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Re: [TCML] LTR/STR and spark length

Hi, and thank you to everyone for your responses-

Bart, it's very interesting that our coils are so very similar..... except for that whole, underperforming thing on my part. Let me give you a little more info on my specs before we go on. My first topload was a dryer-duct, covered with foil tape, type, 19 3/4" X 3" I had arcs off of it, but from all over the place, even with a screw/breakout point taped to it. So for the moment, at least for consistency purposes, I'm sticking with a 10" ss sphere with a 12 5/16" steel rod inserted into it. All the arcs are headed relatively straight up now. My gap is single static, quenched with a blower/motor from a microwave. The electrodes are round, "almost flat" surfaces, 1" across, made out of brass (old drawer pulls). I'd like to stick with a ssg for now, but, if I feel ambitious, I do have a couple little motors around that could probably give me at least an asrg. Since my last email I tweaked a couple things, and I'm getting easy 24+" arcs now. I opened up the gap a little bit, but still backed off if I got any arc on the safety gap. I also ground a mild point on the rod sticking out of the sphere. Racing arcs were mentioned earlier, but the only time I experienced them was very briefly while adjusting the primary tap. *Could you explain how one goes about determining the resonance for a given system, so that they could know (within the proverbial ballpark's range) as to whether they are str/ltr/R? Thanks everyone,


Hi Neal,

Just thought I'd share my little coil with you since it's similar (4" x 20" these days) and uses a supply voltage about 10.6kV at 200mA (modified 12/60 NST), so similar to your power supply. I'm also running a static gap on this coil. Early on and in the pics below I have had some primary strikes but hardly get those any longer. In the pics (at the link below), the coil ran with a rather tight coupling. Some months later after these pics, I ended up catching the bottom of the secondary on fire (bottom turns shorted). When I realized the glowing red spots, I decided to just continue and let disaster happen (which did). I ended up removing about 1/2" of winding which also lowered coupling. The coil these days is painted red, but nothing else has changed other than a slightly looser coupling. No more problems with the sec bottom turns. This coil has also ran very long runs (which I did mainly to verify coupling was good for it's duration and I was curious as to how everything would do over a long duration). I was happily surprised.

Well, I just wanted to show why I think your coil could probably do better than it is now. BTW, the MMC is 18.8nF, so I also am running STR with this setup. Other than maybe the gap and toroid, our coils are probably not that different. Also, on this coil, I typically run about 90 to 100 volt input via a variac to keep sparks out of harms way.


Take care,

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