NEC-LIST: Ground Constants at 1.161 kHz for "Good" Ground

Jack, et al.:

I ran my "Longmire and Smith" ground constants model for their
standard case (epsilon r equals 5.0 at infinity), and I iterated on
moisture content (by volume, in g/cc) to find a match at 1.161 kHz and
a conductivity of 15 mS/m. I got a value of mv = 0.145 g/cc, and
corresponding values of epsilon r of 3477.5 and dissipation factor
(AKA loss tangent) of 67.1. The complex relative permittivity,
assuming e to + j omega t, is:

epsilon r complex = 3477.5 -j233476.3

So you did get really good ground, but your value of 30 for epsilon r
(relative dielectric constant) is way too low. But since the loss
tangent is about 67, with sigma greater than omega epsilon, the
epsilon r value difference probably wont affect your results or
conclusions.

George

P.S. I still believe that independent measurements taken as E vs
distance on several (3?) azimuths, for a CFA set up as certified by
the designers to be correct, is still the best way to resolve the
controversy over the efficiency of this most interesting of
antennas. It would be useful to measure the ground constants at the
test frequency at the antenna location and out the radials at selected
test points to check the modeling vs the measurements. Also, using a
"reference" antenna for the modeling and the measurements is a good
idea, but having them too close together so that the mutuals are
invloved is not a good idea.

George H. Hagn
Received on Mon Jul 26 1999 - 17:56:04 EDT