[RTTY] Airlink Express with N1MM Logger

[Dave AA6YQ]

MMTTY offers 4 different RTTY demodulators, with configurable filter shapes
for each. Configurable bandpass and notch filters are also provided. The
AA6YQ-FIR-512 profile yields the best weak signal decoding attained so far
with MMTTY.

MMVARI offers 2 RTTY demodulators, with a choice of 4 bandpass filter
widths. The FFT demodulator with the ~200 hZ bandpass filter yields the best
weak signal decoding attained so far with MMVARI.

Using a -10db SNR file generated by Moe AE4JY's Pathsim, I used Alex
VE3NEA's RTTYcompare to compare MMTTY's weak signal decoding with MMVARI's.

Configured as described above,

 - MMTTY produced an 18% character error rate

 - MMVARI produced a 19% character error rate

MMVARI's weak signal decoding is not better than MMTTY's when both are
configured optimally.

   73,

       Dave, AA6YQ