Finishing First Coil

From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Wednesday, June 03, 1998 6:38 AM
To:  Tesla List
Subject:  Re: Finishing First Coil

Tesla List wrote:
> ----------
> From:  djQuecke [SMTP:djQuecke-at-worldnet.att-dot-net]
> Sent:  Tuesday, June 02, 1998 6:58 AM
> To:  Tesla List
> Subject:  Finishing First Coil
> The closer I get to finishing the longer it takes <g>.
> A couple of Q's:
> 1.  How closely must the chokes match?  I've built two, one is 3.81mH and
> the other is 2.38mH.  Is 2.38mH enough with a one or two NSTs (15kV,
> 30-60ma) so that I can simply derate the larger choke?
> Chokes are 22g on huge Flyback ferrites (mismatched ferrites resulted in the
> differing values).

Shouldn't be too critical, but matched sizes would be much bettter. Most
critical is insulating them from the core and end-to-end, since the
voltage developed across them can be considerable.

> 2.  I need to verify grounding data.  Just what gets hooked to signal ground
> and what needs a separate ground.
>     a.  NST has two input leads, two output leads.  I currently have built
> the safety gap as two gaps between NST out leads and NST case.  Schematics
> I've viewed indicate case should be connected to signal ground?
>     b.  What about NST input ground lead?  (Actually I guess the question
> is: Should the ground lead on the NST input line be connected to the case (I
> don't think so), to signal ground (I don't think so), a separate ground
> (seems plausible) or don't connect it at all (seems strange to me but...).
>     c.  What ground should strike rail connect to?

The base of the resonator, center electrode of the safety gap,
strikerail, and the case of the NST's should all be tied to a good RF
ground which is separate from the AC Mains ground. 

> 3.  I see ton's of pix with coils running in garages.  I can't imagine
> firing mine off in the garage (or in a kitchen as I've also seen).  I have a
> rather crowded bench with electronic gear etc, flammables (paint, etc) and
> other misc.  How far does the coil need to be from such gear? From a parked
> car?

Move the car out to prevent any damage to the paint, and move all
flammables beyond striking distance. You didn't say how large a coil
you're driving, but a 15 KV 60 MA source can easily provide 4 foot (or
longer) sparks on a well-designed system. Your garage door opener may
get toasted no matter what protective measures you use - simply
unplugging it will not prevent damage. This is especially true if it
takes a hit... :^)

> Should just be a matter of a day or two now (but I've been saying that for a
> week <g>).
> Thanks,
> dj

Good luck, and safe coilin' to you!

-- Bert --