Hello, I am a uBitx v5 owner and modder. I am opening this thread again as I am considering placing a p-channel JFET in parallel to the signal entering the 1st IF amplifier as a means to control the RF gain. I am currently trying to figure out a circuit to be added right before the product detector and perform envelope detection on the 2nd IF signal, then use the DC voltage to do AGC.
I have found out by simulation - not built any test jig yet - that the gate voltage to the JFET should range between zero and 5 V in order to control the RF gain as such. However, the envelope detector produces a voltage that is both much smaller and ranges over much smaller values, of the order of mV.
What do you think of that approach? Could that be a good way to have IF-derived AGC on uBitx? How can I use the output of an envelope detector as a way to produce a 0...5 V AGC voltage signal? I'm really stuck on that.
73, George, SV1DEQ
George Metaxas (SV1DEQ)