Garmin G1000 Pilot's Manual page 18

OPERATION
If transmit-interlock is not activated, all the selected
receivers are heard at all times. Without transmit-inter-
lock, during simultaneous transmission, interference may
be heard on the COM receivers. Transmission by one ra-
dio produces static or squeal, resulting in loss of commu-
nication on other radios.
Dual COM performance varies significantly depending
on the distance between the antennas and the tuned fre-
quency separation.
6A-16 Garmin G1000 Audio Panel Pilot's Guide 190-00378-02 Rev. A