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>

Updated data inserted,

> 
> 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
  Frequencies swept as follows:
  fo reads at 151.2khz with the start of the rise at 134.3khz and
falling off at 159.1khz
  so i'll give as:
  134.3khz < 151.2khz > 159.1khz
second res. at:
  348.6khz < 368.3khz > 379.1khz
third res. at:
  520.6khz < 554.8khz > 570.2khz 
small twitch at 737khz,
I could barely detect a rise at 50.3khz, very slight but i'm sure it was
there.
> A quick check of selfC measures at 40pf from inside wire outward and
> 38pf from outside end inward (measured just for giggles)

Checked selfC with the gen. rad. bridge and it held firm at 39.8pf using
a twisted pair for the test leads.
One thing i noticed with this type coil is that very little interference
is noted by objects (my hand) approaching on the horizontal plane at the
edge of the coil. If my hand breaks above or below the plane of the coil
form disturbance is noticed. the higher above the edge or below the
edge, the more pronounced the disturbance. It seems initially that the
fields are very localized or in a strange shape in the vertical plane of
the windings? much more playing to do with this one.
On to the primary and tank circuit now.


> 
> 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