Jerry,
I have experienced with baying arrays, which is horizontally split, but not
vertically stacking them. I can also tell you of a setup I had years ago.
First, as far as the two antennas. You'll need a phasing kit which consists of
a T-connector and two lengths of 75-ohm cable to match the two antennas as they
will be fed in parallel. I don't remember the length of the phasing cables, but
you can get them already mead up as part of a separation kit from Cushcraft.
The other thing you need to consider is the phasing of your transmissions. It
used to be that the birds were left-hand circular polarized, if I remember
correctly. SSB is horizontal, and FM is vertical. Which mode will you use the
most? If satellite, then you need to circularly polarize it if that is still
necessary for the newer birds. My experience if from Oscar 13 days.
A second consideration is that if you phase your two antennas, you will be
narrowing the beam width. That will mean that you might need to track them more
precisely.
Some thirty years ago, a brilliant friend of mine, Wa8LMF, came up with the idea
that I could put up a pair of 8-el HyGain two-meter beams and phase them either
vertically, horizontally, or righthand or lefthand circular as my operating mode
changed. The way we did this was to put one beam up oriented with the elements
going from upper left to lower right. The lefthand beam on the horizontal boom
had its elements going from upper right to lower left. The two feedlines
entered the shack and fed a T connector to the rig. If I wanted to change the
phasing, I inserted either a quarter wave in the left or right feedline for
circular polarization if I recall, or a half-wave phasing line in one side to
switch to horizontal polarization.
I do know this much. If you worked FM and switched it to horizontal
polarization, you had a considerable drop in signal strength. And, when talking
with an FM station, running circular polarization seemed to reduce the amount of
picket fencing.
Steve, K8SP
----- Original Message -----
From: "Jerry Neufeld" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, May 21, 2007 2:21 PM
Subject: Stacked arrays on VHF & UHF
I have 2 CushCraft dual-band, 5-element yaggies for VHF & UHF that I'd like
to use for satellite work. Does anyone have any experience with stacked
arrays of this type? Any ideas where I might obtain accessible material on
how to optimize stacked, dual-band antennas? Any suggestions on this would
be much appreciated.
Also, I have a MFJ antenna analyzer, the 269 to be specific. Although this
analyzer provides for UHF measurements, it does not have a pick-off for RF
which I need for my MCount morse-code frequency reader. Anyone have any
ideas on how I might gain access to the RF output of the analyzer without
significantly influencing readings, especially for UHF?
Thanks to anyone who has advice on these matters.
Jerry VE3QSO
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