[aprssig] BPSK decoding

[scott at opentrac.org]

I've had PSK31 code working on the OpenTracker for some time now, but as far
as I know, there's no inexpensive hardware-based demodulator for the mode.
Your options seem to be either a soundcard or an expensive multimode TNC.

Is there a simple circuit somewhere for single-channel BPSK demodulation?
Specifically, can it be done with an XR2211?  Seems like you ought to be
able to have it track the carrier frequency and use the phase detect output
to detect the 180-degree phase reversals.  Or does that cause the '2211 to
lose lock for too long?

I think it'd be cool to have a PSK31 QRP rig for backpacking that'd do APRS
and hook up to a PDA for text messaging.

Scott
N1VG