Owen,

The antenna is a short loaded vertical. The base is about 1.1 meters
long and 90mm in diameter, the coil is about 160mm long and about 80mm
in diameter, the top is 3 meters. The coil wire is 12 gage and the
spacing is about .5. As a model cross check, the impedance of the coil
measures about 60 uH.

- Dan

Owen Duffy wrote:
Owen Duffy wrote in
:

dansawyeror wrote in
:

...

I think a summary is that at 3970KHz, the feedpoint Z looks like about
45 +j0 and you reckon the radiation resistance should be around 4+j0,
suggesting the earth system contributes around 40 ohms of resistance.
Observations at a single frequency provide a limited view of what
might be happening.

Dan,

I asked your for the details of your antenna and measurements, and how
you did your calculations, but I am still left wondering how you have
what appears to be a purely resistive feedpoint impedance and a radiation
resistance of 4 ohms. The second implies a short vertical, and if that is
the case, the first implies some form of loading... but you didn't
mention loading of any kind. Loading, if you have used it, may introduce
an equivalent series resistance at the feedpoint.

Once again, a dansawyer problems leaves us guessing to fill in the
missing dots before attempting to joint them up to make a picture.

Often, solving a problem is about being able to draw the picture, once
the picture is draw, the answer becomes trivial.

Owen