I just finished the RASCAL board from K4ABT.
The web site is 'www.packetradio.com
'. The card
has all the ground loop isolation and PTT on the
board and works like a dream. For 25 bucks, you
could do worse. There is a variable resistor in
the transmit audio line. I set mine to mid-scale
and did the adjustments with the sound card windows
contained in DigiPan. PSK is one fun mode to run.
I am making contacts all over the U.S. with 10 watts
to a mobile antenna with a scrap wire counterpoise.
Be sure to turn your TX power down. Take it to about
40% of normal. We don't want to support the makers
of the final transistors!! Looking forward to making
a contact on PSK31. 73 de Carl K0BZV