01-06-2012, 03:33 PM
(01-06-2012, 01:23 PM)AlanBeckett Wrote: It looks to me as though the pot simply varies the bias on the 6BA6 . . .
Why it's returned via the Aerial coupling winding I couldn't say.
Alan
That pot. is the circuit designer's idea of an R.F. gain control. With strong signals arriving at the aerial, the R.F. amp. needs a larger -ve bias that when weak signals are received. So with strong signals, the wiper of the pot is towards chassis / ground. In this condition, the pot. also attenuates the level of the aerial signal reaching the R.F. amp. For weak signals, the inverse: less bias; less attenuation. Hence, the pot. does double-duty as an R.F. gain control.
Al.
