# E-Tesla6, was RE: Sphere/Toroid Comparison Chart

```Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Terry,
I've been looking at E-Tesla6 and noticed that it requires as input
the "Measured Secondary Inductance". I was sort of expecting to have to
enter the "number of turns" somewhere, something more like ACMI which takes
as input the dimensions of the coil and wire and then calculates inductance.

If I am going to use E-Tesla6 to estimate the Fres of a coil _before_ I
build it do I use Wheeler: "R**2 * N**2 / (9*R + 10*H)" formula for inductance?
How accurate is that anyway, what about Lundin's formula?

I'm in the process of building 3 coils (approx 4x12, 3.5x15, 3x18) each
hopefully with identical Fres (with the same 2x8 toroid), so I'ld like to
use E-Tesla6 to find the exact winding length and number of turns to get
identical Fres. Then I'll use ACMI to adjust the height of each one to get
exactly the same K (of 1/7) for each. Then see if there is any difference
in operation.  Not that I expect there to be any, this is just for fun,
after all its a hobby(!).

-Peter Lawrence.

>Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
>Hi John,
>
>"E-Tesla6" a program I wrote that was vastly improved by others, can find
>the resonant frequency of a one or two torroid (or sphere) Tesla coil
>secondary system within a percent or two.  It does all the nasty
>electrostatic field calculations and even has elements of Paul's TSSP
>project added.  It is freely available at:
>
>http://hot-streamer-dot-com/TeslaCoils/Programs/E-Tesla6.zip
>
>A web page with info is at:
>
>http://hot-streamer-dot-com/andrewb/
>
>It is very useful for determining the resonant frequency of a secondary
>coil and top terminal before they are built.  Everyone seems to like it a
>lot and it seems to work very well.  I ton of effort went into the darn
>thing ;-))
>
>Cheers,
>
>	Terry
>

```