In King and Harrrison's _Antennas and Waves_, they show a plot of
calculated antenna feedpoint impedance as X vs R up to about 5
wavelengths. Antenna wire radius is 0.008496 wavelength. The Z of an
infinite length antenna is indicated by locating the centers of the
circles and noting that the center converges. The point of convergence
for this particular wire radius is about 250 - j170 ohms.

In the chapter on experimental measurements, there's a plot of the
calculated admittance of an antenna of radius 0.000635 wavelength up to
about 10 wavelengths. Superimposed are measured values from another
source which show very good agreement. The theoretical values converge
at 214 - j189 ohms, and the measured values at 218 - j174 ohms.

Dervivation takes about a chapter of very heavy math, and numerical
results were obtained with a computer.

Roy Lewallen, W7EL