4. Detector
While factoring each particular JFET’s characteristics, the physics behind this detector at various signal levels and Q-multiplier amplitude settings looms complex. I’ll just give a hypothesis for some points.
The detector is directly connected to the Q-M tank. To decouple it, I center tapped the main inductor.
A review of regenerative receiver operation
AM
For maximum AM sensitivity on a signal, advance the Q-M amplitude pot until you hear some high pitched AF noise or oscillation. Then slowly lower the Q-M amplitude just enough to eliminate this audio buzz. Instead, for weak signal listening, we may choose to autodyne the signal by further increasing the Q-M amplitude while adjusting the fine tuning capacitor to zero beat.
SSB/CW
For SSB, advance the Q-M amplitude pot until you hear some hiss and then go look for the familiar duck quack of a SSB signal. Fine tune around the signal and tweak the Q-M pot until you hear your desired audio quality. CW is straight forward — just find a nice beat frequency. If you run the RF gain too high, signals may get phase or frequency modulated.
Of course, for AM, or SSB/CW, a delicate interplay exists between the various controls so that you’ll often dial in the best sounding audio by expert knob tweaking — the so-called, “art of regen” stuff that conjures mystique and nostalgia. This takes practice — regen receivers sure engage you!
Regen #5 Particulars
Further muddying the waters, I ran a front panel switch that the places an 8K2 resistor in parallel with the 22K detector source resistor to make a “higher current” setting. In my particular case, that’s ~5974 Ω which sets the JFET source current to 441µA. I’ve probably mislabeled this switch on the receiver’s front panel: it might be better to just say lower current and higher current mode than SSB/AM.When switched to the lower current setting, the measured source current = 138 µA.
