Satgen280  Satellite Profile No 8B Oscar 13 AO13  by GM4IHJ      6 Aug 94
BID of this msg is SGEN280  Please use this BID if you retransmit this msg

The main features of AO13 were described in sgen279. This second part
reports several unusual features which AO13 operators may encounter.
a. Matching Frequencies. It is not easy to tune your transmitter exactly
to the frequency of a station you wish to talk to. One of the least
obtrusive ways to do this is to use your receiver clarifier tuning and
transmit a CW carrier. Tune to his signal on USB, then switch in the
offset clarifier, Key your transmitter in CW position and tune for zero
beat on the down link, ( you are off his frequency so you do not interfere
). Then switch your Tx to LSB and switch off your clarifier and start
talking. If you have the clarifier offset exactly right you should have
compensated for the exact difference between your LSB carrier and CW
carrier, and be right on tune with him, having caused no qrm . You can
practice setting this up on a clear frequency until you get it exactly
right.
b. Solar Resonance. Oscar 10 launched in 1983 and it still has a high
altitude perigee low point clear of drag . But Oscar 13 perigee is several
thousand kilometres below its launch perigee and it is danger of being
dragged down into the lower atmosphere with fatal results. The problem is
that AO13's apogee high point has been occuring when the sat was nearest
the Sun. Though the Sun is a long way away repeated little pulls by solar
gravity at each apogee have slowly increased AO13s apogee height by
pulling the orbit further from earth at apogee. Unfortunately this pulls
the satellite nearer the earth at perigee. If as is possible this
continues to occur AO13 will be dragged out of orbit long before AO10
ceases to operate. This solar resonance has also meant that AO13 apogee no
longer occurs near its highest latitude north . So northern hemisphere
coverage is not as good as it was.
c. Mutual QRM. AO10 and AO13 have both been above the horizon together in
recent weeks. IHJ's old ears prefer AO10 with no spin modulation, but when
operating AO10 he gets called by stations operating AO13 with signals he
cannot read because of weakness and spin mod. IHJ calls CQ AO10 but many
AO13 ops fail to appreciate what this means and QRM ongoing AO10 QSOs.
PLease , say what sat you are on when you call and be aware the other sat
may be there on a different bearing where your weak sigs may be unreadable
but still cause damaging QRM.
d. Pirates. Has anyone else noticed European pirates around the 145.949
downlink.They appear to be operating a net of one controller and several
outstations in Spanish. If you hear these pirates please inform your local
PTT and ask them to get on to the PTT in the pirates country. IHJ has done
so, but one voice rarely gets results and this sort of illegal operation
over Europe is becoming an epedemic. We have them coming up to sats on
both 2m and 70 cms, virtually all speaking Spanish onto satellites in
range of Spain. If it continues , genuine amateur radio in the country
concerned is likely to suffer. Recent Sporadic E events on 2m have pin
pointed one group of pirates who seem to be in the Madrid area of Spain.
Spanish radio amateurs please help, or we will lose 2m usage over Europe
as they interfere not only with the analog voice sats but also the packet
uplinks. 73 de GM4IHJ @ GB7SAN