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Observed AO-40 FEC coded telemetry ?

Hi all,

On Saturday June 7th 2003 around 03z, 
I am sure that I observed the experimental transmission of FEC coded
telemetry of AO-40 on the S2 beacon.

Normally, the bird have been sent the blocks in the sequence of
A,E,A,K,A,E,A,L,A,E,A,M,A,E,A,N and then repeat them. However, on that
day, the IHU-2 turned on around 0245z, and a new sequence initiated since 0252z.
The sequnce I observed was an ordinally A block in 13 seconds first,
then (possibly) a FEC coded A block in around 13 seconds followed by
idle 28 seconds. The two LEDs of 'CAR' and 'CLK' on 'the Phase 3 400bps
PSK demodulator mkII' designed by James G3RUH were always active even
FEC coded blocks were sent. Unfortunately since I'm not ready to decode
the FEC coded blocks, I coundn't confirm what contained in the 13 seconds. 

I logged the sound into some .wav files by AO40Rcv written by Moe
Wheatley, AE4JY and placed them below. 


The waterfall pattern is so interesting. After the conventional A block,
the many peaks around 1600Hz turned broad ones. I think it means the
scrambler in the onboard FEC encoder works well.

73, Kazu Sakamoto, JJ1WTK   kazu@jj1wtk.jp
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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