Trying to determine if this is true:
Tuning both HF radios to the same frequency could cause damage to the non-transmitting radio while the other transmits. This is slightly confirmed on the following webforum, but it is not specifically related to aircraft and may assume two antennas when I understand most aircraft have only one HF antenna.
Two HF Transceivers --- do I need to take precautions ? [Archive] - QRZ Forums
I would hate to damage expensive radios, but it's the first time I've heard this and if it's true we should keep educating each other on it.