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Re: Wire Length

Original poster: "Gary Peterson" <g.peterson@xxxxxxxxxxxx>

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

The Wikipedia definition is incomplete in that it implies that the only way to generate a spread spectrum signal is to modulate a single frequency one. . . .

Yes, I agree with you. The first spread-spectrum transmitter shown in Tesla's 1903 patents, "System of Signaling" and "Method of Signaling" has two primary tank circuits tuned to two different frequencies (see http://www.tfcbooks.com/articles/control.htm ).

. . . That's not necessarily true as there are other ways to
generate a "wide band of frequencies" . . .

When looking at the RF energy distribution of the above transmitter on a spectrum analyser, peaks would be seen at the resonant frequencies of the individual resonators. The question is this: would a portion of the transmitted energy appear in the intervening portion of the RF spectrum, and, if so, how much?

Tesla was using a narrow band transmitter and receiver for each of his frequencies . . .

In 1898 Tesla was using a single Tesla coil RF transmitter with a single primary circuit that oscillated at a single frequency. The secondary resonated at one of two different frequencies depending on whether the primary break was open or closed. As with the multiple resonator transmitter, the question arises as to whether a portion of the transmitted energy appears in the region between these two frequencies.

. . . and correlating the outputs to decide whether or not a [two tone] signal was present. . . .

This is the AND-gate logic function; when all of the inputs to the gate are on an output will be provided. The question arises: if there is RF energy in the intervening portion of the band, does this energy contribute to the operation of the receiver?

. . . Two (or several for that matter) relatively narrow band signals don't equal a "wide band of frequencies".


Strictly interpreting the Wikipedia definition, frequency hopping is not a spread-spectrum technique either. This is a repairable problem, and does not alter the fact that Tesla's 1898 flat-spiral oscillator was, indeed, a spread spectrum transmitter.