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Re: Tesla coil for wireless data transmission?



Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Ed,

Yes, I'm referring to "METHOD OF SIGNALING, U.S. Patent No. 723,188, Mar. 17, 1903 and "SYSTEM OF SIGNALING, U.S. Patent No. 725,605, Apr. 14, 1903.

Regarding the definition of Spread Spectrum wireless telecommunications, I think of this as a method in which the energy of the transmitted electromagnetic wave is distributed up and down within the EM spectrum, in either 1) the frequency domain or 2) the time domain. A modern example of the first technique is Direct Sequence-Code Division Multiple Access. While not identical to DS-CDMA, Tesla's method of creating a wave complex through the simultaneous operation of multiple resonators each tuned to a different frequency also exists within this category."

    I agree with your conclusion under this definition.

"The second technique is digital Frequency Hopping Spread Spectrum, described as, "the continual switching of transmitted frequencies based on a shared algorithm to minimize unauthorized interception or jamming of a radio transmission." While development the technique is often credited to Hedy Lamarr and George Antheil (SECRET COMMUNICATIONS SYSTEM, U.S. Patent No. 2,292,387, Aug. 11, 1942), the seed of this idea is present in the Tesla patents cited above."

I didn't see any inference to a time-sequenced schedule of transmit frequencies in the Tesla patents but will dig out the book and look again. I thought (maybe because of my mind set) he was talking about simultaneous transmissions. The "Hedy Lamarr" patent referred to the use of a specific frequency shifting pattern which was known and used by the intended receiver once it has established synchronization, whether that be by clock time or recognition of signal patterns. There are a vast multitude of such systems in use at the present time, a typical one being the "Have Quick" system. You may have read about the background to the Lamarr patent, which I found to be quite interesting. Apparently she was a pretty sharp gal and listened to conversations of her husband, who was a Swiss (as I recall) arms merchant. She seems to have understood most of what she heard and out of that came this idea, which was apparently novel at the time. People had of course been using clock time to schedule the frequency of individual message communications almost since the beginning of wireless but her system involved a much more rapid switching and hence greater potential security.

"Of course, the simple alternative to both of the above-described techniques is single-frequency transmission.

Best regards,
Gary"

Agreed. Simplest, cheapest, and usually the best unless frequency hopping is used to increase the possibility that at least some of a message will get through in the presence of uncontrollable and uncertain interference on any particular frequency.
Ed