Posted for Tammy and Mike Salzman <arrow54t@yahoo.com>:

 Hi Gary,
 
 I would think that the PTT circuit would not be capable of causing this
 problem.  Usually, the PTT is used as a small amplitude signal to make
 the audio panel close the transmit relay...
 
 The more likely antagonist is RF from your Xmit antenna or coax cable
 inducing noise in your avionics.  If you can, try temporarily
 relocating the antenna and see if anything changes.  If you have access
 to a 50 ohm dummy load of adequate power rating for your radios output,
 you can substitute that in place of the antenna for testing.  I don't
 recommend transmitting without an antenna installed, you could blow the
 transistors in your radio.
 
 Keep us informed of your troubleshooting.
 
 TruTrak has provided me with superior technical assistance with my
 installation.  They are your best bet at this point.
 
 Mike Salzman
Fairfield, CA
 LNCE