# Re: Capacitance of toroids

```Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>

```
Use sec coil form dia. x 3 or 4 for major toroid dia., and then use major toroid dia. to minor toroid dia. of 3:1 ratio to determine correct sizing of toroid. x 3 gives more streamers and x 4 gives single longer streamers ---
```depends on what you like.

Dr. Resonance

```
```Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>

Isn't interal diameter essentially a function of the
external diameter and tube diameter?

InteralD = ExternalD - 2xPipeD

Baciscally if you have any of the two you can derive
the thrid measurement.  You don't need all three...

Curt.

--- Tesla list <tesla@xxxxxxxxxx> wrote:

>
> Hello to everyone,
>
> I almost finish the construction of my TC, but i
> have a little problem.
> I need a top load of 29pF, than i think is ok, and
> i'm going to make it by
> using a extensible aluminium pipe, that is pretty
> cheap and easy to put in a
> toroid shape.
>
> My question is, how can i calculate the capacitance
> of that toroid i'm gonna
> build?
>
> i found on internet two different way to calculate
> it, but  both use only
> two parametes witch are , in one case: internal
> diameter and external
> diameter, or in the other case: external diameter
> and size of the pipe.
>   And of course, i obtained 2 quite different
> measurements. What i need, is a
> formula that use all three parameters toghether:
> inside diameter(d) ,
> external diameter(D), and size of the tube(x).
>
> do you know the answer?
>
```