Sun Dec 2 13:03:06 CET 2007


need ramp-up and ramp-down to prevent clicks. ramp-up time should be
in the order of 20ms = (50Hz)^(-1)

after ramp-up, carrier fade in should be used. this can use the
'attenuation' variable. OK. using 25ms ramp to bias.

now, how to intialize the phase?

  OOK: can start envelope with -128 (amp = -1)
                 carrier with -64 (amp = 0)

  BPSK: needs carrier fade-in.

looks like BPSK sounds smooth enough without envelope fade-in when
starting the carrier at phase = -PI/2

doing the same now for AM, so there's no problem with envelope
frequency = 0.