Mark Keith wrote:
I see a diagram, but no pattern plots or current distribution plots.
I'm curious to see how your's compared to mine. So far, after juggling
many different coil inputs, about the best gain I can get broadside is
3.54 dbi. "three 1/2 wave elements set end to end as a single wire
with the coils in the proper places on the wire ends" With separate
sources, I can get nearly 5 dbi. One note...End to end 1/2 waves is
not an optiumum spacing for max gain...

That difference in gain is because one cannot model a phase reversing
coil with a lumped inductive reactance. A workaround is needed and
yours is to use multiple sources. Mine is to use inductive stubs.

Again, wasn't using eznec, but I looked in eznec for that feature and
couldn't find it. Is it in the demo version?

I'm using DOS EZNEC 2.0 but I assume 3.0 has the same features. On
2.0 a Ctrl-I changes the current display from magnitude only to
magnitude and phase.

Dunno, mine seem to be fairly well in phase. But not as good a
pattern or as much gain as using separate sources and elements. But
being as the overall current distribution seems little changed either
way, I'm not going to speculate on the reason at this point.

That's the point. The current distribution is NOT the same either way.
I'm pretty sure you are displaying the current magnitude, not the
current phase. Given that the EZNEC lumped inductive reactance cannot
reverse the phase, the phases will always be 180 degrees apart in
adjacent 1/2WL sections and will not result in maximum gain or
minimum beamwidth.

This is quite possible. But I still don't think this would cause
noticable error when modeling short coil loaded antennas, or arrays
where the coil didn't act as a phasing device.

If I remember correctly, all you asked for was an example where EZNEC
didn't provide the correct results. Antennas using phasing coils is
that example. The lumped inductive reactance will not model a phasing
coil. It's not a big deal since there exist workarounds. I'm going to
try a parallel inductance and capacitance and see what happens to the
phase of the currents in EZNEC.
--
73, Cecil, W5DXP