On Jun 4, 4:40*pm, Roy Lewallen wrote:
Richard Fry wrote:
The equation for the radiation resistance of short antennas given in
that paper is independent of the resistive losses in any loading coil
or r-f ground system.

And the same fundamental equations are used by modeling programs. The
problem is that interaction between the antenna, an abbreviated ground
system, and the Earth can modify the radiation resistance as well as
adding loss resistance.

Could you please explain why, if the same fundamental equations given
in antenna engineering textbooks and I.R.E. papers are used by
modeling programs, the results of their use do not always support each
other very well?

If it is accepted that the radiation resistance of a short monopole is
independent of the loss resistance in the loading coil and r-f ground
either alone or together, then what is the basis for the variation in
radiation resistance that you report?

BTW, the equations in the Carl Smith paper I referred to earlier in
this thread produce a radiation resistance of 0.113 ohms for a 1.65
MHz, 9.84' (3-m) x 0.25" OD, base driven monopole -- which is not
_hugely_ different than the values calculated by EZNEC.

RF