Mark said: >What is the use of the "glow" ??? Just wated energy :) In the case of a tantalum anode tube, the glow means that the plate is hot enough to absorb gas - a few metals have this property - so tantalum anode tubes are meant to be run so hot. In any case, there's no more waste of energy than in a tube running at the same efficiency and RF output with no glow. 73 Peter G3RZP