Glen Jenkins WB4KTF
To answer the questions:
1 - I am using an Icom IC-7610.
2 - The PC Audio output SLIDER DOES move down during the transmit cycle, stating about 4-6 seconds into the cycle. The Rig's ALC is ZERO, meaning there is no reading of ALC on the meter throughout the full TX cycle. If I do raise the PC Audio output level very high (>90%), then I do see ALC reading on the meter display, so I keep it below that value of output. This auto output decrease even occurs when I have power slide on the WSJT-X display at-10db, and also when I have the Power setting on the 7610 set to 25% (about 25 watts), so it's probably not RF feedback at such low power.
3- The power output in all other modes does NOT change when keyed down (AM, FM, CW, etc), it stays full power, so this is likely not RF power foldback. It's something in the PC that's driving the audio output to reduce?
Thanks to all who help, I've got to resolve this.