Nikola Tesla's Work In Wireless Power Transmission Page 3

1. 1892-1893: Conceptual idea (stratospheric conduction) Tesla entertained the concept of wireless power transmission early, before, it would seem, there was sufficient phenomenological evidence to support such a concept. In his 1892 lectures delivered in London and Paris, he remarked, in connection with his demonstration of "no wire" motors, "Alternate currents, especially of high frequencies, pass with astonishing freedom through even slightly rarefied gases. The upper strata of the air are rarefied... There is no doubt that with the enormous potentials obtainable by the use of high frequencies and oil insulation, luminous discharges might be passed through many miles of rarefied air, and that, by thus directing the energy of many hundreds or thousands of horsepower, motors or lamps might be operated at considerable distances from stationary sources." (Martin's work, p. 235) In his 1893 lectures delivered in Philadelphia and St. Louis, Tesla remarked, in connection with a 'transmitter' connected to an antenna and ground and a 'receiver' similarly connected, "...I do firmly believe that it is practicable to disturb by means of powerful machines the electrostatic condition of the earth and thus transmit intelligible signals and perhaps power. In fact, what is there against the carrying out of such a scheme? We now know that electric vibration may be transmitted through a single conductor. Why then not try to avail ourselves of the earth for this purpose? We need not be frightened by the idea of distance." (Martin's work, p. 346)

2. 1897-1899: Electrical Review article and patent on the stratospheric conduction idea On September 2, 1897, Tesla applied for the patent "System of Transmission of Electrical Energy" which was granted March 20, 1900, as No. 645,576. The Electrical Review of New York, in its issue of October 26, 1898, published an advance text of the patent 17 months before its issue together with a supplemental loose sheet carrying an 8 1/2 x 11-inch photograph print of Tesla's quarter-wavelength spiral coil, the centerpiece of the system, in action. This coil configuration, which he considered the apotheosis of design, is specifically described in the patent, and the photograph carried the caption, "Actual with of space traversed by the luminous streams issuing from a circular single terminal over sixteen feet.--Area covered by the streamers approximately 200 square feet.--Effective electrical pressure two and one-half million volts." The method of power transmission expressed in this patent makes use of excellent conduction properties of a moderately- - 3 -