Re: Newbe Question

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

Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Hi Gary,

Im thinking that a 12 inch coil will be too big for a 1000VA source.   The
Cres of your power source is 35 nf.  If you do a static gap, your tank cap
should be around 55 nf.  Keep in mind that LpCp = LsCs or put differently,
Cp/Cs = Ls/Lp.  For a 12 inch coil, lets start with an H/D ratio of 4.5 so
the winding height should be around 54 inches.  Next choose a wire guage
that will give you about 1400 turns.   You probably will want to have a
toroid on top of the coil that is proportionate to the coil size lets say an
8x36 toroid.  Now run these parameters thru JAVATC to find what size primary
you will need for resonance, and the generated top load voltage.  The
topload voltage needs to be greater than the toroid breakout voltage.

My guess is that the primary will need to be disproportionately large to get
the primary resonance down to the secondary resonance of a coil that large.
Now comes the fun, you can play with the geometries to get a frequency match
by lowering the primary frequency (using larger number of primary turns) or
raising the secondary frequency (like using a smaller toroid or going to a
lower inductance secondary).  On the secondary side, you can change the wire
gage, number of turns, the H/D ratio, and the major and minor diameters of
the toroid. You can always get it to work but the asthetics may not be
pleasing.  With a coil this large, many people get frequency match by
increasing the tank cap which means a larger power source.

Bottom line is there are many variables and many solutions.  Find one that
you like and even consider a smaller coil (maybe 6 or 8 inches)

Take care,
Gerry R



 > Original poster: "Gary Gonnella" <gary-at-ridepix-dot-com>
 >
 > I have done some playing around with coils in my younger days but now want
 > to build real one. I have available a 12 inch diameter 5 foot long PVC
pipe
 > that I plan to use as the secondary. I have four 9000 volt 30ma neon sign
 > transformers that give me 120ma in parallel producing about 1000 watts,
 > presently on a Jacobs ladder. For this size coil what wire would be
 > recommended and should it be close wound or have some spacing between
turns.
 > I want to make a coil that would be hefty enough to stand an upgrade to a
 > pole pig from the neons in the future.
 > I hope this question isn't too elementary for the list.
 >
 > Thanks
 >
 > Gary Gonnella W6RYO
 > http://www.w6ryo-dot-com
 >
 >