Re: Seibt Photo

["Tesla list" <tesla@xxxxxxxxxx>]

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.

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.

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%.

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.

Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400