Re: [amsat-bb] Question, FM on AO-40

[Jim.Walls@xxxxxxx]

Gary asked (in part):
> I find it hard to believe that the average power level of FM would be
> any higher than the digital modes being used presently. RTTY and PSK31
> have a constant carrier and SSTV has close to half of the bandwidth of
> FM.

Guess again.  SSTV has the same bandwidth of SSB at about 3 KHz (RTTY is
narrower), whereas a narrow band FM signal (the commonly used FM in amateur
service) is 15 to 20 KHz wide.  Also, as a general rule of thumb, it takes
a considerably stronger signal to hear a FM carrier than SSB.  PSK31 is
designed as a very weak signal mode and both SSTV and RTTY work pretty well
with weak signals.

> I understand that the bandwidth consumed by FM is much larger then the
> other modes but band congestion is not generally a problem with the
> satellite.

That is true enough.

73
-----------------------
Jim Walls - K6CCC
k6ccc@amsat.org
Mobile Radio Operations
Southern California Edison Co.
Ofc:   626-302-8515   -   PAX   28-515
FAX:   626-302-7501   -   PAX   27-501



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