VTTC 1 - Dual 811A
This was my very first documented VTTC. It used a pair of 811A vacuum tubes purchased from RF Parts. At the time I considered this coil to be a great success, but looking back I think even longer sparks were possible from the pair of tubes. Never the less, I think it is a good design and is well suited for new-comers. The maximum spark length was 7" from a guessed input power of 500W. This was a very reliable setup and could run indefinitely without the tubes overheating. The schematic below includes all the needed specs on this coil.