Re: primary/secondary coupling height ranges

["Bert Hickman" <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: "John Morawa" <morawaj-at-interaccess-dot-com>
> 
> Hello,
> 
> Just for design considerations I'm trying to get an idea of what the
> "typical" distance might be between the plane of a flat spiral primary and
> the lowest winding of the secondary.  I was figuring about 1" below the
> secondary.  I know there is probably much within the design of each coil
> that would have an affect on this but I am just looking for an "average".
> Also,
> what have people heard of others using for the lower and upper extremes.
> 
> Thanks,
> John M.

John,

It depends somewhat on the length of the secondary and the effective
diameter of the tapped primary. A typical range is to have the bottom of
the secondary winding in the range of 1-2" below the plane of the
primary (maximum coupling) to 2-3 inches above the plane of the primary
for a flat primary. More secondary elevation may be necessary if you use
an inverse conical primary. The best position for your system will need
to be determined experimentally AFTER you've got the system properly
tuned and running smoothly with the secondary elevated 1-2" above the
plane of the primary.

The optimal coupling position will be a function of how well your gap
quenches and how efficiently you lose energy to streamers. Begin slowly
lowering the secondary in 1/4" increments followed by short (10 second)
full-power test runs in a darkenned room. The best spot will give you
the longest streamers with no racing sparks. If you begin to see "racing
sparks" on the secondary (flashovers that typically jump between the
upper area of the secondary to lower areas of the secondary), raise the
secondary up a bit to reduce coupling. My 10" system runs best with the
secondary 1" below the plane of the primary. 

Safe coiling to you, John!

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-com
Web Site: http://www.teslamania-dot-com