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AO-40, Orbit 381 S2 Tx Glitch




On orbit 381, at MA =44, the RUDAK connections shut off as programmed but 
the middle beacon did not come back on.  An EME class station, Gunter 
Wertich, DF4PV, reported hearing normal telemetry blocks very weakly.  This 
was reassuring that the IHU-1 had not crashed.  It was suspected that the 
solid-state matrix IF connections had not "latched" properly during the 
switch-over at MA=44.  In that case, Gunter, would have been hearing "bleed 
through" of the middle beacon through the IF matrix.  When I had AOS, 
shortly after 22:00 UTC, we cycled the MB->S2 Tx matrix connection manually 
off and on and the middle beacon popped back up.  For now the schedule has 
been left as it is, though RUDAK has been turned off temporarily.  Thus, 
for the moment, from MA=30 to 44, there will be no middle beacon and no 
RUDAK.  Note also, that, as before, the middle beacon is off from MA 
220-250 because of eclipses.

This "glitch"  has occurred once and perhaps twice before, both soon after 
the December incident and may be related to critical timing issues in the 
MUX output to the IF matrix.  This event will be studied further, and we 
will watch closely for several days to see if this occurs again.  If so, 
the fix may be to simply add additional timing delays to the automated 
Matrix switching software.

---W4SM for the AO-40 Command Team

--
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
   Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  _______________________________________________________________________

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