Re: Improved coil and questions

In a message dated 99-08-30 06:27:45 EDT, you write:

<<  I just recently improved my small 4", 12000 60ma Tesla coil, which was
> previously giving off only 9" streamers.  My previous coil had about 1300
> turns of 28 gauge magnet wire on the 4" pipe.  My primary coil was getting
> extremely large and expensive, about 17 turns of 1/4 inch tubing, so I tried
> to find how I could limit it.  What I found was that my coil had too many
> turns, and too small of a primary capacitance to have a smaller primary
> coil.  


I use 1300 turns or more of #28 wire on my 4" secondary, but I use 
#12 insulated wire on my primary.  This wire can be close wound and
gives a compact primary, I'm using 22 turns at the moment, but at times
I've used up to 34 turns.  I'm using a .0147uF cap, and I get 42" sparks
from a 12kV, 30ma NST.

I suspect that your coil is not tuned correctly, you probably still need
a lot more inductance in your primary.  Why don't you just add some
turns of #  12 wire to the outside of your existing primary as a test to
see where it tunes?  Or build a simple scrap wire primary using #12 wire.
The tune point at 5 turns you tried is most likely incorrect.  The reason
your coil doesn't work well with a large top terminal is because a large
top terminal demands even more primary inductance (more turns).  Add
more turns, and the fire and brimstone will pour forth from your coil (if
your gap is OK, and if your cap size is reasonable).  NST's work well
with sync gaps (if the cap is the right size), async gaps are
generally NG for an NST based TC.  I don't think you mentioned your
cap size?     

Another thing you could do is keep your copper tubing primary, but
make a new secondary wound with #22 wire or so, which will give the
coil a much lower inductance and make it more likely to tune correctly
with your primary.  It's best to do some calcs, or use a TC computer
program to calc the number of turns needed so it will tune OK, etc.

John Freau
> -Andy >>