Re: Tuning an OLTC ... basics ...

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Original poster: Davetracer@xxxxxxx 

I have an old fashioned, spark gap Tesla Coil ...

I wandered by WinTesla and the Java calculators. Here's the bare bones:

12,000 volts, 60 ma, which would like a cap of 0.0135 (13.5 nf) for Z match.

Primary winding is what you'd expect, 10 turns, flat. The primary will go 
"twanggg" at 240 Khz if I hang a 0.0241 mfd (24.1 nf) cap on it.

Secondary is 12.5 inches of #25 wire, for 589 feet. 3.5" diameter.
1/4 wave length is 354 feet, which makes me wonder if they calculated it 
right (grin).
H/D aspect is 3.57 and likely number of turns is 643.

The secondary would like to twang at 693.72 khz, except if I put a toroid 
on it,
which will bring it down to 240.40 khz, which will match the primary.

A couple questions:

How far do you generally have to move the primary "clip" to get an effect? 
A quarter turn? An eighth?

I'm running with tinfoil on plastic now for caps and clearly don't have 
enough capacitance. My 'scope shows a strong frequency being emitted around 
800 Khz, with all sorts of lovely harmonics. Is it getting time to string 
up some MMC's? Or should I go beer bottles (grin)!

I do have a scope, can I use it to help me tune this puppy in? I do not 
have a signal generator, alas, and although I hear rumours that there are 
directions in how to build one from some 555 timers somewhere, I have not 
yet found that!

Do you think I should load this into my Jeep and drive up to Terry's and 
shamelessly offer him a bribe?

Many thanks for helping this relative newbie,

    Dave Small