```Jim/all,

```
There also appears to be some interaction between the Ctop and Csec based on their physical separation. I don't have my notes handy but at one point I measured the Fsec with a toroid sitting right on top of the last winding and one spaced a distance above it. What I found was the layout with the toroid right on the secondary had a higher Fsec (therefore less total capacatance) than the layout where the toroid was above the secondary. If I recall properly the effect with a ball topload was much more pronounced.
```
Regards,
BrianB

On 2015-01-22 08:52, Jim Lux wrote:
```
```On 1/22/15 5:40 AM, Jim Lux wrote:
```
```On 1/22/15 5:26 AM, Tim Flood wrote:
```
Yes, just be sure the total surface area of all your tubes is close to
```the
surface area of the toroid.

Tim

```
On Thu, Jan 22, 2015 at 8:10 AM, Jim Lux <jimlux@xxxxxxxxxxxxx> wrote:
```
```
```On 1/22/15 12:30 AM, JoeBonanno wrote:

```
```this is an interesting thread!

i have to build my own in a few week! For calculating the final
capacitance
i can use the same formula of solid one? right?

```
```
That's what I would do. Short of using a finite element tool of some
sort.

```
```

```
Well.. I would think that the charge on the surface of the tubes that is "inside" the toroid would be less than the charge on the outside, so on a surface area basis, maybe 1/2 the sum of the tube circumferences might
```be a better approximation.

```
Greg Leyh's Electrum had a tube topload in the shape of a sphere. The C
```of a solid sphere is easy to calculate, and if Greg ever measured the
tube top load C, we could calibrate with that.

```
```Having found some data at
http://www.lod.org/Projects/electrum/techdata/electrumspecs.html

Greg has his secondary L at 0.13 Henry, and two resonant frequencies,
one with topload (7 foot sphere) and one without at 27.92 and 52.60
kHz respectively.
Working backwards, that gives a total secondary C of 135.5 pF for
"with topload" and 70.4 pF for "without", a difference of 65 pF

a 7 foot diameter sphere is 1.06 meters in diameter. I calculate a C
for a sphere of that size as 119 pF.
That's about twice what would be implied from the frequency shift
calculation above.

I don't know that this is conclusive (there's a lot of interaction
between the field of the topload and the field of the secondary, for
instance)..

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
```
```_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
```