Owen,

I did not want to concentrate on that; however it is a fair question.
The frequency is 3970 kc and the methodology is based on use of an hp
network analyzer. The analyzer has both polar and Cartesian displays.
The outputs were cross checked.f
The feed line was calibrated using a 25 Ohm termination to 180
degrees. The return measured about -9.4db (close to what is predicted
with line loss). This was checked against an open circuit confirmed the
calibration by a reading 1 degree and 1db. (very close to what is
predicted)

For the actual measurement the return loss was measured at just over
-26db at 0 degrees. (no feed-point network) Three models were used to
calculate the input resistance of the antenna. They all predicted an
antenna resistance of about 3 to 4 Ohms. (the suggested input network is
120 pf)

To focus on the question is: Why is the ground resistance so high? It is
not important at this stage to determine its precise value. The point is
it is high enough to cause a return of 0 degrees. This puts the 'system'
at over 50 degrees. Even if the antenna were 6 to 8 Ohms the ground loss
would be at least 42 to 44 Ohms.

- Dan

Owen Duffy wrote:
dansawyeror wrote in
:

Dan,

You refer to calculation of ground resistance and later to measurements.
It would help if you explained what you measured, the frequency of
measurement, and how you measured it, then how you calculated your
results.

Perhaps the regimen of that might help you to an answer.

Owen


All,

This question is: How can the ground system for a vertical be improved?

The RF ground calculates to about 52 Ohms. It consists of 16 radials
varying in length from 24 to 45 feet. Four are buried and 12 are on
ground. The location is the Pacific Northwest part way up a hillside.
The surface is grass, the subsurface is clay. The value varies a little
with rain, it has measured as low as 46 to 48 Ohms.

Just as additional information, the antenna is a loaded vertical,
overall about 4 meters. The coil is about 35% from the base. The
antenna
is raised about 1 meter. I am aware the configuration is not optimum
and
a top hat would help, those changes will be made independently.

Several articles indicate this radial system should yield well under 20
Ohms, some estimates are under 8 Ohms. At this point my first target is
under 20 Ohms. Little that I do seems to affect it. My question is:

What am I missing?

The problem is the value does not appear to change very much. I started
with 4 radials and have been adding them periodically. Those changes do
not seem to have a measurable effect. (However I must admit that
earlier
numbers not as good as the current measurement. I believe the current
measurements are better then 10%.)

Thanks - Dan