05-07-2020, 08:39 AM
(This post was last modified: 05-07-2020, 08:46 AM by Murphyv310.)
Interestingly I tried a 10 inch speaker and output transformer yesterday and at least two stations were listenable at a pinch.
Amie you are correct about the lack of a DC path on the detector diode. I have also seen some sets with no DC path on some manuals but the set appears to work fine.
In this case the input impedance to the AF amp is extremely high and even adding a 1 meg grid resistor reduced output greatly, only when the values went above 10 meg did I see any improvement.
The audio stage has very good gain indeed and I suspect that the RF stage with the positive feedback is producing very good gain as well, for an extremely simple TRF the results are spectacular, the current drawn from the 9v supply is tiny (I'll measure it today) and the volume is considerably more than I would have imagined. In fact yesterday when driving the speaker my mobile phone microphone was able to pick the audio up just fine.
Amie you are correct about the lack of a DC path on the detector diode. I have also seen some sets with no DC path on some manuals but the set appears to work fine.
In this case the input impedance to the AF amp is extremely high and even adding a 1 meg grid resistor reduced output greatly, only when the values went above 10 meg did I see any improvement.
The audio stage has very good gain indeed and I suspect that the RF stage with the positive feedback is producing very good gain as well, for an extremely simple TRF the results are spectacular, the current drawn from the 9v supply is tiny (I'll measure it today) and the volume is considerably more than I would have imagined. In fact yesterday when driving the speaker my mobile phone microphone was able to pick the audio up just fine.
