Thanks for the suggestions! I will probably end up making my second coil a four inch one like the one you suggested, but for now I want to see how efficient I can make a tabletop coil so that I can make the rest of my coils as efficient as the tabletop one. I am on a low budget, so I will make a vacuum gap until I can afford a SRSG. the calculations I have used say that an .0088 uF capactior is best, so I was wondering if an .01 uF capacitor would be OK. Also, my local Home Depot doesn't sell 2" aluminum ducting, so I was wondering what material i should use for the toriod. Finally, where could i get all of the parts for the Terry Filter?
Thanks again! Blake
Well either capacitor size you mention should work fine. Just don't make the spark gaps too wide, so the NST is protected. Small capacitors can work well in a coil but will not give very long sparks. For example I have a small coil at my website that uses a 9/30 NST. It uses a rather small 0.00125uF cap. It gives 9" sparks from a 1.5" x 4.5" toroid. I used the bottoms of either plastic 2 liter coke bottles to make the toroid. Not the black plastic, but the clear inner plastic of the bottle. You may be able to use some sort of metal bowl type item as a toroid. I don't know where to get the Terry filter parts. You can use smaller resistors than Terry recommends, they'll just run hotter. I forget how small he said they can actually be.