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Re: [TowerTalk] Tower grounding

To: Skip K3CC <>
Subject: Re: [TowerTalk] Tower grounding
From: David Gilbert <>
Date: Wed, 28 May 2008 21:36:13 -0700
List-post: <">>
I have an Ohms Law question for you with respect to that comment.  Let's 
assume the tower base is secured within the concrete (and therefore the 
lightning has an extremely low impedance path into the concrete).  If 
the ground wires attach to the tower above the concrete base they 
provide a shunt path to ground that bypasses the concrete.  If the same 
gauge and number of ground wires are attached to the tower but happen to 
pass through the concrete, they still provide the exact same shunt path 
to ground bypassing the concrete.  Can you or anyone else please explain 
to me how there is any difference in the electrical paths?  Why would 
the path through the concrete have any less shunting ability than the 
one above it?   Please be specific.  If the wires vaporize as some have 
postulated, they're going to vaporize in either case and remove the 
shunt, and I can't see how they are any more likely to do so simply 
because they pass through the concrete ... at least not in terms of the 
energies involved.

By the way, every electrical code I'm aware of requires that the tower 
be connected (Ufer grounded) to the rebar cage.  The electric potential 
from lightning, induced or direct, is therefore absolutely going to be 
available within the concrete, and only a significant shunt path for the 
current is going to be able to protect it.  Polyphaser says that the 
Ufer ground from the rebar cage is sufficient for that purpose since it 
acts as a massively distributed shunt path through the concrete, so why 
would additional ground wires running from the tower through the 
concrete to ground ... an additional shunt path ... be a bad idea?  
Please be specific.

Dave   AB7E

Skip K3CC wrote:
> I would never ever ground the re bar or anything in the concrete.  I have 
> seen 2 tower bases that had taken an indirect lighting hit though the 
> ground.  The water boiled in the concrete from the heat and exploded the 
> concrete bases. One other base was within 100 ft of the others and was not 
> grounded and it was fine.
> de Skip  K3CC 
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