Re: [TCML] can you connect the secondary *directly* to the primary?

[Scott Bogard <teslas-intern@xxxxxxxxxxx>]

Tim,

     After looking over your design, and given the specs you gave us,
there are a few problems, but I think you can fix them.  Firstly, ditch
the chokes, as you said they will kill your NST.  To properly filter
your NST you should use a Terry filter.  Back when I used to run OBITs,
I did not use a filter at all, and they lasted a long time (they still
run), just do not open your spark gap any wider than it can start an
arc without the rest of the Tesla circuit cap installed, this will
ensure your tank voltage is clamped at the NSTs rated voltage.  Your
secondary proportions area little off, What kind of wire are you using?
how many Turns?.  If I was you, I'd go for broke (go to the hardware
store) and get a 3-in PVC pipe, and wind it with 28AWG wire, about
17.5-in.  That would make for a well balanced, and more powerful
secondary.  Your spark gap needs some work, but the good news is, not
as much as you may think.  My first spark gap was two bolts, mount them
in "L" brackets, screwed down to something plastic, like a cutting
board (broad side facing each other, and try to use brass, and not
steel, which is lossy and gets real hot).  Don't use wood, it incurs
losses (although some people get away with it, I always had problems,
especially on humid days).  There are lots of easy spark gap designs
out there, just peruse the archives and some coiler webpages.  Are you
sure your capacitor is 1 uf and not 1 nf?  1 uf is a huge capacitor, 1
nf is probably a little small, but your secondary is small so it may be
good.  If worse comes to worse, use glass bottle caps (lossy yes, but a
great learning tool, infinitely adjustable, practical on small coils
where not a lot of caps are needed, as cheap as capacitors come, 35.7
seconds to make one, and the corona around the edges looks really
cool!).  This will also ensure you return the cap in working order. 
Find yourself a topload, you didn't mention it, unless I missed it. 
And most importantly, disconnect your secondary from your primary, and
hook it to some large grounded metal object (like a ground rod, or even
a metal support beam, cold water pipe (if you know it is copper to the
source, this implies you installed it yourself)).  Since it is an NST,
the primary tank circuit should not be grounded as it is a center
tapped transformer (most likely), but you should ground your NST case
to the ground (I used mains with my OBIT coil, but I think you are
supposed to use the RF ground to be proper).  It sound like you have a
lot of measuring tools at you disposal, that is good, it puts you at an
advantage for starting out.  Also if you do design a new secondary,
make use of Java TC, it will do a lot of number  crunching for you,
once you get acclimated to using it, or have somebody show you how it's
done.  Best of luck!  Let us know how it goes.



Scott Bogard.




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