Re: Ctop Measurement vs. Calculation

• To: tesla-at-pupman-dot-com
• Subject: Re: Ctop Measurement vs. Calculation
• From: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Tue, 23 May 2000 05:53:18 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

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 
 

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