If you are phasing them for additional gain and to have a more full
radiation angle, it is probably better to use identical antennas and I would
mount the lower one halfway up. If you are looking to spray your signal in
two directions than using dissimilar Yagis will be fine, you don't even have
to match the feedline lengths. If you are looking to beam in multiple
directions the antennas can be spaced pretty close but you also have to be
careful that the boom on either one is not resonant on any of the bands if
you intend to point them 90 degrees apart. The best way to really see what
it happening is by modeling both antennas. DF2BO may help be able to help
you with this question since he has the EZNEC models.
GL
John KK9A
Douglas Ruz EA3DZ wrote:
Hello,
I am new to the list. I am Doug, EA3DZ.
I would like to add a second tribander to a 22m (66ft) self supporting
tower. I have an Optibeam OB-16-4 on top of the tower.
This tower is a little bit wide, so, probably I will add something like an
OB-7-3 or similar with 1 meter or more free area in the central part of the
antenna.
The tower has piramidal shape. It is about 50cm wide in the top section
(5m) and about 90cm (3ft) in the zone 10m below the OB-16-4.
What is the minimum distance allow between antennas to avoid interaction
with the top tribander?
Any idea?
Thanks,
Doug, EA3DZ
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