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Re: [TowerTalk] Lightning Protection

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Lightning Protection
From: Jim Lux <jimlux@earthlink.net>
Date: Mon, 08 Jul 2013 07:33:56 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 7/8/13 7:18 AM, john@kk9a.com wrote:
I also have a shack on the 2nd floor and I also disconnect all cables
going to the tower. I only use the station for major contests so doing
this is not really inconvenient. Disconnecting however is not a reliable
means of protection as the energy can be induced into anything nearby. I
am not sure if there is any way to stop this from occurring. Even if you
disconnect it is a good practice to have multiple lines of ground rods a
single point ground and MOVs or GDTs on every rotator and relay.

John KK9A



I'm not sure about the value of the multiple lines of ground rods *from the entrance panel*. I just don't see the physics of what it's doing there. The goal at an entrance panel is to have everything tied to one reference voltage, and let that go up and down.

For fast transients, the inductance of the wiring to the ground is going to be dominant impedance, not the resistance to "earth".

Consider that lots of communications installations are on the top floor of a tall building, and have essentially NO direct connection to ground. (for instance, the TV transmitters in the Empire State Building, where the antennas have been hit countless times.. so often that lightning researchers hooked up stroke recorders to them)


Transient suppression devices to suppress differential mode, most definitely. But to "chassis"? I'm not so sure it's useful.




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