We have 3 VHF radios in a Bell 206L-1. The #1 is with a Garmin 420, the #2 is a Collins and the #3 is a Technisonic. If I am monitoring all 3 radios and transmitt on the #3 there is very loud noise level on the side tone. If I have the #1 and #2 on the same frequency only the #1 is a problem. I appears that the #3 when transmitting is breaking ...