Re: I want 2-footers, and I want 'em now! (fwd)
Your main problem is that a 30 mA current source is not enough to rapidly
re-charge a .03 MFD cap for the number of bks/second you need for efficient
operation. 30 mA matches up to a .01 MFD cap really good, but for .03 MFD
you need around 120-150 mA of current. Start paralleling transformers.
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Thursday, October 14, 1999 5:54 AM
Subject: Re: I want 2-footers, and I want 'em now! (fwd)
>Original Poster: Tesla List <mod1-at-pupman-dot-com>
>---------- Forwarded message ----------
>Date: Wed, 13 Oct 1999 09:48:58 EDT
>Subject: Re: I want 2-footers, and I want 'em now!
>Apologies for the long-winded text that follows, I figured the more detail
>gave, the better your advice will be.
>I'm a newbie. I'm using a 15,000 V -at- 30 ma NST for my first TC and what I
>have been reading here indicates with a good design I should get 2 foot
>streamers. I can''t seem to break the 6" barrier.
>Heres' what I started with:
>The TC is loosely built around plans in the current Nuts&Volts, so I've
>followed their schematic.
>Primary: 8 turns of 14 awg copper on a 9" diameter circle, spaced 1/2"
>Secondary: 800 turns of 28 awg on a 3.5" diameter by 14" PVC form. Coil is
>Capacitor: flat plate type just like in the article, 4 pieces of 10x10
>aluminum flashing with .030 polystyrene separators (I had it laying around,
>think it's polystyrene - white, flexible, opaque, and dirt cheep). The DOS
>software I downloaded indicates this is .0054 uf.
>RF coils: just like the article, 21 turns of 18 awg on 1.5" PVC pipe (which
>is really closer to 2" dia), one coil in series with each secondary of the
>Input xfmr: 15,000 volts at 30 ma NST
>Regular spark gap with 1/4" cap nuts.
>Toroid made from two 1 1/4" plumbing "J" traps, cut and soldered together -
>"Ground" rod from one side of primary to a point about 5" above center of
>I sent the above info to Nick off-line and he suggested doubling primary
>turns and quadrupling # of plates in the cap. Here's what I did:
>I doubled the primary turns by halving the spacing (16 turns at 1/4"
>and finally experienced "tuning" at 11 turns. Now I have a feel for the
>difference between resonance or not.
>This gave me 5-6" streamers but still required a 3/8" gap, and I started
>getting secondary-to-secondary strikes between points about an inch or two
>apart on the coil. I also saw the capacitor arcing between the connection
>points and the opposite plates (sneaking through the gap between the
>separators), even though there's a good 1" overlap on the separators.
>So, I took the cap apart and found I mis-measured the thickness, it's .047
>not .030. I siliconed between the separators near the terminals and added
>more plates. The DOS software I have indicates this should be 1.2nf per
>of plates. I assume that means 8.4 nf for a 8-plate cap (1.2 x 7).
>Now it tunes at 6.5 turns with a gap of 1/4" but I still can't get more
>6" streamers. The cap no longer arcs, but I still get some sec-to-sec
>strikes even after spraying with high-dielectric conformal coating. Help!
>want 2-footers by Halloween. I can build caps and/or wind a new secondary
>primary between now and then but I'm stuck with the NST I have. I could
>maybe build a more complex spark gap, but not enough time for a rotary or
>I also have these questions:
>1. The DOS software suggests 5.3 nf is perfect for my NST, but it seems
>you guys go by the "bigger is better" principal. What's up?
>2. I see a lot of talk of refrigeration tubing for primaries. Why? We're
>only talking about low currents, right? What's the advantage of refer
>over 14 awg wire?
>3. I see discussion of primaries, secondaries, caps and spark gaps, but no
>mention of RF coils like the Nuts&Volts article uses. Should they be used
>are they just insignificant enough to not warrent discussion?
>4. The N&V article did not mention any particular grounding other than
>connecting the bottom of the secondary to the NST ground (which is
>to electrical ground). This is what I have. Good? Bad? Ugly?
>I would love to see someone elses work, and a working TC, but it sounds
>you guys are scattered everywhere. I'm in Atlanta. Anybody close?