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Re: Circular polarity - Don't Bother!




Hi all,

I always bite my tongue and walk around the chair 3 times before replying to
the list but here goes.

As we say here in OZ  "it's horses for courses".
If you are talking about a "power-house in the sky" like ao-40 promises to
be then a minimal setup may suffice. Some amateur satellites can be worked
using nothing more than a hand-held radio. But if you are talking about
(let's say) the 38k4 digital birds like uo-36 and TiungSat-1 then let me
assure you that CP does matter. I have switchable polarity yagis and if I
leave the system work on auto and go off to do something else I return to
find an overall d/l efficiency of 30 - 40 % and total download of maybe
500 - 600 kilobytes. If I'm here in the shack and watching the 's' meter for
polarity fades, the overall d/l efficiency is close to 100% and the total
downloads 2.6 to 2.8 Megabytes per pass. I have watched polarity fades take
uo-36 from (remember these are FM readings) hard-over on the 's' meter to
below the noise level in a matter of seconds. Below the noise level equates
to data lost.

I guess most of the discussion on this list has centred around ao-40
recently so this post may  be viewed by some as telling people how to suck
eggs but there may be others who would interpret some of the recent posts as
applying to all amateur radio satellites .... Not so!

Regards to all,

Bill Magnusson ... vk3jt
Milawa Australia


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