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Re: [TowerTalk] Ground wire impedance

To: "" <>
Subject: Re: [TowerTalk] Ground wire impedance
From: "Jim Brown" <>
Date: Wed, 12 Jul 2006 19:26:40 -0700
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On Wed, 12 Jul 2006 19:42:21 -0500, K4SAV wrote:

>Given that a 0.5 inch wide strap is about the same as a wire.. what 
>about multiple wires in parallel.. If they are spaced apart far enough, 
>the inductances will be parallel.

One of the virtues of wide copper strap is that it DOES reduce the 
inductance as compared to a single conductor. So it is good from both a 
skin effect and inductance point of view. And it has long been good 
engineering practice to have multiple bonds to earth in parallel to reduce 
the total impedance. 

BTW Jerry -- you will see my graphs of the resistance (taking skin effect 
into account) and the inductive reactance of a straight wire. And yes, for 
all practical wire sizes, and for all frequencies above a few hundred Hz, 
reactance dominates the impedance, NOT resistance. 


See also Henry Ott's classic text on EMC, "Noise Reduction Techniques in 
Electronic Systems," first published 1976, second edition 1988, still in 
print and considered the bible. Henry comes out of Bell Labs, and still 
teaches excellent seminars on EMC. 


Jim Brown K9YC


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