On page 18 of Care and Feeding of Power Grid Tubes (Varian):
"a thoriated filament will produce a specific PEAK emission of about
70 to 100 mA per watt of filament heating power. This is normally 5
to 10 mA of CW plate current per watt of filament power."
The specific peak emission is what is applicable to the parasitic
"theories". That is the absolute maximum emission current available
under any bias voltage condition.
Other tube design and engineering books agree with this, the highest
number I've found is 125 mA per watt.
The CW emission capability of a metal oxide cathode tube is typically
200-300 mA per watt of heater power, about 30 times the CW emission
of a thoriated tungsten tube.
I may be confused, but I thought we were discussing 811's and
73, Tom W8JI
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