G'day Alberto, Steve and all,
its great to see the concept of FDK and its friendly implementation in
Jason. But, one question came to my mind: Instead of using a 4-bit pair for
each 6 bit character, why not take it all the way and transmit 6 bits at
once? Of course, this would mean 65 frequencies instead of 17, four times the
bandwidth at first glance.
But then you could double the symbol duration and halve the FFT bin bandwidth
to 42 mHz, picking up some SNR on the way. Additionally, even with a Hamming
or Bartlett window, the noise in channels only two bins apart should have no
significant correlation. Thus the total occupied bandwidth would increase
from the current 4.12 Hz to no more than 5.42 Hz.
What do you think?
73 de Markus, DF6NM