[Antennaware] Re: Too good to be true
Guy Olinger, K2AV
olinger at bellsouth.net
Wed Apr 7 11:03:22 EDT 2004
Thank you. At some point my brain just shut off and would not see
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
Will have to reconstruct the area around the sources to fix those
segmentations, but easily done. Will repost after the corrections are
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
> I ran your model in GNEC, since the format lent itself to that
> 1. You did not specify in your note that the triangle was open at
> peak, but I assume this is intentional.
> 2. The Averga Gain Test yields a value of 2.222 in free space,
> 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
> score is, the less reliable that a corrective is for establishing
> modeled gain.
> 3. Taking theta patterns, The maximum gain is virtually straight
> I cannot say what the model problems may be, but I suspect that many
> wires at the base--and perhaps even underground--may be too close
> accuracy. As well, for accuracy, the segments on either side of the
> segment(s) should be equal in length to the source segment(s), and a
> feed should use segments of equal length. I did not fully analyze
> source segments, but if at a corner, NEC often has difficulty in
> equal currents in both segments if the wires are not in a roughly
> form or if the segments are not centered within a wire having
> segments on either side of the source segments.
> All of this is quite rtentative, but I hope there may something
> L. B. Cebik, W4RNL /\ * / / / tel:
> 1434 High Mesa Drive /\ / \/\ ----)(---
> Knoxville, TN 37938-4443 / / / \ / / || / e-mail:
cebik at cebik.com
> USA / / / \ ||
W4RNL at ARRL.org
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