Correction:

Roy Lewallen wrote:
. . . An experienced
EZNEC or NEC modeler would immediately run an Average Gain test and seen
that the reported gain is about 16.7 dB too high due to numerical
problems. If desired, this can be subtracted from the reported gain to
give the gain that's much closer to reality.

I should have said "experienced *and not careless*". The average gain is
about 30.4 dB, not 16.7.

. . . In this case, the model
violates at least one NEC rule by spacing two 40-foot #14 wires 1/2 wire
diameter (0.032") apart. (NEC guidelines specify that parallel wires
should be at least several wire diameters apart.) It would be a great
challenge to actually construct this antenna. But, even at that, the NEC
results are probably not bad once the average gain correction is made.

The wires are just about one wire diameter, not 1/2, apart.

This antenna is a very difficult one for NEC. In a few minutes of
fiddling, I couldn't get a decent average gain at much less than about
0.3 foot wire spacing, and then it required specific segmentation. I'll
modify my earlier statement to say that this is an antenna that is
indeed pretty difficult for NEC to handle. But it's easily recognized as
such by looking at the average gain result. If you don't know about the
average gain test, look in the EZNEC manual -- included also with the
demo program -- index under "Average Gain". It's an important and
valuable tool.

Roy Lewallen, W7EL