Jim w8zr wrote:
"Seems to me this problem may not be so troublesome......"
I have to agree with Jim on this, for various reasons:
There is no reason why a DC filament supply should not be centre tapped, most
simply with a resistive bridge;
The bias on the tube is related to the average of the emission over the whole
of the filament, and this is static with a DC filament supply;
Those of us who are old enough will remember battery tubes (such as the 1T4 and
many others). These (obviously) had a DC filament, and significantly an HT
voltage which was sometimes as low as 22.5V. Any problems due to a voltage
gradient along the filament would likely be much worse than with a power tube
with several kV on the plate. Yet they worked;
And most significantly. I cannot find any recommendation by Eimac or other tube
manufacturers against using DC filament supplies. This is despite their
specifications going into great detail about other matters such as permissible
filament voltage variation.
73 Roger
VE3ZI
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|