Re: [Amps] complicated Bias circuit

[Steve Gorecki VE3RX <ve3cwj@gmail.com>]

Paul, it looks like +ve bias for the cathode of the tube, meaning it is
likely a grounded grid design. R20 is for RX as well, I suspect, providing
further bias to cut off the tube idle current (reduce idle current to a
smaller value). Shorting R20 makes the two zener bias diodes (one selected
of course) set the proper bias for the mode in question.
Steve VE3RX
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