|If your transceiver has VOX
(most do), then you do NOT
need a separate PTT line to operate most digital modes.
99% of the schematics you see on the Internet tell us that we need to control the PTT line to put our transceiver into transmit mode, but that is NOT always the case. VOX works just fine to key the rig. I operate PSK31 using Fldigi, and I don't have a thing connected to my transceiver's PTT line.
The audio from your computer's sound card going into your microphone input is ALL you need to key the rig.
Turn on your radio's VOX feature, and play with the VOX GAIN and VOX DELAY controls.
Magic, isn't it? :-)
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http://www.w0btu.com/digital_modes.html - Last Edited July 16, 2013