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RE: Off-axis primary inductance
Use a variometer (goniometer) coil to tune a high current circuit. A
variometer can be made with a coil inside another coil. one of the coils is
gimballed so it can rotate to aid or oppose the other. As the movable
coil's axis is rotated 180 deg, the total inductance smoothly varies from
max to min.
You could probably make a variometer out of a continuous length of welding
cable with no joints or splices. Just wind a turn or two on a 8 in pvc,
leave some slack and wind a few more on a short 4 in pvc. Now put the small
one inside the big one on a dowel so you can rotate the small one "end for
end" inside. With care, you can get a full 180 deg with just the slack in
the welding cable. When the coil wires go in the same direction on both
forms, inductance is max.
Will
> ----------
> From: Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: Wednesday, December 02, 1998 13:39
> To: tesla-at-pupman-dot-com
> Subject: Re: Off-axis primary inductance
>
> Original Poster: Terry Fritz <terryf-at-verinet-dot-com>
>
> At 07:05 AM 12/2/98 -0700, you wrote:
> >On Tue, 1 Dec 1998, Tesla List wrote:
>
> >> Actually if you guys took a good look at the photos of Dr. Tesla's
> >> colorado spring coil you would see that he to used an off-axis
> >> tunable inductor to fine tune his primary and secondary circuits...
>
> Where can I find more information about this method of tuning? Or a basic
> description of how I can try this on my coil? It sounds like an
> interesting thing to do. And it would probably help me tune it. :)
>
> Travis
>
>
> <<<< Hi Travis,
>
> Perhaps I can simply answer this question. All they are talking
> about is
> using a second inductor in the primary LC circuit to tune the coil. There
> is the primary inductor but any other inductance simply adds to the
> primary
> coils inductance and can tune the primary frequency. This tuning inductor
> can be anywhere in the primary circuit.
> There are some brush inductors used in HAM stuff but the current in
> the
> primary circuit is so high they usuall burn up. A simple coil with taps
> is
> all it really takes. Of course, you can only add inductance and not
> reduce
> it with this method but since the primary is usually tapable too this
> isn't
> a big deal. A second tuning coil in the primary is really nice on fancy
> coils that have pretty fixed primary coils that can't be tuned any other
> way. If you see a coil that does not have an adjustable primary, it
> probably has another inductor hiding somewhere or the primary cap is
> adjustable in some way. - Terry >>>>
>
>
>