[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Tube Tesla Coil
Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>
In a message dated 10/28/01 11:09:23 PM Eastern Standard Time,
tesla-at-pupman-dot-com writes:
> where on Earth does one find these amazingly rare and unusual Vacuum
> Tubes? What types should one look for, and what differentiates one (Tesla
> applicable) tube from another? Also, I would like to ask why does the
output
> from VTTC's vary so much from that of a traditional SGTC's? Thanks for the
> help friends.
> Best Regards,
> Rick Harris
Rick,
Welcome to the world of tube coils.
Tubes can be bought at a hamfest, at ebay, from surplus houses,
etc. The proper tubes are high powered transmitting or industrial
triodes, or tetrodes. (triodes are prefered). They should be rated
for an RF output of 200 to 1000 watts each, or so. Tubes having
graphite plates are especially robust. Some tubes are, 833A,
833C, 813, 811, 304TL, 4-400A, 3-500Z, 4-1000, 3-1000Z, 810,
805, 845, 4-250A, HF-300, etc. In many cases, one tube can
simply be removed, and another type of tube substituted. In some
cases the filament voltage will need to be adjusted, or other
parameters changed slightly.
Tube coils are Class C power oscillators coupled to a resonator.
They are much less "efficient" at producing long sparks than
a spark gap coil, because there is no real storage of energy
with quick release as occurs in a spark gap TC. The sparks
are fed in real time from the power supply as CW energy,
similar to a radio transmitter. In slow motion video, tube coil
sparks look very similar to normal spark gap TC sparks. Tube
coils are tricky to set up correctly.... takes some time
fiddling with the various interacting parameters.
AC operation gives long sparks, filtered DC operation gives very short
plasma-like sparks. Pulsed (staccato) mode is interesting and
"efficient".
Cheers,
John