Re: Spiral coils?

>From: Marcus E Young <E.Young-at-mailbox.uq.oz.au>
>>Do spiral secondaries work?
>They do, but from things Ive heard, they dont seem like a great secondary
>resonator. Their geometry alone makes them a pain. 
>For an inductivley coupled secondary supplying a tertiary coil in a magnifier
>system, this type of coil is more usefull.
>A spiral magnifier tertiary can be centre fed, with the loading capacity on
>outer turn....but alas I drift a bit off the subject here. 

Hello Coilers,
        I am working on a magnifier using this very design.  The driver I
built consists of a flat 62 turn 16 gauge flat pancake (spiral) coil, and
the primary is solenoidal in shape, constructed of 1/4 inch tubing, wrapped
on plastic sheets around the outer perimeter of the pancake driver.  The
outer turn of the pancake coil is grounded, and the center turn becomes the
high voltage lead to the extra coil.  Initial tests have been very
promising, and the coefficient of coupling is very high.  (I have computer
simulation results for this geometry, and a burned out neon transformer as
experimental evidence.  Haven't measured K yet quantitatively.)  More on
this in about a month when I have more time for coiling.
        Pancake (spiral) coils are inherently poor performers as
conventional tesla coils because they have relatively high self capacitance.
They are also a bit of a pain to wind, although not too bad as a driver.
Tesla experimented with them quite a bit, and are shown in a number of his
Mark S. Rzeszotarski, Ph.D.