If it only happens on one frequency in one a/c, it can't be a problem with the headset. Maybe a 2nd radio tuned to that frequency and audio from both piped to the headphones?
(Although it would require pretty impressive rejection by the 2nd (non transmitting) radio for it to only happen on the frequency it was tuned to. When both radios/antennas are so close I would expect a lot of noise to come through even off frequency. So I might expect the echo to happen on all frequencies, but much more obviously when radio 2 is tuned to the same freq that radio 1 is transmitting on)
Last edited by double_barrel; 11th Sep 2019 at 05:39.