Nikola Tesla Books
Books written by or about Nikola Tesla
it again began to play periodically. The storm was now at a distance greater than 200 miles at least. Later in the evening repeatedly the instrument played and ceased to play in intervals nearly of half an hour although most of the horizon was clear by that time.
This was a wonderful and most interesting experience from the scientific point of view. It showed clearly the existence of stationary waves, for how could the observations be otherwise explained? How can these waves be stationary unless reflected and where can they be reflected from unless from the point where they started? It would be difficult to believe that they were reflected from the opposite point of the Earth’s surface, though it may be possible. But I rather think they are reflected from the point of the cloud where the conducting path began; in this case the point where the lightning struck the ground would be a nodal point. It is now certain that they can be produced with an oscillator (This is of immense importance)
Measurement of inductance of oscillator secondary 36 1/2 turns on tapering frame repeatedly referred to. The approximate dimensions and form of same are indicated in the sketch.
On the base it was about 51 feet and the sides were inclined at an angle of 45°. The sides were formed of light lattice work notched for the reception of the wires. The first turn of the secondary began some distance from the ground so that the average turn was smaller than it ought to have been, judging from dimensions, that is nearly 145 feet. Nevertheless more wire was actually coiled up owing to the fact that there was some loss in the corners, and the wire not being perfectly straight added still further to the length so that 6 coils of wire were rolled up, their lengths being: 1000 + 1000 + 1005 + 1002 + 762 + 546 = 5315 feet total, No. 10 B. & S. wire. Deducting ends left gave very nearly 5280 feet or a mile = 1610 meters approx. The wire was wound on by the help of a stand rolled on the floor and supporting the reel. The resistance of the wire was 5.55 ohms. The readings were as follows:
| ω | ||||
|---|---|---|---|---|
| motor | E | I | ||
| 2115 | 212 | 6.2 | from this average values were |
I = 6.17 E = 211.33 ω = 883.42 |
| 2100 | 211 | 6.16 | ||
| 2120 | 211 | 6.16 | ||
$! {E \over I} $! = 34.25 $! {({E \over I})^{2}} $! = 1173 R2 = 30.8 L = $! {{\sqrt{({E \over I})^{2} - R^{2}}} \over ω} $!
gives L = 3826 x 104 cm. or 0.03826 henry.
62
July 4
Discovery of "standing waves" created by natural discharges Tesla described and commented on in articles "The Problem of Increasing Human Energy" in 1900(41), and "Electrical Energy Transmission Without Wires" in 1904(1). He didn't write about these waves in patents he submitted approximately one month later(9,10). With most details and numerous data, the phenomenon of "standing waves" is described in patent "Electrical Energy Transmission Method Through Natural Media" submitted on May 16, 1900(42). There Tesla says that on the basis of numerous data found that one wavelength was, approximately, between 25 and 70 km. On the basis of these results and some theoretical deductions he concluded that the waves of this kind could propagate in all directions on the earth globe and could be of some other wavelengths which in the final case depends on the earth globe, its dimension and characteristics. Tesla described the earth globe as a "perfectly smooth conductor, of negligible resistance with evenly distributed capacitance and inductance along the symetrical axis of a propagating wave". In order to get such conductor i.e. earth globe in resonance according to Tesla the following conditions should be met:
- 1. The radius of the earth globe has to be an odd multiple of one quarter of the wavelength.
- 2. The oscillations applied have to be such that the energy radiation in the shape of Hertz electromagnetic waves is small. Further orientation, Tesla says that frequencies have to be below 20 kHz, and that minimal frequency at which the effect of standing waves appears is 6 Hz.
- 3. The most important condition is that oscillations last a certain period of time - not less than .08484 second, which time is necessary for the wave to leave and return back from the point on opposite side of earth globe from the place where the receiver is. Briefly described, the patent request, based on discovery of standing waves consists in improvement of method for obtaining and use of standing waves on the earth globe of various wavelengths, with free choice of moving the locations of nodes and amplitudes.
According to Tesla's writing in 1904(1), the event which he described on July 4 in the notes took place on July 3. Tesla was obviously very impressed with this discovery therefore he devoted much attention to it. It appears, however, that others didn't have as enthusiastic impressions but, it is certain that his ideas had impact. According to Eccles(12), in summer 1899 there was a rumor that "one American company will construct radio stations in New York and Ireland for the purpose of communication across the Atlantic. These stories were probably based on Tesla's preparations in the U. S. for communications over long distances by means of continuous waves instead of sparks. On one side that caused the drop of cable dividend values on stock market, and on the other side it stimulated the discussion on the waves propagation along the ground." Eccles writes about experiments which Tesla performed in 1899: "Tesla's attempt in 1899 to send the signal over a long distance with very long continuous waves was not successful, although his method for producing the waves and wavelengths choice, approximately 20,000 m, proved to be extraordinary for ocean distances later on, when more sensitive receiving devices than his were invented. But his work helped in efforts to use long waves and next step in improvement of arcing telegraphy was directed in that direction". As far as electrical discharges and waves created by them, however large, before Hertz' research on electrical waves were published pointed to the possibility that discharge of lightning is oscillating in nature similar as a discharge of Leyden's Jar. In 1895 Popov detected remote disturbances with his receiver(32) and showed that they were due to electrical discharge which follows them, and created natural electromagnetic waves which the antenna receives. Feriyi registered discharges at distances of approximately 150 km in 1901, and Turpain on the basis of numerous observations showed in 1903 that notes on discharges could be used for weather forecast.
Later, the natural electrical discharges were used for determining some parameters on waves propagation in the range of extremely low (6 to 3,000 Hz) and very low frequencies (3 to 30 kHz), as well as for determining so called Schwnann resonances. In wave propagation analysis from the mentioned fields it is assumed that the entire earth globe is ideally conductive as well as the ionosphere. On borderline surfaces of sphere wave conductor, which creates the earth globe and ionosphere, currents appear which could be with some reservations considered as Tesla's "conductive currents". Tesla's assumption on the earth globe resonances is proved by Konig measurements and others in 60's of this century. The resonances were found at approximately 8, 14, 20 Hz and at high frequencies(34). The measurements of fading at propagation of extremely low frequencies (1 to 2 dB at 1000 km at approximately 50 Hz.) showed that Tesla was right when he was talking about small fading. Standing waves about which Tesla talks are confirmed by measurements, but they are emphasized around anti-poles and not everywhere around the earth globe because the ground is not ideal conductor except at frequencies in the range of 1 Hz. It has to be mentioned however that disregarding the obvious similarity of Tesla's ideas and experiments. Tesla's name, it appears, was not related to modern researches until 1974, when Wait(21) wrote about it.
