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Re: flat secondary



Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Metlicka Marc by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>

>   I was wondering what the best primary config would be? I would think a
> helical coil around the circumference might do, and a flat spiral across
> the edge? I think i'll try several setups, I have a 12\30 nst setup with
> a triggered gap ready to go so any suggestions will be appreciated.

You could try a direct coupling instead of a magnetic coupling. Works in
the same way, and you can place the primary and the secondary coils
where you want them. The basic configuration, assuming an NST with
grounded center, would be (fixed-width font to see):

   o---+---C1'--+------L2------Terminal
       |        |
  NST  o gap    L1
       o        |
       |        |
   o---+---C1"--+---Ground
              
A good ground is required for safety. 
For correct tuning: L1*C1=(L1+L2)*C2.
Voltage gain: sqrt(C1/C2).
C2=~Self-capacitance of L2 + terminal capacitance.
C1'=C1"=2C1.
This circuit works exactly as a regular Tesla coil. The limitation of 
this configuration is that you can't separate the voltage gain from the 
"effective coupling coefficient" "k". 
One is the inverse of the other: "k"=1/Av. The "magic values" for "k"
are
"k"=(b^2-a^2)/(b^2+a^2), where a and b are two positive integers with
odd
difference, as (1,2), (5,6), (10,13), etc. With one of these, there is
perfect energy transfer after b oscillation semicycles, ignoring losses.

Antonio Carlos M. de Queiroz