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Re: [RFI] Long distance grounding

Subject: Re: [RFI] Long distance grounding
From: Tim Long <tlong8@earthlink.net>
Date: Mon, 11 Jun 2007 22:40:29 -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.  It will be resonant 
at some frequency.  If you ever take a lightning hit, the current 
through your ground wire will create a potential difference (voltage) 
between the ends of your ground wire which could wipe out your 
equipment.  This isn't a DC current - it's RF.  The impulse of the 
lightning strike is composed of a set of all frequencies.  The geometry  
I prefer for the ground system is the asterisk  pattern.  This 
arrangement minimizes the potential difference from one end of your 
ground system to the other and consequently from one piece of equipment 
to the other.  Good luck & 73.  Tim, W2UI
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