mch wrote:
> Steve S. Bosshard (NU5D) wrote:
>
>>Reply:
>>
>>Please refer to modulation index and Bessel functions. The frequency
>>response is 300 to 3000 hz emphasized at 3db per octave. Transmitter
>>instantaneous deviation is supposed to be limited to +/- 5 kc deviation
>>from center. Significant sidebands in FM extend beyond the deviation
>>limit, hence emission designator 20K0F3E that equates to about 16 khz
>>occupied plus a guard band on either side.
>
>
> I'm not going to argue over 1 kHz of bandwidth - especially when you are
> using a LARGER BASELINE (5 kHz deviation as opposed to 4.5 kHz). Isn't
> it odd that the extra 500 Hz adds up to 1 kHz (your figure). Again, I'll
> paraphrase what I said before: just because the TX CAN do +/- 5 kHz
> doesn't mean it has to be set for +/- 5 kHz. In fact, if you do this in
> the commercial service, you're pushing your legal limits. (and not
> following the manufacturer's instructions, in all likelihood).
>
In fact, you'll actually be exceeding limits because that +/-5 Khz is
TOTAL deviation-including CTCSS/DCS/whatever! And since the spec for
CTCSS/DCS is +/-500 to 800 hz, and the spec for LTR signalling is
+/-1Khz, voice deviation cannot exceed +/-4.5 Khz (4Khz for LTR). And
the equipment is designed for that. So all you hams out there need to
keep your voice deviation down to no more than that!
--
Jim Barbour
WD8CHL
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