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Re: Tesla Coil RF Transmitter

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


Original poster: William Beaty billb@xxxxxxxxxx 

> I notice that you're talking about the Tesla-coil transmitter as if
> it was intended as a source of "radio waves."  The Tesla system does
> not work by the propagation of what are called "radio waves" in the
> narrowest sense of the term,

Right and wrong.  Whenever the transmitter and receiver are separated by
more than a wavelength or two, then there is no direct coupling; no
capacitor connecting the two.  The connection is via waves.  They might be
waves in a waveguide, but that's irrelevant; they're still waves.

In the case of an operating Tesla-coil RF transmitter-receiver system using the ground and atmospheric conduction technique, I agree that waves are involved. I do not believe these are "radio waves" as I recognize them.

> Operating a 20 watt SSTC transmitter at
> 108 kHz a couple of years ago,

How long an antenna?

The resonator was 38" long. The wire connecting the resonator to the topload was about 8' long. The topload itself was an aluminum disk about 24" in diameter.

. . . do you imagine that Tesla's plans for Wardenclyffe DIDN'T include any vertical antenna? . . .

As for Tesla's plans for Wardenclyffe, the drawing associated with the Wardenclyffe patent (see http://www.tfcbooks.com/images/patents/tower.gif) shows a vertical cylindrical conductor connecting the helical resonator to the topload that is about 1.6 times the length of the resonator. I recognize that this portion of the launching structure is responsible for the emission of "radio waves," i.e., far-field electromagnetic waves that have closed back upon themselves and are no longer associated with the launching structure. However, I do not view the cylinder as being an "antenna" as the emission of "radio waves" is not its intended purpose. Additionally, Tesla included the following line in the patent text, ". . . coil B [the helical resonator] . . . if desired, may be extended up to the terminal D [the topload]," so yes, I can imagine that Tesla envisioned a Wardenclyffe-type plant that did not include this relatively short conducting cylinder.

> I found that noise is all that you hear with an LF receiver at 1,000 > meters. 

You're transmitting DC and expecting to *hear* a signal?!!!!!!!!  That
doesn't make much sense.


Not DC, I was transmitting CW at 108 kHz.

Also... what receiver? What antenna?

The radio receiver was a Realistic DX-302 Quartz-Synthesized Communications Receiver with a preselector. When used about 60 meters from the transmitter, I had a 20-foot piece of wire for an antenna. I heard nothing but electrostatic noise at that distance. Pursuant to your suggestion, I'll modulate the signal by keying the transmitter during the next tests. Also, I'll be more agressive with the "radio-wave" receiving antenna design. 108 kHz is about 2,800 meters, so a quarter-wave vertical antenna would be nearly 2,300 feet long. This not being practical, I'll have to use shorter vertical wire along with a loading coil in order to maximize the radio receiver's antenna performance. Another problem with the S5 reception at 1,000 meters is that the receiving transformer was much too close to the TC transmitter. In my estimation the distance from the transmitter has to be at least 15 kilometers for a Tesla-coil transmission / reception demonstration to be truly meaningful. A further problem is the 108 kHz operating frequency. Moving down to 75 kHz would be a step in the right direction, while at the same time keeping the transmitter's helical resonator and topload dimensions managable. A 25 kHz resonator is my ultimate goal.

> Bring a tuned receiving
> transformer with the secondary removed close to the receiver's
> antenna and the electrostatic noise goes away, to be replaced by
> "dead air" created by the CW Tesla-coil transmitter.

That's not a signal, that's just the receiver's AGC kicking in.

I'm absolutely certain that the full-quieting effect that I perceived was due to the CW signal coming from the transmitter and interacting with the receiving transformer. Perhaps you would have to be there to appreciate this fact.

If the two [a Tesla-coil transmitter and a Tesla receiving transformer]
are separated by more than a wavelength, then circuit-concepts
no longer apply, and we have to model it as radio waves travelling in a
waveguide.

As you know diiffering models can describe the same observations equally well.
Instead of starting out by applying the "radio waves in a waveguide" model, which is more applicable to Tesla's earth resonance system, my approach will be to observe a small-scale type-one system in operation and then develop a physical model that best describes its behavior.

. . . That's not radio waves in free space, but neither can you
model it as capacitive coupling.  Weird things occur.  For example, if the
transmitter and receiver are placed into a high-Q resonant waveguide, then
the impedances act VERY different than those for a normal transmitter and
receiver.

It's important to keep in mind that Tesla had the two ground-based methods, Earth Resonance and Atmospheric Conduction. I can see that you're investigating the former. It's my intention to pursue an investigation of the latter.

Anyone can "prove" that Tesla's ideas don't work:  just eliminate any long
antenna, . . .

Tesla identified the short 1 : 1 helical resonator and tall slender mast topload used at Colorado Springs as an error in design. The corrected configuration is a high aspect ratio resonator with the topload positioned at or just above it.

. . . then run your transmitter at a frequency which is not at one of
the Earth resonances.  Or even better, run your transmitter at frequencies
well above 1KHz.

Ken and Jim Corum believe that when attempting to excite a terrestrial-resonance mode, the transmitted energy should have an ELF component corresponding to the frequency of interest, and also a VLF component that's associated with the Tesla-coil oscillator frequency. Insertion of the ELF component would take place through a second primary positioned just above the upper turn of the master oscillator secondary.

If we want to demonstrate Tesla power transmission, . . .

The purpose of my research is not to demonstrate Tesla power transmission. My experimental goals are as follows:

1) To develop and operate an efficient type-one Tesla-coil RF transmitter.
2) To develop and operate an efficient type-one receiving transformer
3) To characterize the performance of these two systems when operated jointly.

. . . then we MUST include all the critical parts:

  1  Transmission frequency well below 1KHz
  2  Transmission frequency tuned *exactly* to an Earth resonance.
  3  Very low impedance ground connection
  4  Tall vertical antenna (wire, or UV beam, or x-ray beam)

You may find that # 4 is not such a critical element. The wireless power transmitter that Tesla developed for exciting earth resonance consists of two toploaded helical resonators, each having an independent ground connection. Early circuit drawings have one of these resonators driven with a primary and the other shown as a free oscillatng system (see CSN, pp. 191 & 200, fig. 6 for example). An illustration from the article "Radio Power Will Revolutionize the World," Modern Mechanix and Inventions, July 1934 shows this same configuration, although in this case the drawing suggests that both resonators are driven elements.

William J. Beaty 

Gary Peterson