Re: Top capacitance

From: 	Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
Reply To: 	elekessy-at-macquarie.matra-dot-com.au
Sent: 	Wednesday, August 27, 1997 5:48 AM
To: 	Tesla List
Subject: 	Re: Top capacitance

Tesla List wrote:

> From:   Per Niva[SMTP:pna-at-pp.gellivare.se]
> Sent:   Tuesday, August 26, 1997 7:21 AM
> To:     Tesla List
> Subject:        Top capacitance
> Malcolm Watts wrote, concerning discharge terminals
> on top of the secondary:
> >
> > [...snippage...]
> >
> > This has been researched in more depth on the builder's list and was
> > first seriously experimented with by TCBOR. The main advantage to a
> > large top-C is to give a large instantaneously available source of
> > energy to strengthen streamer ionization. We are talking about the
> > top terminal aren't we?
> Yes, we are. This reply helped clear some things up inside my
> coil-constructing head. I thought along the lines that the top-C
> was there mainly for it's role in the LC oscillator of the
> secondary circuit. Then, if I get this right, it is a good thing
> to have such a large top-C as possible. This must be determined
> from how much effect you could put into your primary tank?
> So, this coil I'm currently constructing would use a primary C
> variable up to around 10nF. The secondary would be about 500' of
> #24 wire on a 3" OD HDPE pipe (not the black stuff) ~= 600 turns.
> This would give a resonance frequency in the unloaded secondary
> coil of slightly above 850kHz. With top-C some 6 or 7pf it would
> drop to around 600kHz. This means I'd have to tap the primary at
> the 6th turn.
> But the right thing to would be to rise the top-C to just about
> as big as my transformers could drive? Looking up some toroid
> tables I found somewhere... 800-1000 watts, that would allow
> maybe 15pf of top-C. Is there any way to calculate this? 15pf
> of top-C would bring down the resonance freq down to around
> 430kHz. Then I'd have to tap the primary at the 8th turn instead.
> The 4" coil with a 15pf top-C would lower the resonance freq
> down to about 360kHz. This is even better then? If I have too
> big top-C, would that mean that sparks would not break out?
> Interested, but somewhat confused,
> Per
> ----------------------------------------------------
> pna-at-pp.gellivare.se                 +46 (0)970 20976
> "Beware - the world will never be the same again..."

I run around 20pf topload on my 900W coil and the sparks breakout
easily. I have tried with a large sphere also (around 30pf) and they
still breakout.

Peter E.