Rik,

  probably your idea would work, but I think that if you can achieve
phase coherence then the
best technique would be to compute the two correlations between the
received signal and
what the signal should be in case either of a "1" or of a "0", then
select the symbol that
gives the highest correlation value. And. if you have CPU cycles to
spare, which probably is
the case for low signaling rates, then you could even correct for small
phase errors by
computing several correlation sums, each shifted by a few degrees,
finding then the peak.
And adding a convolutional FEC coding with a soft-decision Viterbi
decoder would  certainly
be of no harm...

73  Alberto  I2PHD

 

I wonder if the new narrow version of JT65 would give us something to play with. Not the complete transmission bandwidth, but just the couple of characters that occur in close vicinity to the sync tone. I believe this uses a similar decoding algorithm and needs to be locked to within a second of the receiving station. I must read the help files again.

There is also a narrowband version designed for laser communication. However, even this narrowband system is still 10Hz wide for the full character set.

 

Both can use class C D E etc.

 

73

 

David