[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

RE: FT-847 question


I used Station for some time, and it worked fine for 2 m and 70 cm
downlinks, where the Doppler shift is relatively small, and probably more
importantly, all the temperature sensitive frequency elements are in the
shack.  However, at mode S frequencies, the frequency residuals, even with a
system which is kept on 24/7, can at times exceed 2 KHz, which is more than
software or hardware TLM decoders can handle.

With an averaged GPS lat/lon, fresh keps, and a WWV or GPS system time hack,
Uni_Trac, TrakBox, WISP, Station, and the gold standard, ITrack, all give
within a couple of Hz of the same answer.  It just isn't quite good enough
with my hardware, which includes a UEK-3000 at the antenna.  Interestingly,
the calculated agreement is very good near perigee, and deteriorates at
other parts of the orbit.

Oh yes, VP9MU, author of The Station, used a real G3RUH decoder to control
the downlink frequencies as well.  He has a nice system to capture the radio
frequency along with the TLM, and is going to do a comparison with the
various orbital models.  I am doing somewhat the same thing, though by hand
and with a spreadsheet.



To get the attention of a large animal,
be it an elephant or a country, it
helps to know what part of it feels
pain. Be very, very sure, though, that
you want its full attention!

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org