writes:

There is absolutely no difference in qualilty between AM & FM if they
are designed to the same specification. If you modulate an AM or FM
transmitter with up to 3KHx of audio they will sound identical. What
you put into the transmitter comes out of the receiver assuming there
isn't a fault.

Not so. The major causes of environmental noise in AM affect the
amplitude of the signal. FM modulates frequency, so changes in
amplitude are not important. Noise that changes frequency is much
more rare in the environment, so FM has less noise. That's the key
advantage of FM.

FM maintains a low background noise longer than AM and the only
difference is at low signal levels when FM very quickly becomes
totally unreadable. AM can still be heard and understood, depending on
the ability of the person listening. With all the noise in an aircraft
a little bit of low level background noise is not significant.

With a lot of background noise, additional noise in the channel is
even more of a problem, since the margin of safety is smaller.

Digital has some merit but again when the signal reaches a threshold
it stops completely.

But the merit of that is that the transmission is either clean or not
there at all. Errors are rare or nonexistent.

The whole thread is futile as the centre of the 'aviation universe'
may well be the US but you aren't going to get the rest of the world
to change. Even having regultions which are supposed to be accepted
worldwide doesn't work. Most counties have exceptions.

The world seems to be cooperating pretty well on aviation so far.

About the only thing which is standard is the use of the English
language. Even then the locals will use their own language! Have you
ever worked controllers with Spanish English, Finnish English,
Canadian English, New Zealand English, Cyprus English, Bahamian,
Caribbean or even Amereican English. That's where the differences can
be heard. AM radio is adequate for the job and if you don't think so
then get your installation checked out by a qualified engineer, you
may be suprised.

If people are speaking with accents, noise reduction is even more
important, as the redundancy of language is even more reduced.

As for increasing the number of frequencies Europe has introduced
8.3KHz spacing. Fortunately at the lower GA flight levels it's not
required but the higher commercials now require new radios.

Most radios are dual NAV/COM so not only would you need a new COM but
a new NAV too... It isn't going to happen...!

So nobody from the USA can fly in Europe now?

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