"matt weber" wrote in message
...
On Sun, 12 Oct 2003 18:37:51 -0400, "AbbN"
wrote:

Hi,

How about using the ground in a 3 prong electrical socket???? Better than
nothing??? Dangerous??? I'm in a high rise
These are often very poor radio frequency grounds. A DC ground, or
for that matter a 60Hz ground has a very large skin depth (about .85cm
at 60Hz), so the entire conductor is useful, and the DC resistance to
ground is about all you have to worry about.

A good DC or even 60Hz ground can be an awful Radio frequency ground.
Even at 1 Mhz, the skin depth is a small fraction of a 1 mm, so all of
the corrosion and garbage occurs on the part of the conductor you
need.


Wait a minute. Are you saying the depth of the skin effect is the same for
poor conductors as good ones? Wouldn't the increased skin depth of a poor
conductor get the current down to the good conductor?


In addition the length of wire to the physical ground can be
very large, and even a straight wire has inductance, so long ground
line in addition to having poor conductivity, may also have
substantial inductance. Both make for a high impedance path to ground,
which is the last thing you want.

Inductance and capacitance! And they work together in such a way that if
your ground conductor is 1/4 wave or an odd multiple of a 1/4 wave it
presents such a high impedance that it isn't an RF ground at all :-(.

But wait. It still might work just fine, because now it's a counterpoise
:-)!



If it is a steel frame building, the building frame is probably a
much better RF ground then the ground lead in an outlet.

Steel frame buildings are almost always commercial buildings. Shouldn't you
ask the building supervisor to help find the framing and punch a hole
through the wallboard? And wouldn't the steel beams have a thicker buildup
of rust and paint and crud than galvanized steel conduit?

To the original poster, I say -- Experiment safely and keep track of your
results!

Frank Dresser