Karl Lindheimer's mini coil:
Name: Karl Lindheimer
Address: Warren, NJ USA
Transformer: Franceformer model 4020. 4kV/20mA, 9 shunts removed (half), measured current of 36.5 mA at 117 VAC input.
Tank capacitor: A 25nF/12,000 VDC MMC cap, made of six 0.15uF/2kV, Cornell Dubilier polypropylene caps in series. A 10Meg 1/2W bleeder resistor is across each cap. MMC can be easily varied through jumpers to give 30nF and 37.5 nF all within allowable voltage tolerances.
Primary: A flat spiral of 3/16" refrigeration tubing 8 1/2 turns.
I.D. = 5.0", O.D. =11." Tubing is fastened very securely with ty-wraps through holes in HDPE top plate. Inductance is tunable from 0.3 uH through 16.0 uH. With current setup, best tuning is at turn 6 1/2.
Secondary: 3.0" O.D. clear acrylic tubing, 17.75" winding length (1313 turns) of #28 AWG magnet wire, polyurethane coated. Calculated inductance is 19.03 mH. H/D ratio is a tall 5.9:1 Lexan baffles at either end provide threaded nylon connection to base and topload.
Pri-Sec coupling: K = 0.1 first secondary turn is 0.25" above primary. There is a 1" clearance from secondary windings to first turn of primary to allow for future secondary upgrades.
Gap: Single static cylinder gap. Consists of two 1.0" diameter x 4" long copper pipes, spaced 0.06". Future upgrades will include Terry Fritz's SISG electronic SIDACTOR/IGBT gap.
Top load: Stainless Steel Sphere 8" diameter. Calculated capacitance of 10.79 pF. Ordered from a garden supply shop as a hollow gazing ball. Breakout point is an acorn nut held to sphere with a strong little magnet.
Grounding: NST frame and secondary are grounded through the AC ground.
Power source: 500 VA 0-130 VAC variac into a line filter. For my run yesterday, the taps on my variac were connected to only provide 0-100 % voltage range. At the full 100% stop, the measured voltage read 118.6, VAC which is pretty much the standard here. The actual measured current at that setting was 36.5 mA from the NST secondary.
Calculated system resonance is ~273 KHz, capacitor joules = 0.392 at 25.0 nF.
Design Software: I modeled this coil extensively before purchasing/fabricating/assembling parts. I used TeslaMap version 5.7 by Kevin Wilson, MANDK Version 3.1 by Mark Rzeszotarski, and ScanTesla version 7.50 by Terry Fritz. These programs are available at http://drsstc.com/~sisg/files/
Elevation: 418 ft. above sea-level.
Best performance: At least four streamer hits per minute to an ungrounded metal target on wall measured 18.125" away from breakout point on sphere.