Jumping in with both feet?

From:  Chuck Curran [SMTP:ccurran-at-execpc-dot-com]
Sent:  Wednesday, January 28, 1998 4:51 PM
To:  Tesla List
Subject:  Re: Jumping in with both feet?

            Welcome to the list and Tesla Coiling in general.  I see Bert's
given you a complete reply so I'll simply wish you luck on your project!


-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: 'Tesla List' <tesla-at-pupman-dot-com>
Date: Wednesday, January 28, 1998 12:00 AM
Subject: Jumping in with both feet?

>From:  SBJohnston-at-aol-dot-com [SMTP:SBJohnston-at-aol-dot-com]
>Sent:  Tuesday, January 27, 1998 3:48 PM
>To:  tesla-at-pupman-dot-com
>Subject:  Jumping in with both feet?
>Hello, Tesla-listers!
>Please allow me to introduce myself:  Steve Johnston, in York,
>  I'm 34, with 21 years as a ham radio experimenter and 15 years as a
>Broadcast Engineer (so I'm not a newbie to high voltage/current RF
> I've had a passing interest in Tesla coils for years, but never took the
>time to fully study the details and build a system.  Over the past week,
>however, my interest has intensified greatly as I was fortunate enough to
>come upon a nicely-crafted TC whose owner had died (hopefully his passing
>not related to TC experiments!).
>This coil stands about 5 feet high not counting a top discharge terminal.
>  The primary is made of 11 turns of 3/8" Copper tubing, spread about 12"
>high and 26" in diameter.  The tubing is air-wound, held separated by
>(nylon?) spacers.  The secondary is wound with about #22 wire around a
>cylinder of 1/2" wide varnished wooden strips spaced about 1/2" apart.  It
>consists of two sections in series, each 2' long, about 3 inches between
>two sections, for an overall winding length of 4'.  It is 16" in diameter
>with about 13 turns per inch.    The secondary sits about 2/3 of the way
>the primary -- perhaps by design to set the coupling between windings?
>There is a dome-shaped metal cover about 8 " tall and 6" in diameter that
>probably intended to be a top discharge terminal.   It could connect to the
>center contact bolt on the top of the secondary with a short length of
>The "exciter" (if that is an appropriate term?) is built into a metal
>and consists of a Variac driving a 15 KV 30 ma neon sign xfmr (half the
>winding is used, centertap to one end),  a small series inductor, and four
>caps in parallel.  The caps are of unusual physical design (to me) but not
>homemade -- the four together measure about 0.02 uF.  The spark gap is also
>commercially-made with circular, D-shaped electrodes with cooling fins
> -- the gap is easily adjusted.
>Any opinions as to the capabilities of this rig?  Would it be meaningful to
>temporarily short the spark gap and attempt to grid-dip the primary tank
>see where it resonates?   Does the secondary self-resonate with distributed
>capacitance?  To what spacing should I set the gap when I start testing?
>Am I asking too many questions?  I guess I'm way too excited and eager to
>Thanks for any opinions and information!
>Steve Johnston