pparatus for Transformation by Condenser Discharges; Damped Waves

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EXCERPTS:
IV. Apparatus for Transformation by Condenser Discharges; Damped Waves
Tesla
This work [Fig. 31] was begun already in 1889. This type of apparatus is identified with my name as
certain as the law of gravitation is with that of Newton. I know that some have claimed that Professor
Thomson also invented the so-called Tesla coil, but those feeble chirps ne'er went beyond
Swampscott. Professor Thomson is an odd sort of man; very ingenious, but he never was a wireless
expert; he never could be. Moreover, it is important to realize that this principle is universally
employed everywhere. The greatest men of science have told me that this was my best achievement
and, in connection with this apparatus [referring to schematics of Fig. 31], I may say that a lot of
liberties have been taken. For instance, a man fills this space [break D] with hydrogen; he employs
all my instrumentalities, everything that is necessary, but calls it a new wireless system -- the
Poulsen arc. I cannot stop it. Another man puts in here [referring to space between self-inductive
lines L L] a kind of gap -- he gets a Nobel prize for doing it. My name is not mentioned. Still another
man inserts here [conductor B] a mercury[-arc] rectifier. That is my friend Cooper Hewitt. But, as a
matter of fact, those devices have nothing to do with the performance.
Figure 31. Method of Transformation of electrical energy by oscillatory condenser discharges described in U.S. Patent No.
462,418 of November 3, 1891. Application filed February 4, 1891. Announcement of this invention was made in Tesla's
lecture before the American Institute of Electrical Engineers at Columbia College, May 20, 1891, where it was predicted that
lecture before the American Institute of Electrical Engineers at Columbia College, May 20, 1891, where it was predicted that
this apparatus afforded vast possibilities and would play an important part in the future. Illustrated and described in T.C
Martin book, Figs. 126 and 127, pp. 191-194.
If these men knew what I do, they would not touch my arrangements; they would leave my apparatus
as it is. Marconi puts in here [break D] two wheels. I showed only one wheel; he shows two. And he
says, "See what happens when the wheels are rotated; a wonderful thing happens!" What is the
wonderful thing? Why, when the teeth of the wheels pass one another, the currents are broken and
interrupted. That is the wonderful thing that happens? The Lord himself could not make anything
else happen unless he broke his own laws. So, in this way, invention has been degraded, debased,
prostituted, more in connection with my apparatus than in anything else. Not a vestige of invention
as a creative effort is in the thousands of arrangements that you see under the name of other people
-- not a vestige of invention. It is exactly like in car couplings on which 6,000 patents have been
taken out; but all the couplings are constructed and operated exactly the same way. The inventive
effort involved is about the same as that of which a 30-year-old mule is capable. This is a fact.
This is one of most beautiful things ever produced in the way of apparatus: I take a generator of any
kind. With the generator I charge a condenser. Then I discharge the condenser under conditions
which result in the production of vibrations. Now, it was known since Lord Kelvin that the condenser
discharge would give this vibration, but I perfected my apparatus to such a degree that it became an
instrument utilizable in the arts, in a much broader way than Lord Kelvin had contemplated as
possible. In fact, years afterwards when Lord Kelvin honored me by presenting to the British
Association one of my oscillators of a perfected form, he said that it was "a wonderful development
and destined to be of great importance."
[Returning to a discussion of Fig. 31], [E] is supposed to be a condenser. That [A] is the generator.
Now then, supposing that this is a generator of steady pressure. I can obtain oscillations of any
frequency I desire. I can make them damped or undamped. I can make them of one direction or
alternating in direction as I choose. At G are devices which operate -- lamps, or anything else. Some
experimenters who have gone after me have found a difficulty. They said,
"No, we cannot produce a constant train of oscillations."
Well, it is not my fault. I never have had the slightest difficulty. I produced constant oscillations and I
have described how I produced them. Anyone who has no more than my own skill can do it.
Figure 32.
Quenched spark gap. (Tesla at that time pointed out the future of quenching and showed that oscillations can be maintained
without a spark being visible to the naked eye between the knobs.) Illustrated in T.C. Martin book, Figs. 135 and 136, p. 211.
This [Fig. 32] is another improvement in that particular device, which was the weakness of the
invention and which I tried to eliminate. This device incorporated many spark gaps in series. It had a
invention and which I tried to eliminate. This device incorporated many spark gaps in series. It had a
peculiar feature; namely, through the great number of gaps, I was able, as I have pointed out in my
writings, to produce oscillations without even a spark being visible between the knobs. This device is
now known in the art as the "quenched spark gap." Professor Wein has formulated a beautiful theory
about it, which I understand has netted him the Nobel prize. Wein's theories are admirable. The only
trouble is that he has overlooked one very important fact. It is this: If the apparatus is properly
designed and operated, there is no use for the quenched gap, for the oscillations are continuous
anyway. The radio men who came after me had the problem before them of making a bell sound,
and they immersed it in mercury. Now, you know mercury is heavy. When they struck their bell, the
mercury did not permit it to vibrate long because it took away all the energy. I put my bell in a
vacuum and make it vibrate for hours. I have designed circuits in connection with an enterprise in
1898 for transmission of energy which, once started, would vibrate three years, and even after that
the oscillations could still be detected. Professor Wein's theory is very beautiful, but it really has no
practical meaning. It will become useless as soon as the inefficient apparatus of the day, with
antennae that radiate energy rapidly, [are] replaced by a scientifically designed oscillator which does
not give out energy except when it gets up to a tremendous electromagnetic momentum.
Figure 33.
The discharger working in an atmosphere, chiefly consisting of hydrogen, still further weakened by heat. The use of
hydrogen in this connection has been claimed as a discovery and patented. Presented in TesIa's lectures before the Pranklin
Institute and the National Electric Light Association. T.C. Martin book, Fig. 167. pp. 307-308.
In this form of break [Fig. 33], I changed the atmosphere in which the arc was operating. The
atmosphere was mostly hydrogen, and with this device I performed my experiments before the
Franklin Institute in Philadelphia and the National Electric Light Association in St. Louis. This has
been used by Poulsen and it is now called the "Poulsen arc" and "Poulsen system." But, of course,
there is no invention in it. I am on record with prior publications, and besides, the hydrogen does not
have any other effect except that it lowers the tension under which the device can operate. It has the
disadvantage of producing asymmetrical or distorted waves, and the impulses obtained are not best
suited for tuning.
Figure 34.
Oscillatory apparatus with interrupter in oil. Exhibited in the Chicago Exposition of 1893 before Helmholtz. Described in U.S.
Patent No. 514,168 of February 6. 1894. Application filed August 2, 1893.
This [Fig. 34] is the apparatus used in the Chicago Exposition of 1893, at which time I explained for
the first time to Professor Helmholtz my plan for transmitting energy. After I had shown Professor
Helmholtz and other scientific men there certain phenomena, he asked me,
"Now, what is all this intended for?"
I told him I was trying to develop an apparatus for transmitting energy without wire for telegraphy,
telephony, and other purposes. When I explained to Professor Helmholtz the whole idea, I said,
"Excellency, do you think that my plan is realizable?"
He replied,
"Why, certainly it is, but first you must produce the apparatus."
I started then and there to produce the apparatus.
Counsel
Was that conversation at the the Chicago Exposition?
Tesla
Yes. It took place in a pavilion which was built especially for exhibiting my inventions and
discoveries. I believe Professor Wedding was there and some other scientists whom I cannot
remember now. I showed Professor Helmholtz my vacuum tubes and performed many other
experiments.
Counsel
Will you describe this apparatus in a little more detail?
Tesla
The apparatus [Fig. 34], as you see, comprised primary and secondary coils immersed in a large
tank of oil. The break was automatically effected by means of a turbine. The oil was circulated by a
pump, and the current [i.e., stream flow] of oil drove the turbine which effected the make and break.
Owing to the fact that the oil used was a very good insulator, rapidly flowing and of great dielectric
strength, these make-and-break points were very close together, and the arcs extremely short. The
effects were accordingly more intense. Here [T in Diag. 1 of Fig. 34] is a cooler through which the oil
was circulated. The oil was forced through the gaps at great speed, and as it flowed out it was
supplied again to the tank and the current driving the turbine.
Counsel
That device [Diag. 2 of Fig. 34] you call a turbine?
Tesla
Yes. It had vanes like those of a propeller and constituted a rotary break in the circuit.
Counsel
What was your prime source [of power]?
Tesla
The primary source was an alternator with a frequency of 133 cycles and, if I recollect rightly, the
pressure [at the secondary] was about 20,000 volts. I may have had 10,000 volts. I am not sure what
it was, but it must have been certainly from 10,000 to 20,000 volts -- within that range.
Counsel
I notice you have two sets of transformers in there marked S and S', have you not?
Tesla
This [S'] is my oscillatory circuit. That [S] is the transformer from which the condenser was charged.
Here [at S] we had 20,000 volts, or whatever it was, from the commercial transformer and here [at
S'] is my secondary which generated the high frequency currents. The rotary gap is shown in detail
[Diag. 2 of Fig. 34].
I had a special reason for showing this. To meet that great man Helmholtz and other scientific men,
and to bring before them for the first time the results of years of previous labor, was an important
moment in my life -- particularly because Professor Helmholtz gave me the assurance himself that
what I explained to him was realizable, provided that I could produce the apparatus. I was very much
encouraged.
Figure 35.
Apparatus with mechanical break as installed on a large scale in the laboratory at South Fifth Avenue and subsequently at
46 East Houston Street. Described in U.S. Patent No. 645,576 of March 20, 1900. Application filed September 2, 1897.
This [Fig. 35] is the apparatus I had at 35 South Fifth Avenue and also Houston Street. It shows the
whole arrangement as I had it for the demonstration of effects which I investigated.[*] This cable you
see [square loop in top half of Fig. 35] is stretched around the hall. These are my condensers. There
is the mechanically operated break, and that is a transformer charged from the generator. That is the
way I had it for the production of current effects which were rather of damped character because, at
that period, I used circuits of great activity which radiated rapidly. In the Houston Street laboratory, I
could take in my hands a coil tuned to my body and collect 3/4 horsepower anywhere in the room
without tangible connection, and I have often disillusioned my visitors in regard to such wonderful
effects. Sometimes, I would produce flames shooting out from my head and run a motor in my
hands, or light six or eight lamps. They could not understand these manifestations of energy and
thought that it was a genuine transmission of power. I told them that these phenomena were
wonderful, but that a system of transmission, based on the same principle, was absolutely worthless.
It was a transmission by electromagnetic waves. The solution lay in a different direction. I am
showing you this [diagram] simply as a typical form of apparatus of that period, and if you go over
the literature of the present day you will find that the newest arrangements have nothing better to
show.
Counsel
What was the make and break frequency that you got from that apparatus?
Tesla
It was 5,000, 6,000 -- sometimes higher still. I had two oppositely rotating discs which I will show you
and with which I could have reached, probably, 15,000 or 18,000.
Counsel
What wave frequencies did you develop?
Tesla
I could operate from a few thousand up to a million per second, if I wanted.
Counsel
What did you actually use?
Tesla
In these demonstrations, which I showed these effects, these most powerful effects that were the
sight of New York at that time, I operated with frequencies from 30,000 to 80,000. At that time I could
pick up a wire, coil it up, and tell what the vibration would be, without any test, because I was
experimenting day and night.
Figure 36.
Isochronous mechanical break used in the laboratory at 35 South Fifth Avenue. Described in U.S. Patent Nos. 568,179 and
568,180 of September 22, 1896. Applications filed July 6 and 9, 1896. (Diagram taken from Patent No. 568,180.)
This [Fig. 36] is a form of break which I developed in working with alternators. I recognized that it
was of tremendous advantage to break at the peak of the wave. If I used just an ordinary break, it
would make and break the current at low as well as high points of the wave. Of this apparatus I had
two forms; one in which I drove the break right from the shaft of the dynamo and the other in which I
drove it with an isochronous motor. Then, by a movement of these knobs (K K), I would make the
adjustments so that the makes would occur exactly at the top of the wave. That is a form of break
which is embodied in hundreds of patents and used now extensively.
Figure 37.
Mechanical break with two oppositely rotating discs used for the purpose of increasing the number of breaks and alternating
oscillations practically undamped. (Subsequently patented by others.)
Here [Fig. 37] I show an apparatus that was installed in the Houston Street laboratory prior to the
other break because I wanted to get as high a number of impulses as possible. The drawing dates
from the spring of 1896. It is a break with which I could reach from 15,000 to 18,000 interruptions per
second. I used it very much until later I found it was not necessary. That is the innocent device which
Marconi thought a great invention.
Counsel
This is also a rotary gap?
Tesla
Yes, and it consists of two discs of aluminum, with teeth of aluminum on the side. They were rotated
by two motors in opposite directions, and as they rotated they alternately closed and opened the
circuit. In some instances I used an uneven number of teeth on one and and even number on the
other so that I could produce as many breaks as I desired. I will show you later an apparatus more
perfect than this one, and of a different kind, in which I have 24 stationary contacts, and 25 rotating
elements that established the contact and broke it, so that by one revolution I obtained 24 times 25,
or 600 interruptions [per revolution].
Counsel
Whenever you say "the break", you mean "a spark gap"?
Tesla Yes; otherwise I use the term "circuit controller," preferably.
Figure 38.
Use of multi-phase generator with mechanical break. Experiments in the laboratory at 35 South Fifth Avenue and
subsiquently.
This [Fig. 38] illustrates another development in a different direction. In order to increase the number
of breaks, I employed currents of different phase. I had in my laboratory, permanently, a two-phase
dynamo and could get phases between; that is, from two phases, 90 apart, I could obtain four
phases, 45 apart. Here is an arrangement shown as I had it, working with three phases [60 apart,
and could obtain six phases, 30 apart], and later on I had one with four phases [45 apart, and could
obtain eight phases 22 1/2 apart]. You see, as I multiplied the number of the phases, I increased the
number of the fundamental discharges.
Counsel
What is the date of this apparatus?
Tesla
This I employed already in the 35 South Fifth Avenue laboratory, because I remember that I gave
entertainments to several scientific societies and it was then present there. I know on one occasion
there was the Society of Architects, and another, the Electrotherapeutic Society, and then I had
distinguished men like Mark Twain and Joseph Jefferson -- I gave them a demonstration which was
published in Martin's article in the Century Magazine of April 1895, and I know that on these
occasions I used a two-phase arrangement. Later on I made it four phase. That apparatus existed,
therefore, prior to the destruction of my laboratory in 1895.
Counsel
Do you recall any publication in which this diagram was illustrated?
Tesla
I made no publication, and I vividly remember that when I installed my apparatus on Long Island I
had an arrangement with four transformers and four phases 45 apart. After I had been using this
apparatus there, several years afterwards, I ran across a patent, I believe held by the General
Electric Company, describing precisely the same arrangement.[*] It was a similar experience as with
that patent of Fessenden on the compressed air condenser. Any time I want to use these
improvements all I need to do is to produce my records and that will settle the patents.
Counsel
When was that drawing [Fig. 38]?
Tesla
This is from an old patent drawing which was made by Mr. Netter.
Counsel
But that did not go to patent?
Tesla
No. I have hundreds of inventions that were to be patented but side-stepped. The expense was too
great and I could not do it. This form of apparatus with two and four phases was used prior to the
destruction of my laboratory in 1895, and it was installed on a large scale with four phases in my
plant on Long Island with which I was to telephone around the world, but that is a long story.
Counsel
In that use you made of it at your laboratory, was that connected up as shown there [Fig. 38], to an
antenna?
Tesla
I used the apparatus, yes, in connection with the antenna too, but this is from a patent drawing in
which an antenna is shown; I mean, I used it in every connection. [Fig. 38] illustrates an antenna with
my transmitting circuit, but the apparatus was used in all my work, in all my investigations.
Counsel
And when this was connected in and used in an antenna, did you use it as in other instances -- go
off and listen to the notes which you received?
Tesla
Oh, certainly. But I remember that, besides this, I had different kinds of apparatus. Then I had a
sensibly damped wave because at that time I still was laboring under the same difficulties as some
do this day -- I had not learned how to produce a circuit which would give me, with very few
fundamental impulses, a perfectly continuous wave. That came with the perfection of the devices.
When I came to my experiments in Colorado, I could take my apparatus like that and get a
continuous or undamped wave, almost without exception, between individual discharges.
Counsel
Speaking of your not having perfectly undamped waves at that time, you were referring to that
character of circuit?
Tesla
Yes, but with another kind of circuit I could, of course. The advantage of this apparatus was the
delivering of energy at short intervals whereby one could increase activity, and with this scheme I
was able to perform all of those wonderful experiments which have been reprinted from time to time
in the technical papers. I would take energy out of a circuit at rates of hundreds or thousands of
horsepower. In Colorado, I reached 18 million horsepower activities, but that was always by this
device: Energy stored in the condenser and discharged in an inconceivably small interval of time.
You could not produce that activity with an undamped wave. The damped wave is of advantage
because it gives you, with a generator of 1 kilowatt, an activity of 2,000, 3,000, 4,000, or 5,000
kilowatts; whereas, if you have a continuous or undamped wave, 1 kilowatt gives you only wave
energy at the rate of 1 kilowatt and nothing more. That is the reason why the system with a
quenched gap has become popular.
I have refined this so that I have been able to take energy out of engines by drawing on their
momentum. For instance, if the engine is of 200 horsepower, I take the energy out for a minute
interval of time, at a rate of 5,000 or 6,000 horsepower, then I store [it] in a condenser and discharge
the same at the rate of several millions of horsepower. That is how these wonderful effects are
produced. The condenser is the most wonderful instrument, as I have stated in my writings, because
it enables us to attain greater activities than are practical with explosives. There is no limit to the
energy which you can develop with a condenser. There is a limit to the energy which you can
develop with an explosive.
A common experiment, for instance, in my laboratory on Houston Street, was to pass through a coil
energy at a rate of several thousand horsepower, put a piece of thick tinfoil on a stick, and approach
it to that coil. The tinfoil would melt, and would not only melt, but while it was still in that form, it
would be evaporated and the whole process took place in so small an interval of time that it was like
a cannon shot. Instantly I put it there, there was an explosion. That was a striking experiment. It
simply showed the power of the condenser, and at that time I was so reckless that in order to
demonstrate to my visitors that my theories were correct, I would stick my head into that coil and I
was not hurt; but, I would not do it now.
Figure 39
Apparatus furnishing direct currents of high tension, producing undamped electrical oscillations of high frequency. (This is
also shown in [Fig. 27]). Apparatus built in 1895.
[Fig. 39] shows a four-phase machine which was furnished me by the Westinghouse Electric
Company at the close of 1895. My laboratory burned out in May, and I urged my friend, Mr. Albert
Schmidt, who was the Superintendent, to give me this alternator as soon as possible. He worked day
and night until he got it out, and he certainly did notable work because while the machine was rated
at 30 horsepower, I have run it at 150 horsepower.
By the way, and this is a painful reflection, it was Schmidt and I who developed this type of frame
and this general arrangement which is universally adopted now -- a base, with the magnets cast
below, split at the center line, and a corresponding upper part. That is now used everywhere. I
remember years ago, some of my friends, Messrs. Crocker and Wheeler, started with those long
magnets and I told them, "The sooner you throw these away and adopt this construction, the better it
will be for you." They have got it now; it is all right.
Counsel
How is this machine [Fig. 39] shown in connection with that?
Tesla
This dynamo [Fig. 39], you see, is a two-phase machine; that is, I develop from it currents of twophase.
Now, there are four transformers. You see them down here [lower left of Fig. 39] that furnish
the primary energy. From these two phases I develop four phases. [However,] this involves
something else which I have referred to before; namely, an arrangement which enables me to
produce from these alternating currents direct currents and undamped -- absolutely undamped --
isochronous oscillations of any period I like.
This is accomplished in the following manner: The secondaries of the four transformers could each
develop 44,000 volts. They were specially built for me by the Westinghouse Company. They could,
however, be connected in such a way that each would give 11,000 volts, and then I would take these
11,000 volts and these four phases and commutate them by a commutator consisting of aluminum
plates, or aluminum segments, which were rotated in synchronism with the alternator. Then I
obtained a continuous pressure; that is, direct current of a tension of 44,000 volts, and with these
44,000 volts I charged my condensers. Then by discharging the condensers, either through a
stationary gap or through a gap with a mechanical interrupter, I obtained any frequency I desired,
and perfectly undamped waves. This arrangement was installed in 1901 in my wireless plant at Long
Island, with which I was to telephone around the world.
Counsel
Who built that machine?
Tesla
The Westinghouse Company, [under direction of] Mr. Albert Schmidt, Superintendent. It was
especially built for me and furnished to my laboratory on Houston Street.
While I was with the Westinghouse Company, I did two things in addition to bringing my motors to
them. I had discovered that Bessemer steel was a much better material for transformers and motors
than the soft iron which was previously used. When I came to Pittsburgh, my motors gave results
which their motors could not at first produce, and I told them that I had used Bessemer steel. I
discovered, in following up the analysis of the steels which were used, that the Bessemer was not
steel but really soft iron. The Westinghouse people then adopted my suggestion. At first, Mr.
Shallenberger and other electricians there objected very much, but I persuaded them and when the
transformers were built we found that we could get 2 1/2 times the output we got before.
The Westinghouse people kept it a secret for a long time and no one understood how they could
make such fine transformers, but all they did was to use the Bessemer steel, on my suggestion,
instead of the soft iron the General Electric and other people used. Mr. Westinghouse especially
requested me to join efforts with Mr. Schmidt and improve the design of his machines, and we did
so. We evolved this design, introduced the ready-made coils, which are pressed on the armature,
and other improvements. I took a couple of patents out with Mr. Schmidt, and Mr. Westinghouse was
very nice about it. I think he compensated me with $10,000, or something like that, for my
suggestions.
Counsel
You have spoken of the use of that machine at Houston Street. In what way was it used?
Tesla
I used this machine, as I said, either to produce alter- nating currents and then interrupt them with a
mechanical break at the high peaks of the wave; or, I used alternating currents and interrupted them
with an independent rotating break having a great number of teeth. Or, I generated continuous
currents by commutating the high tension alternating currents of the transformer. At that time I had
two transformers from which I obtained a constant pressure, charged the condenser, and produced
undamped waves of any frequency I wanted. As to the machine here [Fig. 39], that is the way it was
arranged. It was for the generation of continuous electromotive force and production of undamped
waves -- from 1895 and on.
Counsel
What sort of apparatus was it connected up to for the purpose of absorbing these waves?
Tesla
It was the same as shown here [Fig. 38]. It was con- nected to the condensers, and these
condensers were discharged through a primary which excited the secondary; the antenna was
included in the secondary. At other times we discharged the condensers directly so that I could use
the antenna without the secondary.
Counsel
In the same way did you note the operation of these waves?
Tesla
We did, of course, only in most cases the instrument of reception was different. When I operated
with these continuous, or undamped, waves, generated in this way, I usually went to high
frequencies. I did operate [at] a very few thousand, but that gave me a smaller output. Such a
machine you have to operate at high frequencies to get power.
Counsel
What do you mean by high frequencies?
Tesla
I mean frequencies of 30,000, 40,000, 50,000, or something like that.
Counsel
And by means of that machine, you put undamped waves of frequency about 50,000 into that
antenna at Houston Street in 1895?
Tesla
No, not in 1895. Late in 1895 the machine was furnished and I began to operate in early 1896. That
is when I began to operate.
Counsel
Then you did this, that I speak of, in 1896?
Tesla
Yes, from 1896 to 1899, right along.
Counsel
When you used frequencies like that in your antenna, was your antenna tuned or untuned?
Tesla
I could not use it untuned. That would be absurd.
Counsel
What form of device did you use, and where did you use it, for noting the generation of these
oscillations or waves in the antenna?
oscillations or waves in the antenna?
Tesla
I suppose I had hundreds of devices, but the first device that I used, and it was very successful, was
an improvement on the bolometer. I met Professor Langley in 1892 at the Royal Institution. He said
to me, after I had delivered a lecture, that they were all proud of me. I spoke to him of the bolometer,
and remarked that it was a beautiful instrument. I then said,
"Professor Langley, I have a suggestion for making an improvement in the bolometer, if you will
embody it in the principle."
I explained to him how the bolometer could be improved. Professor Langley was very much
interested and wrote in his notebook what I suggested. I used what I have termed a small-mass
resistance, but of much smaller mass than in the bolometer of Langley, and of much smaller mass
than that of any of the devices which have been recorded in patents issued since. Those are clumsy
things. I used masses that were not a millionth of the smallest mass described in any of the patents,
or in the publications. With such an instrument, I operated, for instance, in West Point -- I received
signals from my laboratory on Houston Street in West Point.
Counsel
This was then the machine that you used when working with West Point?
Tesla
I operated once or twice with it at that distance, but usually as I was investigating in the city. My work
at that time was to prepare for the development of a commercial plant, and with me the question was
not to transmit signals, but to see what intensity I could get to put me in position to calculate out my
apparatus, the dimensions and the forms, before I began the undertaking. It was nothing but
preparatory work for the construction of a commercial plant, and I demonstrated its practicability
through my experiments, a plant which was to accomplish much more than all others.
Counsel
What was the horsepower activity in the oscillating circuits when you used this machine?
Tesla
Usually something like 50 horsepower, and I would get, I should say, approximately 30 horsepower
in the antenna; that is, I would get 30 horsepower in the oscillating circuit.
Counsel
I understood a little while ago when you made the statement of using several thousand horsepower
put into a condenser, you could take out of the condenser a million horsepower. I wondered if you
got the same condition with this machine.
Tesla
Yes; I charged the condenser with 40,000 volts. When it was charged full, I discharged it suddenly,
through a short circuit which gave me a very rapid rate of oscillation. Let us suppose that I had
stored in the condenser 10 watts. Then, for such a wave there is a flux of energy of (4 x 104)2, and
this is multiplied by the frequency of 100,000. You see, it may go into thousands or millions of
horsepower.
Counsel
What I wanted to get at was, did that depend upon the suddenness of the discharge?
Tesla
Yes. It is merely the electrical analogue of a pile driver or a hammer. You accumulate energy
through a long distance and then you deliver it with a tremendous suddenness. The distance through
through a long distance and then you deliver it with a tremendous suddenness. The distance through
which the mass moves is small -- the pressure immense.
Counsel
Did you find that that was the best condition for transmitting energy without the use of wire?
Tesla
No, I did not use that method when I was transmitting energy. I used it only in the production of those
freaks for which I have been called a magician. If I had used merely undamped waves, I would have
been an ordinary electrician like everybody else.
Counsel
You have referred to some delicate receiving instruments. Did you have any trouble with those
burning out on account of static?
Tesla
My dear sir, I burned out so many instruments before I discovered what was the matter with them!
They burned out instantly until I learned how to make them so that they could not burn out. Yes, that
was a great trouble in the beginning.
Counsel
Did you succeed in getting them so they would not burn out?
Tesla
Yes. If lightning struck close by, it would not burn out my instrument that has a millionth of the
smallest mass used in the instruments of others.
Figure 40.
Apparatus and method of conversion by condenser discharges applicable to both alternating and direct currents. Described
in lectures before the Franklin Institute and the National Electric Light Association early in 1893. Illustrated in T.C. Martin
book, Fig. 165, pp. 302-317.
This [Fig. 40] is a systematic representation of the various ways which I gave in my lecture before
the Franklin Institute and the National Electric Light Association, embodying the general
arrangements for the obtainment of continuous waves, undamped or damped waves, from direct and
alternating current supply. On the one side [right] you have direct, on the other side alternating
current supply. Some electricians have had difficulties in operating some of this apparatus. I had
none. I can take an ordinary circuit of 50 volts and produce from it absolutely undamped oscillations
none. I can take an ordinary circuit of 50 volts and produce from it absolutely undamped oscillations
and never have the slightest difficulty about it.
Figure 41.
Illustrating one of the early experiments with a tuned transformer in the laboratory at South Fifth Avenue.
Now I come to a few pieces of apparatus which I used in the Houston Street laboratory and the
South Fifth Avenue laboratory. I have here [Fig. 41] what you might call a tuning coil. I employed
usually another secondary and had my condensers on the table. You see one of the coils in action.
This is a tuned circuit which responds to electromagnetic waves which are sent through the room.
Counsel
This is being used as a receiver of waves?
Tesla
Yes.
Figure 42.
Another illustration of one of the early experiments with a tuned transformer in the laboratory at South Fifth Avenue. (Article
by T.C. Martin ["Tesla's Oscillator and Other Inventions"], Century Magazine, April 1895, Fig. 9, p. 926.)
This [instrument shown in Fig. 42] was used in the laboratory on South Fifth Avenue. Here [large
circular disc lying on top of coil] is the tuning table with the condensers, a thick primary, and another
secondary wire. Sometimes I would operate with two vibrations and I would tune the first circuit to
one and the second to the other. Here [referring to cabinets in back of room] you see some of my
historical apparatus. Professor Fairfield Osborn[*] came once to my laboratory and said to me, "Why
on earth do you keep it in this laboratory?" I had all of this apparatus, 400 pieces, absolutely
priceless, and he offered to take it over to the Museum. But I did not heed his advice, and it is gone.
Counsel
Where were the waves sent from?
Tesla
The whole room was energized by electromagnetic waves and the receiver responded at any place
in the hall. The hall was bigger than this room [shown in Fig. 42], twice as long, and anywhere the
intensity of action was the same. These discs [vertical, on top of tuning table] were, I think, about 14
or 15 inches in diameter, and you could see the streamers [shown as white between the discs]
anywhere in the room. In a hall twice as long as this, wherever I placed the instrument, it would
respond to the electromagnetic waves.
Counsel
In this particular instance you are speaking of, the waves were generated right there at 35 South
Fifth Avenue?
Tesla
Yes.
Counsel
Was that the apparatus in which you had the primaries running entirely around the room?
Tesla
Yes. This was shown to many people and societies.
This [Fig. 43] shows the first single step I made toward the evolution of an apparatus which, given
primary oscillations, will transform them into oscillations capable of penetrating the medium. That
experiment, which was marvelous at the time it was performed, was shown for the first time in 1894.
I remember the incident perfectly. I called Mr. Edward Adams, the banker, to come and see it, and
he was the first man to observe it and to hear my explanation of what it meant.
Figure 43.
Apparatus in action illustrating the first step in the evolution of the magnifying transmitter in the laboratory at 35 South Fifth
Avenue. (Article by T.C. Martin ["Tesla's Oscillator and Other Inventions"], Century Magazine, April 1895, Fig. 15, p. 932.)
This coil, which I have subsequently shown in my patents Nos. 645,576 and 649,621, in the form of
a spiral, was, as you see, [earlier] in the form of a cone. The idea was to put the coil, with reference
to the primary, in an inductive connection which was not close -- we call it now a loose coupling --
but free to permit a great resonant rise. That was the first single step, as I say, toward the evolution
of an invention which I have called my "magnifying transmitter." That means, a circuit connected to
ground and to the antenna, of a tremendous electromagnetic momentum and small damping factor,
with all the conditions so determined that an immense accumulation of electrical energy can take
place.
It was along this line that I finally arrived at the results described in my article in the Century
Magazine of June 1900. [Fig. 43] shows an alternator; not the alternator that was furnished for my
laboratory on Houston Street -- that was another one, [but] at 35 South Fifth Avenue [and] operated
on the same principle. Here [lower left] are the condensers, primary, and all the rest. The discharge
there was 5 or 6 feet, comparatively small to what I subsequently obtained. I have produced
discharges of 100 feet, and could produce some of 1,000 feet if necessary, with the greatest facility.
Counsel
Mr. Tesla, at that point, what did you mean by electro-magnetic momentum?
Tesla
I mean that you have to have in the circuit, inertia. You have to have a large self-inductance in order
that you may accomplish two things: First, a comparatively low frequency, which will reduce the
radiation of the electromagnetic waves to a comparatively small value, and second, a great resonant
effect. That is not possible in an antenna, for instance, of large capacity and small self-inductance. A
large capacity and small self-inductance is the poorest kind of circuit which can be constructed; it
gives a very small resonant effect. That was the reason why in my experiments in Colorado the
energies were 1,000 times greater than in the present antennae.
Counsel
You say the energy was 1,000 times greater. Do you mean that the voltage was increased, or the
current, or both?
Tesla
Yes [both]. To be more explicit, I take a very large self-inductance and a comparatively small
capacity, which I have constructed in a certain way so that the electricity cannot leak out. I thus
obtain a low frequency; but, as you know, the electromagnetic radiation is proportionate to the
square root of the capacity divided by the self-induction. I do not permit the energy to go out; I
accumulate in that circuit a tremendous energy. When the high potential is attained, if I want to give
off electromagnetic waves, I do so, but I prefer to reduce those waves in quantity and pass a current
into the earth, because electromagnetic wave energy is not recoverable while that [earth] current is
entirely recoverable, being the energy stored in an elastic system.
Counsel
What elastic system do you refer to?
Tesla
I mean this: If you pass a current into a circuit with large self-induction, and no radiation takes place,
and you have a low resistance, there is no possibility of this energy getting out into space; therefore,
the impressed impulses accumulate.
Counsel
Let's see if I understand this correctly. If you have radiation or electromagnetic waves going from
your system, the energy is wasted?
Tesla
Absolutely wasted. From my circuit you can get either electromagnetic waves, 90 percent of
electromagnetic waves if you like, and 10 percent in the current energy that passes through the
earth. Or, you can reverse the process and get 10 percent of the energy in electromagnetic waves
and 90 percent in energy of the current that passes through the earth.
It is just like this: I have invented a knife. The knife can cut with the sharp edge. I tell the man who
applies my invention, you must cut with the sharp edge. I know perfectly well you can cut butter with
the blunt edge, but my knife is not intended for this. You must not make the antenna give off 90
percent in electromagnetic and 10 percent in current waves, because the electromagnetic waves are
lost by the time you are a few arcs around the planet, while the current travels to the uttermost
lost by the time you are a few arcs around the planet, while the current travels to the uttermost
distance of the globe and can be recovered.
This view, by the way, is now confirmed. Note, for instance, the mathematical treatise of
Sommerfeld,[*] who shows that my theory is correct, that I was right in my explanations of the
phenomena, and that the profession was completely misled. This is the reason why these followers
of mine in high frequency currents have made a mistake. They wanted to make high frequency
alternators of 200,000 cycles with the idea that they would produce electromagnetic waves, 90
percent in electromagnetic waves and the rest in current energy. I only used low alternations, and I
produced 90 percent in current energy and only 10 percent in electromagnetic waves, which are
wasted, and that is why I got my results. . . .
You see, the apparatus which I have devised was an apparatus enabling one to produce
tremendous differences of potential and currents in an antenna circuit. These requirements must be
fulfilled, whether you transmit by currents of conduction, or whether you transmit by electromagnetic
waves. You want high potential currents, you want a great amount of vibratory energy; but you can
graduate this vibratory energy. By proper design and choice of wave lengths, you can arrange it so
that you get, for instance, 5 percent in these electromagnetic waves and 95 percent in the current
that goes through the earth. That is what I am doing. Or you can get, as these radio men, 95
percent in the energy of electromagnetic waves and only 5 percent in the energy of the current. . . .
The apparatus is suitable for one or the other method. I am not producing radiation with my system;
I am suppressing electromagnetic waves. . . .In my system, you should free yourself of the idea that
there is radiation, that the energy is radiated. It is not radiated; it is conserved. . . .
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