Minimalist Rig Interface

Connect a short ground strap between the transceiver and computer. Connect radio's aux audio output to computer's line in, line out to radio's aux audio in. Use a pot at the radio end of the cable to adjust audio level for transmit. (Accessory plug in many ICOM radios). Connect 220k resistor from serial port RTS to base of NPN transistor. Add a .01 or larger cap between base and emitter. Emitter to ground. Collector to PushToTalk. Adjust audio levels to suit. Voila. The sound card audio output level should be as high as possible to allow the pot to reduce noise as well as control transmit level.

I added a used Sound Blaster Live Value card to the computer so I could run WSPR concurrently with normal ops.