Noise when Microphone is Initially Keyed

I had noticed a similar noise a few months back and finally traced it back to a combination of several things 1) a sensitive, high fidelity mike (PR22UT - I love it!) 2) High compression level, which allowed the rig to pick up the noise made by: 3) A sudden inhale of breath as I prepared to talk as I hit the footswitch....and 4) vibrations form the rig's relay transmitted through the desk and boom to the mike. These combined to produce a loud burst of sound upon PTT. I solved the noise by: a) Controlling my breathing better (The compression reduces gain after I start talking and the breath noise isn't as severe.) b) not using as much compression if I didn't need it, c) adding a shock mount to my boom to isolate the mike from the desk. The shock mount also helped the VOX to be more predictable, because it no longer picked up as much of my finger tapping and other impact noises on the desk. BTW: the VOX on the 6500 works wonderfully IF you are using headphones. It needs a good Anti-VOX if you are going to use stereo speakers. Good luck!