Tesla's Synchronized Receiving Apparatus

Over the course of the last decade, much progress has been made toward the recreation of Nikola Tesla's pioneering work in the area of high power transmitter design. Great understanding has been gained about the resonant relationship between the primary, secondary and extra coil circuits that comprise the Tesla electrical oscillator. At the same time it may be noted that an equivalent emphasis on the design of the required synchronized receiving circuits, that are an extension of this series, is lacking. The following paper is intended to demonstrate that Tesla's work in the development of receiving circuits, using what he called the "condenser method of magnifying effects," was essentially coincident with his work in the development of the Magnifying Transmitter. This fact might be taken into consideration by those groups who are presently engaged in efforts to recreate Tesla's Colorado Springs Experiments.

A review of Tesla's earlier entries into the Colorado Springs Notebook indicates that the designing of properly configured receivers was an area that required his immediate attention. It should be noted that the very first circuit diagram of a complete apparatus illustrates a receiver. This diagram includes a number of design features and components that can be found in many of his later devices. These include an earth connection, an air capacitance, a sensitive device along with a battery for straining its' dielectric and a delicate relay. The next drawing, made seven days later, shows the circuit of an inductance bridge. On June 9, 10 and 11, three more drawings are made. Each is of a device "for detecting feeble disturbances transmitted through a medium." The entry of June 13 marks the first mention of an actual transmitting apparatus. At this time it is apparent that Tesla's attention becomes focused on the work of building the first of the two large scale Colorado Springs oscillators. Diary entries over the course of the next five weeks, with the exceptions of June 19, 24, 27, 29 and July 1, 4, 12 and 15, indicate a period of intense concentration on sorting out the new oscillator.

On July 17, he once again shifts his attention back to the study of receivers or synchronized circuits. Note this entry of July 23:

"In investigating the propagation through the media, and more particularly through the ground, of the electrical disturbances produced by the experimental oscillator, as well as those caused by lightning discharge, to which work a few hours were so far devoted every day, a form of sensitive device used in some experiments was adopted, as the best suitable for these purposes." [1]

It is clear that, during the preceding weeks, a number of hours were dedicated to working on receivers as his account indicates that no fewer than thirty circuit configurations were experimented with.

The next time interval, from July 23 to July 28, is devoted once again to refining the oscillator while at the same time some additional attention is given to the receiving circuits. This can be seen from his entry of the 28th: "The following method was found particularly efficient in applying the method of magnifying effects of feeble disturbances by means of a condenser." The drawing that is included with this entry once again shows a complete apparatus. Because of the detailed description that is given, this model is a prime candidate for recreation. It would appear that this was one of the designs that was settled upon "for the purpose of investigating: the propagation of waves through the ground and telegraphy." The entry of July 30 indicates further work being done, apparently on this unit, in that a new induction coil, both primary and secondary, was wound. Three days later, on August 2, more work is carried out on a receiver with the winding of another new induction coil and a description being made of a type of clockwork for driving a mechanical break and two sensitive devices of the type that was described on the 23rd. Note the words "this final" at the end of the second paragraph of the 2nd. This seems to refer only to the arrangement clockworks. As can be seen from the proceeding diary entries, over the next 12 days, more than 50 different combinations of component connections were considered, culminating with the winding of another and this time larger induction coil meant for use with a further modified receiving apparatus. The last two illustrations of the August 14 entry show details of this receiver in it's finalized state. For nearly two weeks the work is related to the oscillator and the extra coil, the only exception occurring on the 22nd. Once again, beginning on the 27th, a series of entries indicate that ten different variations of receiver design were tested.

On September 4 and 5 drawings were made of both "senders" and "receivers." The entry of the 5th concluded with an illustration of an almost finalized design that appears on the 11th with one small modification along with the following description of the devices use.

"Experiments were continued with apparatus before described and the effects outside at a distance investigated, the chief object being to establish nodal points on the earth's surface. The transmitting apparatus was one giving more rapid vibrations and was improvised as indicated in the left sketch.

The apparatus for investigation comprised the ten" drum, before referred to, wound with 395 turns No. B. & S. and to increase magnifying factor another layer was wound on top, thus doubling the section. It was found that the scheme of double windings is not a good one because the e.m.f. in both wires are apt to be unequal and it is more difficult to make adjustment. The connections of apparatus were as indicated in the right sketch.

The secondary of the induction coil was connected between the two legs of the receiver, this being convenient for eventual reversing. A high self induction L was provided to give initial excitation but the apparatus worked also without it. The batteries B and B' were connected both in the same way and opposite, the former giving best results. The tests showed that without any capacity or wire I the disturbances were recorded about one mile away: 0nly the ground connection was essential as the waves were still fairly long, about 4000 feet (approx.)"[1]

On September 15 and 16 the last two experimental receiving circuits were recorded as were, on the 17th, two units meant for carrying out investigations in the field. The first of these two circuits is identical to the one that is first seen on the 11th. Entries after this date are concerned with both parts of the system however it would appear that Tesla had refined the designs of his receivers to a level that satisfied his requirements for the time being. A count reveals that over the course of the preceding 109 days, he had considered or investigated at least 125 different variations of receiver design.

Any one who builds or operates a Tesla coil of any size, large or small, should seriously consider the addition of a tuned receiving apparatus to circuit. At the very least this unit could consist of a coil of #40 core winding wire wound on a section of paper towel tubing with a short piece of ferrite rod coaxially mounted for fine tuning. This coil is then grounded at its' base and terminated with an elevated body of capacitance. You will find that coarse tuning may be achieved by changing the size of the air capacitance. Another method might be to wind the solenoid using wire of the same size as the transmitters secondary or extra coil. In any case, coupling to the receiving coil may be accomplished with a short secondary connected to a low voltage incandescent lamp or a fluorescent lamp in series connection between the coil and the air capacitance. The operators of units that are instrumented with an oscilloscope set up to read their coil's primary or secondary current may be able to detect small variations in the wave form as the receiving portion of the circuit is introduced and brought into tune. This will be especially true for operators of vacuum tube and transistorized coils which are particularly suited for these experiments. Another experiment that will produce good results is to set up second receiving coil with no load at a point midway between the transmitter and the first receiver. This unit will extent the range over which effects may be produced at the receiver.

Needless to say, observers of this type of demonstration will only be seeing a faint glimmer of Tesla's Worldwide System as most of the existing Tesla Magnifying Transmitters are not energetic enough to overcome the core losses or shunt dielectric losses [2] that are imposed by the mass of the Earth and therefore cannot produce Tesla's legendary Standing Wave.

The receivers or wave meters that were experimented with between June 1 and September 17, 1899, were used to conduct tests related to the study of radio propagation and more specifically to detect the presence of Standing Waves at a points some distance from the transmitter.[1,3] The data collected with these devices along with those collected with simple tuned circuits connected to small incandescent lamps, provided Tesla with the proof that he required in order to set off on the next-phase of his grand experiment, namely the Wardenclyffe Tower.

About seven years later, in a periodical titled "English Mechanic and World of Science," Tesla wrote the following words: "A scientific audience cannot help being impressed by a display of interesting phenomena, but the originality and significance of a demonstration such as [the lighting of arc lamps through the human body and the fusing of a piece of copper in mid-air] can only be judged by an expert possessed of full knowledge and capable of drawing correct conclusions. A novel effect, spectacular and surprising, might be quite unimportant, while another, seemingly trifling, is of the greatest consequence.

To illustrate, let me mention here two widely different experiments of mine. In one the body of a person was subjected to the rapidly-alternating pressure of an electrical oscillator of two and a half million volts; in the other a small incandescent lamp was lighted by means of a resonant circuit grounded on one end, all the energy being drawn through the earth electrified from a distant transmitter.

The first presents a sight marvelous and unforgettable. One sees the experimenter standing on a big sheet of fierce, blinding flame, his whole body enveloped in a mass of phosphorescent streamers like the tentacles of an octopus. Bundles of light stick out from his spine. As he stretches out the arms, thus forcing the electric fluid outwardly roaring tongues of fire leap from his fingertips. Objects in his vicinity bristle with rays, emit musical notes, glow, grow hot. He is the center of still more curious actions, which are not visible. At each throb of electric force myriads of minute projectiles are shot off from him with such velocities as to pass through the adjoining walls. He is in turn being violently bombarded by the surrounding air and dust. He experiences sensations which are indescribable.

A layman, after witnessing this stupendous and incredible spectacle, will think little of the second modest exhibit. But the expert will not be deceived. He realizes at once that the second experiment is ever so much difficult to perform and immensely more consequential. He knows that to make the little filament glow, the entire surface of the planet, two hundred million square miles, must be strongly electrified. This calls for peculiar electrical activities, hundreds of times greater than those involved in the lighting of an arc lamp through the human body. What impresses him most, however, is the knowledge that the little lamp will spring into the same brilliancy anywhere on the globe, there being no appreciable diminution of the effect with the increase of distance from the transmitter." [4]

A point that should be kept in mind is the fact that Tesla's primary goal was to develop a global communications system. He was definitely aware that the transmission of significant amounts of electricity was possible, however his initial plans did not call for the transmission of industrial quantities of electrical power. The preceding quote indicates that at some time prior to March 8, 1907, Tesla succeeded in electrically resonating the Earth to such a degree that it was possible to light a small incandescent lamp at any distance from his transmitter. This incredible claim virtually begs verification.

[1] Tesla, Nikola, "Colorado Springs Notes", A. Marincic, Editor, Nolit, Beograd, Yugoslavia, 1978, pp. 25-97, 184

[2] Kenneth Corum, "Concerning Cavity Q," Proceedings of the 1988 International Tesla Symposium, International Tesla Society, 1991.

[3] Tesla, Nikola, "Art of Transmitting Electrical Energy Through the Natural Mediums," US Patent# 787,412, applied for May 16, 1900; granted April 18, 1905.

[4] Tesla. Nikola, Tesla Said, Compiled by Ratzlaff, John T. Tesla Book Company, 1984, pg. 94