An Appeal to Tesla Coil
Builders
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. Those who are presently engaged in efforts to recreate Tesla’s Colorado Springs Experiments might take this fact into consideration.
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 a number of 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 its’
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 l the disturbances were recorded about one mile away: only 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
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 coils 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 well suited for these experiments. Another experiment that will produce good results is to set up
second tuned receiving coil, with no attached load, at a point midway between
the transmitter and the first receiver.
This relay 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 Earth and
its' atmosphere 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 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 the degree that it was possible to light a
small lamp at any distance from the transmitter. This is an incredible claim that virtually begs
verification.
[1] Tesla, Nikola, Colorado Springs Notes, 1899-1900,
A. Marincic, Editor, Nolit, Beograd, Yugoslavia, 1978, pp. 25-97, 184,
[2] Corum, Kenneth, "Concerning Cavity Q", Proceedings
of the 1988 International Tesla Symposium, International Tesla Society,
1990.
[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, “Tuned Lightning,” English Mechanic
and World of Science, March 8, 1907; Tesla Said, compiled by John T.
Ratzlaff, Tesla Book Company, 1984, pg. 94.