"Larry Dighera" wrote in message
...

"Larry Dighera" wrote in message
.. .

AM frequencies are currently 25 kHz wide. FM would require more
bandwidth. Regardless, where would you place these newly allocated
frequencies?


On Sat, 2 Sep 2006 09:10:19 -0700, "RST Engineering"
wrote in
:

That's just not true. For a given voice signal, I can squeeze the same
amount of fidelity into an FM channel that I can into an AM channel.

That's the first time I've heard that.

The current actual transmitted bandwidth of a VHF AM signal is about 4
kHz..

Does that mean the highest audio frequency transmitted it 2kHz?

Standard deviation on a VHF FM signal is 3.5 kHz.. Bessel and Armstrong
to
the rescue once more {;-)

BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going
to
be a challenge for us AMers to meet.

I believe they were just implementing that when I left avionics work 20
years ago. The main reason for the relatively wide spacing was poor
frequency stability. The real problems with any changeover would/will be
the large amount of existing infrastructure in place and the need for
radically "better" adjacent channel rejection. And you don't dare to
"improve" the adjacent frequency rejection of the receivers that much untill
you are really sure that the transmitters in service can meet the new
standard ... and so forth ...

And, I suspect, it would be completely impossible for FM to fit within
8.3 kHz channel spacing with the same fidelity?

Wouldn't be much of a problem, IIRC the hams have been doing it forever. I
just don't know of and good reason to choose one modulation scheme over the
other, and certainly not to change from one to the other!