TELECOM Digest OnLine - Sorted: Re: Spectrum of a Modem Signal

Re: Spectrum of a Modem Signal

Robert Bonomi (bonomi@host122.r-bonomi.com)
Wed, 10 May 2006 22:06:23 -0000

In article <telecom25.175.7@telecom-digest.org>, <mike7411@gmail.com>
wrote:

> If I plot the spectrum of a short modem signal, what should I expect
> to see?

authoritative answer: "It depends."

On a WHOLE lot of things you didn't bother to mention.

2-wire vs 4-wire. (i.e. dialup vs. lease-line.)

FDX or HDX (two modems talking *simultaneously* to each other, or *one*
talking while the other only 'listens').

Modulation methodology (e.g. FSK, QAM, PEP, PFSK, etc.)

Encoding.

Modulation 'protocol' (e.g. Bell 202T, Bell 208A, V.42bis, V90, etc.)

Data rate.

And the *actual*data* being transmitted at the time.

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