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[aprssig] aprssig Digest, Vol 60, Issue 25

G0JXN Jim g0jxn.jim at ntlworld.com
Thu Jun 25 13:23:33 UTC 2009


Hi Guys

Stephen

You miss my point. Yes FSK only has one carrier as does FM but APRS
effectively has two. So can Carson's rule be applied to a two carrier
system?

----- Original Message -----
From: <aprssig-request at tapr.org>
To: <aprssig at tapr.org>
Sent: Thursday, June 25, 2009 1:00 PM
Subject: aprssig Digest, Vol 60, Issue 25


> That's the whole point of Carson's Rule -- it takes into account the
> total energy in ALL of the sidebands. If it defines the effective
> bandwidth as being where 98% of the energy is located, then only 2% of
> the energy would remain in ALL of the higher order sidebands combined.
>
>
>
> > In any event the argument is flawed in that an FM signal only has one
> > carrier that moves between the deviation limits not two as suggested.
> >
>
> Nothing was said about "two carriers". With FSK, there is only ONE RF
> signal moving +/- 100 Hz from a center frequency (i.e. "carrier
> frequency") midway between the mark and space frequencies. Since you
> never have "no modulation" (i.e. you are always sending either a "1" or
> a "0"), the "unmodulated" center resting frequency of the carrier never
> appears.You are always at either "peak deviation high" or "peak
> deviation low".

73

Jim, G0JXN





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