I am sure this subject has been beaten to death many times but I am
not finding all of the wisdom I seek either on the bookshelf or in
the archives of this list.
I have a TH-11DX at 100 feet. I plan to build a 40/30 meter
rotatable dipole which I want to put above the TH-11. I assume
(uh-oh) that with the close frequency spacing of 20-17-15-12-10m it
will be difficult or impossible to get resonances of the 40-30m
antenna far enough away from all of those bands to get away with
putting the elements in the same plane. This assumption however
leads to two questions:
1) I'm not sure this can be answered in general terms, but: How far
removed from a band does a resonance have to be in order to not
cause significant problems? I don't mind a little distortion of
pattern or a dB loss of gain but significant SWR changes are not to
be tolerated.
2) Is there a simple way to measure said resonances of the 40/30
meter dipole that will be good enough for this purpose? I have an
MFJ antenna analyzer at my disposal.
Assuming putting the 40/30 dipole in the same plane as the TH-11
elements is out brings me to my next question.
3) If mounted in the same plane Will the boom of the TH-11 cause
problems for the 40-30 meter dipole? How far above the boom should I
be trying to mount it for good performance? Four feet could be done
very easily but I worry that may be too close. I could get a few
feet more with extra work and expense. Anything beyond 8 feet is
probably not possible in this instance.
I would appreciate any comments or advice I can get before I get too
deep into this project.
Thanks,
Paul N1BUG
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