--- In firstname.lastname@example.org
, "Graeme Zimmer" <gzimmer@...> wrote:
> half way down the page http://crystalradio.net/tubeplans/
> is "Six Volts Work This Blackout Emergency Set" uses two 6G6
> I hope people aren't getting too fed up with all this.
> ............... Zim
Not me, Zim. I find it very interesting (and it's icing on the cake that so many of these low voltage receivers were designed and built by Arthur Miller). The principle seems to be: reduce heater voltage to reduce cathode emission, use the control grid and the screen grid to accelerate what emission there is, thereby allowing the radio to work on exceptionally low B+ voltages, turning the pentode into, in effect, a low mu triode. Regulation of the heater voltage is apparently important, but that's no problem today. I imagine the current drawn by the control and screen grids would not be too much. It's an approach worth playing with. The 6AK6 power pentode and the 6BH6 sharp cutoff rf pentode should be good tubes to experiment with (both have 150mA heaters). Have you built any of these designs? I suspect they might need two stages of audio amplification to get a reasonable amount of headphone volume.