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Re:L1 revisited

Kevin Schuchmann said:

>   I also went trolling through the archives and found a note from DB2OS...
>"Command station G3RUH (James Miller) reported that commanding
>AO-40 on L-band frequencies was fairly easy, thus it appears the
>L-band receiver seems to be work nominally" (1)

..as it does today.

>this was after recovery and the satellite had just been reloaded and rudak 
>not on yet on,so if its hard to command now Stacey
>something has changed.

The L-band interference comes and goes and there is no cause/effect 
association with RUDAK.  I have many, many L-band command notes with RUDAK 
on and there was no interference whatsoever.  For example, RUDAK was on 
during December 2001 and there was no L-band interference.  Once when RUDAK 
was on and we had the interference, we turned RUDAK and all of the 
experiments off with no effect.  I have often turned RUDAK on to check the 
power budget.   ....no effect on commanding was noticed.  RUDAK has been on 
a lot and we have had two major "sessions" of the interference in the last 
six months or so, so of course they overlap.  The last problem with 
interference on L-band did end very soon after RUDAK was turned off, but it 
did not end immediately after RUDAK was turned off.  I have noted on 
several occasions that the interference is less at high squint 
angles.  This strongly suggests origin outside the spacecraft.


>I know the answer is out there, and I bet it is already known or

The command and RUDAK teams have absolutely no more information on this 
topic than you do.  I do not precisely know what causes the 
warble/interference, but it has never been directly correlated with RUDAK's 
power status.

Here is what I do know:

1. When there is warble on the downlink from L-band uplink, there is 
difficulty commanding on L-band.  The usually single bit corruptions 
indicate pulse, RADAR-like hits.
2. Generally when there is interference on L-band there will be some on 
U-band as well.
3. Sometimes L is worse than U, sometimes the reverse.
4.  At the moment there is no interference on L-band and very mild on U-band.
5.  RUDAK on/off and/or experiments on/off has not affected this.
6.  L2 seems more immune to the warble, probably because it is 6dB deafer.

If you want to look for a pattern, use the telemetry archives and 
P3T.  Perhaps you can spot something.

  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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