"The Mighty Corona Cone"
From: Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent: Wednesday, February 11, 1998 8:59 AM
To: Tesla List
Subject: Re: "The Mighty Corona Cone"
Tesla List wrote:
> From: SBJohnston-at-aol-dot-com [SMTP:SBJohnston-at-aol-dot-com]
> Sent: Tuesday, February 10, 1998 3:41 PM
> To: tesla-at-pupman-dot-com
> Subject: "The Mighty Corona Cone"
> Hi list:
> I added a 17" dia toroid made of 4" aluminum duct to the top of my 16" dia
> 48" long secondary, yet the top few turns are still streaming with corona.
> In fact, the effect may be stronger with the toroid than without. It is a
> solid, sharply-defined, glowing vertical cone streaming up and away from the
> coil and topload.
> Using my URM-25 signal generator with Hi-Z output and built-in VTVM indicator
> (perfect for this job!) I measured the secondary's resonant freq as134 kHz
> bare and 119 kHz with the top loading. My 11-turn primary is resonant at
> about 116 kHz with my 0.018-0.020 uF tank cap, so it should be tuned OK. I
> distrust the primary measurement to some degree, as I would expect the
> resonance of the secondary to affect the primary .
> Breakout was suppressed with the toroid in place until I used an inch of wire
> to encourage the discharge out the side. The strikes and streamers from the
> toroid were only slightly stronger than with just the top insulator bolt or a
> vertical wire as top terminal.
> As I increase the input voltage, the corona from the top few turns of the
> secondary increase proportionally more than the streamer and strike length
> from the top terminal. Before I redesign the exciter for increased output,
> it looks like I need to supress this wasteful discharge from the top turns of
> the coil.
> Initially, I mounted the toroid directly on the top of the six inch ceramic
> insulator. This placed the bottom of the toroid within a few inches of the
> top of the coil. I raised it up at least 8 inches higher on a feed-thru
> insulator stud - no difference, I was still running "The Mighty Corona Cone".
> Short of submerging the entire coil in mineral oil, any suggestions?
> Steve Johnston
The toroid outer diameter should be at least twice the coil diameter to
be most effective... and even larger if possible. This is necessary to
adequately change the electrostaic field shape at the top of the coil,
protecting it, and also to add enough of a topload for best performance,
especially if you plan on increasing output power. Make a much larger
diameter toroid and this problem should go away. Try it - you'll like
Safe coilin' to you, Steve!
-- Bert --