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Re: Wire Length

Original poster: "Gary Peterson" <g.peterson@xxxxxxxxxxxx>

Ed, Bill, and Mike,

It's good to know we are all in agreement that Tesla's 1898 flat-spiral type transmitter is, in fact, a spread spectrum Tesla coil RF transmitter. The unanswered questions are 1) is the transmitted energy spread out in the intervening portion of the RF spectrum between the upper and lower frequencies, and, if so, how much of the transmitters RF energy appears in this region? 2) If there is RF energy in the intervening portion of the band, does this energy contribute to the operation of the wave complex receiver?

As for my comment about Tesla being able to "generate practically undamped waves," I was giving him benefit of the doubt in regards to one of his methods, which had been used, and still is, for creating damped waves. A search for "undamped" in "NIKOLA TESLA ON HIS WORK WITH ALTERNATING CURRENTS and Their Application to Wireless Telegraphy, Telephony and Transmission of Power : An Extended Interview" produces results directly related to the 1898 flat-spiral transmitter. For example,

    "In the meantime, as I was developing all this, I had
already struck a new line of effort toward producing vibra-
tions; namely, I had developed a system permitting me
to take the ordinary current of any main and transform it
into any kind of vibrations I desired, either damped or
undamped." [p. 11]

Speaking specifically about the RF alternator Tesla said,

    ". . . My idea was to construct a machine with a certain
small number of poles, rotate it an enormous speed,
and thus generate sudden impulses which would pro-
duce the same effect as the arc discharge in my so-
called "Tesla transformer."  Originally, this machine had
64 poles.  Then I reduced them to 32, and finally to 16,
and in that form I have produced with it any oscillations,
continuous trains or undamped oscillations of any fre-
quency I desired. . . . I have perfected a scheme enabling
me to take, for instance, this machine, which will give me
3,000 or 4,000 oscillations, and from these oscillations
develop 100,000, and there will be a continuous train of
undamped waves." [p. 14]

It is clear from the above description that while Tesla was not seeking a pure sinusoidal waveform from the alternator, it is desirable that the AC power supply's output be precisely constant in frequency. (Ed, I think this will interest you.)

    "I come now to a large machine which was built in my
laboratory on Houston Street.  Immediately after the des-
truction of my laboratory by fire, the first thing I did was to
design this oscillator.  I was still recognizing the absolute
necessity of producing isochronous oscillations, and I
could not get it with the alternator, so I constructed this
machine.  That was all a very expensive piece of work.
It comprised four engines.  Those four engines were put
in pairs and there was an isochronous controller in the
center, and furthermore, that controller was so arranged
that I could set two pairs of engines to any phase or
produce any beat I desired.  Usually I operated quarter
phase; that is, I generated currents of 90 degrees

    "By the way, now, for the first time you see my appara-
tus on Houston Street, which I used for obtaining oscilla-
tions, damped and undamped as well.  But, it is neces-
sary to state that while others, who had been using my
apparatus, but without my experience, have produced
with it damped oscillations, my oscillations were almost
invariably continuous, or undamped, because my circuits
were so designed that they had a very small damping
factor.  Even if I operated with very low frequencies, I always
obtained continuous, or undamped, waves for the reason
that I designed my circuits as nonradiative circuits.  I will
explain that later." [pp. 43-44]

Discussing his related U.S. Patent "Method and Apparatus for Electrical Conversion and Distribution" Tesla said,

    ". . . 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 any-
thing 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. [pp.

Speaking about his 35 S. 5th Ave. Tesla coil RF transmitter Tesla said,

    ". . . 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 perfec-
tion 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 ex-
ception, between individual discharges."


    "Speaking of your not having perfectly undamped
waves at that time, you were referring to that character
of circuit?"


    "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 incon-
ceivably 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 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 instru-
ment, as I have stated in my writings, because it enables
us to attain greater activities than are practical with ex-
plosives. ["High Frequency Oscillators for Electrothera-
peutic and Other Purposes"]  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." [pp. 61-62]

    ". . . This dynamo, you see, is a two-phase machine;
that is, I develop from it currents of two-phase.  Now,
there are four transformers, you see them down here,
that furnish the primary energy.  From these two phases
I develop four phases.  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. . . ." [p. 64]


    "You have spoken of the use of that machine at
Houston Street.  In what way was it used?"


    "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 con-
tinuous currents by commutating the high tension alterna-
ting currents of the transformer.  At that time I had two trans-
formers from which I obtained a constant pressure, charged
the condenser, and produced undamped waves of any
frequency I wanted.  As to the machine here, 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. . . ." [p. 65]

    "I can take an ordinary circuit of 50 volts and produce
from it absolutely undamped oscillations and never have
the slightest difficulty about it." [p. 70]

And, this is what Tesla had to say about his hermetically enclosed mercury break described in U.S. Patent No. 609,245 of August 16, 1898.

    "Here I come to another device.  That was another
solution of the problem of producing currents of very
high frequency.  An alternator was difficult to construct;
if one went into too high frequencies, it became inef-
ficient and worthless.  But, in this way, I was able to get
any frequency up to 200,000 per second, or more, in a
perfectly reliable manner, and I could get a couple of
kilowatts output very easily.  That was especially built
for telegraphy, telephony, and similar experiments.

    "The arrangement was simply this.  I had a number
of studs with cups which were insulated, 24 if I recollect
rightly.  In the interior was a mechanism that lifted the
mercury, threw it into these cups, and from these studs
there were thus 24 little streamlets of mercury going out.
In the eantime, the same motor drove a system with 25
contact points, so that for each revolution I got a product
of 24 times 25 impulses, and when I passed these im-
pulses through a primary, and excited with it a secondary,
I got in the latter complete waves of that frequency."


    "What frequency, then, did you get in your secondary?"


    "Oh, I could get in this, 600 per revolution."


    "You mean 600 trains?"


    "No, 600 waves.  Assume then, 600 impulses per revo-
lution and suppose that I rotated it 100 times per second;
then I would get 600 times 100, or 60,000 primary impulses,
and in the secondary a frequency of 60,000 complete cycles.
The primary impulses were unidirectional.  They came from
the direct current source, but in the secondary they were
alternating -- full waves."


    "How persistent were those waves?"


    "They were entirely persistent.  I had 60,000 per second
absolutely undamped waves; they could not be damped."
[pp. 77-80]

In speaking about the generation of continuous waves at the Colorado Springs station Tesla said,

    "The method was this:  I had a 550-volt current with
which I charged the condensers.  These condensers I
discharged through a primary in the form of an arc,
sometimes I also introduced in this arc a mechanical
break of several thousand per second.  And I obtained
a perfectly continuous train of waves as has been des-
cribed in my patents.  The reason why I show the con-
denser here [Fig. 83] is that that is synonymous with
undamped waves.  If I had shown the whole apparatus
as arranged there, then I might still have damped waves;
but whether I use an alternator or some other way of get-
ting energy to that condenser, the condenser is usually
there.  For instance, if I use an alternator, I shunt its ter-
minals with a condenser in order to magnify the current
in the primary.  I then tune this circuit to the alternator,
and magnify the current in the primary in the ratio of the
inductance to the resistance.  Therefore, this condenser
here stands for either method, and simply means that
in this system, as is obvious from the description in the
patent, the waves are undamped because high rises of
potential would not be obtained otherwise.  Whenever I
wanted to obtain a high potential, I had to observe these
rules in order to force the potential up to that value."
[pp. 146-147]

Getting back to the RF alternator and the associated problems, Tesla said,

    "All the alternators ever designed failed to give
isochronous impulses, but the alternators of high
frequency which were designed in later years by my
followers were very much worse in this respect than
mine for the simple reason that they were built for
much higher frequencies -- the higher the frequency,
the greater are the departures from isochronism.
You see, certain definite fluctuations of speed will
have a greater effect on the isochronous character of
the oscillations if the periods are shorter; therefore,
the higher the frequency of the dynamo the less
isochronism there is.  The dynamo of Alexanderson,
designed for 200,000 cycles, cannot fail to show a
very strong departure from isochronism - much greater
than in my dynamos of 1891 and 1892." [pp. 170-171]


    Could you tell, just in a few words, the mechanism
actually used by you in Colorado for getting the contin-
uous waves?


    I produced these continuous waves in several ways;
but before I answer that question, let me define what a
continuous or undamped wave means.  That is so elastic
a term, and there is such confusion in this respect, that
unless I elucidate that a part of my remarks will not be

    I have pointed to this already, and I have given a
mechanical analogue by a bell.  If you put a bell in mercury
-- a dense, heavy medium, and you attempt to make this
bell vibrate, you will find that, unless the blows of the
hammer with which you try to keep the bell swinging are
delivered in a very rapid succession, the vibrations of the
bell will die out between the successive blows.  But, if you
take a bell and put it in a vacuum, with no resistance, with
nothing to take up energy, then you can tap the bell once
in every half hour and still it will ring with practically the
same note, the same intensity.  Therefore, before we talk
of these continuous or undamped waves, we must realize
what conditions there existed to keep up waves of this
character.  It makes a vast difference.  In one apparatus
the waves will die out quickly; in another one, they will not.
Even when I operated as in some instances with a few of
these hammer blows, even then, owing to the design of
my circuit, the waves were practically continuous; but I
have had several ways of obtaining absolutely undamped
waves, irrespective of the manner in which the energy
was taken out from them. . . ." [NTAC, p. 174]

Original poster: "Gary Peterson" <g.peterson@xxxxxxxxxxxx>
Original poster: Mike <megavolts61@xxxxxxxxx>
Original poster: Ed Phillips <evp@xxxxxxxxxxx>

. . . Tesla was able to generate practically undamped waves with his
improved oscillators.

 Ummmmmm   he had high speed alternators that enabled him to produce pure
sine waves when he wished.

   He did, and the first ones at that.  Haven't seen anything to
suggest he ever used more than one at a time.