After reading Don N2IRZ's great article on PSK31 in the August 2003
issue of CQ magazine I decided to give this digital mode stuff a try.
I stuck a headset microphone on top the the speaker of my TS570,
rubber-banded a pair of headphones to the hand microphone of the
TS570, adjusted the VOX sensitivity, and downloaded the Digipan
software. It worked! I was even able to pull off a couple of QSOs.

Next I decided to try and build a "sound card interface" cable as
described by Don in the article. Basically this interface connects the
line in and line out from the PC's sound card to the Audio Out and
Audio In pins on the ACC2 jack of the TS570. I left out the PTT
circuitry since I already have an RS232 cable between the rig and the
PC, assuming I could just use that PTT circuit. Receiving works great,
other than some noise coming in on the line, the signal is getting
decoded and displayed properly. Transmit, however, is not working.
When I switch to TX mode in the software the rig is keying up, and
switching to TX mode, although the audio does not seem to be making
it. Basically it's tramsmitting an un-modulated signal. I did notice
that the mic is open though, as when I tap on it the ALC and power
meters move. A quick check with a multimeter shows that something is
getting through the interface and to the correct oin on the ACC2
connector.

So, finally, my question. Do I need to use the PTT line on the ACC2
port to get the TS570 to "hear" the audio coming in on the ACC2
connector, or should the PTT on the serial cable work? I guess the
simple answer to my question is "build the PTT circuit and find out!",
eh?

Cheers,
Steven K4RVA