Ed, several years ago I had to find out why an almost identical
antenna system as you have discribed operating on similar frequencies
didnt work very well. System also used an ATU. Analysis showed data
very similar to the EZNEC values. I t was not practical to increase
the hiegth of the antenna so I went vertical using a 30ft fiberglass
whip, gov surplus. Also used inductors and capacitors switched in to
bring the antenna to resonance at the desired freq. Although we only
really used one the others had to be available. Although the ATU was
still used it was completely unneeded as only 3 frequencies were being
used seies inductance and capacitance selected by remotely controled
relays provide a match with the VSWR less than 1:.5 on any frequency .
Communication from NC to GA, FL, and DC were routinely possible with
100watts PEP SSB.


That could certainly be an option.... especially since this antenna is
on top of a government building. Aesthetics is an issue here.

However, the pre-existing antenna can easily be made to work well in
our situation simply by shortening it to resonance on 3975, and possibly
just adding traps or another dipole off the feedpoint for the other two
frequencies of operation. There is room. The reason for this silly
situation to begin with is just the misconception held by our ARES people
that the internal tuner of the FT900 could handle the mismatch.

Ed