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First Light!!! Now, how to tune it?
Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-uswest-dot-net>" <vanyo-at-echoes-dot-net>
Well, I just fired up my first coil for the first time, and it worked!
I was running it outdoors (my only option with my low ceilings), in
daylight, so it's hard to say how long the streamers were. Perhaps a
foot or so, which is far less than I should be able to get with three
15/60 NST's. It was exciting to see it work though. I can't wait to
see it at night.
Here are the specs:
Power Supply: Three 15/60 NST's, with Terry's protection filter on the
high voltage side, and redundant line filters and a 50 amp variac on the
Capacitor: A Maxwell 30 kV, 0.06 uF cap (model # 37321). I know, it's a
bit large even for LTR.
Static Spark Gap: My own invention, sort of. 9 copper pipes mounted on
two PVC rails, but one rail slides, with a compression spring on one
end, and a bolt on the other end. Turning the bolt causes the one rail
to slide, which adjusts the spacing between all 9 copper pipes
simultaneously. This is all mounted on a blower box. So it's a typical
copper pipe static gap, with a one knob gap adjustment feature. The gap
can be continuously adjusted from a closed position to wider than would
ever be used.
Secondary: 1000 turns of 22 awg, 6.5" (closer to 6 5/8) diameter, 27.5"
Primary: Flat spiral, 19.5 turns of 1/4" copper tube, 1/2" spacing on
centers. Inside diameter 9.5". It's way oversized - I had it tapped
at about 5 1/2 turns. (I was originally planning on less power and a
Toroid: 6" aluminum dryer duct wrapped around an 8" diameter disk
(actually two aluminum pie
pans). Used a thumbtack as a breakout point, but there were streamers
coming out all over (is that a good sign?).
Ground: Currently only a 32" segment of copper clad iron ground rod.
All interconnects are 1/4" copper tubing, except I use welders cable to
my primary tap clip (the welders cable is both heavy and very flexible),
and 15kv rated high voltage wire from the power supply to either side of
the spark gap.
Misc: Strike rail, and plexiglass cover over primary.
So how to go about tuning? (I don't have access to any fancy equipment)
Coupling? I didn't even think to adjust the coupling during the first
run. Currently, the bottom winding of the secondary is about 1" above
the level of the primary.
Tap point? I got 5.8 out of the JHCTES program, but only used a guess
of 15pf on the toroid.
Static gap width? What's the basic idea here? I noticed with the gap
set narrow, it seemed to fire much more steadily, while when wider it
had a rather chaotic sound.
Most helpful would be a methodical way to adjust the tap point and gap
width for optimal performance. Can I adjust the spark gap first? How
to know when it's right? And then how picky will it be about the tap
point? Do I need to wait until dark to tune it, or should I be able to
see the streamers in daylight?
Toroid? Does it need to be bigger? How big?
Ground? Would it make a big difference to have better grounding?
Any further help would be most appreciated, and thanks to the group for
helping me get this far. This thing has been many months in the making,
and my wife will be quite happy when I'm done working on it.