If you're using linear loaded 40m elements, they are most likely not
resonate on 15m and your spacing is probably adequate. I have had almost
no interaction mixing 20m and 40m beams if that is an option. Of course a
program such as EZNEC will easily show any 15/40 interaction as well as how
four long boom 15m beams will work at your proposed spacing. If you
purchase OptiBeam antennas, Tom will most likely do the modeling work for
you to ensure good results. Perhaps other antenna manufactures do the same.
John KK9A
To: TOWERTALK@contesting.com
Subject: [TowerTalk] Proximity of monobanders
From: Cqtestk4xs@aol.com
Date: Thu, 18 Nov 2010 19:48:50 EST
Plans are proceeding for the new station. I need some expert advice.
It's a long story but for several reasons I may need to put the 15 meter
stack
on the 40 meter tower. I know this is not an optimal situation but I hope
to mitigate it somewhat by a decent sized spacing between the 40 and 15
antennas.
Plans call for a 4 high stack of 6 or 7 element stack of 15 meter Yagis
(48 ft boom) on the same tower with (2) 4-element M2 Yagis for 40. This
will
be a rotating tower so all booms will be parallel at all times. Heights
for the 15 stack will be 144/108/72/36. Heights for the 40 meter Yagis
will
be 200/90. With this spacing, I would have 18 feet between the 15 Yagis
at 72 and 108 and the lower 40 meter beam.
My gut feeling is this should be enough to mitigate just about all
interaction. Am I right? Anybody out there who has run a program to
analyze
this
situation?
Any thoughts would be appreciated.
73 Bill KH7XS/K4XS
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