02-28-2021, 09:11 PM
More thoughts on the detector. Maybe this will help.
Correct me if I am wrong,
The detector is not operating as class A. It just occurred to me that the detector is bias just at cutoff with no signal coming from the IF. That would mean no plate current. When the IF hits the grid only the positive going half of the signal turns on the tube thus acting as a diode. This is filtered by #16 but only to the point of audio frequencies giving us the recovered audio.
In other words if you ground the grid there should be very little plate current. The positive bias of the cathode resistor should almost cutoff the tube current. There must be some plate current to cause bias on the cathode resistor in the first place. So very little plate current to start with. That's why the plate voltage is so high. Didn't you say there is no signal?
Correct me if I am wrong,
The detector is not operating as class A. It just occurred to me that the detector is bias just at cutoff with no signal coming from the IF. That would mean no plate current. When the IF hits the grid only the positive going half of the signal turns on the tube thus acting as a diode. This is filtered by #16 but only to the point of audio frequencies giving us the recovered audio.
In other words if you ground the grid there should be very little plate current. The positive bias of the cathode resistor should almost cutoff the tube current. There must be some plate current to cause bias on the cathode resistor in the first place. So very little plate current to start with. That's why the plate voltage is so high. Didn't you say there is no signal?
!!!!!!!!!!!!!!!!!!!RESISTANCE IS FUTILE!!!!!!!!!!!!!!!!!!!!!!
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[Image: http://philcoradio.com/phorum/images/smi...on_eek.gif] Chris
