NEC-LIST: Reconciliation of rad eff and driving point resistance

It has been suggested that I join this list to seek help in explaining
results that I have obtained with 4NEC2.

I have been experimenting with 4NEC2 to model the behaviour of quarter wave
verticals with a variety of radial systems and over grounds of different
kinds.

Except in the case of a perfect ground I always get radiation efficiencies
that have no relation to the real part of the driving point impedance at
resonance.

For example, with a driving point resistance at resonance of 71ohms the
indicated radiation efficiency is 20%. The efficiency is 98%.

>>From the latter it is apparent that the conductor loss is negligible.

If one calculates the radiation efficiency by comparing the radiation
resistance, 36ohms, for a quarter wave monopole with the indicated
resistance of 71ohms one obtains about 50%, not 20%. Although I have
illustrated this with a particular case I never ever get sensible and
consistent data.

I would expect the calculated integrated radiated power compared with the
electrical power input to give a value of rad eff that is consistent with
the radiation resistance and driving point resistance. Am I missing
something here?

I would appreciate guidance on this and perhaps an example file that
demonstrates a successful simulation.

Regards

Garth
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