To All, I have built a little 6in by 1.5in tesla with a flat spiral primary. I have calculated the windings etc. with tc-cad and they all match (resonant freq. 1.457Mhz). It has a 4in by 1in toroid and runs off a 3kv transformer with a 0.1 uf cap and a 4mm spark gap. I would appreciate any advice on small teslas as the performence is not quite up to scratch. Nick Field