Re: overcoupling

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 9/15/03 6:37:37 AM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:


>In a recent post Dr. R.  mentioned that with a high power large secondary a
>conical primary will overcouple , I am in the process of building a coil
>with a 12" secondary and a 16 turn 30 degree inverse conical primary, power
>initialy will be 4 15/30 nst's with SRSG 120 bps , will overcoupling be a
>serious problem ? should I rebuild the primary to flat spiral and replace
>the SRSG with a sucker gap? could someone tell me what some of the effects
>of overcoupling are? I can also raise the secondary about 5" if this would
>lower the coupling equal to flattening the spiral.......suggestions?
>
>thanks
>
>Lance


Lance,

When I first built my 6" secondary, I used a 30 degree saucer shaped 
primary.  Don't know why I did that, I suspect maybe advice from another 
coiler at the time - and I did not know any better.  It worked well at 
lower power levels.  12 and 15 kv, up to 60 ma.  As I scaled up the power, 
I had racing sparks and too many discharges from the toroid to the elevated 
outside edges of the primary.  I finally rebuilt the primary to a flat 
configuration.  My advice is to always build flat primaries.  You can 
always raise or lower the primary or secondary to adjust coupling as 
needed.  Believe me, you can easily adjust a flat primary to over couple 
(i.e. flat primaries provide all the coupling that you need) - so - there 
is no reason and no advantage that I know of to build dish or saucer shaped 
primaries.

Ed Sonderman