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Re: Character Revisited



11/26/96

Forwarded post 

>>>>

Rick,
  
Sure, no problem.  Please be sure to state that this was very informal 
testing.  I was really trying to prove that tube and transistors could 
each do the job well to an old, die hard tube fan, and just screwing 
about in general.
     
Were I going to publish any of this, I'd want to revisit some of the 
testing, and have learned a bit more about how the RF wattmeter acted 
to less spectrally pure signals, etc.
   
I would not describe these results as definitive, but they did show 
that for the one secondary coil tested, the spectral content had more 
to do with delivered arc length than did the driver technology.
     
In all this messing about, there were two specific drivers that might 
be exceptions, but I suspect this probably had more to do with 
impedance matching than anything else.
     
An argon thyratron made a really frighteningly good driver.  One cold 
winter night we had corona everywhere, while angry masses of plasma 
danced inside the tube. St. Elmo's fire oozed along the plate 
electrode and the ozone grew so thick we pulled the plug for fear of 
damaging the secondary insulation.
     
No attempt was made to measure of control the spectral content, but 
the DC input power was rather low for the display we received. (I 
would not have brought my test equipment NEAR that thing!)
     
A similar display was given by an old diathermy machine that was given 
to me by Bob (Mr. Tesla coil) Golka himself.  This ancient example of 
state of the art electronic snake oil uses a pair of self oscillating 
triodes with exceptionally thick plate structures.
  
While these oscillate at a frequency quite a bit above the self 
resonant frequency of the coil we used, it was quite spectrally broad, 
being a sort of odd, square wave multivibrator circuit.
     
This drivers shows that indeed, the higher the frequency, the longer 
the arc for a given power level.  You know, I was just cleaning up in 
the basement, and I ran across that old diathermy machine chassis. I 
wonder what ever became of that thyratron?
     
This is a guess, but if you were to drive a given coil at it's 
fundamental, and push the even harmonics was up (dV/Dt?) so that there 
were lots of higher frequency harmonics, I think you would find 
greater arc lengths for the same input power.  That's how I recall 
things acting.  It makes some sense on conventional, and less 
conventional levels.

snip . . .
     
Oh yes, the die hard tube fan grumbled a lot, and pointed out that the 
thyratron and diathermy machines both made more impressive displays, 
with less circuitry than did ganged solid state amps.  The primary 
power levels were a different story, so we agreed to disagree.  He 
forever did gain a respect for Phase Linear power amps though, even of 
here chock full of bipolar transistors! 


>>>>>>

______________________________ Reply Separator 
_________________________________
Subject: Re: Got your emails.
Author:  rwall-at-ix-dot-netcom-dot-com (Richard Wayne Wall) at SMTP
Date:    11/23/96 7:18 AM


11/22/96
     
    
May I forward portions of your posts to the Tesla List.  I think they 
would be extremely intereted in your experiments mimicing gap 
discharges with solid state drivers in TCs and getting similar outputs 
from the secondary.  
     
This is original research and you might consider publishing.  But, I 
know your time constraints.
     
RWW