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[Fwd: Re: (Why?) OLD Tubes/Coils]




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Robert, All,

Yes, truly there is another wonderful world of coiling in the tube coil
realm, and you post many good reasons why this is so.  

Having built a number of tube and spark gap coils, I'd like to make one
comment:

Regarding constuction, set up and tuning, I always find tube projects more
difficult and time consuming than disruptive coils.  I'm speaking here about
new designs, not replicating other's designs.  In a spark-gap coil, assuming
an experienced builder and "normal" coil parameters, there are only a few
main things to adjust; gap, ballasting, tune point, and coupling.  And these
adjustments do not tend to interact too much, at least not to a "overly
sensitive" degree.  

In the tube coil on the other hand, especially large (26" to 36" sparks)
ones, adjustment and set up is super-critical.  Yes, a quickly cobbled system
may produce some sort of spark, but optimal performance requires a
time-consuming, trial and error balance of; coupling, tuning, grid feedback,
grid leak resistance, and also calculated or trial and error matching of the
tube to the power level, matching of tube to tank impedance, etc.  If just
one element of this synergistic dance is out of step, the results can be
disasterous -- one eye must be kept on the spark while the other is observing
the tube plates, and all the while the ear is listening for the proper
full-throated "power-roar" which often heralds tube coil synergism and
kick-butt output.

John Freau

<<     -- Tube coils can operate 24-hrs. per day , 7-days per
            week without straining anything.
 
 >        -- It's a different modality - new territory to explore.
 
 >        -- Their relative silence makes them practical in family
            settings; in urban neighborhoods; even in small
            apartments. [Why do you think they call spark-gap
            coils "disruptive"?]
 
 >        -- Co-laterally, the capacitors are much more gently treated
            in a tube coil and stand a chance of lasting =forever=.
 
 >        -- The rf in a tube coil can easily be modulated if desired
 
         -- There's less fabrication involved, size for size.
 
 >       -- Plus, it's much faster to assemble a tube coil and
            get it running.
 
  >       -- They are less finicky, more predictable.  For example
            there's no spark-gap to be unceasingly fiddling with.
 
 >        -- No spark gap means less ozone and nitrogen oxides formed
            during operation.
 
 >        -- No spark gap means less short-wave ultra-violet to hide
            from.
 
  >       -- They can be tuned electronically, if desired, to within
            a  Hertz or so.
 
 >        -- Their operation is less fearsome - so a better thing
            to use in introducing novices to the hobby.  They don't
            look intrinsically dangerous or perhaps as something
            which ought to be illegal.
 
 >        -- They tend to be a better bet for theatrical and classroom
            demos.
 
 >        -- Spark-gap coils are like a fraternity beer-bash; Tube coils
            are a sophisticated cocktail party.   [ Those who prefer
            the one usually wouldn't want to be caught dead at the
            other ]
 
 >   I could go on (and on, and on) but (maybe) you're starting to get the
 >   point.  Tesla coils are a lot like sex -- wild and uninhibited
 >   (and risky) has its rewards, but then again so does just
 >   snuggling up next to a camp fire, holding each other tight, and
 >   gazing at the stars.
 >
  >                                       All coiled up,
 
 >                                       Robert Michaels
  >>

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