The
Generation and Transmission of Electrical Energy
The Dynamo-Electric Machine and Two-Wire
Transmission
1886
patent illustration, showing elements of an electrical generator connected to a
closed two-wire circuit.
The above illustration taken from
Nikola Tesla’s 1886 patent “Regulator for Dynamo-Electric Machines” shows portions
of a closed two-wire circuit consisting of a generator and multiple loads wired
in series. As described in the patent,
M and M’ are “one core of the field magnets,” and “a and b are the positive and
negative brushes of the main or working circuit, and c is the auxiliary
brush. The working circuit D extends
from the brushes a and b as usual, and contains electric lamps or other
devices, D’, either in series or in multiple arc.” [Dr. Nikola Tesla Complete Patents, pp. 8-11] This is a direct current machine, such as
might have been used as part of Edison’s DC power distribution system.
Radio-Frequency Power Supplies
The Radio Frequency Alternator
Nikola Tesla’s
research in the area of wireless telecommunications and alternating current
power transmission began in 1888. At
the time he was involved in the design and manufacture of rotating machinery
for the fledgling electric power industry.
In the course of this work he occasionally had opportunity to run a
particular alternator at high speeds (in the area of 10,000 RPM) developing
currents around 2,000 cycles per second, or 2 kHz. The circuits also included, “transformers, etc., and
condensers.” The phenomena he observed
“were entirely new” and of a nature leading him to believe that a solution to
the problem of wireless energy transmission might be found therein. [Inventions, Researches and Writings of Nikola
Tesla, 1894, pp.
152-155; Nikola Tesla On
His Work With Alternating Currents and Their Application to Wireless
Telegraphy, Telephony, and Transmission of Power, pp. 1-8]
This machine was run up to 12,000 rpm, and had an output of about
8 kilowatts. It had an internal
resistance of only 1/40 of an ohm and was used by Tesla “for all sorts of
wireless demonstrations.” Tesla’s
symbolic representation of an electrical alternator appears to the left. [Nikola Tesla On His Work With
Alternating Currents and Their Application to Wireless Telegraphy, Telephony,
and Transmission of Power,
p. 16-17]
The “Inductorium” or “Commercial Coil”
“Inductorium” is an archaic term for the commercial iron-core
induction coil transformer, common during Tesla’s time. Once again, the symbolic representation is
to the left. [EXPERIMENTS
WITH ALTERNATE CURRENTS OF VERY HIGH FREQUENCY AND THEIR APPLICATION TO METHODS
OF ARTIFICIAL ILLUMINATION, Delivered before the American Institute of
Electrical Engineers, Columbia College, N.Y., May 20, 1891 (Inventions, Researches and Writings of
Nikola Tesla, pp. 145-197).]
The high-tension induction coil or
“Tesla coil”
Tesla made improvements to the commercial coil resulting in the
design shown above. In operation, the inner
turns of the two secondary windings are held at a relatively low
potential. This strengthening reduces
the chance of arc-over to the coil’s primary windings. [EXPERIMENTS
WITH ALTERNATE CURRENTS OF HIGH POTENTIAL AND HIGH FREQUENCY, Delivered before the Institution of
Electrical Engineers, London, February 1892 (Inventions, Researches and
Writings of Nikola Tesla, pp. 198-293).]
The Transmission of Radio-Frequency Electrical Energy
Two
striking results lead Tesla to the conclusion that the wireless transmission of
electrical energy was feasible. Both
involved the operation of the high frequency alternator paired up with an induction
coil transformer.
One-Wire Transmission
The first
to be demonstrated was the operation of light and motive devices connected by a
single wire to only one terminal of the high frequency coil, presented in the 1891
lecture EXPERIMENTS WITH ALTERNATE CURRENTS OF VERY HIGH FREQUENCY AND
THEIR APPLICATION TO METHODS OF ARTIFICIAL ILLUMINATION (Inventions, Researches and Writings of Nikola
Tesla, pp. 156-172; Nikola Tesla On His Work With
Alternating Currents and Their Application to Wireless Telegraphy, Telephony,
and Transmission of Power, p. 7).
Apparatus for the demonstration of
one-wire transmission
I have stated above that a body inclosed in an
unexhausted bulb may be intensely heated by simply connecting it with a source
of rapidly alternating potential. The
heating in such a case is, in all probability, due mostly to the bombardment of
the molecules of the gas contained in the bulb. When the bulb is exhausted, the heating of the body is much more
rapid, and there is no difficulty whatever in bringing a wire or filament to
any degree of incandescence by simply connecting it to one terminal of a coil
of the proper dimensions. Thus, if the
well-known apparatus of Prof. Crookes, consisting of a bent platinum wire with
vanes mounted over it (Fig. 18 / 114), be connected to one terminal of the
coil—either one or both ends of the platinum wire being connected—the wire is
rendered almost instantly incandescent, and the mica vanes are rotated as
though a current from a battery were used: A thin carbon filament, or,
preferably, a button of some refractory material (Fig. 19 / 115), even if it be
a comparatively poor conductor, inclosed in an exhausted globe, may be rendered
highly incandescent; and in this manner a simple lamp capable of giving any
desired candle power is provided.
While a single terminal lamp connected to one of an induction coil’s secondary terminals does not form a closed circuit, “in the ordinary acceptance of the term” the circuit is closed in the sense that a return path is established back to the secondary by what Tesla called “electrostatic induction” (or so called displacement currents). This is due to the fact that the lamp’s filament or refractory button has capacitance relative to the coil’s free terminal and environment and the secondary’s free terminal also has capacitance relative to the lamp and environment.
More on One-Wire Transmission
Tesla gave some additional thoughts on the concept of energy transmission through one wire without return in the lecture ON LIGHT AND OTHER HIGH FREQUENCY PHENOMENA delivered before the Franklin Institute, Philadelphia, February 1893, and before the National Electric Light Association, St. Louis, March 1893 [Inventions, Researches and Writings of Nikola Tesla, pp. 294-373].
In Fig. 20 I / 184 I. is shown a plan which has been
followed in the study of the resonance effects by means of a high frequency
alternator. C1 is a coil of
many turns, which is divided into small separate sections for the purpose of
adjustment. The final adjustment was
made sometimes with a few thin iron wires (though this is not always advisable)
or with a closed secondary. The coil C1
is connected with one of its ends to the line L from the alternator G and with
the other end to one of the plates C of a condenser C C1, the plate
(C1) of the latter being connected to a much larger plate P1. In this manner both capacity and
self-induction were adjusted to suit the dynamo frequency.
As regards the rise of potential through resonant action, of course, theoretically, it may amount to anything since it depends on self-induction and resistance and since these may have any value. But in practice one is limited in the selection of these values and besides these, there are other limiting causes. One may start with, say, 1,000 volts and raise the E. M. F. to 50 times that value, but one cannot start with 100,000 and raise it to ten times that value because of the losses in the media which are great, especially if the frequency is high. It should be possible to start with, for instance, two volts from a high or low frequency circuit of a dynamo and raise the E. M. F. to many hundred times that value. Thus coils of the proper dimensions might be connected each with only one of its ends to the mains from a machine of low E. M. F., and though the circuit of the machine would not be closed in the ordinary acceptance of the term, yet the machine might be burned out if a proper resonance effect would be obtained. I have not been able to produce, nor have I observed with currents from a dynamo machine, such great rises of potential. It is possible, if not probable, that with currents obtained from apparatus containing iron the disturbing influence of the latter is the cause that these theoretical possibilities cannot be realized. But if such is the case I attribute it solely to the hysteresis and Foucault current losses in the core.
Generally it was necessary to transform upward, when
the E. M. F. was very low, and usually an ordinary form of induction coil was
employed, but sometimes the arrangement illustrated in Fig. 20 II., has been
found to be convenient. In this case a
coil C is made in a great many sections, a few of these being used as a
primary. In this manner both primary
and secondary are adjustable. One end
of the coil is connected to the line L1 from the alternator, and the
other line L is connected to the intermediate point of the coil. Such a coil with adjustable primary and
secondary will be found also convenient in experiments with the disruptive
discharge. When true resonance is obtained
the top of the wave must of course be on the free end of the coil as, for
instance, at the terminal of the phosphorescence bulb B. This is easily recognized by observing the
potential of a point on the wire w
near to the coil.
Two additional examples of one-wire transmission
Tesla shows two additional examples of one-wire transmission. In the arrangement labeled I above, his intention is to show the effect of resonance in promoting the movement of energy along conductor L. Arrangement II diagrams a self-induction coil with a tap near one end, effectively dividing the coil primary and secondary sections. It shows one-wire transmission from the transformer’s free terminal to a single terminal lamp. In both cases, conductor L1 constitutes a part of the return circuit. Also notice the two vertical lines to the extreme left and right in the illustration. These appear to represent the walls of an enclosed space, or, perhaps, nearby parts of the general environment.
Wireless Transmission
The second result demonstrated how energy could be made to go through
space without any connecting wires.
This was the first step towards a practical wireless system.
The
most striking result obtained – two vacuum tubes lighted in an alternating
electrostatic field while held in the hand of the experimenter.
The wireless energy transmission effect involved the creation of
an electric field between two metal plates, each being connected to one
terminal of the induction coil’s secondary winding. Once again, a light-producing device was used as a means of
detecting the presence of the transmitted energy.
The ideal way of lighting a hall or room would, however, be to produce such a condition in it that an illuminating device could be moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically connected to anything. I have been able to produce such a condition by creating in the room a powerful, rapidly alternating electrostatic field. For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal being preferably connected to the ground [type-one]. Or else I suspend two sheets as illustrated in Fig. 29 / 125, each sheet being connected with one of the terminals of the coil [type-two], and their size being carefully determined. An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous. [EXPERIMENTS WITH ALTERNATE CURRENTS OF VERY HIGH FREQUENCY AND THEIR APPLICATION TO METHODS OF ARTIFICIAL ILLUMINATION, Inventions, Researches and Writings of Nikola Tesla, pp. 188-189; Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony, and Transmission of Power, pp. 7-8]
.top
Transmitter type-one: a source consisting of a single metal sheet suspended a distance from the ceiling on insulating cords and connected to one terminal of an induction coil, the other terminal being connected to the ground. [NTAC]
Transmitter type-two: a source consisting of two metal
sheets suspended a distance from the ceiling on insulating cords, each sheet
being connected with one of the terminals of an induction coil.
Theory of Wireless Transmission
In working to develop an explanation of the two observed effects mentioned above, Tesla recognized that electrical energy could be projected outward into space and detected by a receiving instrument in the general vicinity of the source without a requirement for any interconnecting wires. He went on to develop two theories related to these observations.
1) By using two type-one sources positioned at distant points on the earth’s surface, it is possible to induce a flow of electrical current between them.
2) By incorporating a portion of the earth as part of a powerful type-two oscillator the disturbance can be impressed upon the earth and detected “at great distance, or even all over the surface of the globe.”
Tesla also made an assumption that Earth is a charged body floating in space.
A point of great importance would be first to know what is the
capacity of the earth? and what charge does it contain if electrified? Though we have no positive evidence of a
charged body existing in space without other oppositely electrified bodies
being near, there is a fair probability that the earth is such a body, for by
whatever process it was separated from other bodies—and this is the accepted
view of its origin—it must have retained a charge, as occurs in all processes
of mechanical separation.
Tesla was familiar with demonstrations that involved the charging
of Leiden jar capacitors and isolated metal spheres with electrostatic
influence machines. By bringing these
elements into close proximity with each other, and also by making direct contact
followed by their separation the charge can be manipulated. He surely had this in mind in the creation
of his mental image, not being able to know that the model of Earth’s origin
was inaccurate. The presently accepted
model of planetary origin is one of accretion and collision.
If it be a charged body insulated in space its capacity should be
extremely small, less than one-thousandth of a farad.
We now
know that the earth is, in fact, a charged body, made so by processes—at
least in part—related to an interaction of the continuous stream of charged
particles called the solar wind that flows outward from the center of our solar
system and Earth’s magnetosphere.
But the upper strata of the air are conducting, and so, perhaps,
is the medium in free space beyond the atmosphere, and these may contain an
opposite charge. Then the capacity
might be incomparably greater.
We also
know one of the upper strata of Earth’s atmosphere, the ionosphere, is
conducting.
In any case it is of the greatest importance to get an idea of
what quantity of electricity the earth contains.
An additional condition of which we are now aware is that the earth
possesses a naturally existing negative charge with respect to the conducting
region of the atmosphere beginning at an elevation of about 50 Km. The
potential difference between the earth and this region is on the order of
400,000 volts. Near the earth's surface there is a ubiquitous downward directed
E-field of about 100 V/m. Tesla referred to this charge as the “electric
niveau” or electric level [As noted by
James Corum, et al in the paper "Concerning Cavity Q," PROCEEDINGS OF
THE 1988 INTERNATIONAL TESLA SYMPOSIUM, and others.]
It is difficult to say whether we shall ever acquire this
necessary knowledge, but there is hope that we may, and that is, by means of
electrical resonance. If ever we can
ascertain at what period the earth's charge, when disturbed, oscillates with
respect to an oppositely electrified system or known circuit, we shall know a
fact possibly of the greatest importance to the welfare of the human race. I propose to seek for the period by means of
an electrical oscillator, or a source of alternating electric currents. . . .
Assume that a source of alternating currents be connected, as in Fig. 21 / 185, with one of its terminals to earth (conveniently to the water mains) and with the other to a body of large surface P. . . . I think that beyond doubt it is possible to operate electrical devices in a city through the ground or pipe system by resonance from an electrical oscillator located at a central point. But the practical solution of this problem would be of incomparably smaller benefit to man than the realization of the scheme of transmitting intelligence, or perhaps power, to any distance through the earth or environing medium. If this is at all possible, distance does not mean anything. Proper apparatus must first be produced by means of which the problem can be attacked and I have devoted much thought to this subject. I am firmly convinced that it can be done and hope that we shall live to see it done. [ON LIGHT AND OTHER HIGH FREQUENCY PHENOMENA, delivered before the Franklin Institute, Philadelphia, and the National Electric Light Association, St. Louis, 1893, (Inventions, Researches and Writings of Nikola Tesla, 1894, pp. 294-373).]
The High Tension Induction Coil
The above described arrangements refer only to the use of commercial coils as ordinarily constructed. If it is desired to construct a coil for the express purpose of performing with it such experiments as I have described, or, generally, rendering it capable of withstanding the greatest possible difference of potential, then a construction as indicated in Fig. 17 / 113 will be found of advantage. The coil in this case is formed of two independent parts which are wound oppositely, the connection between both being made near the primary. The potential in the middle being zero, there is not much tendency to jump to the primary and not much insulation is required. In some cases the middle point may, however, be connected to the primary or to the ground. In such a coil the places of greatest difference of potential are far apart and the coil is capable of withstanding an enormous strain. The two parts may be movable so as to allow a slight adjustment of the capacity effect. [Inventions, Researches and Writings of Nikola Tesla, pp. 172-173]
A Tesla high-tension induction coil
The optimized type-two transmitter consists of two
elevated metal plates, each plate being connected to one of the terminals of a
Tesla high-tension induction coil.
Modification
of the optimized type-two transmitter.
This circuit is the result of interpolation of the preceding and
following diagrams, which are of historical record
The modified type-two transmitter
shown above consists of two elevated metal plates, each plate being connected
to one of the induction coil’s high-voltage terminals. While the coil’s left-hand primary winding
remains the same, i.e., it is still closely coupled to the left-hand secondary,
the right-hand primary has been removed.
This means the right-hand coil is no longer energized by induction. Using Tesla’s terminology, it is now an
extra coil. [Some adjustment might be
required to bring the extra coil back into resonance with left-hand
secondary.] The extra coil is energized
or receives energy by one-wire transmission through the interconnecting section
of wire.
A further
modification of a type-two transmitter, this circuit represents the preferred
prototype transmitter design developed in 1899 at the Colorado Springs
experimental station. The transmitter
circuit now consists of separate two elements, an alternator-driven oscillator
and an adjacent free oscillatory system.
In the further modified
type-two transmitter shown above the two halves of the transformer have been
physically separated. The transmitter
now consists of two discrete units. The
oscillator is on the left with its elevated plate still connected to the upper
secondary terminal. The free system on
the right consists of the original elevated plate connected to the upper
terminal of the extra coil. Instead of
a wire connecting the lower secondary and lower extra coil terminals, the two
coils are now connected to individual earth grounds. These ground connections are constructed so as to introduce the
least possible resistance to the earth.
In operation a powerful current flows through the subsurface between the
two ground terminals. An interaction
also takes place between the two elevated terminals. Tesla believed the electrical disturbance would extend to a great
distance from the transmitter, possibly across the globe.
Colorado Springs Experimental Station
In 1899 Tesla established the Colorado Springs experimental station. The apparatus he assembled there served as a test bed with which to evaluate the type-two and type-one transmitter configurations described above, along with variations of the same. Tesla settled upon the six arrangements shown in the Colorado Springs Notes on pages 190 and 191, and also on page 200.
Tesla’s own sketches of the 6 transmitter configurations
developed at the Colorado Spring’s experimental station [C/S #s 1, 2, 3, 4, 5
& 6]. Tesla’s rendering the last of
these at a slightly larger scale than the rest reflects his enthusiasm for the
design. [CSN, pp. 190-191, 200]
Figure 1 is a type-one transmitter and 2 through 4 are modifications thereof; 5 and 6 are type-two transmitters. Tesla felt arrangement #6 was the most promising. It shows up with slight variations at a number of places in the Colorado Springs Notes, most significantly on pages 191, 200, 197 and 170 (see also pages 161, 162, 174, 177 and 184). In the corresponding text on page 191 Tesla writes, "In Fig. 5. & 6. it is found best to make [the] extra coil 3/4 wave length and the secondary 1/4 for obvious reasons." This two-coil/two-ground configuration was incorporated into the initial Wardenclyffe design.
This is a basic rendering of the type-two transmitter configuration, the same design as that illustrated in the Colorado Springs Notes [type-two, C/S #6]. A receiving circuit is standing out to the right. This general configuration was to be incorporated into the initial Wardenclyffe design, but it was not implemented. [RARE NOTES FROM TESLA ON WARDENCLYFFE, Leland Anderson, Electric Spacecraft Journal, Apr./May/June, # 26, 1998; See also “Wardenclyffe and the World System.”]
The U.S. AND-logic gate patents Method of Signaling, No. 723,188 and System of Signaling, No. 725,605, show a similar arrangement; only the transmitter consists of two electrically driven oscillators tuned to different frequencies instead the single-frequency oscillator-plus-extra coil combination. Also, the transmitter has a common ground. The original application filing date is July 16, 1900 and it is probable that the Wardenclyffe installation, as initially proposed, would have taken on some attributes of this configuration, along with some modifications. For example, each transmitter secondary could be provided with a dedicated ground, and perhaps an independent high voltage power supply as well. Also, it has been suggested that if each transmitter was to be nearly in tune with its partner—say having only a 12 Hz difference in vibration rate—a low-frequency beat tone would be produced, thus introducing an ELF component to the wave complex.
Drawings from the U.S. AND-logic gate patent METHOD OF
SIGNALING, No. 723,188
[improved type-one, C/S #1]. [Dr. Nikola Complete Patents, p. 409]
The Wardenclyffe Plant
The initial conceptual plan for Wardenclyffe discussed above was tied in with the idea Tesla had that it might be possible to produce global displacements of the earth’s charge using a powerful type-two transmitter. In theory, the local electrical current flowing in the earth between the two ground terminals causes this widespread charge displacement. By using an appropriate resonant frequency, that is to say, one at which Earth itself would oscillate, the degree of charge displacement would increase over time.
The initial Wardenclyffe design
plan called for the installation of two 600-foot tall towers in relatively
close proximity to each other. The
two-tower idea could not be implemented due to financial constraints, which led
to a series of modifications. The first
of these led to the arrangement shown in a sketch dated May 29, 1901 (to the
left in figure below). An electrical
oscillator or discharging circuit, consisting of a resonance transformer and an
extra coil, is coupled to the tower structure through an adjustable air
gap. The tower cupola is supported on
electrically conducting legs, which, in turn, are attached to a substantial
grounding system. The capacitance of
the cupola relative to the environment and the high-potential oscillator
terminal, along with the inductance of the tower legs comprise a separate
resonant LC circuit which Tesla designated the “free system.”
Two design drawings,
with variations, of the initial Wardenclyffe transmitter design of 1901
[modified type-two, C/S #5/6]. Notice
the independent grounds. [Tesla
calculated the legs would have to be at least 600 feet in length.] Notice also the alternator-driven oscillator
and the adjoining free oscillatory system. . [RARE NOTES FROM TESLA ON WARDENCLYFFE, Leland Anderson, Electric
Spacecraft Journal, Apr./May/June, # 26, 1998]
The right-hand diagram above
includes a low-frequency alternator and high-voltage power supply transformer
connected to a disruptive-discharge type oscillator. The circuit incorporates a dual inductor-capacitor [LC]
arrangement in the oscillatory transformer primary tank circuit along with dual
secondary windings. Independent tuning
the two sides of the circuit to different frequencies (n/4 lambda, n being an
uneven number) would result in the development of a higher order wave complex
beyond the fundamental resonant frequency of the extra coil. [“The transmitter was to emit a wave-complex
of special characteristics. . . .” MY INVENTIONS; “. . . the transmitter was designed to emit a
wave-complex exactly matching the [receiver] combination in the number and pitch
of individual vibrations, their groupment and order of succession. . . .” TESLA'S TIDAL
WAVE TO MAKE WAR IMPOSSIBLE, English Mechanic and World of Science, May 3,
1907, p. 296.]
Modified Wardenclyffe transmitter
design. [RARE NOTES FROM TESLA ON
WARDENCLYFFE, Leland Anderson, Electric Spacecraft Journal, Apr./May/June, #
26, 1998]
In the above figure the straight conducting
legs have assumed a spiral form. An
obvious advantage would be a reduction in the structure’s overall height above
ground level. Also, notice that the
number of turns varies from leg to leg.
This would also result in the development of what might be called a
higher order wave complex by the transmitter—allowing a form of spread-spectrum
frequency-division multiplexing.
Tesla began operational testing of the Wardenclyffe plant in July 1903 and it appears that he was not at all satisfied with its’ performance. While it is possible a type-two transmitter could be made to work properly, it can be seen that he experienced difficulty with the single-tower implementation of the design. His experiments with the 1899 through 1901 configuration led him to write his underwriter J.P. Morgan on November 5, 1903,
Dear Mr. Morgan:-
The enclosed bears out my statement made to
you over a year and a half ago. The old
plant has never worked beyond a few hundred miles. Apart of imperfections of the apparatus design there were four
defects, each of which was fatal to success.
It does not seem probable that the new plant will do much better, for
these faults were of a widely different nature and difficult to discover.
As to the remedies, I have protected myself
in applications filed 1900-1902, still in the office.
Yours
faithfully,
N.
Tesla
The "old plant" refers to the Colorado Springs Experimental Station or perhaps an initial Wardenclyffe installation bearing some resemblance to it.
As for the "remedies" protected in applications filed between 1900 and 1902, and "still in the office," the only patented invention meeting these criteria is APPARATUS FOR TRANSMITTING ELECTRICAL ENERGY, No. 1,119,732, issued Dec. 1, 1914. Comparing the two basic circuits the most obvious difference is the elimination of the stand-alone extra coil or free [oscillating] system and the plasma coupler [type-two, C/S #6]. The entire transmitter is now comprised solely of the discharging circuit—an oscillatory transformer with an extra coil connected directly to the elevated terminal [type-one, C/S #1].
The Magnifying Transmitter
The 1902 transmitter constituted a departure from the earlier type-two transmitter planned for the Wardenclyffe facility. The new design was a type-one transmitter in which a second conducting path would be established in the upper half-space between plant’s elevated terminal and that of the distant receiving facility. [Type-one, C/S #1; APPARATUS FOR TRANSMITTING ELECTRICAL ENERGY, No. 1,119,732, Dr. Nikola Tesla Complete Patents. p. 435]
Other defects of the Colorado apparatus could have been the antenna feed point (see CSN, pp. 170, 197) and also the slender mast in contrast to the large diameter elevated capacity—either an oblate spheroid or toroid shaped—used in the Wardenclyffe design), the 1:1 aspect ratio C/S extra coil verses the 9.1:1 aspect ratio extra coil shown in the 1914 patent, and the shallow Colorado ground plate verses the 300-foot long section of pipe at the bottom of a 120-foot deep shaft [see The Connection to Earth]. [Further differences between the Colorado Springs layout and the Long Island plant?] Also the considerable distance (about 350 feet) between the high-voltage power supply transformers and the tower-side components, including, at the very least, a helical resonator, could have been a problem on Long Island. Two other seemingly applicable patents filed for within the specified time period and patented in 1900 are “Means for Increasing the Intensity of Electrical Oscillations,” No. 787,412 and “Method of Insulating Electrical Conductors,” No. 655,838, reissued as No. 11,865. Both of these inventions might have been useful for improving the Wardenclyffe plant's performance; the first for the magnifying transmitter itself, the second for improving high-voltage power transmission between the lab building and the tower structure.
In any case, it can be seen that some major modifications were made to the design. He later said,
I used the antenna. I used it right along up to 1907. I made my measurements and experiments, and I transmitted for the purpose of tests, energy and all that, but it never went further than is shown in the picture. [Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony, and Transmission of Power, Leland Anderson, Twenty First Century Books, p. 154]
