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Re: RE: AO40 12m WAV files



Hi,

On Sunday 21 January 2001 17:47, Rick wrote:
> Bob,
> 
> This is very good work. The signal is quite strong but I can't decode it
> with AO40rcv (Alpha V0.1) or the IZ8BLY decoder (V0.3). Phil, are you
> able to use these files to design an optimized decoder?  I was hoping
> for some feedback so Bob (WB4APR) would know his efforts are
> appreciated.
> In the AO40-2001-01-18-B.wav file I noticed a pattern of nulls in the
> carrier that occur at intervals of approximately 1.36, 0.95, 1.05, 1.36,
> 0.95, 1.05, ... seconds. Thus a repeatable set occurs at a rate of once
> every 3.36 seconds suggesting a satellite rotation rate of 17.86 RPM. I
> assume the nulls within this repetition are caused by obstructions like
> the 400N nozzle because we are looking at the antenna from the side as
> it rotates.

I took a look at these .WAV files. The fades are really deep and every time
it happens it destroys at least 10 symbols.
Forget it, no way to decode these without even a simple FEC and interleaving.
How is this telemetry stream generated? I suppose that the bit-banging is done
by the IHU-1 processor. In this case it should not be very difficult to implement a
K=6 R=1/2 convolutional code, should it?

  -- Jens
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