Etienne,I've found like many others here that spark gap and top load are infinitely important to a well functioning coil. Grounding is not so important to performance, as it is to coil longevity (transformers will break down from RF injected into the supply) and of course the safety of electronics on the other end of the line. An ARSG should help a lot, John Freu figured out a formula of how to size your top load, it is approximately .5 - .9 * SQRT of input watts = capacitance in pF for best performance, this is likely based in part off of the "standard" geometries we use (4.5/1 ratio, 1000-1500 turns, etc...) Just my two cents, others should have proper advice like gap designs etc.
Scott Bogard. http://bogard.110mb.com/TeslaCoil.htm On 3/12/2011 8:06 PM, Etienne Dreyer wrote:
Hi gang, I've just completed a coil, but am not getting the spark lengths that I expected. I am only getting weak 20" max, whereas I saw from sites like loneoceans and greg's garage tesla that TCs very similar to mine easily make 3ft and beyond. Could you guys give some suggestions on what I could do to get longer sparks? Here are some of my specifications: It is tuned Dual mot with voltage doubler 4" x 18" (actual coil length) secondary wrapped with 26AWG 10 turn primary 45nF @ 20KV capacitor It is not well grounded- simply a sheet of aluminum foil on the ground It does not have a very large toroid - 3" air duct with diameter of 13" Single static spark gap (I'm going to upgrade to a ARSG) Could the latter three issues be making such a big deal? Very much appreciated, Etienne _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla