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Re: Ctop Measurement vs. Calculation

Hey Guys, 

I tested the toroid tonight. Here were the results: 

Ctop = 34" x 7.4" and calcs to 36.9pF (70.3kHz) 

Test #1: 

Toroid at top plane of secondary. Measured 86.2kHz. 
Ctop then calcs to 17.2pF (53% error from original calc). 
  

Test #2: 

Toroid raised 22" up. Measured 75.7kHz. 
Ctop then calcs to 28.2pF (23.5% error from original calc). 
  

Well, it's obvious that probably any top load on a large diameter coil is going
to loose a significant amount of capacitance and thus drop the overall capacity
of the resonator. In the above case, the overall capacitance change is 22%. At
first glance, you might think a larger toroid is the answer. I don't think so.
It will depend on the top size and surface texture, and power required to break
out. I have no problem breaking out on this toroid even at low power. However,
as I raise ROC in conjuction with the size leaving the surface as is, then I
can say I definately need more C, but if I leave the toroid size alone and
change the surface to say very smooth, then it may be ok as is. Hard to say,
since that is just trial and error testing. I think John F. could answer that
based on his experiments better than I. 

Take care, 
Bart 
  
>
> Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> 
>
> Hi Bart, 
>              Trying to get a figure for a terminal above the coil is a 
> really nasty business as even the lead wire going up to it contributes. 
> Same deal with an "isolated sphere" (like just how isolated is it with a 
> signal/measuring wire going to it?).  The whole business is full of 
> fish hooks. Tesla tried this at Colorado Springs and ended up with 
> some pretty dodgy figures. I've had similar problems in the past. 
> You can't stick a source inside the sphere and hope for a clean 
> measurement of the e-field on the outside either since the sphere 
> now has what amounts to an inner plate. 
>       BTW - raising and lowering the terminal above the coil is a great 
> way of fine tuning without having to mess around with the primary if 
> the primary tuning is close enough to begin with. 
>
> Regards, 
> Malcolm 
>
> On 23 May 00, at 5:53, Tesla List wrote: 
>
> > Original Poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> 
> > 
> > Hey guys, 
> > 
> > Terry - thanks for running E-Tesla5 and plotting the graph. It's been a 
> > while since I've used your program. I did it a long time ago with my coil 
> > back in MN. Took forever on my snail pc. I think I'll do it again with my 
> > latest test and check the results to my measurements. I am presuming the C 
> > output of 30.5pF was the resononator C. This would work out almost perfect 
> > to my calc of 9pF for the sphere from the frequency measurement. 
> > 
> > Tonight I placed the sphere on an insulated column, but couldn't stop 
> > breakout, even insulating the wire from the top of the secondary through a 
> > horizonal pvc pipe to the sphere. Breakout just screws up any possible 
> > measurement on the scope. But, I did raise the sphere 18.5" and retuned for
>
> > 0.02uF. The sphere was 26.5 inches above measuring from the horizontal 
> > center of the sphere to the secondary top plane. The frequency was now 
> > 89.3kHz bringing Ctop to 14.7pF. This is quite a jump for the sphere being 
> > raised only 18.5 inches. My tuning is off some but I think the test shows 
> > significant change (40%!). The overall C changes then by 16%. 
> > 
> > I am really amazed at the amount of change here. As Malcolm and John 
> > pointed out, if the top terminal is too small in relation to the secondary,
>
> > the secondary can swallow it up. Since my sphere is only 2 inches wider 
> > than the secondary around the perimeter, then this may be the leading cause
>
> > of capacitance drop for this setup. 
> > 
> > I'll do the same test with my two toroids which should not be swalled up as
>
> > much - about 2.7 times larger than the secondary diameter. 
> > 
> > Bart 
> > 
> >