[Boatanchors] Checking grounds and ground rods

[Bob Kester]

To continue the ground rod thread a little further -- now that I have
some grounds installed, how do I check them?

As it has been pointed out, a DC ground may be different from an RF
ground, and a lightning protection ground still different.

I've asked what DC resistance I should find from one ground to the
rest, and the variety of answers is astounding.  Even the means of
checking gives a variety of answers.

If I use an ohmmeter from one ground to another, battery action
probably will give a false reading.  My favorite method on a decent
ground is to run a wire to the hot side of the 120v system and use a
clampon ammeter to measure current flow.  But, this only works for
real good grounds.

Giving an example of what I've seen using this method -- I dug a
trench that was from 24" on one end to 36" on the other end, and 24
foot long.  I dropped in a piece of 3" copper pipe, and half way along
that drove an 8 foot ground rod.  Soil conditions were hardpan and
heavy clay.  A month after filling the trench, I was able to flow 9.5
amps at 117 volts.  I'm sure over time that will change.  (This ground
was to be used for lightning protection primarily.)

Outside of arranging for a lightning strike, how do I determine how
good a ground is for some purpose?

...Bob, K2JJT

--
There are 10 kinds of people in the world,
       those who understand binary,
          and those who don't.