Greetings to all,
As I recall, EIMAC' s "Care and Feeding of Power Grid Tubes" says
that the getter material, if any at all, is in the cathode (filament) of the
tube, not the anode. It is the heating of the filament, containing the
getter material, that causes internal gas to be ionized, emulsified, and
bonded back into the metal of the anode (plate) of the tube. This is why an
operator can "burn" the gas out of an EIMAC tube, but can not, in tubes like
the Penta Labs PL-172, which has no getter material.
With this in mind, the color of the anode (plate) of the tube has
nothing, or very little, to do with "getter action", but rather the thermal
reaction of the metal in the anode to heat. Of course they run with color,
when ran any near their rated plate dissipation.
Also, every tube chart I have looked at (note I did not say all)
shows that third, and fifth, order IMD is better (less) with higher anode
voltages. That is why most amp manufacturers recommend that their amps be
operated with the highest anode voltage offered when operating in SSB.
Lon W. Cottingham
1110 Golden Bear Ln.
Kingwood, TX 77339
281-358-4207
281-795-1335 Cell
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