[Antennaware] Re: Too good to be true

[Guy Olinger, K2AV]

LB,

Thank you. At some point my brain just shut off and would not see
anything else.

Yes, the cut at the top is intentional.

Will respace the ground mat wires and see if gain suddenly ramps off.
Same with mat height above ground, which is now a couple of wire
diameters.

Will have to reconstruct the area around the sources to fix those
segmentations, but easily done. Will repost after the corrections are
made.

Again, thanks.

Guy.


Notes to other readers as well:

Wire 4 is to simulate a supporting tower, and like the tower, its
bottom is just in the ground and subject to whatever loss that may
cause if the base of the tower is carrying a current.

I am calling this a "cut triangle", which in some sizes HAD appeared
to have less ground loss than other antennas. If anyone knows an
earlier attribution of this antenna (e.g. W9WXYZ triangle), it would
be nice to know.

Some experimenters in this area have these in the air and report
"good" results, but none of them have attempted split feed against a
folded current sink, as in this model, which allows distinct phasing
and current in the two elements.

Nor has anyone been able to attempt optimization of the antenna's good
points through modeling.

I have some requests for the .EZ version. I will put that off until
LB's points are incorporated.


----- Original Message ----- 
From: "cebik" <cebik at cebik.com>
To: "Guy Olinger, K2AV" <olinger at bellsouth.net>
Sent: Wednesday, April 07, 2004 5:58 AM
Subject: Re: Too good to be true


> Guy,
>
> I ran your model in GNEC, since the format lent itself to that
program.
>
> 1.  You did not specify in your note that the triangle was open at
the top
> peak, but I assume this is intentional.
>
> 2.  The Averga Gain Test yields a value of 2.222 in free space,
indicating
> an essentially unreliable model, with gain values well above (by
more than 3
> dB) the correct value.  However, the further off the ideal that the
AGT
> score is, the less reliable that a corrective is for establishing
the true
> modeled gain.
>
> 3.  Taking theta patterns, The maximum gain is virtually straight
up.
>
> I cannot say what the model problems may be, but I suspect that many
of the
> wires at the base--and perhaps even underground--may be too close
for
> accuracy.  As well, for accuracy, the segments on either side of the
source
> segment(s) should be equal in length to the source segment(s), and a
split
> feed should use segments of equal length.  I did not fully analyze
the
> source segments, but if at a corner, NEC often has difficulty in
getting
> equal currents in both segments if the wires are not in a roughly
symetrical
> form or if the segments are not centered within a wire having
numerous
> segments on either side of the source segments.
>
> All of this is quite rtentative, but I hope there may something
useful here.
>
> Regards,
>
> LB
>
======================================================================
===
> L. B. Cebik, W4RNL              /\   *    /  /    /     tel:
865-938-6335
> 1434 High Mesa Drive        /\ /  \/\    ----)(--- 
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> Knoxville, TN 37938-4443   /  /   /  \  /  / || / e-mail:
cebik at cebik.com
> USA                       /  /   /    \      ||
W4RNL at ARRL.org
>
>