[TowerTalk] Measuring ground resistance

[Jim Brown]

On Tue, 8 Jul 2008 22:46:27 -0400, Noid Wilson wrote:

>Looking for a little insight from your experience.  I have used many meters
>to measure the final 'network' resistance number for grounding.  Clamp
>meters, quad push resistance, triple clips, etc but I am in the midst of
>ensuring that the final install with the tower, vertical, and SE is the
>lowest value obtainable.

First, study the links below, which are a summary of the concept and how to 
measure the resistance to earth of a ground electrode system. 

http://www.lyncole.com/articles/Ohms_Law_and_Ground_Resistance_Testing_part1.asp

http://www.lyncole.com/articles/Ohms_Law_and_Ground_Resistance_Testing_part2.asp

http://www.lyncole.com/articles/Ohms_Law_and_Ground_Resistance_Testing_part3.asp

Now, let's clarify what the resistance to earth is. It has NOTHING to do with 
the performance of an antenna. It is ONLY there for LIGHTNING PROTECTION. Now, 
we see that you're in Tampa, so lightning protection is certainly a very big 
deal. 

Note also that these measurements are ONLY the resistance of the path at or near 
DC (the AEMC clamps work around 1-2 kHz, depending on their vintage). Lightning 
is NOT DC, it's an impulse, so 99% of the energy in lightning is centered around 
a very broad peak (a couple of octaves wide) 1 MHz, so the IMPEDANCE to earth 
that lightning sees may be very different, AND it includes the inductance of the 
path. None of the methods discussed are capable of measuring these values at RF. 

73,

Jim Brown K9YC