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Old March 12th 05, 07:54 PM
JB
 
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Look at the specs of your VHF FM Ham rig. It says bandwidth is
16K0F3. That's 16 kHz for 5 kHz of Dev. at 1 kHz modulation
frequency.

So to stay within 5 kHz bandwidth you need to reduce the audio
bandwidth and dev A LOT less than 5 kHz dev.

Consider 900 MHz and other 12.5 kHz channel radios that are 10K0F3
and sound like dirt.

There is another "gotcha" in your description above. If you vary

the
carrier at, say, 1000 Hz, from say, 146.999 to 147.001, the actual

bandwidth
will be somewhat wider than you expect, and it will be dependent on

the
frequency of the modulation. I know this doesn't make sense, it

has to do
with some weird math. If you studied Fourier series back in school

it was
some abstract mathematical thing that had nothing to do with the

real world.
Well, guess what. Fourier has everything to do with radio! The

result is
that to stay within the 5 kHz bandwidth, the highest modulating

frequency
has to be somewhat lower than 5 kHz. This is one reason why the

FCC
prohibits amateurs from broadcasting music; reasonable fidelity of

music
requires higher bandwidth than voice.

..