RE: [TCML] Tuning a new coil

["S&JY" <youngs@xxxxxxxxx>]

Alex,

You didn't say if you removed or shorted your secondary while making primary
measurements.  Unless you remove the effect of the secondary, you will have
a difficult time determining the resonant frequency of your primary.

You should measure your coil/top load with a horizontal wire, the length of
your anticipated streamers, stretched outward or upward from your top load.
The streamer will add some capacitance, resulting in a lower secondary
resonant frequency.  Or, just tune your primary to about 93-95% of your 323
KHz secondary frequency.

Primary tuning should be OK with the tap within a few inches of the ideal
point.  With the effects of the secondary removed, you can easily measure
how the primary resonant frequency varies as you move the tap point.

--Steve Y. 

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of b alex pettit jr
Sent: Friday, May 16, 2008 5:32 AM
To: tesla@xxxxxxxxxx
Subject: [TCML] Tuning a new coil

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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