On Apr 10, 2:24 pm, "Antonio Vernucci" wrote:
I am also surprised by the high resistance you are seeing with the
hairpin wires removed. From what you posted before, and from the 3-
element NBS and the 6-element designs I ran in EZNEC, I would expect a
lower feedpoint resistance than that. If I put a pure inductance in
parallel with your 42.4-j39 ohms, I get the same answer as you did,
that it moves to 78 ohms resistive.

My offer to look at your EZNEC file is still open, of course. Maybe I
could see something in it--I know that I can look and look at
something and not see an obvious problem, even when I know perfectly
well what to look for.

If your personal mail on the newsgroup is correct, I could send you the EZNEC
file of my antenna.

Also--in the model before you split the D.E. into three wires, did you
get a more reasonable feedpoint impedance (with no hairpin, just
looking at the D.E. feedpoint)? I think we were expecting something
like 19-j58 ohms. If you get that, then I would look for the reason
things change (so very much!) when you split the D.E. into three
separate (but connected, end-to-end) wires. I can understand a small
change but not so large a change. Is the total number of segments for
the three wires making up the D.E. still about the same as it was in
the original version of the model, with just one wire for the D.E.?

I am also surprised as I would have expected a much lower resistance (as you
suggested)

I did the test you have suggested and I noted some change, but not much. With a
"solid" D.E., i.e. not broken in three pieces (and without the hairpin of
course), impedance is 43.27 - j 40.97 ohm, not terribly away from 42.4 - j39
ohm. In that test I configured EZNEC for 17 segments, whilst when the D.E. was
broken in three parts I had used 17 segments for the two outer arms and only 5
segments for the 10-cm center section, due to its much shorter length (I see
that result depend somewhat on the number of segments).

73

Tony I0JX

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