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"The Mighty Corona Cone"
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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
sbjohnston-at-aol-dot-com