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Re: Tube coil ideas using 600W tetrodes?
Jim, all,
I also would agree with Rob. Use the tubes as they were intended, and
search for some triodes. I am liking my 833C's, but am limited to only
~2500 watts, so I have yet to try all four paralleled (hard two get two
cherry red at that power, well, maybe not!). Also, the ceramic tubes are
harder to cool, unless you have the proper sockets, chimney, etc. ;-)
I would think one could do a 30" discharge while using less then 2000 watts
power, it is still a goal for myself. The trick is to use ~20-30 PPS
(Staccato), and use "level shifting". The hardest part I have found is to
determine the best grid feed back for a given coil, and impedance matching
primaries, etc. Trial and error is not the most efficient process :-p
Problem is the ARRL Handbook (although, invaluable), and all "radio" theory
goes out the door when designing a "tube coil"... At least that the way it
seems to me, a "novice".
Anybody got some good VTTC "design software"?
Regards,
David Trimmell
Tubin' in Oregon
http://www.pond-dot-net/~davidt
At 11:29 AM 2/11/00 , you wrote:
>Original Poster: "Area31 Research Facility" <rwstephens-at-hurontario-dot-net>
>
>Jim,
>
>I shy away from employing tetrodes in high powered Tesla coil service
>because they are just too much trouble. It is very easy to melt the screen
>grids out of them in a tuning accident. I stick with triodes almost
>exclusively. Besides having to fabricate an extra screen grid supply, you
>really should provide a means of detecting oscillator load variations in
>some sort of a feedback path to correct the screen voltage and therefore
>the SOA of the tetrodes. As you are aware, Tesla coils are certainly a
>extreme example of an RF power source subject to wild load variations.
>
>If your desire is to make a *BIG* vac toob TC, call around your local AM
>and FM radio stations and try to make buddies with someone in their
>engineering staff. You might be able to obtain a 3CX10,000D or better a
>3CX10,000A7 (flying fil. leads) as a serviceable 'pull'. Such a tube can
>make a pole pig work for its reputation.
>
>I have built a unit employing three EEV BR1160 (5 kw dissipation each)
>triodes in parallel that can source lots-o-RF watts in the 80-120 KHz
>region. This machine is affectionately called the ''Coronatron'. Tube
>biasing was easy!
>
>Vac toob TC's is one area where one should follow the KITS principle. Keep
>It Triodes S........!
>
>These ideas represent merely my own opinion. Flames from overheated pole
>pigs driving vac toob powered (any flavor) Tesla coils welcomed!
>
>Robert W. Stephens
>Director
>AREA31 Research Facility
>www.area31-dot-org
>>>>snip<<<<<<