| Paul Cardinale 2007-06-27, 5:25 pm |
| On Jun 26, 9:25 pm, j...@specsol.spam.sux.com wrote:
> In sci.physics.electromag Paul Cardinale <pcardin...@volcanomail.com> wrote:
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> I'm well aware of the myriad of techniques to encode and decode
> digital information.
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> The question remains; does this meet the classical definition of
> "modulation"?
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I answered it. Reread.
> If so, what kind of "modulation" is it?
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Voltage.
> My gut feel is that calling digital information on a DC "carrier"
> some kind of "modulation" is just semantic tom foolery.
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If changes in parameter X of thing A cause analogous changes to
parameter Y of thing B,
then the X of A is modulating the Y of B. In the case of TTL, binary
data modulates DC voltage.
> I would be convinced if someone could come up with a defining
> equation, e.g. AM is x(t) = xc * [1 + m * sin (wm t)] * sin (wc t)
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> Problem is, for DC, wc = 0.
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> What to do with the annoying carrier term that is required for a
> classical definition of "modulation"?
>
You seem to think that all modulation must be based upon amplitude
modulation of a sine wave. It isn't (see above). As for an equation
for TTL, it's trivial: Voltage = (high_level) * (binary data).
Paul Cardinale
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