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Audio Frequency responce of a VTTC plasma discharge
Original poster: "David Trimmell by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>
I have completed a series of simple tests to determine the frequency
response on the CW plasma discharge of a VTTC. First I obtained a old Bogen
PA amp (yeah! no more fussing with that tube amp, at least for now!), 35
watts RMS with 25V 4.5, 8, 16, 18 (?) ohm output also a couple 70V 140 ohm
outs, all with many inputs, etc.
First: I ran the output from the Signal Generator (Thanks Terry!) into the
Amp, with every thing in the operational setup, using the 16 ohm output of
the Amp (no power to the tubes!), I placed the scope probes across the
output of the audio coupling (voltage/signal boosting transformer). This
was too test the distortion/clipping of the audio signal.
Results: <60 Hz signal caused the amp too distort/cutoff at 500V P/P; >100
to 10K Hz it would distort at 1000 to 1100V. Knowing the limitations of my
setup is essential.
Second: I fired up the coil (scope probe removed), running with 1.5 to 2.5
inch discharge, I fed the amp with Audio F signals from the Sig Gen
(keeping output well below the above shown Voltage limitations). Using my
ears and a scope with probe/antenna to detect results.
Results: below 100 Hz distortion is very evident and will easily cut off RF
output (flat line...) low volume output (wish I had a DB meter!), no live
Voltage measurement. 100 to 300 Hz was similar, but volume would triple
before flat line. >1KHz I could do close to setup max before flat line. (I
need many more data points here).
There is a Equalizer on the Amp that lets me adjust the output on the 80,
300, 1K, 3K, and 10K Hz bands. This also shows best response with the 80 Hz
all the way down, the 300 Hz halfway down(+10 to 0 to -10), -5, and other
bands at 0. This was tested with Music (Rock and Classical). One other
thing to note is that the larger the output of the coil, the better the low
frequency response, but only slightly.
This is all done with the design shown on my web site, except the secondary
is 4"x16" #28, and tuned to about 380 KHz. www.ChaoticUniverse-dot-com
Has anyone else tried Grid Audio modulation of a VTTC? Or Audio modulation
of a SSTC? I am really interested in verifying my suspicions regarding
Frequency response of the plasma/spark discharge. Possibly something else
is happening? Plate modulation (don't have that mongo amp!), or SSTC
testing would verify?