[Elecraft] rcv ON xmit

[Paul Milward]

very wierd occurence today
I was monitoring 20m SSB and cruising the internet simultaneously
listening to a video with music on internet when I heard a station I was waiting for on SSB
instead of closing the internet video I simply plugged in the stereo cables I use for PTT on digimodes, thus muting the audio portion of the internet.
I donned my headset/mic, when the station called CQ I activated my footswitch but instead of the K3 going into XMIT....I heard music in my headset. I immediately unkeyed and the K3 went back to RCV.
I was confused so I attempted to key with the XMT on the front panel....same result...music in the headphones.
I shut the rig down and restarted it and I rebooted the computer. Everything normal now.....Then I thought about it....I restarted the video, left the stereo cables (PTT) plugged into the computer and keyed the rig......same result, music in the headphones...so I unplugged the stereo cables from the computer and heard the same music playing on the computer speakers.. Plugged the stereo cables back into the computer and now when I key the rig...you guessed it...same music in the headphones.
I guess that the computer is passing the sound card audio to the K3 via the stereo cables...much like it passes sound card audio when I am operating PSK. and oh by the way...transmitting the computer audio!!!!

So the bottom line is unplug stereo cables or shut off computer so that you don't inadvertently key the PTT with sound card audio.
I have used this set up for digimode PTT and keyboard CW for 3 or 4 yrs with my K3. Today was the first time I have ever encountered this phenomenon. 

Be careful
73 NU4C Paul