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Hi all,

I am trying to understand the circuitry, which controls the bias of the PA. My reference circuit diagram is dated 8/14/10.
What I am assuming: Q5 / BS170 controls the 2N2222 collector supply voltage by acting as a variable voltage divider R37-FET-R41.
What I don't understand is the function of D3 and Q4, they seem to control the gate bias of Q7 and Q8 thru T3.
Would highly appreciate any help.

Thanks and best 73
Felix, DB9FN

What I don't understand is the function of D3 and Q4, they seem to control the gate bias of Q7 and Q8 thru T3.

Felix,

There is a description here

73 Alan G4ZFQ

Great, Alan! This is exactly what I was looking for.
Thanks for ufb help.

Best 73, Felix DB9FN