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Re: Seibt Photo

Original poster: Kurt Schraner <k.schraner@xxxxxxxxxxx>

Hi Bob, Ed,

Thanks Bob. My comments, interspersed.

Tesla list schrieb: 
Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>
Hi Kurt,
 > Original poster: Kurt Schraner <k.schraner@xxxxxxxxxxx>
 >
 > I'm yet wondering, what's wrong about using Medhurst/Lundin (or even
 > Wheeler) for these coils, as a preliminary design tool...
 >
 > Best regards,
 >                Kurt
I am surprised this question still comes up.

You are completely right, it was an unreflected silly question, without considering what is obvious - now. I've been just mislead by my former positive results with TC designs, were a deviation of not more than about 10% was experienced for my longest coil, with H/D = 8.6, typically, for usual coils in the range of H/D=3...5, the error was only around 1%...5%. 
Medurst built his tables to determine the parallel C that had to be added to
a much larger parallel C to correctly (<1%) predicted the resonance
frequency in the usual equation.
Its is only valid for large parallel C's, isolated, one end earthed coils.

Yes, I had a look at Medhurst's text again... 
At and near resonance with a lightly top loaded coil, the coil current is
not constant a long its length which is the conditions that Medhurst
measured his coils.
The none constant current leads to significant errors relative to Medurst
conditions. About 18%.

In the case of my H/D=38 Seibt, the prediction is ~22% low vs. exp. 
There are also other errors caused by other none Medhurst conditions like a
ground plane and using it in a series. Some of these tend to cancel the
errors caused by the variable coil current in many usual Tesla coil
configurations. I suspect in a long coil the dominate error is the none
constant current hence the error.
If you want an idea of what frequency your coil will resonate, Medurst
remains a very convenient way to ESTIMATE it.

A good ESTIMATE was also my only idea. 
Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400

It should also not been forgotten, to remember Paul's well founded evaluation of Medhurst at:

http://www.abelian.demon.co.uk/tssp/misc.html

Best regards,
              Kurt