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Re: AO-40 data mode

> The MB is only 400 bps so that's probably not a good example....

The example was to compare how much better telemtry with FEC performs
compared to telemtry without FEC

>  My limited experiments with PSK31 are  that the bandwidth is not
sufficient to allow the >AFC to keep the doppler  under control...

This is is a limitation of the AFC algorithm in some PSK31 versions, I
believe there is a version around tweaked for satellite use. Again, the
illustration was the advantage of PSK modulation with FEC vs conventional

> 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

This is mixing apples and oranges. FEC can be applied to any modulation
technique and is a baseband function. The whole purpose of FEC is to reduce
the amount of power required by obtaining a higher BER for a given C/N by
correcting individual bit errors post demodulation.

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

This could be an option but I know there are readers of this list that are
better qualified than me to comment.

Howie AB2S

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