--Previous Message-- Thanks for your help,
: : --Previous Message--
: I am new at coiling. Just completed my first coil. I a question
: the length of the streamers. My secondary is 4" inner diameter and
: about 20" long. I am using a 9kV NST and I built a MMC. The MMC
: consists of 190 capacitors rated at 16kVDC .068 microfarads. I have 10 in
: series and 19 parallel. My primary is 50' 1/4" copper tubing spaced
: 1/4" apart. I have a single spark gap and the toroid is made of
: 4" ducting. I am getting many streamers, but they are only about
: 8" long. I believe that I could achieve longer streamers, and my
: question is of course......how. I am thinking possibly get a 15kv NST and
: a larger torroid along with tuning it, but I would like the opinion of a
: Hi Jim,
: Welcome to the hobby - the smell of ozone is addictive, isn't it... :^)
: Lack of performance can be cause by a number of factors. My first
: suggestion is to reduce the size of your MMC capacitor from its present
: value to about half the value if you're using a 9 kV/60 MA NST, or about
: 1/4 the present value if you have a 60 kV/30 MA NST. The present MMC may
: be too large for your current NST. Instead, use 9 strings in parallel (for
: a 60 MA NST) or 5 strings for a 30 MA NST for your MMC. You'll also need
: to retune the primary (by moving the tap to outwards) in order to get the
: system back into tune.
: My second suggestion is to use a fan or blower to keep the spark gap
: electrodes cool or, better yet, convert to a spark gap that has more
: electrodes so that you have more small gaps (using inexpensive copper pipe
: segments as electrodes). This will improve "quenching" which
: keeps more energy in the secondary so that you can get longer sparks. Stay
: away from any rotary gap (at least for now).
: Some other things to verify or try: Did you use polypropylene capacitors
: for your MMC? If you accidentally used Mylar caps, they'll be quite lossy
: and will dramatically reduce coil performance. Also, Make sure you've
: adjusted the primary tap for longest spark. An out of tune coil will
: perform poorly and can damage your NST or MMC.
: Make sure your toroid is relatively smooth - if you are getting multiple
: sparks instead of single streamers, the toroid may have rough or
: projecting points. Multiple simultaneous sparks prevent you from forming
: nice long streamers. Also, did you use the aluminum foil type corrigated
: dryer duct? Cheaper aluminized Mylar ducting tends to work very poorly,
: since it has projecting wrinkles that generate corona and multiple sparks.
: Finally, once you've tuned the coil for longest spark, try lowering the
: secondary (or raising the primary) to increase coupling? Do this in
: 1/4" increments until you begin to get racing sparks (sparks that
: begin to go from the top portion of the secondary winding to lower
: portions or even the base of the secondary winding). Once you get these,
: excessive corona between the primary and secondary, or sparks jumping
: between the secondary and innermost primary turn, reduce the coupling. You
: may need to do these adjustments in a darkenned room so that you can see
: any misbehavior.
: If, after trying these changes you still have problems, let me know and
: we'll take a deeper look at your system.
: Good luck and play safely!
: -- Bert --
The smell of ozone is definitely addictive. I did use polypropylene capacitors, but my toroid is nowhere near smooth and I never adjusted (tuned) the height of my secondary. I am going to try your suggestions this weekend, hopefully I get some good looking streamers. Thanks for the tips; I'll get back with you if I have any trouble.
Thanks for your help,