Re: [TCML] Tuning a new coil

["DC Cox" <resonance@xxxxxxxxxxxx>]

If you use JAVATC for the design, the tap will shift less than 1/4 turn.
Best to use a scrap wire pri first and then replace later with copper
tubing.  I usually add one more turn than JAVATC indicates to allow for a
full range of tuning.  I always use 4-5 extra turns on the scrap wire pri to
hit the best res. point.

Dr. Resonance



On Fri, May 16, 2008 at 4:31 AM, b alex pettit jr <a_pettit_jr@xxxxxxxxx>
wrote:

> Hi All,
>  First post :
>
>  I am planning on powering up my new coil - designed from many hours of
> searching on line information and validated by JAVATC.
>
>  SecCoil 4.5" x 21"  920 turns 24ga PVC  tube
>  3" x 12" toroid top load
>  PriCoil 8.5" ID of 2 TPI .25" copper tubing
>  Cap : 0.0187 uF via two strings of 16 each CDE 942s
>  Gap : ring of 10 pcs 1" dia x 3" long copper spaced 0.02" & fan cooled
>  Power 12KV/60ma NST  ( 133 uF power correction )
>  TerryFilter / NoiseFilter
>
>  The measured coil/top load rings at 323 KHz. using a Sig Gen / Freq
> Counter & Scope with a mini antenna .
>
>  I found that I obtained that value whether grounding the SigGen and
>  inducing the signal into the base of the coil , or grounding the coil and
>  inducing  the signal through the primary winding via a 50 ohm resistor.
>  ( cap disconnected )
>
>  Tuning the Primary setting with the Cap installed and Secondary in place
> was a bit challenging to ambiguous. It seems that the nominal pri inductance
> may close to what JAVATC predicted, but JAVATC calculated a 10% lower
> secondary resonance freq. ( is this to be expected ?) But there was no clear
> resonant point. Half Turn shifts in tap point did not show a great deal (if
> any) of difference in amplitude shown on the Oscope.
>
>  QUESTION :
>  How sensitive is the tuning of the Primary Coil :
>
>  As a benchmark,  lets say I am using 6 turns and that last turn is ~ 15"
> in dia ( circumference about 45 inches )
>
>  1) Will the tuning point be anywhere within several inches, an inch, or
> fractions of an  inch ?
>
>  2) How greatly does that tuning point shift with power input ? If I tune
> at a low power and just use a few spark-gap points and then shift to full
> 720 watts, how much ( in  inches or % of inductance ) will I expect the
> tuning point to shift ?
>
>  Best Regards,
>  Alex P
>  Orlando FL
>
>  FYI, my first Tesla Coil was build in the mid 1950s using a Model-T spark
> coil I found in the attic and a secondary maybe 2" dia and 12" tall. Thin, 2
> - 3 inch sparks  were still impressive to a young boy.
>
>  ... times have changed .... as Tim Allen put it : More Power !!
>
>
>
>
>
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