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MOTs Rule!



Fellow Coilers,

I've just tested my twin MOT supply with dual voltage doublers on my 4" x
24" coil.  The supply is based on two MOTs salvaged from discarded 900 Watt
ovens.  I borrowed the idea for it from Finnish Coiler Marco Denicoli.  I
normally run the coil with two 9KV/60ma neons.  I use a single static
vacuum gap made of 1" copper pipe fittings (yes, beefy) and a .023uF MMC.
Toroid is 3.5" x 14".  I had to close the gap a little to get reliable
firing from the MOTs, so I'm guessing voltage is in the 8KVAC range.   I
used no ballast--the MOTs go as hard as they want to.  I ran the vacuum
cleaner motor on my gap at full throttle in hopes of quenching the higher
current. 

Results were pretty satisfying.  The streamers aren't any longer than with
the NST supply, but they are much thicker, brighter, more intense, and more
chaotic. They look as hot as lightning bolts.  There also seem to be more
of them.  The spark gap sounds different too--much lower in pitch--almost a
mechanical grinding sound.  It gives me the creeps.  Best spark length is
about 30" (to my strike rail), and rarely a single streamer may reach out
36" or so.  This thing really wants a bigger tank cap & larger toroid.  I
plan to remedy both very soon.

Current is provided by a 230V, 20A window air conditioner outlet in my
garage.  The unballasted MOTs run warm, the doubler diodes & caps run cool.
 Oddly enough, the only weak link seems to be my 100 Ohm, 55 Watt RF filter
resistors.  They run hot as pistols!  I'll have to go up to 100 Watt
resistors I guess.

Right now it's just a crude lashup literally taped together on my work
bench.  I'll package the MOT supply properly over the next few days with
neat, soldered connections, safety gaps, etc.  I may even immerse the MOTs
in oil to enhance cooling.  I can't wait to try some longer runs.

Low budget coilers unite!  MOTs rule!

Greg Hunter
Cochran, GA