[amsat-bb] Re: SO-50 eludes me
glasbrenner at mindspring.com
Fri Nov 28 12:10:11 PST 2008
Let me point something out here. The PL tone on SO-50 or AO-51 does not
prevent QRM. It just makes it where you do not hear it. The offending signal
is still present at the satellite receiver, and will still block you out if
it is stronger than your signal.
Considering we have shut down several stateside Echolink nodes that thought
145.850 was a pretty good spot to operate, it's very important to have some
means of monitoring the uplinks. PL does a fine job of saving power, which I
suspect is it's primary purpose on SO-50, but it is actually detrimental to
preventing QRM on the uplink. Fortunately we identified these guys via
There are other effects of the PL that we have observed on AO-51 when
several legitimate users are in competition for the uplink. When collisions
occur, often none get through, and none of them know why because nothing
gets repeated so the situation continues. With an open uplink, all stations
can hear the logjam and hopefully enough stand down to unclog the uplink.
This is why we stress the importance of full duplex operation.
The issue is moot with SO-50 anyways...AFAIK the satellite is primarily
hardware driven. Considering it was an unexpected gift from the Saudis,
let's not look in the horse's mouth too much.
A simple way to solve this is to use U/V instead of V/U for future FM
satellites. SO-35 was a dream to operate, with a strong downlink easily
heard, and an uplink that swept itself clean due to Doppler shift.
73, Drew KO4MA
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