[Prev][Next][Index][Thread]

Re: Primary Q's and Spark Gaps

Hi all,
         Mark Barton writes in response to my post.....

> >Stats : Lp = 11.8uH (including a couple of feet of stray wiring)
> >        Cp = 102nF  (extended foil)
> >        Static Gap firing voltage = 7.5kV
> >        
> >Measured Q (using sig gen and scope - i.e. no spark gap) about 50
> >        => Rp about 0.22 Ohms
> >              
> >Measured Q (operational using ping test and decrement calc.) =11.5  
> >        => Rtot = 0.95 Ohms
> >        
> >        => Rgap about 0.73 Ohms!! (accounts for 3/4 of all losses)
> >  
> 
> I guess this means your Fo ~= 150KHz.  That 0.1uF cap seems a bit large 
> for that freq.  Tesla ran the Colorado lab at 80-100KHz with 0.12uF.  
> You know what to do now.  Switch to 0.015uF, about 1/10 what you are 
> using now and use a rotary gap.  The reactance of the primary 
> components will be 80ohms instead of 10ohms.  Your Q should go way up, 
> tuning get tighter, and (hopefully) sparks get longer.
> 
Hate to disappoint you, but I'm afraid that particular coil's staying
right where it is. I built it for my own interest initially, but they
insisted on paying for it at work, and I no longer treat it as my own
property (i.e. I'm not investing any more time in it). I do have plans
to build a better one at home. I'm particularly keen to see how peak 
power scores against average power. Incidentally, I still get better 
than 4 feet for 1800W with it. Not the best, but certainly not the 
worst. The next coil I build will eclipse it by a mile. I've been 
hanging off and hanging off while getting the theory together. Almost
ready, but still one or two things to sus.

Malcolm