Re: Variable Coil Tuning

Hi Jeff,

	I modeled this today,  The bottom almost has to be a toroid too because
the sharp metal edges of anything else will provide streamer breakout
points.  I ran a test (computer simulation) where I just used a pizza pan
on the bottom with a 2 inch radius tube attached.  The top turns of the
coil were the first streamer break out point! (that's bad...)  then the 2
inch diameter edge of the pan assemble breaks out.  And then the top will
breakout.  Since one needs pretty good spacing between the terminals, you
really appear to need two good terminals to prevent unwanted streamer
breakout as this shows.

The voltage distribution plot is at:

The voltage stress plot (voltage change per distance) is at:

	It is hard to see, but the top of the secondary will breakout first
followed by the first terminal and then by the top terminal.  One needs to
carefully look at how two terminals will interact especially with the top
terminal moving to such a great degree during tuning.  It is tricky to keep
the streamers on the top terminal only and I bet you need a good terminal
on the bottom.  However, perhaps you could use a "pan" terminal on the top
and accomplish the task and still avoid the cost of a second toroid???



At 08:36 AM 10/29/1999 -0700, you wrote:
>Does the bottom terminal have to be a toroid? What about
>a metal plate that extends a couple of inches past the
>edge of the secondary?...
>> I ran some numbers today on how varying the distance between two top
>> terminals would affect secondary tuning.  By varying the distance 12
>> I got a frequency tuning range of 11.5% !!  I am now thinking that having
>> dual terminals and having some motor deal that will vary the distance
>> remotely is a very good way to accomplish the remote tuning function