[Lowfer] PSK Update

[Lyle Koehler]

I agree with John's observations about PSK. PSK31 is a great mode for HF,
and even for local work on LF. For some reason, though, the slower speed
variants don't seem to yield much performance improvement. I don't believe
that phase stability over the propagation path is the problem, because
VE2IQ's BPSK programs work pretty well even at MS1000 (1 baud).

I monitored Dex's frequency all night and could often see the signals on the
spectrogram plot, but got only garbage characters on the digimode receive
terminal. The frequency should have been within 0.1 Hz -- I was using the
HP3586 with a homebrew TCXO add-on (similar to Ralph's idea), and calibrated
everything against an oven-stabilized 10 MHz reference at the start of the
run.

I still have a sigma-delta board here. COHERENT BPSK, anyone?

Lyle, K0LR