On Apr 11, 11:54 am, "Antonio Vernucci" wrote:
Yes, the email should be right. I do have Eznec5+, so I can check
against Roy's suggestion. I'm sure he'll be happy to help with things
that may be related to how NEC/EZNEC behaves, if we can identify them.

Cheers,
Tom

Tom,

the mistery seems to be solved:

- with the "real" hairpin the program does not yield correct answers, neither in
terms of gain nor in terms of impedance. Roy W7EL anticipated that the problem
is due to the feedpoint being in a short loop. I did the test he suggested (i.e.
calculating the Average Gain) and the result I got clearly showed that there was
a problem.

- instead, with the hairpin simulated by means of a shorted piece of
transmission, the results are fully consistent. Firstly the gain does not vary
with and without the hairpin. Secondly the impedance I read removing the hairpin
is 24.5 +j65.37 ohm, a value fully consintent with the pure 200 ohm I get with
the simulated hairpin.

At least I learned one should not try to model "real" hairpins.

At this point I would not further bother you, by sending you files that would
not tell you much. It was a real pleasure for me to have such an interesting
discussion with you and, if I may, I will write you should some other strange
situation occur in the future.

73

Tony I0JX

Hi Tony,

I suppose you are not using EZNEC 5+. If that is the case, I would be
happy to run your model on the 5+ version with double-precision
calculations, and see if that makes a difference. It should be easy
enough to run it. It it no problem to me, just a fun diversion. And
of course I would be happy to have discussions with you in the future.

Cheers,
Tom