I know what those are. It's another design from N6BT, who I believe
used to own Force 12. As I said in a different post, he also came up
with the VOR that coils the bottom half of a vertical dipole around the
base. He also made the antennas that had a short vertical section with
spiral coiled elements on both ends of the vertical section (I don't
remember what they were called). Essentially your H-shaped antenna with
the horizontal sections wrapped in a coil. They worked well also ...
but none of those configurations are marketed anymore because there are
simpler ways of achieving similar performance, even for portable
operations. A 17 foot extendable whip (you can buy cheap ones for as
little as about $35 on eBay) with three or four radials can be set up in
less than 10 minutes without any tree or other support and outperform
almost any similar alternative. Several folks have done YouTube videos
on exactly that configuration, and I've made my own version ... which is
how I know it can be set up in less than ten minutes.
And I still say that there is no practical advantage for trying to force
a vertical antenna into being a dipole. At least I can't find one that
offsets the additional hassle of it. If you think otherwise, I'd like
to hear it. Maybe the fact that the feedpoint impedance of a vertical
dipole is higher than a quarter wave version with radials or some sort
of counterpoise, but it's high enough (greater than 50 ohms) that you
still need to match it.
Dave AB7E
On 1/13/2026 12:34 PM, john@kk9a.com wrote:
A vertical dipole can have shortened elements, making height less of an
issue. Force 12 used to make sideways H shaped verticals that were center
fed. I have used one on 40m and it was surprisingly good. Here is a
Force12 80m Sigma vertical:
https://dxsupply.com/en/amateurradio/verticals-6-80-m/force12-80m/
John KK9A
David Gilbert ab7e wrote:
"Assuming you have the height"
That's the kicker, though, and it takes twice as much of it for
relatively little additional performance. I've modeled a 20m ground
plane with four elevated radials and a 20m vertical dipole, both of them
being 4 feet off the ground. The elevation pattern is lower with the
vertical dipole (17 degrees versus 23), but the maximum gain is almost
identical.
I agree that your suggestion (feedpoint at the bottom with a serious
choke) is a practical way to make a vertical dipole, but you have to
trim for tuning at the top whereas you can trim a ground plane at the
radials near the ground.
73,
Dave AB7E
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