[amsat-bb] Re: AO7 mode switch

Paul Stoetzer n8hm at arrl.net
Wed Jul 31 10:25:50 PDT 2013

I know there was some question as to why the satellite comes up in Mode B
nearly all of the time after coming out of eclipse.

The "AMSAT-OSCAR 7 Technical Operator's Plan And Experimenter's Guide"
found starting on page 75 of this PDF (
http://ka9q.net/AMSAT-Newsletter-1974.pdf) says that the clock
automatically switches the satellite to Mode B at 0000 GMT. If the clock is
reset by eclipse to 0000, it stands to reason that it would always come up
in Mode B out of eclipse.

The satellite apparently knows somehow that it hasn't just been launched
since it's designed to come up with only the 70cm beacon operating after


Paul, N8HM

On Wed, Jul 31, 2013 at 12:31 PM, K4FEG <K4FEG at k4feg.com> wrote:

> Hello Satellite People;
> it is my opinion that we are quickly approaching the end of the Eclipse
> Cycle for AO7 this season. I had previously estimated the "final" eclipse
> to be on August the 2nd between 0200 and 0300 UTC but upon closer check
> with fresh Kep's  it looks like the eclipse durations are decreasing by
> approximately 10 seconds per orbit at this time and with the current
> durations of the orbits the final eclipse of 20 seconds will end at
> 21:00:50UTC, when the satellite is rising over Australia.
> I would guess that at that point the 24 hour mode switch will begin once
> the satellite is in full illumination once again. It appears to have been 9
> full weeks of eclipse's for AO7 and over 98% of the time it seemed to come
> up in Mode B, I know there were reports over Europe of a Mode A pass on
> individual orbits and I had noted the same for the USA as well, but once
> the satellite had gone into eclipse on the next orbital pass it would come
> back up in Mode B.
> In May of 2014 I hope to look at the beginning of the Eclipse Cycle and
> work at predicting the beginning and end of it better.
> This has been a fun exercise for me and I appreciate those from around the
> world that forwarded their observations to me.
> Now it is time to sit and wait to see if the switches start back on August
> 2, 2013 at @21:00UTC
> 73 ALL FRM
> EM55aj84ta
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