[AMPS] Bias for Triode

[Peter Chadwick]

Firson says:

	>In old ARRL Handbook (1969), in chapter Triode Transmitting tube 
	>Datasheet still have 304TL employing for AB1.


The 304TL can be used in Class AB1. However, the data for it is in Class AB1
grounded cathode push - pull audio service. For use at RF, it would need to be
in AB1 grounded cathode, not grounded grid. A pair in either push - pull or
parallel would give around 600 watts out with 2500 on the plate. More power
could be obtained with a higher plate voltage, although you would need to do the
calculations on plate dissipation. It would need about 75 volts rms of drive at
600 watts. Using a 50 ohm resistor from grid to ground would result in a drive
power of about 112 watts; because of the shunting input capacity, probably about
125 watts. Even with a 50ohm resistor to ground, it would really need
neutralising at the higher frequencies. The bias should not be regulated, but
should be from a low impedance supply in case you draw grid current without
meaning to.

It really is not suitable for use in grounded grid.

73

Peter G3RZP



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