I was using headphones to listen to my 6700 (SSDR 1.16). When I transmit, I hear my voice echo in the headphones some of the time. I assume that this is some sort of RF feedback. Tx monitor is off. The radio was putting out 100 w into an amplifier in standby mode. If I put the amp into operate, the amp drops that exciter power to 15w and puts out about 450w. There is no echo in the headphones. I would have thought that increasing the RF would have made the echo first.