Re: flat secondary

["Tesla list" <tesla-at-pupman-dot-com>]

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

Thank you Antonio,
I think that this will be a good experiment and will try it, I'm sure i
will have more questions as i get there.

Paul, Terry and all,

Flat coil update from Marc M.:

  I finished unwinding and rewinding the 20" OD coil, It is flat and has
very little "lifted turns".
I have so far (last night) checked some parameters and have gotten:

20" coil wound with 28g heavy build mag wire, all windings are tight,
But in using duct tape as a holding surface, the coil looks kinda like a
"brick wall" due to the tape overlaps. I don't think it will effect
operation, But it may be note worthy?
  I have counted 756 turns from a 3\8" ID around a brass bolt, outward.
Sooo:
756 turns
10" radius
dc resistance checks at 125.46 ohms
Inductance measures at 93.06mh -at- 1khz
series Q = 4.3
A quick check of selfC measures at 40pf from inside wire outward and
38pf from outside end inward (measured just for giggles)

All measurements were made with an esi model 250 DE universal impedance
bridge.
All measurements were made with the coil 38" from the floor, positioned
on an all wood bar stool, 5' clear space on all sides and a ceiling
height of 7' 8". There are some heavy metal items against the wall and
around the coil starting at 5' away (drill press, hobby lathe, "HUGE"
heat sink on an ac drive leaning against wall) so if needed i will clear
further.

Tonight i will sweep for fo, double check selfC with my general radio
capacitance bridge and do some playing around, also try to get Paula to
count turns for accuracy (after counting the 3k coils turns twice for
me, this may be difficult?), I will post results.

Any further suggestions for testing will be greatly appreciated and I
will promise to give 110% to get accurate results.

Take care,
Marc M.

Tesla list wrote:
> 
> 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