| jimp@specsol.spam.sux.com 2007-06-27, 5:25 pm |
| In sci.physics Floyd L. Davidson <floyd@apaflo.com> wrote:
> Paul Cardinale <pcardinale@volcanomail.com> wrote:
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> Wrong answer though. You need to research the standard
> definitions of terms when there is such a question, not
> just continue on assuming that your perception of what
> the word means is necessarily correct.
> From The Collaborative International Dictionary of
> English v.0.48[gcide]:
> 4. (Electronics) The alteration of hte amplitude,
> intensity, frequency, or phase (of the carrier
> wave of a radio signal) at intervals, so as to
> represent information to be transmitted.
> From WordNet (r) 2.0[wn]:
> 2: (electronics) the transmission of a signal
> by using it to vary a carrier wave; changing the
> carrier's amplitude or frequency or phase
> However, the most authoratative and definitive cite
> perhaps comes from the Federal Standard 1037C,
> "Telecommunications: Glossary of Telecommunication
> Terms" at http://www.its.bldrdoc.gov/fs-1037/
> modulation:
> The process, or result of the process, of varying
> a characteristic of a carrier, in accordance with
> an information-bearing signal.
> carrier (cxr):
> 1. A wave suitable for modulation by an
> information-bearing signal.
> 2. An unmodulated emission.
> Note:
> The carrier is usually a sinusoidal wave
> or a uniform or predictable series of
> pulses. Synonym carrier wave.
> Obviously a DC voltage is not defined as a "carrier" and "modulation"
> cannot be applied to it.
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> That is encoding, not modulation.
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> The binary data might well change the DC voltage, but it
> cannot modulate a voltage, only change it. If the
> changes carry information, we say it is encoded, and can
> be decoded.
> If an AC signal is varied, *that* is modulation.
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> True, but he didn't say that is was. He merely said
> "e.g.", which is not the same as "i.e." (one is "for
> example", meaning there could be many other different
> examples, the other is "in essense", meaning all
> examples are essentially the same).
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> That does not define a modulated signal though. *By*
> *definition* it defines information encoded using
> voltage.
> --
> Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
What you said.
My take is "modulation" is only defined for a carrier of 0 < Fc < infinity.
Though I'm wavering about whether or not there should be absolute value
bars around Fc.
--
Jim Pennino
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