Re: [amsat-bb] Circular Polarity

["Frederick M. Spinner" <fspinner@xxxxxxxxxxx>]

>      I believe that a signal that leaves the bird from an  RHCP antenna
>would want to see an LHCP antenna on the ground, unless a dish were in use
>which would reverse the polarity on reflection to the focal point.  I 
>think...

No.. the dish feeds are wound (or phased) LHCP as once they are reflected 
off the dish they become RHCP.  (Just like your face in the mirror getting 
transposted left-to-right, right-to left.)

>
>      There must be someone out there who knows the S-band antenna
>characteristics for AO-40.  Any help directing me toward the path of
>righteousness would be appreciated.  Especially at these prices!
>

The helixes are RHCP on AO-40.

I sometimes wonder if linear polarization won't be just fine on the
downlink once the sat is 3 axis stabilized-- and the feed designs are much 
easier for linear feeds.

MMDS antennas are very tempting to try for Mode-S and are linear.

Hey, has anyone else ever tried a MMDS converter other than a Drake
2880?  It'd be good to find a cheap replacement.

Fred W0FMS
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