Re: How to Tune a Flat Spiral Coil

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 2/25/02 1:29:05 AM Eastern Standard Time, tesla-at-pupman-dot-com
writes:



>
> >You lost me here. Are you saying that changing the primary inductance in
> the tank won't tune the coil?
>
> Hi Bart,
>
> Today I fired up the trifilar coil and tried tapping the primary at 2.5
> turns instead of the full 3.5 turns.  The frequency did not change and the
> voltage went through the roof.  Actually, it snapped pretty strong through
> the 1/4 inch Plexiglas and 1/4" hot glue.  I'm going to put another 1/4" of
> Plexiglas under the primary for a total of 1/2" of Plexiglas and 1/4" of hot
> glue.  The dielectric strength should be well over 500,000V.  And if this
> doesn't work, I'll add another layer.
>
> I did not have the 30" plates on the coil with today's test.
>
> The plasma ball on top of the trifilar glowed red, instead of green, and 5"
> tongues of bright plasma shot up from the base inside the plasma ball.  I
> couldn't run it for long due to the breaching of the Plexiglas.
>
> My test run is not conclusive, but it does suggest that the primary coil
> does not affect frequency but only voltage.
>
> Dave




Hi Bart, Dave, All,
         It really sounds like there are some confounding variables at work
here. Two different value inductances resonating with the same capacitor cannot
have the same resonant frequency. Either stray capacitance is playing a part or
possibly field distortion is altering the effective capacitance between the
coils. This definitely calls for independent corroborating research. I think I
can start on a spiral coil this spring. 
         Should be an interesting research project.
Matt D.