With a fixed bias supply , do you really need a grid resistor as
such ?

Yes, because the fixed bias I have chosen causes the tube to operate in class B,
whilst I wish it to operate in class C.

how is the -Ve bias reaching the grid ? ....with the
cathode earthed .. the fixed bias is 'required' .. I would think for
a given drive level ... increasing the -Ve grid bias would reduce
the conduction angle and slide the stage from class b to c as
the peak drive level would need to overcome the bias to allow
the grid to conduct .. thus the conduction angle is reduced ?

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I agree with your statements but they do not help me much with regard to my
original doubts

The original data has guide lines on the vlaves use in class C
telephony .....

http://www.r-type.org/pdfs/829b.pdf

I have several data sheets for the 828B of various manufacturers but with the
grid resistor value they specify I obtain less output power than with a lower
resistance value

73

Tony I0JX

G ..