Re: On the fly tuning of a TC

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

On 16 Apr 01, at 11:08, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <FutureT-at-aol-dot-com>
> 
> 
> Jason,
> 
> A good way to tune the primary is to build a metal roller that
> contacts the primary copper tubing.  THen you make the whole primary
> so that it can rotate around the center when driven by a gear motor. 
> As the primary rotates to a new position, the roller will roll along
> the primary copper tubing, and the tuning will change gradually.   As
> you can see, the roller always contacts the tubing with this method,
> so there will be no showers of sparks as the tuning changes.  The
> roller has to be build as an arm mechanism that can move in or out as
> it follows the primary spiral. The arm could be something like the arm
> on a record player (phonograph).
> 
> John Freau

Another variation would be to have a separate tuning inductor 
connected in series with the primary and made adjustable by 
compression/elongation of the windings or if you are really game, 
moving a (large) ferrite core in and out. The effect of a separate 
inductor will be to lower k in proportion to the extra "off-axis" 
inductance. 

Malcolm