Re: toroid height adjustment - what does it really do?

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John,

Tesla list wrote:

> Original poster: "John Morawa by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<morawaj-at-interaccess-dot-com>
>
> Hey everyone,
>
> I am curious about what raising or lowering the height of the toroid
> actually changes on a functional tesla coil.  What are we talking here?  A
> change in the shape of the field (sending sparks in a different direction) ,
> altered capacitance (and thus frequency) of the secondary system of a coil,
> or what?  Obviously it increases the distance from the breakout point to the
> primary coil and depending on your arc length may thus help reduce primary
> strikes.  But what else does it really do???
>
> Thanks much,
> Curious John

The toroid affects the operating frequency of the coil by altering the
resonator capacitance. The
resonator (coil and top load) capacitance is always affected by the
proximity of one to the other, the
toroid to ground, and the toroid to objects. Raising the toroid increases
the proximity of toroid to
ground and toroid to coil, but may not increase the proximity of toroid to
objects (depends where the
objects are located). Because the proximity is increased, the capacitance
of the resonator changes and
this changes the operating frequency. But, one can only go so high on the
toroid before the top winding
of the coil produces breakout. The toroid does shield the top winding from
breakout. If coilers run
with a large toroid height above the coil, they usually use a corona ring
or something to acheive a
shielding affect.

Malcolm had mentioend in an old post the coil can be finely adjusted simply
by changing the coil to
toroid height. Obviously, if the coil is too far off tune, the toroid
height adjustment can't fix it.
But if it's close enough, then it can be used to tune the resonator to the
primary tank.

The top load is a very integral part of a Tesla Coil. The major and minor
diameters in comparison to
the coil, the radius of curvature, the proximity to coil and objects, all
affect your coils operating
frequency, spark growth, spark formation, etc...   and it's just a big
metal object.

Take care,
Bart