Richard Harrison wrote:
I miswrote. FM requires about twice the bandwidth of AM.
Quoting my 1957 ARRL Handbook: "Narrow-band f.m. or p.m.,
the only type that is authorized for use on the lower
frequencies where the phone bands are crowded, is defined
as f.m. or p.m. that does not occupy a wider channel than
an a.m. signal having the same audio modulating frequencies.
Narrow-band operation requires using a relatively small
modulation index." It goes on to say a modulation index
of 0.6 is about optimum for those conditions.
Is NBFM still allowed?
--
73, Cecil
http://www.w5dxp.com