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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