My towers have been hit a number of times. I think installing a lot of
ground rods and a SPG is a worthwhile investment.
John KK9A
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Does prevailing grounding scheme promote large
ground loop
From: Steve London
Date: Tue, 26 Jul 2016 07:37:08 -0600
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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