Be careful. The antenna modeling program is great when you don't have
interaction. I finally decided to build a 12 meter beam in 1992 and put
together a W2PV 3 el that looked great that was to mount 5.5 feet below the
KT-34XA. Well up it went and the antenna was centered on 24.500 not 24.930
plus the KT-34XA 10 and 15 shifted too.
I pulled that down and was reading the material Brice W9PNE had published on
a 2 el X beam. I was familiar with the X beam as Dick Bird G4ZU designed
that along with his G4ZU birdcage quad. Moxen and others stated the problem
with the X beam was side radiation. Brice came up with side back wires and
his design calculations are in one of the first ARRL Antenna Compendiums. I
used the lower spider and aluminum from the G4ZU birdcage, cut the antenna
to 24930, used a Collins coax balun and it came out to just above 24945 and
was below 1.2 across the narrow 12 meter band. Changed the 10 meter
frequency on the KT-34XA slightly (both in SWR reading and on the MFJ 259
analyzer. 15 stayed right on 21.200 as before. My DXCC count went from 114
in 1992 to 320 today.
There used to be a program by K6STI that also modeled interaction and this
would be needed too
if other antennas are nearby. I had to put the X beam where it is and the
alternative was to continue using the 40 meter beam with its cloverleaf all
or virtually nothing pattern.
73 Dave K4JRB
> Dave,
>
> My strong opinion is that if you use a good modeling program you can
> build it and put it up without any need for adjustment.
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