By comparison, VTTCs seem to have topped out at a 4" x 20" secondary, driven by one to four 833A tubes. The consensus seems to be that you can get just about as good performance from one 833A as with 4 of them, if you design the coil right. Perhaps 36" discharges seem to be the limit for VTTCs on a good day. Is there some physical or electronic limitation to the design and construction of a really big VTTC? With the availability of big surplus power tubes (10 kW or more) on eBay, and the possibility of multiple parallel free MOTs for input power, is there a physical reason why no one has built a 12 x 60 or 18 x 90 VTTC? Ten foot sword like discharges would be neat to watch! Dave
Dave, VTTC's are not as efficient as disruptive coils so you need a lot of power for a given spark length without staccato. Figure spark length inches = 0.5*sqrt input power. So for a 10 foot spark you need to use 60kW without staccato. With staccato you can lower this to 20kW or so for 20PPS sparks. But the peak power still needs the 60kWs in a sense. It would help to used filtered DC but it gets more dangerous and harder to staccato control. It can be done nicely using large tetrode tubes. Using filtered DC you get some storage power in the filter caps. This is similar to the DC disruptive compound storage staccato system that I built way back when. But in this case it's applied to a VTTC. I tried that too on a small scale back then. There is no theorical limitation on VTTC output if you have enough power to run the system.John