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Re: Tuning?
Hi Travis,
Thanks for posting your stats, this helps out the *fun* when troubleshooting
performance. My comments are below:
Tesla List wrote:
> Original Poster: Travis Tabbal <bigboss-at-inquo-dot-net>
> 6.25" x 25" secondary 22 AWG
> 15 turn 1/4" copper tube primary tapped at 13 for now
> .01 uF rolled poly cap (calculated, no meter yet)
> 15KV 60 mA neon transformer
> 4" x 24" toriod
> RCR filter (Thanks Terry!)
> RQ Gap
My first look at this is your primary winding length (inductance) and cap
size.
Since your cap value is not measured, one can only guess. It may be probable
your cap value is slightly lower than calculated. This should not be a problem
unless your primary length does not allow enough tuning length. 15 turns works
out just about right for a .01uF cap based on your secondary dimentions (1/4"
t-t spacing), but if your actual cap value is say 0.08uF, you'll want about 17
turns. The spacing between turns does not make a huge difference. This is
where
a variable second-stage tuning coil would come in handy.
Knowing the actual capacitance would greatly help ball park your tap setting.
If you don't have a meter handy, just take your cap to the nearest electronic
store and see if they will measure it for you.
> I think I'm out of tune. I can't seem to find a better place to tune it so
> if anyone has ideas I'm listening. I started with a bigger toriod (8" z
> 24") but at the advice of another list member trimmed it down.
I think you could tack on a 8 x 28 inch toroid. Looking at top capacitance vs.
Cself, the coilers with long arc lengths have on average a top load
capacitance
which is about 2.8 times their Cself. Your Cself is about 11.4pF x 2.8 = 32pF
=~ 8" x 28" toroid. I tend to beleive the 8 x 24 would have been fine.
> I can open the gap to 6 gaps at .030" and run at full power without firing
> the saftey
> gaps with the tap at 13. If I move it I can only get to about 1/2 power on
> the variac before the saftey gaps go nuts. Same thing happens if I open
> the gap further. I don't have a fan on the gap yet.
> Also, I am running on a counterpoise for the RF ground, it's a large sheet
> of metal screening. The ground is frozen so I can't get a real RF ground
> in for a while. I would like to get better performance out of this setup
> if I can.
I haven't tried a metal screening but I do suspect this to be a big player in
poor performance.
> I am getting thin purple streamers about 1 foot to a grounded rod. I got
> this from the old toriod as well, but they are a bit thicker now. I tried
> various points on the primary and this seems to be as good as it gets.
> >From posts on the list and web pages it seems like I should be able to get
> more output from this configuration.
Well, using three different equations (assuming 0.01uF cap), the range is 18"
all the way up to 51". But, I would say 18" should not be a problem, and there
are some acheiving impressive arc lengths for the small amount of input power
(and energy) being pumped in. I tend to beleive your output arc length could
acheive 30" to a ground rod once dialed in. And then possibly more as you
tweak.
> Any ideas?
>
> Travis Tabbal
FWIW,
Bart