[AMPS] Re: Variable Screen Voltage!

[Peter Chadwick]

Colin says:

>Any comments about whether this would work.  Since the manufacturer does
not
>provide data for this operation, should it not be done.  Is this the 300
mpg
>carb that Rich says is impossible?  Since the screen was varied at one
>point, is it incapable of working? 

If you go back to my favourite work (Pappenfus et al) he goes into this into
some detail. He says 'tetrode tubes can be used in cathode-driven
amplifiers. The power gain is considerably higher (than zero bias triodes)
and is in 20 to 50 region.'

Then there's semi and super cathode driven, where some RF is applied to the
grid as well.


	>However, the same negative feedback could be introduced into a grid
driven,
	>grounded cathode design.  In fact, simply installing a resistor in
the cathode of a 
	>grid driven circuit introduces negative feedback.

	I'm not happy about just a resistor - I use a resistor (about 8.2
ohms 5 watt carbon)with an RFC  across it to prevent 
	bias shift at envelope rate.  But sure it works - and well. But the
basic NFB idea is fine.

	73

	Peter G3RZP



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