Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>4.5 or 5:1 works well with pole xmfrs. With NST types you can use 6:1 or 7:1. Most critical for good performance is a large radius on the sec coilform. Use 4, 6 or 8 inch dia. sec. for NST powered coils unless you are going to extremes. Pole xmfrs like 18, 20, or 24 inch dia. sec coilform for good performance.
Use approx 1400 turns for good performance with NST and around 1200 turns for good performance with a pole pig.
With an NST if you use a 6:1 height/dia. ratio with a 6 inch dia sec, this dictates a 36 inch long winding length for the sec coil. Divide this distance by 1,400 and this will give you the correct dia. for the copper wire. Use ARRL Radio Amateur's Handbook, available free at any local library, to determine wire gauge from wire dia. Best to use 150 or 200 degree C. rated wire as this has thicker and better insulation to resist RF tracking --- main nemesis of small coils.
Typical NST setups like like use 26 or 28 AWG 200 degree C. wire and 30 AWG if you are using a 3 or 4 inch dia. coilform.
The cap value really depends on the size of the topload and the available mA or driving current your NST will provide. Typical value is to calculate the reactance at 60 Hz for the size xmfr you and using and then multiply this value of cap x 1.5 to get optimum cap size for long single streamers. You can find this data in the Geek groups MMC online listings or via Terry Fritz at the archives.
If you prefer the romance of multiple streamers then multiply x 1.3 to provide a higher current ratio. Also use a slightly smaller toroid like a 12 x 5 instead of a 24 x 6 to get multiple streamers.
Dr. Resonance
Original poster: ben eells <squeels2171@xxxxxxxxx>I'm sure this subject has probably been discussed here several times, but I haven't been able to find the answers I'm looking for. When designing a coil, what dictates the length, diameter, and wire gauge of your secondary, and how do you go about finding a capacitor that will work best with your transformer? I'm sure many people here have varying opinions on what works best so I would like to hear them. I've found length to width ratios of 4/1 or 3/1 but nothing saying "x diameter works best with y setup." The best answer I've found for the cap question is to consult a tesla coil design program, which is good advice, but I'd like to know the science behind it. Thanks.