This competition began when two coilers noted that they were each building coils using the same France 4/20 NST. “Wouldn’t it be cool to see who gets the best results?” Then we thought it would be even nicer if we extended the challenge to others, again, using the same France 4/20 NST as the entry requirement. Since there were complaints that the specified France 4/20 NST was not universally available, I thought I could accommodate more contestants if an additional entry class were created that used an NST similar to but not identical to the France 4/20 NST.

1) To create a world-wide competition to get the longest sparks, using a specified NST power supply.

2) To keep entries similar enough that spark length indicates design “goodness”.

3) To keep entry rules open enough that a large number of people are able to participate.

4) To keep the rules specific enough that we’re all striving for the same end result without loopholes.

5) To provide a forum to post the results to so that the coiling community may benefit and learn what works best and what doesn't.

1) To provide material awards for best entry. The only reward is your relative ranking on the results web site.

2) To verify the performance and rules-compliance of all entries. This is an honor system and I have to judge entries based solely on the information provided.  Please observe the letter and the intent of the rules.

Category 1 is for entries powered only by faceplate-rated 4kV/20mA NST’s. The rules are more restrictive here so that this is the purist form of competition - everyone starts with the same power supply.

1) The power supply must be a 4kV/20mA NST. Any manufacturer, and either 120V or 240V mains voltage is okay.

2) NST primary voltage may not exceed the faceplate value, typically 120/240VAC. If your mains voltage is abnormally high, you must Variac down.  If you must overdrive your 4/20 NST, you may enter it under category 2.

3) Removing some NST current limit shunts IS allowed. Short circuit secondary current must be measured with nominal primary voltage applied, and this current may not exceed 50mA.

Category 2 is to accommodate people who may not have access to a 4/20 NST, or may already have a similar NST that's close in terms of power. While close, the use of other voltage NST's does represent an apples/oranges comparison to the 4/20's, and for this reason, there is a separate category.

1) The power supply must be an NST.

2) Overdriving the NST primary voltage above the faceplate rating is permitted in category 2 only.  

3) The product of the NST open circuit secondary voltage, Voc, times the secondary short circuit voltage, Isc, at the mains voltage that you will be operating at, must not exceed 200VA. If you operate the NST primary at an elevated % primary voltage, you must boost the faceplate Voc by the same %.

Category 1 and category 2 entries will be ranked separately.

1) The coil must operate in a mode such that the resulting discharge appears to the eye to be continuous. It is not permissible to use the power supply to charge up a large capacitor for occasional single-shot discharges.

2) The coil must be operated continuously for 5 non-stop minutes in advance, on the day of the competition run. The coil may rest and cool down for as long as you like before the competition run, and gaps may be cleaned, but not adjusted. This rule is to ensure that the coil is not running in a way that is overtaxing the components, in particular the NST.

3) Coils may be any type - CW or disruptive, magnifier or 2-coil, and gaps may be static, rotary, or solid state.

4) Qualifying streamers must connect to a target at least twice within a 60 second interval. One-time wonders do not qualify. Measurement shall be the straight-line distance from the point on the target nearest to the top load, to the point on the top load nearest to the target. In other words, it doesn't matter where on the target the discharge strikes. Length must be stated in increments of 1/8". Entries stating identical lengths will be further ranked as follows: Lower Isc * Voc VA ratings will be tanked higher, and among identical VA ratings, lower Voc entries will be ranked higher, since lower voltage systems are at an efficiency handicap.

5) It is not permissible to alter the atmospheric composition or temperature in the neighborhood of the top load discharge. It is permissible to alter the spark gap medium.

6) It is assumed that most coils will be operated at or near sea level. For entries that are operated above 1000 feet above sea level, a discharge derating factor of TBD per 1000 feet above sea level must be applied to the measured streamer length. Both measured and corrected figures will be posted, but ranking will be by the derated figure.

The NST short circuit current may be measured with a multimeter with an AC mA range. Connect the two leads across the secondary terminals and double, then triple check that the test leads are in the proper jacks for mA measurement and that the range/function switch is set correctly. Failure to do so may instantly fry your meter.

If your multimeter lacks an AC mA range, you may connect a 1K 3 Watt or higher resistor across the NST secondary and measure the AC volts across the resistor. The number of volts is equal to the short circuit current in mA.

There has been much debate on the Pupman List as to whether NST modifications and overdriving are permissible. It is clearly impossible to satisfy all points of view. The reasons for my rule choices are as follows:

1) The underlying goal of the competition is to keep the input power supply as constant across all entries as possible. Setting a maximum secondary Isc * Voc VA rating achieves this to a degree, but I acknowledge that this is an imperfect measure.

2) NST shunt removal is permitted to the extent that the modified VA limit is not exceeded. Some have suggested that no modifications should be permitted while others have suggested that anything goes. I want people to be satisfied with the outcome of their construction, and it would be a shame to hobble the performance of a small coil by not permitting shunt removal. I do not object to shunt removal because there are no known ill effects to the NST if done in moderation.

3) For category 1 entries only, I decided to limit the input voltage to the NST to the faceplate-rated value. This seems contrary to my shunt removal position, but I'd like to keep as many things constant as possible. Builders are at liberty to overdrive their NST when not competing since no changes are necessary. It is not so easy to remove and replace shunts.

4) I originally proposed restricting category 1 coils to static gaps with a specified maximum gap width, to prevent operation at unhealthy voltages, and to further keep as many things in this category constant. This would have provided the most level playing field where variations in performance were due to yet-to-be-identified characteristics, rather that the well-known but destructive benefit of wide open gaps. But the most vocal sentiment on the List preferred no such restrictions.

Entries must be emailed to the organizer, Gary Lau, at (NOT the Pupman Tesla Coil List). If mail to this address bounces, please try .  I will post news of changes in first place to each category to the Pupman List, although everyone is certainly welcome to blow their own horn. Each entry submission must supply the following information:

1) Your name, city, state, country, & email (will be posted on this page)

2) NST faceplate rating, i.e. 4kV/20mA, and model/manufacturer if known

3) Intended category

4) NST secondary short circuit current.

5) NST primary voltage when operating.

6) Specs/descriptions of tank cap, primary, secondary, top load, gap, etc.

7) Have you performed the required 5 minute preconditioning run? (Y/N)

8) Longest recorded discharge, per the rules above.

You may optionally include:

1) A text of any length describing any or all specs, construction details, and special features of your coil.

2) One photo of your coil. I reserve the right to crop, shrink, adjust contrast, etc, to keep all photos similar and reasonable in byte & pixel size. I would prefer a well lit photo of the whole coil, not operating.

3) A link to your own web site with further details and photos.

Category 1