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Re: AO-40 data mode



At 11:59 AM 10/23/2003 -0500, Howie wrote:
>Good examples of ham radio applications that achieve the
>same results are PSK31 and AO-40 telemetry with FEC.  Using BPSK or maybe
>MSK with FEC (forward error correction) would produce many more usable QSO's
>on AO-40 and maybe eliminate LEILA from our ears.

The MB is only 400 bps so that's probably not a good example.  And it's 
running at least 10db above QSOs.  My limited experiments with PSK31 are 
that the bandwidth is not sufficient to allow the AFC to keep the doppler 
under control (though I am not computer controlling my transceiver so I 
don't know if that would make a difference.)  I'm not sure but I think 
using an FEC corrected PSK modulation like QPSK will now introduce two 
other problems.  The first is that you will need at least 3db more power 
and the tuning is now more critical due to the sensitivity of the Viterbi 
decoder.

I don't know much about the response envelope of AO-40s transponder but I'm 
assuming a spread spectrum signal wouldn't be acceptable because it will 
raise the noise floor?

- Emily




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