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Re: AO-40 and switchable CP requirement?




>I'm dredging from not fully formed memory:
>If I recall correctly, AO-10/13 used RHCP antennas that had really big
>sidelobes (I seem to recall they were like -4dB peak and made the whole
>volumetric pattern look like a 3-D fleur-de-lis).  So switchable CP made
>a lot of sense since the sidelobes would be LHCP and often at usable
>signal levels (when polarization matched).
>I haven't seen the same statements made about AO-40.  Are the antenna
>patterns cleaner?  I haven't noted anyone on the list mentioning the
>need to polarity switch yet but perhaps that's an implicit assumption.


Hi Scott,

I remember the same thing about O13.  My experience with O40 is certainly
different in the short time I've used it.  The "good passes" here are too
often in the wee hours of the morning, so far...

I've tried at various times at the same pointing angles, with widely varying
signals, and reversing polarity on the uplink has ALWAYS been better with RHCP.

Changing polarity on the uplink (my downlink is with a dish RHCP) has never
indicated an increase when switching to LHCP.

It seems as though the major lobe is not consistent with what the off pointing
indicates.  Any comment from anyone?

            73, Dave wb6llo@amsat.org
                    Disagree: I learn....
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