[amsat-bb] Working SO-50

Ib Christoffersen oz1my at privat.dk
Sat Dec 3 12:45:54 PST 2011

Working SO-50.

I think it is time to look at how one can operate over SO-50 and the
problems that can be encountered.

First the normal and nominal data:

Uplink is at 145.850 MHz.  Downlink at 436.795 MHz.

If it is not ON - use 74.4 Hz CTCSS tone to activate the transmitter for 10
seconds to have it on for nominally 10 minutes - when on use 67 Hz CTCSS
tone during your transmission.

That was the intended normal operation.

Now to the deviations from the normal scheme.

The downlink frequency sometimes jump approximately 5 kHz. Therefore I have
two different frequencies pairs to be used in SATPC32:


If you do not use Full Doppler Tracking it is not much of an issue. Just
tune for best downlink.

Talking about SATPC32 here are the entries for the CTCSS tone:


The first data is for the ICOM IC-910 radio. If you use another radio please
look at the information in SATPC32.

Next problem is the change of polarity of the downlink signal during a pass.
The polarity changes during the pass. At least I have to switch polarity a
few times from RHCP to LHCP to optimize the downlink signal. That has been
confirmed by others. How it works using linearly polarized antennas I do not
know - but I think there will be some fading.

And if that is not enough - at least here over Europe - we have to put up
with QRM on the uplink from a lot of different sources like repeaters and
people using our frequencies as cheap phone connections.
The result of the QRM is that it sometimes is difficult to turn SO-50 on.
Also the QRM may turn the transmitter off.

And since the inclination is not sun synchronous we have to live with a
steady change of pass times over the year. 

Some may think I am not a fan of SO-50. That is not the case. It is a very
good satellite we got for free and it works very well.
Already more people are using it over Europe after AO-51 is not with us any
more. That just took a couple of days.

73 OZ1MY/Ib

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