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Old November 14th 05, 02:18 AM
Jim - NN7K
 
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Default Phase mod vs. FM in Yaesu HTs

Other things enter into the equasion: includeing how WIDE the signal
is-- Most repeaters have recieve filters that accept modulation to:
+- 4.9 KHZ (and that ONLY if you are relatively close to the input
frequency) over +- 800 HZ can accentuate clipping of your signal-
if you exceed +- 5 KHz, you will lose some audio, due to "clipping",
and it gets worse , if you are off frequency ! "tis a case of TOO MUCH
audio being WORSE than too little! Essentially, Phase modulation
is the same as Frequency modulation, and there should be little diff.
between the 2, as far as the recievers are concerned. The "Modulation
Index" is the limiting factor- Keep in mind that a Commercial FM station
(150 KHz +- deviation) , has also , many subcarriers in the signal, that
you don't hear (like background music for stores, sterio piolets, stock
market data, ect) ALL in their carrier- you can detect those with
filters at the appropriate freq, and BANDWIDTH. and, there are outfits
that sell adapters for fm recievers to decode them (but you wont hear
the normal broadcast, thru them!) Television stations do similar things
with their audio, and video! These are called SUB CARRIERS. In sum
total, IF your modulation index exceeds the bandwidth of your reciever
,the audio will be limited (or eleminated)! But that doesn't mean that
your audio isn't there, only that the reciever refuses to accept your
overmodulation-- dont try to speak LOUDER, try whispering, and see if
you get a response! Jim NN7K




Falky foo wrote:
Didn't do detailed analysis.. just realized that the VX-6 was hitting
repeaters better than the VX-150, even when using the same antenna.
Wondered if that difference was because of the different modulation types.