RE: Flat coils & undamped waves (was Wire Length)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>

Hi Gary,

I also noticed that bifilar wound coils made lousy Tesla coils.  They make
great electromagnets, however.

It should be evident from Tesla's widely spaced coil windings that he tried
everything he could to reduce the internal capacity.  Most coilers tend to
think only of the internal resonance.  However, there is external resonance,
too.  That is why placing your hand near a coil changes the frequency.  The
environment is as important to tuning a coil, as is its internal structure.
Hence, the insulation and dielectric used to separate the coil from its
environment must be an integral part of coil design.

In fact, understanding how the environment changes the resonance becomes an
advantage when building a tunable secondary.  I build my secondaries as flat
spirals and give them a coat or two of epoxy, just enough to maximize the
resonance.  Then I can use thin flat Plexiglas discs as removable layers of
dielectric, which lowers the resonance.  This gives a certain degree of
latitude for matching the resonance of a secondary and extra coil.

In addition, when I build solenoid coils I wind them on a tube of PVC, then
insert the wound tube in another tube of PVC and fill the gap with
transformer oil.  I call these "jacketed coils."  This considerably sharpens
the resonance of the coil and increases the potential to its max.  It also
lowers the resonance, so it is necessary to build the coil to a resonance
slightly higher than the target. It's like building a musical instrument for
a world-class concert.

As an added bonus, the jacketed coil turns into a very strong electrophorus
after use.  It will remain electrostatically charged for hours no matter how
often it is discharged.  I have had one jacketed coil still holding an
electrostatic charge after a week of sitting idle.

Dave

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Friday, January 19, 2007 10:07 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: Flat coils & undamped waves (was Wire Length)
>
> Original poster: "Gary Peterson" <g.peterson@xxxxxxxxxxxx>
>
>
> >Original poster: Ed Phillips <evp@xxxxxxxxxxx>
> >
> >. . . Tesla describes coils wound with bifilar wire and mentions the
> >increased capacitance as a virtue . . .
> >
> >Ed
>
>             "The one fatal defect most frequently present in
> oscillatory systems is a large internal capacity." -- Nikola Tesla, ca.
> 1916
>