Hi Michael,The 9/120 NST is a good find! Congrats on that NST! The coil will work great as is, but I would opt for a larger coil size if your up to winding another coil. But do try the 4" x 24" coil first. You might be happy with it as is. However, a larger coil will probably do better overall. Either 6" or 8" would be ideal.
A 6" x 30" coil using 22 awg magnet wire at 1075 turns would be optimum in my opinion for your supply. Coils do better with larger geometry (and I don't mean h/d ratio, although that plays into it also). Mainly larger diameter coils do very well. However, wire size and h/d are part of it.
If you designed your 4" x 24" coil well with top load and cap size, even that coil will do excellent. But, the larger coil will likely do a little better due to it's larger diameter. There is an inductance increase (for same wire size) although I don't believe this is why larger coils do well.
Take care, Bart Michael Bellah wrote:
Hello list,
I have decided to build my first coil and have sourced a NST from a local sign shop. Its rated output at 115v is 9kva/120ma. I was planning on using a secondary coil form around 4x24, but I was also planning on a smaller transformer. I am wondering if I should go to perhaps 6 or even 8 inch diameter due to the 120ma out of the transformer or is this a wash because it is only 9kva out? Thank you in advance for your help.
Michael Bellah
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