Subject: 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