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Re: Pulsed Tube Coils



In a message dated 97-01-10 00:53:38 EST, you write:

<< 
> Mark, John, All,
 
> I have employed audio modulation of a CW vacuum toob TC on several 
> occasions.  The straight forward feed back coil regenerative triode 
>oscillator with grid leak bias responds well if run from a well 
> filtered DC HV supply and powered through a transmitteer type plate 
>modulation transformer with a big audio amplifier sized to deliver 
> 50% of the average oscillator plate input power (just like some commercial
AM 
>broadcast band transmitters). 
>snip 
 >Most recently I introduced audio modulation into my 1 kW vacuum tube 
 >TC while it was powered on full wave rectified, filtered DC by placing the
high
> impedance secondary winding of a step up transformer (like a single ended
>class-A plate circuit to voice coil audio transformer) in series in the grid
leak bias
> circuit of the TC.  What I got was negative modulation, i.e., maximum
modulation
> signal amplitude resulted in the smallest output spark.  This technique is
best
>used with triodes and works not too bad.  John is quite correct that the
sound 
 >comes from the expanding/contracting plasma interaction of the output 
>fuzz-ball.  It is definitely a neato or way-cool effect!
 
 >Mark, using your idea and introducing the audio through a suitable 
>impedance transformer winding on the tube filament (cathode) circuit 
 >to ground could work very well, but the audio horsepower required 
>will be even more than that required by plate modulation.  Here's a 
 >similar but quite novel new idea Mark and John. You might 
 >try operating the toob TC oscillator on unfiltered AC and place an 
 >SCR into the cathode circuit.  Once turned on the SCR will stay 
> conducting until the 60 Hz power reversal shuts it off, but you could 
 >gate the turn on time with an audio signal much like a lamp dimmer 
 >application.  If one of you or anyone else tries this, let me know 
>how it works out. 
>  snip
 >I have had plans to attempt voice modulation of the output lightning 
> storm from a disruptive discharge TC for some time now and know 
> exactly how I'm going to attempt it once I finally 'get a round 
 >tuit'.  For now I'll only share that my proposed technique recognizes 
> Niquist's Theorem for audio sampling rate and will necessarily employ 
>a rapid rotary break to sample the audio spectrum where most energy 
>in human speech is concentrated.  This should produce an amazing stage
effect.
 >snip
 
>rwstephens
  >>

Robert,

Thanks for the informative post, it's good to hear from someone who's done
this type of work.  I just happen to have some SCRs....hmmm. 

Your coronatron seems like a real powerhouse!  I'm  looking forward to your
results.

Safe and effective coiling,

John Freau