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Re: Coil design specs comments wanted

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Jonathan,

At 09:21 PM 5/6/2001 -0700, you wrote:
>Howdy All,
>I am trying to get together the specs for my first permanent mounted and
>probably final (?) coil, and would very much appreciate comments and
>suggestions. I already have the cap and transformers listed below, and the
>piece of 6.5˛ PVC pipe. I like the idea of the 44˛ coil for looks, but it is
>way over the 4:1 HD aspect ratio. Is this really gonna hurt performance?

No.  Not at all.  Coils that are a little taller help prevent arcs to the
primary and don't seem to hurt performance at all.

>Proposed Coil Specs:
>Power Supplies available: 12kv/120ma, 15kv/60ma NSTs
>Primary: flat style, 12 wraps of 1/4˛ copper tubing, spaced 1/4˛, first turn
>Secondary 6.5˛ X 44˛, 1200 wraps of 20 AWG, PVC coil form
>Main Gap: static vortex or vacuum if I go resonant cap, or a rotary if I go

Sounds perfect.  I ran some numbers and everything works out right.

>I have a .025 (actually tests to .023) RRI # 208 tank cap. The resonant
>value for the 12kv/120ma is .027. Is this close enough to make a resonant

Yes, the exact value is not terribly critical at all.

>If I have properly adjusted safety gaps and use a static main gap,
>how likely am I to blow the transformer? 

You should be pretty safe.  Only when people go getting "creative" with the
safety gaps setting do real problems start.  There is always a chance it
will blow, but if it blows with good safety gaps settings it was probably
going to blow anyway.

>Can I adjust the safety gap to fire
>just before max power for extra safety? 


>I donšt want to spend the $ for more
>tank caps, but donšt really want to blow the transformer either. However,
>should I decide to throw down more cash, how exactly close would I have to
>get to the magic .0405 (LTR value for the 12kv/120ma) to get the LTR effect?

I get a value of 37nF for a static LTR cap (you can run static gap LTR too)
so another 10nF cap is all you need.

>Ideally I would like to go LTR.
>Will this primary and secondary set up be able to handle the two NSTs ganged
>up together? I would make the secondary adjustable height-wise for coupling.

Since the cap size goes up and the tap point goes down so you should be
fine.  Problems only start when you need 15 turns on your 12 turn primary
:-))  But you should be fine in any case.

>I definitely want to leave that option of using both open. Although I
>shudder to think of what an LTR tank cap for that is gonna cost...

All should be fine for whatever you use.



>As always, many thanks.
>Jonathan Peakall