"Dave VanHorn" wrote:
They need to hear
all the comms, not just between themselves and the tower, but what
the other pilots are saying as well. Add to this, the fact that
aircraft
comms are AM, which is inherently muddy, and it's easy to see why
they take the extra precautions.


The design of newer comms doesn't help either. If they have automatic
squelch, set to break at say 1uV RF in, then obviously it doesn't take
much interference to break squelch. Then, they also may have "audio
leveling" -- a great feature when commonly using headphones -- but the
effect there will be to take a few uV of noise and amplify the audio
component to the level you hear when ATC hits you with as much as 50W,
and it's heard constantly between transmissions, to be hopefully
silenced when ATC talks. But not necessarily the case in monitoring
comms of other aircraft, where especially general aviation,
less-than-properly-functional 7W units can be relatively weak.

Fred F.