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Re: [RFI] Long distance grounding

To: "Tim Long" <tlong8@earthlink.net>
Subject: Re: [RFI] Long distance grounding
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Tue, 12 Jun 2007 07:47:51 -0400
List-post: <mailto:rfi@contesting.com>
> Ground is a relative thing and there is no such thing as 
> absolute ground
> even when you're looking at earthworms.  There is always 
> an impedance
> and your 14 or 20 feet of ground wire will have some.  The 
> more bends,
> dips, and corners the higher the impedance will be.

While all that is true, once you are inside the house or 
radio room it is generally too late to do anything. There 
should be one common point at the entrance to any equipment 
cluster that bonds power line safety grounds and all control 
and feedlines to a common point. Otherwise you will always 
run a high risk of equipment damage no matter what 
protection devices or "ground" layout you have.

As for RF, and I'm speaking of RF and not lightning, it is a 
common myth that equipment with coaxial feedlines or 
properly balanced two conductor lines needs an RF ground. 
Unless the equipment or antenna systems have a serious 
design shortfall there isn't any need for an RF ground. It's 
always better to figure out why we have RF problems then to 
put a band-aide on the real problem while the real problem 
simmers in the background.

That ground running around on the desk or in the radio room 
should be for AC power source safety. If we have to use it 
for RF or lightning we should probably rethink the system.

73 Tom 


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