Nikola Tesla was asked what would an engineer have to do to the wireless systems of today in order to produce very little radiation of electromagnetic waves and produce a large amount of earth currents? What changes would he have to make in the system?
“He would have to construct and operate the apparatus described in my patents and in my lectures.
“It is just like this: In an enterprise of this kind, you have to start with certain fundamental propositions. If you are to build a commercial plant, the question comes up how much money is it to cost. Now, you go to specify before your capitalists the various parts of the plant, and you will find that your machinery and the aerial structure will cost so much. If your capitalists are willing to go deep into their pockets, you can put up a tremendous antenna because, as you know, as I pointed out in 1893, that the effects will be proportionate to the capital invested in that part; but you will find great limits there.
“I designed a plant [Wardenclyffe, referring to Fig. 1 & Fig. 2] years ago with a large capacity and put it before certain architects. They figured that the antenna would cost $450,000 and I had to modify my plans. As you see, you are limited by cost as to the size of the antenna; that is, you are limited as to the capacity and, furthermore, you have selected the frequency. In order to lower the frequency so that there would be no wasteful radiation of energy, you have to employ a large inductance. You have to employ a capacity as large as permissible, and you must use a large inductance in order that you may reach the low frequency which is economical.
[Fig. 1]. Wardenclyffe Tower
[Fig. 2]. Improved transmitter described in U.S. Patent No. 1,119,732 of December 1, 1914. Application filed January 18, 1902.
“In a patent which appeared in April 1905, the application of which was filed on May 15, 1900 [Fig. 3], I have enunciated the law of propagation, which I have explained, and have stated that the frequencies should not be more than 30,000 or 35,000 cycles at most, in order to operate economically.
[Fig. 3]. Art of Transmitting Electrical Energy Through the Natural Medium. Patent No. 787,412, dated April 18, 1905.
“The currents are proportionate to the potentials which are developed under otherwise equal conditions. If you have an antenna of a certain capacity charged to 100,000 volts, you will get a certain current; charged to 200,000 volts, twice the current. When I spoke of these enormous potentials, I was describing an industrial plant on a large scale because that was the most important application of these principles, but I have also pointed out in my patents that the same principles can be applied to telegraphy and other purposes. That is simply a question of how much power you want to transmit.
“In Colorado I used the so-called Tesla transformer [Fig. 4]. I did not have the high frequency machine with me which I could develop as much energy for the experiments, but with my transformer I could get any amount of energy I needed. That is why I used the transformer.
[Fig. 4]. Tesla Patent 593,138 Electrical Transformer.
"The D P [in Fig. 2] is a curved plate. The plate has a large radius of curvature. You see, it is to be borne in mind that, in a general way, electricity will accumulate in the same way as the curvature of the surface has a smaller radius. This is an old truth which has been recognized 200 years ago. The design contemplates an arrangement whereby nowhere is electricity accumulated in excess. I am at a substantially uniform distribution of electricity in this structure, not only in the structure, but along the whole circuit where there is a high potential. This, of course, is simply to illustrate the principles. If you design a machine like that [referring to Fig. 2], it will be very much superior to those now in existence, but I have since that time introduced refinements and can produce very much better results than it would be possible with just exactly that construction.
"I had a 550-volt current with which I charged the condensers. These condensers I discharged through a primary in the form of an arc, sometimes I also introduced in this arc a mechanical break of several thousand per second. And I obtained a perfectly continuous train of waves as has been described in my patents. The reason why I show the condenser here [Fig. 2] is that that is synonymous with undamped waves. If I had shown the whole apparatus as arranged there, then I might still have damped waves; but whether I use an alternator or some other way of getting energy to that condenser, the condenser is usually there. For instance, if I use an alternator, I shunt its terminals with a condenser in order to magnify the current in the primary. I then tune this circuit to the alternator, and magnify the current in the primary in the ratio of the inductance to the resistance. Therefore, this condenser here stands for either method, and simply means that in this system, as is obvious from the description in the patent, the waves are undamped because high rises of potential would not be obtained otherwise. Whenever I wanted to obtain a high potential, I had to observe these rules in order to force the potential up to that value.”
***In a pre-hearing interview with his legal counsel in 1916 to protect his radio patents from the Guglielmo Marconi and the Marconi Company***
“Nikola Tesla On His Works With Alternating Currents and Their Application to Wireless Telegraphy, and Transmission of Power.” Twenty First Century Books, Breckenridge, Colorado, 2002.