First Tesla Museum and Science Center International Conference on NIKOLA TESLA

October 6-8, 2006, Long Island, New York, United States of America

Brookhaven Town Hall, 1 Independence Hill, Farmingville. N.Y. 11738

ABSTRACT

Nikola Tesla and the Development of RF Power Systems : Part 1

K.L. Corum

and

J.F. Corum, Ph.D.

"Is there, I ask, can there be, a more interesting study than that of alternating currents?"

Nikola Tesla, Vice President of the AIEE

. . . The electrical generation of RF currents can be traced to Lord Kelvin (then William Thompson) who, in 1853, while contemplating the spark discharge of a Leyden jar through a coil, first employed conservation of energy to formulate a system differential equation, obtain the underdamped RLC transient response, and predict the frequency of the oscillations. (Actually, RF currents were present in Benjamin Franklin's wet kite string because of the Trichel pulse emissions from the points that Franklin used.) Kelvin charged up the capacitor and then brought the spark balls on the top of the leyden jar and coil close enough together for a spark discharge to occur. Writing the now classic second order differential equation, Kelvin was able to obtain the complex exponential underdamped solution. Even though Kelvin's paper did not address RF, it did form a basis upon which Hertz could later construct a VHF transmitter.

While a graduate student under Hermann Von Helmholtz, the idea occurred to Heinrich Hertz that, instead of using a parallel plate capacitor, he could open up the capacitor plates and let the connecting wires form a small inductance. If the plates were charged up to a high voltage and discharged across a spark gap located at the geometrical center of the configuration, then during the spark (a conducting short circuit) one would have the same electrical circuit as was studied by Kelvin and, therefore, an underdamped oscillating current would flow in the structure. While the disruptive coil that is used to charge the capacitor is shorted out of the antenna system, the antenna current oscillations should occur at a frequency which is readily calculable and characteristic of the physical dimensions of the antenna structure, itself. The induction coil (a buzzer) provides a very low frequency intermittent train of repetitive high voltage pulses to charge up the capacitor plates. As the charging proceeds, it will reach the breakdown point of the center gap, and the capacitor plates then have only the RF portion of the circuit to discharge through. Energy loss is primarily through the mechanism of radiation. This, of course will happen very rapidly and the spark will go out until the induction coil again charges up the capacitor plates and the gap eventually breaks down again. The critical thing is that the RF generated during the discharge is a damped sinusoidal oscillation (in the 50 to 200 MHz range). Hertz's receiver was a capacitively loaded loop antenna with a tiny spark gap for detection indication. His experiments really were quite delicate.

When asked by the press if his experiments would permit wireless communication, it is reported that Hertz responded negatively. Probably justifiably so. The major problem with Hertz's wonderful apparatus was that the power levels which it could radiate were trifling. Letting N be the number of spark discharges per second, and C the antenna plate capacitance, the energy radiated per discharge was on the order of 1/2 CV2. There being N of these per second, the power of Hertz's oscillator was N/2 CV2. Since C is in the picofarad range, even voltages of kilovolts at kilohertz pulse repetition rates gives, at best, radiated powers of milliwatts to a few watts. (The peak power could be large.) There is another problem with this. In order to increase the power level, a larger antenna has to be used (more capacitance). But, this lowers the frequency of operation and the resulting radiating efficiency for the structure decreases.

Nonetheless, as with many others, Tesla stated, "The publication of Dr. Heinrich Hertz's results caused a thrill as had scarcely ever been experienced before." (Electrical Experimenter, May, 1919, pg 28). Tesla, at the time of Hertz's experiments, was deeply involved in the commercial introduction of his ac polyphase power system. However, he found time to invent the oscillation transformer and, in 1892, he went to Bonn to confer with Hertz.

Tesla's stroke of creative genius was to use tuned coupled coils, a ground connection, and to move the energy storage capacitance to the primary side. [See the figures below.] Tesla was the first to inductively couple the secondary circuit (where Cs must be small) to a tuned primary circuit, where the energy storage element Cp may be huge by comparison. This remarkable innovation made possible the generation of RF signals immensely more powerful than Hertz's apparatus. Tesla's transmitters advanced the state of the art (in one technological step) to power levels five orders of magnitude greater than anything available to Hertz!

This approach permitted microfarads of capacitance at tens of kilovolts to be discharged thousands of times per second. Further, since the antenna capacitance was no longer as critical, RF could be generated at any frequency from VLF to VHF. The ground connection permitted the introduction of the radiating vertical monopole. From an engineering perspective, the critical element became the loss tangent of the primary capacitor's dielectric material. It had to be able to dissipate the dielectric loss at radio frequencies without decomposing.

Soon, the whole world was using Tesla's patented system of coupled tuned circuits - including Nobel Prize Laureates. (In one such instance, the circuit used by Guglielmo Marconi for the first North Atlantic wireless transmission, which Marconi disclosed in his Nobel lecture, was obviously Tesla's patented apparatus!) Concerning wireless transmission and his apparatus patents, Tesla was able to say, in 1916,

"Why, there is no other system that is used. Every wireless message that has ever been transmitted to any distance has been transmitted by this apparatus; there is no other way."

Let us now turn to the analysis and RF operation of this wonderful apparatus. . . .

Dr. James F. Corum: Ph.D. in Electrical Engineering from The Ohio State University (1974), MSEE from Ohio State (1967), and BSEE from Lowell Technological Institute (1965).

Dr. Corum taught and conducted research in electromagnetics, antennas, RF telecommunications, astrophysics (radio astronomy), mathematics (tensors and differential geometry) and relativistic electrodynamics for 17 years in academia before turning to private industry. He was an Electronic Engineer for the National Security Agency and a Researcher at the Ohio State Radio Observatory. He was a tenured Associate Professor on the faculty at West Virginia University (where he was the principal thesis advisor to a dozen Masters and Ph.D. candidates), a Professor at The Ohio Institute of Technology, and a Senior Scientist at the Battelle Institute in Columbus, Ohio. He served as Chief Scientist at Scientific Applications and Research Associates, Inc., in Huntington Beach, CA, and as the Chief Scientist for the Institute for Software Research, in Fairmont, WV. Currently, he is Chief Technical Officer for CPG Technologies. Collectively, he has received over a dozen awards for excellence in teaching and outstanding research from these institutions. 

Dr. Corum is a Senior Member of the Institute of Electrical and Electronic Engineers (belonging to the Antennas and Propagation Society, the Professional Group on Microwave Theory and Techniques, the Broadcast Engineering Society, the Professional Group on Engineering Education, and the Plasma Science Society). He was Chairman of the Upper Monongahelia Subsection of the IEEE and Board Member of the Pittsburgh Section of the IEEE. He is a member of the American Geophysical Union, the American Association of Physics Teachers, the American Institute of Aeronautics and Astronautics, the American Society for Engineering Education, the American Association for the Advancement of Science, and the Research Society of North America (Sigma Xi). He is a Life Member of both the American Radio Relay League and the Quarter-Century Wireless Association. He is listed in Who's Who in Engineering, Who's Who in American Education, Leading Consultants in High Technology, Who's Who of American Inventors, Who's Who in Science and Engineering, American Men and Women of Science, and more than a dozen other professional and biographical dictionaries. 

Dr. Corum has published over 100 notes and technical papers (in such prestigious magazines as the Journal of Mathematical Physics, the Proceedings of the IEEE, Soviet Physics Uspekhi, IEEE Spectrum, Microwave Systems News, Transactions of the American Institute of Aeronautics and Astronautics, International Journal of Theoretical Physics, etc.), several monographs, 5 patents (he invented the contra-wound toroidal helix antenna technology), and has contributed chapters to seven books. His primary publications concern relativistic rotation and nonsymmetric affine connections in nonholonomic space geometries. Additionally, he is internationally recognized as a science historian (serving as an advisor and board member for several scientific historical societies), and he has recently completed a compendium of translations of 100 papers on differentiable manifolds and the early asymmetric unified field theories of Einstein, Schouten, Cartan and Schrödinger. 

Dr. Corum was invited as a guest of the Russian Academy of Sciences to the Institute of High Temperatures in Moscow, and his work on Ball Lightning and High Voltage Pulsed RF Sources has appeared in the Soviet literature. He has lectured at Berkeley, Imperial College (London), The Ohio State University, and Belgrade University. He has consulted for private industry and for DARPA, DoD, DIA, IDA, NRO, CIA, AFOSR, NEODTC, ARO, NASA, NIOSH, DOE and other governmental agencies. 

He was cited as a "National Treasure" by The Office of the US Secretary of Defense for his work on the DARPA National Panel of Radar Experts on Ultra-WideBand Radar and Phenomenology. His engineering practice has taken him around the globe, from Moscow, Russia to Kwajelein Atoll. The recipient of many research and teaching awards, his electromagnetic research has been recognized by prestigious scientific organizations and professional societies around the world.

Publications include:

"Nikola Tesla and the Electrical Signals of Planetary Origin," K. L. Corum and J. F. Corum, Ph.D., International Tesla Conference, "Tesla, III Millennium," Belgrade, Yugoslavia. 1996. 

"Nikola Tesla and the Diameter of the Earth: A Discussion of One of the Many Modes of Operation of the Wardenclyffe Tower," K.L. Corum and J. F. Corum, Ph.D. 1996. 

"The Schumann Cavity, J. J. Thomson's Spherical Resonators and the Gateway to Modern Physics," K. L. Corum and J. F. Corum, Ph.D. 1996. 

"Nikola Tesla, Lightning Observations, and Stationary Waves," K. L. Corum and J. F. Corum, Ph.D. 1994. 

"Atmospheric Fields, Tesla's Receivers and Regenerative Detectors," K. L. Corum, J. F. Corum, Ph.D., and A. H. Aidinejad, Ph.D. 1994. 

"Tesla's Egg of Columbus, Radar Stealth, the Torsion Tensor, and the "Philadelphia Experiment," K. L. Corum, J. F. Corum, Ph.D., and A. H. Aidinejad, Ph.D., 1994. 

"Dr. Mahlon Loomis: Terra Alta's Neglected Discoverer of RF Communication," K. L. Corum and J. F. Corum et al. 1992. 

"Some Thoughts on Tesla's Death Beam," K. L. Corum, J. F. Corum, Ph.D. and J. F. X. Daum, Ph.D. 1992. 

"Tesla and the Magnifying Transmitter: A Popular Study for Engineers," K. L. Corum and J. F. Corum, Ph.D. 1990.

"Fire Balls, Fractals and Colorado Springs: A Rediscovery of Teslas's RF Techniques," K. L. Corum and J. F. Corum, Ph.D. 1990. 

"Tesla Coils: 1890-1990--100 Years of Cavity Resonator Development," K. L. Corum and J. F. Corum, Ph.D. 1990.

"Tesla Coils: An RF Power Processing Tutorial for Engineers," K. L. Corum and J. F. Corum, Ph.D. 1988. 

"Spherical Transmission Lines and Global Propagation, An Analysis of Tesla's Experimentally Determined Propagation Model," K. L. Corum, J. F. Corum, Ph.D., and J. F. X. Daum, Ph.D. 1987. 

"Vacuum Tube Tesla Coils," J. F. Corum, Ph.D. and K. L. Corum. 1987. 

"The Transient Propagation of ELF Pulses in the Earth-Ionophere Cavity," J. F. Corum, Ph.D. and A-H. Aldinejad, Ph.D. 1986. 

"A Technical Analysis of the Extra Coil as a Slow Wave Helical Resonator," J. F. Corum and K. L. Corum. 1986.

"Critical Speculations Concerning Tesla's Invention and Applications of Single Electrode X-Ray Directed Discharges for Power Processing and Terrestrial Resonances," J. F. Corum and K. L. Corum. 1986. 

Also:
"Tesla's Colorado Springs Receivers"  
Tesla’s Connection to Columbia University
 

Latest page revision: 08/31/2006