[amsat-bb] Re: AOP-1 Circular Polarization?
ko6th_greg at hotmail.com
Mon May 19 00:17:12 PDT 2008
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.
> From: w5rkn at amsat.org
> To: amsat-bb at 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
> 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
>> 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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