[TCML] Tuning a new coil
resonance at wildblue.net
Fri May 16 15:24:35 MDT 2008
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.
On Fri, May 16, 2008 at 4:31 AM, b alex pettit jr <a_pettit_jr at yahoo.com>
> 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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