AC Input:
15 Amp Variac, 30 Amp RFI
filter, 88 uF 370VAC PFC caps, MOV transient
suppressor.
HV Xfmr:
15KV 60 MA neon sign
transformer, de-tarred and re-potted in Vaseline.
HV Xfmr
protection network:
Per HV Xfmr lead to
RF Gnd:
- 450 pF bypass
capacitor constructed of .09" copper-clad G10 circuit board material. Vaseline for corona suppression (Yuk!)
- Two 0.25" wide safety gaps using
3/8" diameter brass balls
Per HV Xfmr lead in
series:
- 1.6Kohm, 113W
non-inductive resistors, to form low-pass R-C filter with bypass caps.
Grounded Strike rail: - 1/4" Cu tubing,
2.75" above top primary turn
Spark gap:
A one-segment static gap,
spaced 0.34-inches, massive airflow through spark channel provided by a vacuum
cleaner motor.
Tank Capacitor:
.011 uF homemade
"MMC" Multi-Mini Capacitor, constructed out of 192 0.015uF/1600VDC
polypropylene capacitors, in parallel with a .01uF/100KVDC FCI brand commercial
cap from Fair Radio Sales. Total tank capacitor value is .021uF. More recently I scored a used Maxwell .02uF
45kV (p/n 37093) cap, which I use by itself.
Primary coil:
14 turn 15-degree conical spiral 1/4"
copper tubing, 1/4" gap between turns (.5" ctr-ctr),
6.25" ID, 20" OD. 54uH when tuned for 2-toroid
topload.
Secondary coil:
4.25"D x 23.25"L
(approx 871 turns) 22 AWG wound on 1/16" wall dried/sealed PVC SDR
drainpipe. Many
layers polyurethane. Low voltage self-resonant with no
topload at 489 kHz. C-self = 8.4 pF. With 4.5" x 15.5" toroid (23.9 pF), Fr is 290 kHz. With additional 6" x 23"
toroid (total topload of 46.5 pF),
Fr is 190 kHz. Lowest turn is even with lowermost primary turn. 12.9 mH inductance.
Coupling constant - k:
With bottom turns of primary and secondary at
same level, k=0.139. Raising the primary up by 0.25"
changed k to 0.144.
Discharge terminal:
Small 4.5" x 15.5" toroid made from
aluminum flex duct, stiffened and smoothed with 2-part wood filler and spakel, covered with aluminum tape.
Large 6" x 23" toroid made from
aluminum flex duct, covered with aluminum tape. This toroid is placed on top of
smaller one.
Ground system:
One 8 foot ground rod in earth soaked with
water, connected with 15'L x 2"W copper flashing ground strap.
Performance to date:
Max sparks to grounded target (foundation
wall): 58"