Cingular cell phone service - Re: AM electromagnetic waves: 20 KHz modulationfrequencyonanastronomically-low carrier frequency

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Re: AM electromagnetic waves: 20 KHz modulationfrequencyonanastronomically-low carrier frequency

isw

2007-07-06, 3:33 pm

In article <C2B3C3A0. 6DC14%dbowey@comcast
.net>,
Don Bowey <dbowey@comcast.net> wrote:

> On 7/6/07 9:36 AM, in article
> isw-F124E8. 09362406072007@newsg
roups.comcast.net, "isw" <isw@witzend.com>
> wrote:
>
>
> There is no need at all to match the carrier amplitude of the original
> signal. You can use an excessively high carrier injection amplitude with no
> detrimental affect, but if the injected carrier is too little, the
> demodulated signal will be over modulated and sound distorted.
>
>
> Exact, not required. The closer the better, however.

Well, OK, the phase must at least bear a constant relationship to the
one that created the signal. If you inject a carrier that has a
quadrature relationship to the one that created the DSB signal, the
output will be PM (phase modulation). In between zero and 90 degrees,
the output is a combination of the two. If the injected carrier is not
at precisely the proper frequency, the phase will roll around and the
output will be unintelligible.

Isaac

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