3 towers, 
with 5 rotator controls and a number of remote antenna switches) 
terminate on a bulkhead panel about 30 feet from the house. During 
lightning season (May-October), everything is disconnected at the 
panel, except when I am on-the-air. All AC power to the ham shack is 
disconnected, except when I am on-the-air (unplugged - I don't trust 
the small air gap in switches and relays). Yes, this makes it 
inconvenient to be on-the-air during the summer. Even with these 
measures, I have learned the hard way about interconnectedness (K9YC's 
"stuff wired together"). A nearby or direct hit to a tower will 
destroy USB ports on computers and radios, if they are interconnected 
with a USB cable. I have tried commercial USB optoisolators, but have 
found they generate too much RF noise. The latest incident was earlier 
this week. I had a direct hit. The only "stuff wired together" was an 
Astron power supply, connected to a 2 meter radio. Just before the 
storm, these were working fine. I unplugged the antenna from the 2 
meter radio, and the AC power from the power supply. There was still a 
3' long power cable connecting the power supply and 2 meter radio. 
After the storm, the power supply blew fuses. The root cause was a 
fried LM723 in the power supply, causing the voltage to go high, and 
the crowbar protection to be activated.
Sometimes I think moving to relatively lightning-free coastal Oregon 
would be a good idea !
73,
Steve, N2IC

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