Reg Edwards wrote:

I would like to know the input resistance, at resonance, of a
1/4-wavelength counterpoise, at a low height above a ground of known
conductivity.

A physical 1/4 wavelength (234/f) counterpoise is not
resonant at low heights so you must be talking about
an electrical 1/4 wavelength? For a fixed length, the
resonant frequency will change with height.

Can EZNEC be used for some of the configurations?
For instance, given my ground description (0.005, 13)
set for EZNEC, a 62 foot dipole one foot above ground
has a feedpoint impedance of 97 ohms on 7.188 MHz. Would
that imply a radial impedance of 48.5 ohms? The same
dipole 0.1 foot above ground shows an impedance of
112 at 5.94 MHz.

It seems as the wire gets closer to ground, the feedpoint
virtual impedance increases because the forward and
reflected waves on the radial are attenuated by the
ground. This rise in impedance is sometimes separated
out as "ground-loss resistance".

Roy, can NEC4 be used to model an underground dipole?
--
73, Cecil http://www.qsl.net/w5dxp