[TowerTalk] grounding

[Jim Lux]

At 02:35 PM 8/28/2006, Jerry wrote:
>  How do I know if I have proper ( enough ) grounding.  How can I measure 
> it???   Jerry   WA2KDB

Grounding for electrical safety, for lightning protection, or for RF purposes..

electrical safety proper is fairly easy to figure out: Are you in 
compliance with the local codes? Most local codes are based on the National 
Electrical Code (NEC).  http://www.mikeholt.com/ has a Low Voltage Handbook 
(or something like that) you can download for free that describes all the 
NEC requirements for antennas.

Is "code" enough?  That's a whole 'nother question, and a lot depends on 
what your damage tolerance level is.  What you need can vary a lot 
depending on how much lightning you get and whether you mind replacing 
equipment that gets damaged by a nearby stroke.

For RF purposes... it's like a race car, speed costs money and time, how 
fast do you want to go? But, you'd like low a ground impedance as you can 
afford, or, at least til the improvement you'd get from expending the next 
increment of labor or money doesn't buy you anything noticeable.

As for measurement:

You can use 60 Hz AC with the scheme in the ARRL handbook, which will give 
you numbers for power line frequencies.  You can use a ground system tester 
(megger) from Biddle or others, but this is also low/audio frequencies.

For RF, it's very difficult to make accurate ground system impedance 
measurements (what's the second terminal you're measuring relative to?)


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