>...vacuum tubes...don't waste power in ionizing.... errrrr. Last i looked 'hot things that glow' had an effective internal resistance, usually symbolized rp (plate resistance) whith a decidedly non zero value. It would take some math to comapre th efficiencies visavis a classi spark gap arrangment.... And the filament power is also required. grins dwp (Who has fallen behind in mail. AGAIN.)