Tom Horne wrote:

Jim
I had no intention of running a four square with four auto tuners.
Perhaps I should have put that inquiry into a separate posting for the
sake of clarity. We built a four square for field day two years ago.
Because the masts that we had then were only thirty feet high a kind
of capacitance hat was built into the guy lines. We had very good
performance from that four square until a severe thunderstorm
destroyed it. I was wondering if having sixty four foot masts would
allow us to adjust the height to resonance on forty meters so that the
four masts themselves could serve as the elements of the four square.
Since a half wave at 7150 kHz is nearly sixty seven feet I would have
to add three feet worth of additional tubing in order to get a
resonant half wave antenna. I had thought that half wave verticals
did not require a counterpoise was I misinformed? If a counterpoise
is needed it wouldn't be too hard to throw out four radials for each
mast. I was just looking for a quick way to put up a four square and
these aluminum masts seemed like they might fill the bill.
--
Tom Horne


If you put the feedpoint in the middle of the antenna and run the coax
up the middle of the bottom, and have a really good choke, it might
work. (basically, an elevated half wave dipole) There was such an
antenna scheme for a 4 square in one of the ARRL antenna compendiums (I
think they were doing it for 160m, and had a matching network (mostly
inductance) at the feedpoint to deal with the "electrically short" radiator.

Making it actually work is another story entirely. You've got to have a
pretty good choke, or the feedline starts to be a big part of the
system, and since it's laying on the ground, it's a pretty lossy part of
the system. The bottom half of the antenna is closer to the ground than
the top half, so there's those effects too.

SO, even if you sat at the bottom of the antenna with your antenna
tuning meter and carefully adjusted the matching network at the feed to
get 50 ohms, I don't know that when you set it all up, the phasing will
be right.

It might be close enough.. but the odds of not getting as good a F/B as
you want (e.g. null depth) are pretty good. The phasing isn't so
critical for forward gain (you can be tens of degrees off and not lose
much in forward gain, but that will completely kill your 10dB null)

But just feeding the end of a 1/2 wave wire sticking in the air is
asking for difficulties. Your coax is nominally 50 ohm sort of
impedance, and you'd be end feeding a dipole at a high Z point (a
thousand ohms, maybe).