# Re: Propagation - was blank subject.

```Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 07:00 AM 5/8/2006, you wrote:
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```Hi: Langer

Tesla coils for producing sparks and Tesla coils for energy
transmission are likely tuned diffrently.

Sorry Matt:

I have not seen a shred of evidence that would suggest that any of the
following is true.

1) Propagation along a coil is not the same as propagation along a
straight wire.
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Of course it is different ;-)) A coil has turn to turn magnetic coupling. Every turn is magnetically coupled to the next and lesser so to all the others. That is a giant difference and is why people make coils of wire in the first place.
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```2) Adding a topload drops the operating frequency ~50% and alters the
current distribution.
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Paul has shown that the distribution is different and you can do a test like I did too:
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http://hot-streamer.com/TeslaCoils/MyPapers/NSVPI/NVSPI.htm

The difference is not super great, but it is certainly there.

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Of course, by selecting the size of the top load, you can lower the operating frequency almost as much as you want. To lower it 50% is trivial.
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#1)

Velocity factors from radio handbooks describe the velocity down a
single wire with a ballpark figure of around .95C . Proximity to
ground and other factors presumably change this.

Velocity factors for twin leads become even more complicated. If the
current flows in opposite directions you get a diffrent velocity
factor then if they travelled in the same direction.

Velocity factor also change, when we go from an individual pulse to a
chain of sinusoidal pulses.

The only velocity factor measurements for a  Tesla coil that I am
aware of were made by Paul Nicholson and company. His subsequent
computer simulations for coils with a variety of H/D ratios showed
that the velocity factor could go as high as twice the speed of
light.
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No. If you make a coil 10 feet in diameter and 1 inch high with 100 turns of wire, the power propagates to the top turn in about 0.085nS. How can it get there so fast when it normally needs to go through 3142 feet of wire? Magnetic coupling is the answer there. The magnetic forces only needs to go one inch and they do. Otherwise the velocity factor would be 37700 :-))
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```(But our experiments demonstrate that this is not true.)
http://www-personal.umich.edu/~mssd/jed/capacitance.html
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I will have to check this when I have more time...

Cheers,

Terry

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```#2)

We operate coils at the wire length and have found that top end
capacitance requirements are mainly a function of the amount of
current you want to process. Large top ends have not mean a change in
tank frequency.

Large top ends may change the ratio of conduction current to
displacment current, but I would not assume that this alters the
distribution of their sum.

Sincerely: Jared Dwarshuis
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