Ron Natalie writes:

No actually, it's just historical. Early av radio used AM, and for that
reason we still do.

If that were the only reason, nothing would ever change in aviation.
There must be some reason beyond that. Concerns over safety come to
mind immediately, and ecnonomic issues follow; but in the case of
voice communications, they are so bad already that one can argue that
a newer technology would increase safety more than enough to justify
the initial risk of a new system.

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