[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Tesla Coil RF Transmitter

Original poster: "Gary Peterson" <gary@xxxxxxxxxxxx>


Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 07:37 AM 9/22/2005, you wrote: 
Original poster: "Gary Peterson" <gary@xxxxxxxxxxxx>

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

A couple problems:
1) that wavelength thing... It assumes uniform
propagation speed, which is hardly the case,
particularly for propagation over a boundary.

The velocity of the disturbance in Earth's charge is not constant as it travels over its surface. It falls as the distance from the transmitter increases, up to the half-way point, and then it increases back to its initial velocity as it reaches the antipodes.

Why would the velocity change in this manner? We're not talking about an acoustic or mechanical wave here, are we? 

Actually yes, it is possible that we are talking about an ion-acoustic wave.

2) The earth isn't a smooth uniform sphere,
so the paths aren't symmetric

For a Tesla-coil transmitter located on the equator, at least the east-west axis is symmetrical. If Tesla's preferred transmitter design is used (see CSN, p. 200, Fig. 6), with both transmitting elements positioned exactly at that latitude, the induced disturbance will be in predominantly east and west directions.

OK, so you're restricting yourself to transmitting power from one place on the equator to another?

Actually, I was thinking more in terms of a restricted case in which no receiving station would be present. The entire type-two transmitter output would be used to overcome 'transformer' core losses and to search for earth resonance modes. Energy transmission between the transmitter and a distant receiving station should also be attempted.

The variable propagation speed problem rears it's ugly head. (and, as a practical matter, this variability HAS been measured experimentally, at many frequencies and at many times in the last 100 years)

Once again, you're talking about radio-wave propagation. The Tesla system does not work by the propagation of what we call "radio waves" in the narrowest sense of the term, i.e., far-field electromagnetic waves that have closed back upon themselves and are no longer associated with the launching structure. These radio waves are the "Hertz waves" to which Tesla occasionally refers in his writings. When I read the term "radio" I automatically envision a system of wireless transmission that involves the propagation of EM waves of this specific type.

3) Sufficiently powerful transmitter doesn't
have much to do with it, although that will
affect the detectability.

A well grounded Tesla-coil transmitter has to apply about 75,000 watts "to keep the earth vibrating so long as there is no energy taken out at any other place."

That last phrase: "as long as there is no energy taken out"... Is the assumption that the earth is a lossless propagation medium by some magic means? 

Its not magic.  I'll let Tesla explain it.

"Theoretically, it does not take much effort to maintain the earth in electrical vibration. I have, in fact, worked out a plant of 10,000 horse-power which would operate with no bigger loss than 1 percent of the whole power applied; that is, with the exception of the frictional energy that is consumed in the rotation of the engines and the heating of the conductors, I would not lose more than 1 percent. In other words, if I have a 10,000 horsepower plant, it would take only 100 horsepower to keep the earth vibrating so long as there is no energy taken out at any other place."

4) There's no reflection at the antipodes
(which doesn't really exist anyway,
because of #1 and #2), the wave just
keeps on going and eventually gets
back to the start.

Of course there is a corresponding antipode to every point on Earth's surface; the validity of #1 and #2 make no difference. The question is, will the arrival of the disturbance from every direction coincide. Given that Earth is not a uniform sphere, the answer must be no. By placing the transmitter on the equator, as described above, the situation improves. The ideal placement for purposes of mathematical modeling is on the North or South Pole.

I suggest that you look at the extensive analysis and measurements done in connection with the Omega Navigation system (now decommissioned) which studied just this.

Searching the web, I find the "Omega Navigation system" is described as "the first world wide radionavigaton system." And, "The Omega transmitter Paynesville [Liberia] was a transmission site used for the Omega Navigation System . . . . It . . . used as [an] antenna an umbrella aerial mounted on a 417 metre high guyed mast of lattice steel, which was the tallest structure ever built in Africa. . . [Wikipedia] This installation was clearly part of a radio system. Any studies performed with such a system are not directly applicable to the subject of this discussion. This recurring problem is one of semantics, not engineering.

The latter effect is widely noted as "long path"
propagation on radio transmissions.  You
get two copies of the transmitted signal,
separated in time by the differential propagation
delay for the short way and long way.


Of course we're not discussing wireless transmission by radio waves.  The
subject of this thread has boiled down to the wireless transmission of
electrical energy by the "disturbed charge of ground and air method" (CSN,
p. 29).

But the "disturbed charge of ground and air method" IS propagation by an EM wave (or, alternately, it is "magic")

Once again, ITS NOT MAGIC. Yes, with Tesla's system, the propagation is by EM wave, but the EM wave is not a radio wave.

In any case, the propagation around the earth (at whatever frequency) is
sufficiently non-uniform and lossy that you're not going to get any
significant standing waves.  No "ringing like a bell"

The production of insignificant standing waves would be better than none at all.

[Summarizing,] "I have already explained the various steps I have set forth in the introduction to this long talk. I have explained how I produced the apparatus giving the requisite oscillations; the second step how I transformed those oscillations into vibratory energy capable of going to a distance; and, furthermore, how I solved another problem, namely, that of the right wavelengths which are effective in the conduction of energy to a distance.

Before I went to Colorado, the one thing which I needed to find out was, how does the current flow through the earth? In my experiments from Houston Street and around New York, I had already learned that the effect is proportionate to the quantity of electricity displaced, and I was in the position to accurately calculate a plant for transmission, for instance, across the Pacific or Atlantic. Those were simple problems; but I could not yet tell how the current passes through the earth, and until I could do that I could not undertake the design of a plant in all these particulars so that it could be a piece of engineering.

I spent 30 years of my work in the design of machinery of all kinds, and have never yet designed a machine which did not do as I expected, and I cannot imagine why it should not because when one calculates the things out on the basis of experimental data, the machine has to work as intended. This is engineering.

Therefore, when my friends offered to back me up for a plant under my patents, I though it was best to devote some time to an investigation, to find out what I needed, in order to have all my data accurately and guarantee that the plant would work.

The law which I discovered in Colorado is wonderful, and it shows that results undreamed of before and of incalculable moment will be obtained as soon as a plant, embodying these principles, is established on a large scale.

Figure 81. http://www.teslaradio.com/images/081.gif -- Diagram illustrating the mode of propagation of the current from the transmitter over the earth's surface.

To give you an idea, I have prepared a diagram illustrating an analogue which will clearly show how the current passes through the globe. You know that in a solar eclipse the moon comes between the sun and the earth, and that its shadow is projected upon the earth's surface. Evidently, in a given moment, the shadow will just touch at a mathematical point, the earth, assuming it to be a sphere.

Let us imagine that my transmitter is located at this point, and that the current generated by it now passes through the earth. It does not pass through the earth in the ordinary acceptance of the term, it only penetrates to a certain depth according to the frequency. Most of it goes on the surface, but with frequencies such as I employ, it will dive a few miles below. It can be mathematically shown that it is immaterial how it passes; the aggregate effect of these currents is as if the whole current passes from the transmitter, which I call the pole, to the opposite point, which I call the antipode.

Assume, then, that here is the transmitter, and imagine that this is the surface of the sea, and that now comes the shadow of the moon and touches, on a mathematical point, the calm ocean. You can readily see that as the surface of the water, owing to the enormous radius of the earth, is nearly a plane, that point where the shadow falls will immediately, on the slightest motion of the shadow downward, enlarge the circle at a terrific rate, and it can be shown mathematically that this rate is infinite. In other words, this half-circle on this side will fly over the globe as the shadow goes down; will first start at infinite velocity to enlarge, and then slower and slower and slower, and as the moon's shadow goes further and further and further, it will get slower and slower until, finally, when the three bodies are on the plane of the ecliptic, right in line one with the other in the same plane, then that shadow will pass over the globe with its true velocity in space. Exactly that same thing happens in the application of my system, and I will show this next.

Figure 82. http://www.teslaradio.com/images/082.gif -- Diagram illustrating the law governing the passage of the current from the transmitter through the earth, first announced in U.S. Patent No. 787,412 of April 18, 1905. Application filed May 16, 1900. See also J. Erskine-Murray, A Handbook of Wireless Telegraphy, Chapt. 17, pp. 312-330, 1913 edition, published by Crosby Lockwood and Son, London, and Appleton & Company, New York.

This illustrates, on a larger scale, the earth. Here is my transmitter -- mine or anybody's transmitter -- because my system is the system of the day. The only difference is in the way I apply it. They, the radio engineers, want to apply my system one way; I want to apply it in another way.

This is the circuit energizing the antenna. As the vibratory energy flows, two things happen: There is electromagnetic energy radiated and a current passes into the earth. The first goes out in the form of rays, which have definite properties. These rays propagate with the velocity of light, 300,000 kilometers per second. This energy is exactly like a hot stove. If you will imagine that the cylinder antenna is hot -- and indeed it is heated by the current -- it would radiate out energy of exactly the same kind as it does now. If the system is applied in the sense I want to apply it, this energy is absolutely lost, in all cases most of it is lost. While this electromagnetic energy throbs, a current passes into the globe.

Now, there is a vast difference between these two, the electromagnetic and current energies. That energy which goes out in the form of rays, is, as I have indicated here [on the diagram of Fig. 82], unrecoverable, hopelessly lost. You can operate a little instrument by catching a billionth part of it but, except this, all goes out into space never to return. This other energy, however, of the current in the globe, is stored and completely recoverable. Theoretically, it does not take much effort to maintain the earth in electrical vibration. I have, in fact, worked out a plant of 10,000 horse-power which would operate with no bigger loss than 1 percent of the whole power applied; that is, with the exception of the frictional energy that is consumed in the rotation of the engines and the heating of the conductors, I would not lose more than 1 percent. In other words, if I have a 10,000 horsepower plant, it would take only 100 horsepower to keep the earth vibrating so long as there is no energy taken out at any other place.

There is another difference. The electromagnetic energy travels with the speed of light, but see how the current flows. At the first moment, this current propagates exactly like the shadow of the moon at the earth's surface. It starts with infinite velocity from that point, but its speed rapidly diminishes; it flows slower and slower until it reaches the equator, 6,000 miles from the transmitter. At that point, the current flows with the speed of light -- that is, 300,000 kilometers per second. But, if you consider the resultant current through the globe along the axis of symmetry of propagation, the resultant current flows continuously with the same velocity of light.

Whether this current passing through the center of the earth to the opposite side is real, or whether it is merely an effect of these surface currents, makes absolutely no difference. To understand the concept, one must imagine that the current from the transmitter flows straight to the opposite point of the globe.

There is where I answer the attacks which have been made on me. For instance, Dr. Pupin has ridiculed the Tesla system. He says,

    "The energy goes only in all directions."

It does not. It goes only in one direction. He is deceived by the size and shape of the earth. Looking at the horizon, he imagines how the currents flow in all directions, but if he would only for a moment think that this earth is like a copper wire and the transmitter on the top of the same, he would immediately realize that the current only flows along the axis of the propagation.

The mode of propagation can be expressed by a very simple mathematical law, which is, the current at any point flows with a velocity proportionate to the cosecant of the angle which a radius from that point includes with the axis of symmetry of wave propagation. At the transmitter, the cosecant is infinite; therefore, the velocity is infinite. At a distance of 6,000 miles, the cosecant is unity; therefore, the velocity is equal to that of light. This law I have expressed in a patent by the statement that the projections of all zones on the axis of symmetry are of the same length, which means, in other words, as is known from rules of trigonometry, that the areas of all the zones must also be equal. It says that although the waves travel with different velocities from point to point, nevertheless each half wave always includes the same area. This is a simple law, not unlike the one which has been expressed by Kepler with reference to the areas swept over by the radii vectors.

I hope that I have been clear in this exposition - in bringing to your attention that what I show here is the system of the day, and is my system -- only the radio engineers use my apparatus to produce too much of this electromagnetic energy here, instead of concentrating all their attention on designing an apparatus which will impress a current upon the earth and not waste the power of the plant in an uneconomical process. [Nikola Tesla, 1916]