Cecil Moore wrote in message

Scroll on down. It's four 1/2WL array sections separated by a "phase
reversing coil".

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...

I tried modeling a couple of
antennas myself using multiple 1/2 wave elements and inductance as
phasing coils just to test this out. But I used three elements instead
of four. I do not see any major change in current distribution when
compared to feeding all three with three separate sources.

Turn on the CI feature, display the current phase, and you will
see the difference. With EZNEC's lumped coils, the currents in the
outside sections are 180 degrees out of phase with what they need
to be.

I wasn't using eznec...

But I do see a bit less gain with the lumped inductance version, and
not quite as tight a pattern. This *might* be a point of error, but
I'd have to look more carefully into that.

When you turn on the 'display current phase' feature, you will
see the difference.

Again, wasn't using eznec, but I looked in eznec for that feature and
couldn't find it. Is it in the demo version?
The currents in each 1/2WL sections are supposed
to be in phase. With EZNEC's lumped coils, they are out of phase no
matter what coil reactance is chosen.

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. With the
separate source antenna, I placed the elements as close together as
possible in order to be close to the loaded version in total length.

That's why there's more gain
using multiple sources. The errors are minimized using multiple sources.

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. Surely not a short
mobile whip. I doubt even with complex arrays if all the coils are for
loading purposes only. Sure, there may be some error, but not much
anyone can do about it, unless they design a new modeling engine. I
would think any error would be a db or less in most cases. Not really
worth worrying about. Or to me anyway...:/ When phasing elements, I
prefer separate sources anyway. And when designing mobile antennas, I
don't model them.
I calculate in terms of efficiency. The appx pattern and current
distribution is a given...
Seriously speaking...I think you can take Reg's vertload program, and
get as close as you would ever need to get as far as designing a
mobile whip, or short loaded vertical. It will tell you the best appx
place for the coil, the effects of wire dia, coil dia, coil length,
adding lower masts, adding upper stingers, ground loss, etc, etc,
about as well as you will ever need to use for designing such an
antenna. And if you feed it an accurate ground loss number, you know
your appx efficiency. After farting around with it a couple of years,
it seems to be pretty accurate comparing it to the real world. And
it's not even zipped up... MK