The reason for the contradiction is that I got the first result of 1
volt for the base of a 1 meter vertical wire above perfect ground in a 1
V/m field by using NEC with a plane wave excitation source which
produced a 1 V/m plane wave field. The 3 mW value I got later for Reg's
model was obtained by generating a 1 V/m field by putting a conventional
source at the base of a second short vertical. And what I've now
determined after a considerable amount of experimentation is:

The current reported by NEC-2 or NEC-4 to be induced in a wire (or the
voltage in its center or between base and ground) by an impinging field
created by another antenna is exactly half the value it is when the same
field is created instead by an NEC plane wave excitation source, when a
ground plane is present. This doesn't occur in free space models, which
seem to produce correct results.

Unless there's some problem with interpreting the meaning of the plane
wave source's field value, it looks like this is a bug in NEC-2 and
NEC-4. I've posted a query on a mailing list frequented by the real
experts at using these programs, and I'll report back what I find out
from them.

We really need a sound theoretical basis for deciding what the value of
induced current or voltage should be, for a final determination of which
answer is right and which is wrong. I'll try to take a good look at that
tomorrow.

But in the meantime, we do know that the field strength generated by a
short vertical with a source at its base is being reported correctly by
NEC. NEC programs have been used very widely for determining induced
currents and field strengths, and my guess is that the plane wave
excitation feature is relatively rarely used, and less so over ground.
Consequently, I'll put my money on the result obtained by exciting a
second antenna to generate the field rather than on the plane wave
excitation source result.

If this conjecture is correct, then I was wrong when I said in an
earlier posting that the voltage at the base of a one meter wire over
ground was one volt when exposed to a one V/m field -- it should be 0.5
volt. I got the 1 volt result by using an NEC plane wave excitation
source -- ironically, after first verifying that I got the known
theoretical result in free space. And my more recent posting giving the
power in Reg's example antenna load as 3 mW rather than 12 is correct.

I'll post more as I find out more.

Roy Lewallen, W7EL