[30m] Modes for the digital net

[Jason Hsu, AA0II]

The 30m digital net will use PSK-31, MFSK-16, and Feld Hell.  PSK-31 has
a very narrow bandwidth and is the most popular digital mode.  MFSK-16
uses less bandwidth than RTTY and has error correction.  Feld Hell has
great weak-signal capability because of its binary characteristic and
because the human eye can read the writing better than a computer
algorithm.

I've decided against the wider-bandwidth modes (like MT63) because 30m
is a narrow band.  And of course, many digital modes (like PACTOR) are
intended for one-on-one QSOs only, not nets.

I still haven't decided on the times for holding the net.

Jason Hsu, AA0II