For years I've always fed my 30 meter Half Square at a top corner, and it's
done a reasonable job in my opinion. Recently I've discovered 2 Eznec files,
one for a Half Square and another for it's big brother, a Bobtail Curtain.
Both show the feedpoint down just a little bit on the driven element
vertical, and NOT dead on the corner. I've studied both Eznec model outputs
(corner feed and not corner feed) and indeed the different feedpoint does
show a little more gain, about 1.5 DB without altering the antenna impedance
much. The one I modeled for 30 has the feedpoint down about 2 inches from
the corner. Is what I am seeing accurate? Or, is this just another Eznec
anomaly? I realize that 1.5 DB isn't too much to worry about, but if I
should make another one, maybe I should alter the feedpoint. Opinions?
Thanks.

Jim Leder wrote:

For years I've always fed my 30 meter Half Square at a top corner, and it's
done a reasonable job in my opinion. Recently I've discovered 2 Eznec files,
one for a Half Square and another for it's big brother, a Bobtail Curtain.
Both show the feedpoint down just a little bit on the driven element
vertical, and NOT dead on the corner. I've studied both Eznec model outputs
(corner feed and not corner feed) and indeed the different feedpoint does
show a little more gain, about 1.5 DB without altering the antenna impedance
much. The one I modeled for 30 has the feedpoint down about 2 inches from
the corner. Is what I am seeing accurate? Or, is this just another Eznec
anomaly? I realize that 1.5 DB isn't too much to worry about, but if I
should make another one, maybe I should alter the feedpoint. Opinions?

For an antenna like the half-square, I would trust the EZNEC results
as long as you didn't violate any of the EZNEC guide lines.

I once violated the EZNEC guidelines and got an omindirectional antenna
with 20 dBi gain in all horizontal directions. :-(

Another possibility is to feed the half-square at the lowest point
with a matching network to match the high impedance.

Another thought just occured to me - that a 600 ohm feed point must
exist somewhere down the vertical section. Of course, balancing the
currents at that point would be a challenge.
--
73, Cecil http://www.qsl.net/w5dxp