The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com 5" Sparks:  Tesla Oscillator with approx 35W of input power Setup with 38" x 48" masonite posters in the background.  Note the photo in the left background is approximate actual size of the real apparatus. The Pancake coils I have chosen, while side-by-side, are nearly the same physical size as those Tesla used back-to-back in his arrangement. The electromagnet coil I've used is much smaller though, I will try and replicate the large one in the photo. To the right is another collection of "Tesla's Tesla Coils".  We have 5 of these large posters that we use for lectures. Here are the components! Click here for an updated movie! The interrupter mechanism was ceased a bit, but I managed to loosen it enough to have it nearly open to nearly closed.  Depending on the setting of the interrupter, the sparks appear from 4 - 5" on top of the unit.  Even with the dischargers removed, phantom streamers issue from the terminals a few inches perpendicular to the terminals. I used a modern cap.  .5 mfd. Check out the size of the core on the electromagnet! The 3600 turn secondary coils and 24 3/4 turn primary coils are embedded in beeswax.  Finished coils are not more than 6.5" OD! Note the bright sparks in the middle of the sparks! (C) Jeff Behary, 2007, 2008