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Re: Thanks to John

In a message dated 97-02-11 01:45:42 EST, you write:

<< 
 Subscriber: SSNSanders-at-aol-dot-com Mon Feb 10 22:04:48 1997
 Date: Sun, 9 Feb 1997 14:41:26 -0500 (EST)
 From: SSNSanders-at-aol-dot-com
 To: Tesla-at-pupman-dot-com
 >Subject: Thanks to John
 
>Thanks John Freau for the schematics, they are clear and precise and I will
>have it built as soon as I can presuade Richard Hull to dig down DEEP in his
> ham fest booty for those resistors etc I need, heh heh :) Seriously though,
>you mention a 304TL and that a more powerful tube can be used. What is an
> example of a more powerful tube? What is the most powerful tube that I
could
>use that is obtainable from a tube supplier? Can I parallel morthan one for
a
>longer spark? Im going to go to some expense on this one and I anticipate
the
>end result to be a sight to behold. I will definately send pictures of the
>finished product along with some of the other coils I have.By the way,
 >doorknobs dont have a mica dielectric do they? Probably not as I have a few
> of them and could use them on the tube coil, are they suitable?  Stephen
>Sanders
  >>

Stephen,

Yes, the tubes can be connected in parallel for more power handling
capability, but to really optimize the system, the grid feedback, grid
resistance, tank impedance, etc, should be adjusted when multiple tubes are
used.   Using a microwave oven trans, however, the spark will be limited to
about 12"  even using two tubes, since microwave transformers are somewhat
current limited.  You can knock the shunts out of the transformer (usually,
carefully) and it will give more current, but it will become extremely
inefficient.  If you want longer sparks, for instance, 20 ", a plate
transformer rated at 1 kW at 3 kV or higher is best.  An example of a more
powerful tube is the 833A.  One of these can give a 15 to 17" spark, and 2 of
these tubes in parallel can give a 23" spark.  For best results, match the
capabilities of the tube and the transformer, since either one can limit the
spark.  If you put a 20 kW tube onto a 1 kW transformer, you'll still only
get whatever power the transformer can supply, maybe 2.5 kW or so.
 (non-current limited transformers can usually give 2.5 times their rated
power output in a tube tc circuit, but efficiency will plummet at these
loading levels!)   The key to long tube coil sparks is POWER and plenty of
it, (and tubes that can withstand that power.   I and others have posted the
specs for various tubes over the last few weeks.  I have two 4CX15,000 tubes
that I want to use in a coil, but they'll demand so much power, I'll have to
run the system in a DC pulsed mode to limit the necessary input power!

The doorknob caps are probably ceramic and a little lossy and may run hot,
but they will work until they fail, but I have very limited experience with
doorknob caps.  You could try them and see what happens.  I'm sure there are
people on the list who have tested them extensively.

Happy and new types of coiling,

John Freau