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Re: [TowerTalk] multi grounding

To: "" <>
Subject: Re: [TowerTalk] multi grounding
From: "Jim Brown" <>
Date: Thu, 29 May 2008 08:13:40 -0700
List-post: <">>
On Thu, 29 May 2008 11:03:31 -0400, Skip    K3CC wrote:

>If you have more then one ground system tied together as a commercial radio 
>you will get differences in EMF between system. This can an does cause noise 
>in our receivers just as dissimilar metals causing galvanic corrosion, 
>effect a junction diode.

>Or is this another urban myth that I have heard ????

Well, certainly some junk science. Virtually ALL building codes in North 
America REQUIRE that all grounds be bonded together in a manner that provides 
the lowest practical impedance between them. This is a critical element of 
lightning safety. So there ain't no IF about it -- we MUST do it!  

Now, when current flows, there is a voltage drop, AND a field is created around 
the conductor. Any conductor is an antenna, so that current can radiate. The 
effect of that current and radiation on receive noise will depend on the nature 
of the antenna system. There's no one simple answer -- you've got to study the 
RF equivalent circuit for the complete system, including how the power system 
is bonded (and it MUST be bonded to all of these grounds). 


Jim K9YC


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