If a 60 Hz measurement is the only physical test that is available, that is
better than nothing. The experts say that is useless, but I do not agree
100%.

Once upon a time I used a 12.6 V 60 Hz transformer and an AC ammeter to
measure the current between some ham radio ground rods and the building
utility ground and then calculated a resistance value of about 16 ohms. The
substantial current flow helped to overcome an initial high value of
resistance. The ground path did not seem to be perfectly linear at very low
current values.

What the 2 to 30 MHz values were I have no idea. A high power (100 W ) HF
signal and an RF ammeter would have been a better approach. This test has
to be carefully designed to reduce HF impedance effects.

The best approach, I believe, is to use an antenna design that does not
utilize a ground path return impedance. In a balanced system the return
current is through a transmission line, not the earth. A multi-wire ground
plane with a transmission line return path is also a good approach that is
very often used. Common-mode currents that try to return on the outside of
the transmission line must be attenuated using a current balun.

Bill W0IYH

"AG4QC" wrote in message
...
I was wondering if anyone built some sort of ground resistance tester? I
read that the NEC requires 25 Ohms or less.. But I don't understand how to
measure that. I certainly could use a ohm meter between a ground rod and
the test subject, but then the ground rod I use as a reference could be
faulty.. It seems to me it must be measured in some other manner. Maybe low
frequency signal and then measure how much it's absorbed in the earth?.. I
know they sell a clamp on ground resistance tester for big bucks.
Considering it's a clamp on, it certainly don't have any external
reference.. Anyway, I was wondering if anyone had any experience with these
testers and maybe building one?

Joe AG4QC