I use a tandem static gap (12 total gaps using two layers each consisting of seven 1.5" hard copper pipe electrodes, each mounted in a single 12" high, 6" diameter PVC housing). This is similar to a regular static gap except that two sets of gaps are in one housing. A high velocity 5" fan and a 2" PVC “choke” forces cool air through the copper pipes. I'm also experimenting with a vacuum (having “rescued” a discarded ShopVac from the trash). This currently consists of six 30 mil gaps (similar to the one shown in Richard Quick's videotape), but I may push these to .040 or .050 to improve the overall “Q” of the spark gaps. In operation, I get loud streamers exceeding 46" in length. The coil is housed in an enclosed patio by my house, and I've just about max'ed out on spark length versus available space around the coil. Because I live in a residential area, I'm reluctant to run this system outdoors.

Going forward, I am looking at migrating to a rotary gap (potentially a synchronous high break-rate design) once I have completed construction of two high voltage RF chokes, bypass capacitor, and safety gaps. I am interested in experiences other coilers have had with various rotary designs. I'm also interested in building a high power solid state coil, and would like to explore opposing-phase resonator pairs. Any practical experience, designs, or results from coilers who are planning, or currently using, half bridge or H-bridge MOSFET configurations would be of great interest. Also, has anyone coupled back-to-back solid state switches to a capacitor bank for peak power bursts or to support low duty cycle/high peak power operation (sort of like a lower voltage version of a spark gap oscillator)?

End

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FOR SALE - High Voltage Capacitors: High Q Factor energy discharge capacitors ideally suited for Tesla oscillator work. Values .03 MFD, 50 KV and .05 MFD, 50 KV (maximum peak voltage). They work best at 20 KV (rms) and work great with neon sign transformers. Case size is 4X6X11 inches. Units are new construction and never used. Priced at $295 for .03 and $345 for .05 units. Add $4.50 per unit for UPS shipping. Resonance Research Corp., E11870 Shadylane Road, Baraboo, WI 53913. Tel: (608) 356-3647.

FOR SALE - Variable Autotransformers (Variacs): 30 Ampere, 240 VAC Variacs. Units in used but good condition. Priced at $225 per unit. Shipped FOB Baraboo, WI Resonance Research (address and phone above).

ATTENTION! We now have a large metal spinning lathe and are offering spun aluminium toroids for Tesla coils and also 7" and 14" oblates for Van de Graaff generators. This large lathe allows us to spin toroids up to 48 inches in diameter. We are stocking toroids in the following standard sizes: 14x6x4", 24x12x6", and 34x17x8.5". Contact Resonance Research at above given address and phone number.

WANTED - High voltage door knob capacitors, variacs, and ferrite toroids. Please quote including postage to New Zealand. Cliff Rogerson, 27 Humphrey Kemp Ave., Henderson, Auckland, New Zealand.

FOR SALE (or trade for wanted items on my list) - High voltage items, caps, rectifiers, mylar sheet, discharge tube plasma display, etc. SASE for list to Tedd Payne, 769 N. Calumet Ave., Valparaiso, IN 46383 or (219) 464-4791 evenings.

Catalogs Received

EDMUND SCIENTIFICS (1996-1997) catalog for experimenters featuring numerous components and complete units including a Tesla coil, Van de Graaff generator, magnets, optics, etc. Write to Edmund Scientific Company, Consumer Science Division, 101 E. Gloucester Pike, Barrington, NJ 08007-1380

TUCKER ELECTRONICS (1997 Test & Measurement Product Guide) featuring quality test equipment for the professional and amateur electric/electronic technician and engineer. P.O. Box 551419, Dallas TX 75355-1419.

C&H SALES COMPANY Fall 1996 catalog. Offers a diverse inventory consisting of mechanical, electrical, air pressure surplus products. C&H Sales, P.O. Box 5356, Pasadena, CA 91117-9988.