Re: Secondary Coil Tuning

From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Tuesday, December 02, 1997 12:47 AM
To: 	Tesla List
Subject: 	Secondary Coil Tuning

   All -

  The typical method of tuning a classical Tesla coil is to use taps on the
primary winding. With some primary windings that are wound in a bundle the
tuning taps can not be installed. There is another way to do the tuning in
this situation. That is by tuning the secondary coil. This is accomplished
by close winding about 90% of the secondary turns on the coilform. The
balance of the turns are close wound on a sleeve located at the top of the
coilform. The sleeve should be capable of being raised and rotated. It can
be made of several thicknesses of light cardboard wound around the coilform
and well cemented and well varnished. It should be a tight fit but capable
of movement.

  By raising the sleeve the inductance is lowered which can be used to
precisely tune the coil. This also has the advantage that the coil self
capacity is also lowered when the sleeve is raised. The TC design would have
to ensure that the maximum inductance needed would be when the sleeve is
lowest. Even if an error is made all you have to do is change a couple of
turns in the primary.

  I have not tried this tuning method but it sounds like a good solution for
those special primaries with windings that cannot be tapped.

  John Couture