Re: Primary & Secondary coupling?

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 7/31/00 12:59:36 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

> Original poster: "Garth van Sittert" <garth-at-mediasupplies.co.za> 
>  
>  How does one go about calculating the optimum physical size primary in 
> relation
>  to the secondary and power used.  I will be running on about 2 - 3 kVA.  
>  What physical size secondary and primary should I use, or is this more like
>  guess work?  I don't mean turns.

Garth,

If you use a copper tubing primary, it will be quite wide if you use
a lot of turns, or small if you use few turns.  If you use close wound
pvc insulated wire, the primary can be small.  Also using the flat
banded primary, it can be small.  But in any case it doesn't seem
to make much difference as long as the coupling is OK.  
>   
>  What is the optimum coupling factor for a tesla coil, or does this vary 
with
>  individual coils?  How does one go about working out / estimating this 
> coupling
>  factor?

The coupling does vary for various coils, but it's usually somewhere
between k = 0.1 and k = 0.16.  If you make the secondary so it can
be raised, then you can adjust it anytime.  I put my secodnaryies on
a post so I can raise them and tighten a handwheel that holds it in
place at the desired height.
>   
>  I have managed to find some 1" wide 0.12" thick copper strip for my 
primary 
> at
>  a scrap yard.   Will this make a noticable difference for the RF?

A difference.... you mean a difference in spark length or appearance?
No difference will be seen.  The factors that affect spark length are
other types of factors which I've written about recently.  Primary type
is not really very critical as long as the material is reasonable, RF-wise.

Cheers,
John Freau
>   
>  Thanks
>  Garth