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Re: Racing Spark Prediction

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>

You can always see a single prominent fundamental freq usually at or close to the 1/4 lamda freq. We use 0.96C when calculating this freq as the propagation never quite approaches C (speed of light).

When you couple two coils with a nice toroid at least 2 X sec dia. you can see on a scope the fundamental freq. If you increase coupling too much this fundamental will split into two side frequencies each of which starts absorbing energy and creating beat frequencies.

You could be right regarding the interharmonic distortion. I have not investigated this in detail, but we always check our coeff. of coupling right to the peak where it starts to split and then reduce it a bit in our initial design work.

I guess the very best source to help make this clear is the Radio Amateur's Handbook --- they have good drawings in there illustrating my point.

Don't overcouple and racing sparks are simply a non-issue.

Dr. Resonance

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi DC,

I'm a little confused about one aspect of what you are saying. My understanding is frequency splitting occurs at all levels of couplings greater than zero. The greater the coupling, the greater the difference is between the two freqencies that the fundamental splits into are. I'm not understanding why you say this is seen as a 3rd harmonic. Odd harmonics are caused by periodic distortions in a fundamental frequency where symetry is maintained and even harmonics are caused by periodic distortions that do not preserve symetry. Seems like frequency splitting just results in two frequencies that beat with each other. Maybe the two frequencies interact with each other in some way to cause intermod or harmonic distortion.

Gerry R.

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>

Racing sparks caused by two different 1/4 lamda points as measured from the ground end of the coil. As coupling is increased beyond critical value the freq split occurs which produces two different max potential points which are usually down from the top end winding of the sec. With small toploads, and overcoupling, these produce standing waves along the coil which interfere constructively and destructively with each other and also "beat" against the fundamental freq of the sec coil. This is usually seen on an oscope (as you suspected) a rather strong 3rd harmonic of the coil. Again, the cure is reduced coupling from the critical coupling point. Standard physics --- no new magic

A signal generator is used having it's frequency swept in synchronism with the time base of the oscope. The double hump is clearly visible when the primary to overcoupled to the sec coil. Back off this point until the double hump disappears and you have set the optimum coupling point for your coil. No racing sparks will occur. No need for further adjustment as no further gains in performance will be noted if coupling is increased beyond this point. If you decrease coupling from this point you may loose an inch or two of spark length as measured on the Bob Langren scale device but you will never get racing sparks. A loss of an inch of spark is a fair trade off from having overcoupling and racing sparks.

Dr. Resonance

Hi Bob,

I think that the theory is that racing arcs are caused by a reflection of a third harmonic bouncing back from the top of the coil on the first cycle. Paul or Dmitry can confirm that. Having the top third of the coil reverse wound is supposed to squash that 3rd harmonic reflection and perhaps cure the racing arc. At least that is how I understand it.

I imagine there is a "perfect" place for the reverse winding to begin other that the exact 2/3 point up the coil. But something like Paul's program would be needed to find that. The reversed windings would change the inductance quite a bit though so it would be a little hard to make a direct comparison. But if the idea holds true, the difference in eliminating the racing arcs should be dramatic.



At 01:45 PM 5/17/2006, you wrote:

Hi Dest

Is a folded resonator the partly reverse wound coil decribed by Terry?
If not what is it and why is it called a folded resonator?

Can you explain why a folded resonator may cure racing sparks?

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, May 17, 2006 10:10 AM
Subject: Re: Racing Spark Prediction

> Original poster: dest <dest@xxxxxxxxxxxxx>
> folded resonator as one of the possible cures from racing sparks
> Paul wrote: nothing
> ok, Paul - i ask you here (to screen poss mail problems) third time -
> what is the problem with a folded resonator concept? this would be my
> last question to you at all if not answered. you give me no choice > : )
> Terry wrote:
>  > I think the problem is when you reverse wind part of the coil, the
>  > performance would also drop way down.  You can get ride of any
>  > harmonics by making the coil out of dirt too but that is no fun.
> i can`t see how it can be a problem - you`ll lose a very small part > of
> total sec inductance only, since mutual inductance between parts is
> very small, as well as mutual/coupling between pri & reversed part of
> the secondary.