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Noisy signal this night on AO40 orbit 1288 from MA=162



I All,

The noisy signal was on again on AO40 this night august 21 orbit 1288

I recognized it on panoramic receiver at 03:58 UTC  MA=162  about
20 KHz belove the MB

The noisy signal was about 30 KHz wide and 6 dB above the MB level
and the transponder sensitivity dropped down because the L1 Rx AGC was
already at 8,5 dB

The noisy signal was slowly drifting up in frequency with the following
rate of change:

03:58 UTC    was   20 KHz belove MB     +6 dB over MB level
04:07     "       was over the MB and it was impossible detect TLM
04:12     "       was   10 KHz above  MB     +6 dB over MB level
04:15     "       was   20 KHz above  MB     +6 dB           "
04:20     "       was   30 KHz above  MB     +6 dB           "
04:23     "       was   45 KHz above  MB     +6 dB           "
04:27     "       was   55 KHz above  MB     +6 dB           "
04:30     "       was   70 KHz above  MB     +3 dB           "
04:37     "       was   80 KHz above  MB     +3 dB           "
04:43     "       was 110 KHz above MB      +3 dB           " 
04:50     "       was 135 KHz above MB      +3 dB           "
04:54     "       was 150 KHz above MB      +3 dB           "
05:03     "       was 175 KHz above MB       -3 dB belove MB level
05:10     "       was 200 KHz above MB       -3 dB            "
05:18     "       was 225 KHz above MB     -10 dB            "
05:20     "       was 250 KHz above MB     -15 dB            "

At 05:20 UTC the  L1 Rx AGC became normal at around 2,5 dB
and trasnsponder operation started again nominal with full sensitivity
and clear modulation.

I decoded TLM on this orbit 1288 and made the attached L1 Rx AGC 
diagram from MA 166 to MA 182

During this orbit AO40 was in range with Europe, Africa, Asia and
not Americas

I have compared the above diagram with that of orbit 1286 from 
MA 182 to MA 204 and i realized that the L1 AGC has the same
shape of orbit 1288

During orbit 1286 AO40 was in range with only Americas and Pacific
and no Europe not Africa and not Asia was in range.

For the above reason it seams unrealistic that the L1 signal activating
the L1 Rx AGC is radiated from the earth and probably some instability
with autooscillations occurred somewhere in AO40

73" de 

i8CVS Domenico   






















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