Re: PlasmaSonic II tweaking

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com>
 >
 > Dan, anyone ever try to modulate a SSTC using a series modulation
 > transformer? Similar to VT plate mod. ??? Just curious. Now I was told
 > many years ago that one could never get (AUDABLE) audio using a grid to
 > mod a VTTC. I proved that incorrect. I still think that with your
 > success with the PlasmaSonic you should still continue the Plate
 > modulated VTTC. I always Knew grid mod was difficult, but it does work.
 > But plate mod may be the holly grail of Vacuum plasma audio dynamics? I
 > have once heard the great discharge of a AM radio station tower, so I
 > know that decent plasma to air, audio dynamics exists. But yes, I will
 > slowly progress to the second Plasmasonic, without (hopefully) more FET
 > deaths...
 >
 > What mods would it take to get pure un-modulated RF? I am still trying
 > (failing?) to understand a H-Bridge! Could one use a 555?
 >
 > Thanks for any assistance.
 >
 >   David Trimmell

	100% plate modulation will produce a lot more power output, but some of
that power must come from the modulator itself.  Grid or cathode
modulation is commonly known as "efficiency modulation", not a good term
but one indicative of its inefficiency.  With plate modulation the peak
voltage on the RF tube is twice the plate supply voltage and the peak
power output is about 4 times as much.  Look up plate modulation in a
handbook and you'll get lots more information.

Ed

	On the subject of plasma tweeters I have a grim story to repeat.  I
used to have a technician working for me who had been with one of the 50
kW SW broadcast stations (WRUW?) in the general Boston area.  One day he
was sent into the antenna switching yard where open-wire feeder lines
could be switches various directional antennas.  Someone goofed, power
was still on, and he walked into one of those lines.  He said it drew a
1 foot arc "out of his stomach" and that, before he could jump away, he
could hear loud audio from the modulation on the RF!  Left a horrid scar
on him but he survived OK.