Actually, I was thinking about this today... There was an earlier thread which discussed the off-angle performance of a crossed Yagi, and if I recall, the pattern becomes elliptical as you move off the antenna's bore sight. If this is true, then I conclude that it would be better to mount a crossed Yagi in the + orientation, vs X, as that way one of the two antennas will be properly aligned for an off-angle linear station. For satellite work, with accurate keps, this is probably not a significant issue, but for terrestrial work and other situations where the target's position may not be known or tracked, + should be more forgiving than X. At least, that's my theory.
I kind of hope I'm wrong on this... I just got a new 70cm antenna from a swap meet today, and it's already mounted in the X position.
Greg KO6TH
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From: w5rkn@amsat.org To: amsat-bb@amsat.org Date: Sun, 18 May 2008 16:42:02 -0500 Subject: [amsat-bb] Re: AOP-1 Circular Polarization?
Assuming the antennas you reference do produce circular polarization, radiation wise, it doesn't matter whether you mount them in an X or + orientation. The only difference would be the phase of the radiation, and you are not concerned with that. There could also be a difference between right- or left-circular polarization, but whether that matters depends on the polarization the the satellite's antenna. But X or + does not change that.
There might be some mechanical reason for an X or +, such as weather proofing, but not signal wise.
Ron W5RKN
Date: Sun, 18 May 2008 14:28:34 -0400 From: Sebastian Subject: [amsat-bb] AOP-1 Circular Polarization? To: Amsat - BBs Message-ID: Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
Hello all, I'm getting ready to put back up my old AOP-1 antennas (the old Cushcraft antennas that were popular in the days of AO-10 & 13). I'm wondering whether I should follow the same procedure of cross polarization for the 440 beam? It was recommended at the time to place the antenna in an X pattern instead of the cross pattern. Also, at the time, the 2 meter antenna was suggested to be placed in the standard vertical/horizontal polarization.
Please let me know which would be the best method to use for most of today's birds.
73s de W4AS
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