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#24
August 10th 03, 10:17 PM
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Jerry Avins wrote:
Rob Judd wrote: ... Open-air triode?? Do tell, you have me fascinated... Rob I wrote of it before, so I'll be brief and hope I'm not boring. An open-coil hot plate with a ceramic holder to support and contain the nichrome element as filament*. Topped with galvanized window screening, the zinc removed with muriatic acid so as not to noxiously sublime, resting on the ceramic as (literally!) grid. Small glass beads -- around 1/16" -- scattered on it to create a gap and hold the screening flat. Atop that, a pie tin weighted with cooling water to serve as (literally!) plate. With 700 volts on the plate, I got measurable current on my 1000 ohm/volt meter. At -90 volts on the grid, the current was too small to read. The gain was enough to sustain oscillation. Très bizarre! Rob |
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