I await your experiments to determine the impedance Zo of ONE radial
wire and the approximate distance at which it occurs.

You can do N = 36 radials at a later date.
Thank you very much.

Reg, I started to do an analysis of a single radial monopole.
Beginning with a 1 meter length radial I compared the results
with "radial_3". There is such a huge discrepancy between
the programs I wondered if I had made an error someplace.

Just to confirm the antenna dimensions: 9 m monopole,
with a 1 m radial, 25 mm below ground. All wires # 14 AWG,
and the test frequency 8.07 MHz. Ground Er = 16,
resistivity 150 ohm-meters.

"radial_3":
Antenna input Z = 34.21 - j 26.2, and;
radial input Z = 82.7 - j 62.3.

"NEC 4.1":
antenna input Z = 137.8 - j 81.8, and;
radial input Z = 101.4 - j 79.1.

Interesting to note that the input impedance determined
by radial_3 is very close to an ideal monopole above
a perfectly conducting ground.

Frank