He offered this as an option.
The first step should be to look at how a Super Regen works.
Ok the regen is oscillating and the quench breaks those oscillation up. The high frequency spurts are above our hearing range.
Input a modulated signal and the spurts are modulated at and audio rate. (follows the envelope.)
Now the original question. Can it be done with a FET?
I'm using a 2SK669 MOSFET. I bought a reel at 2 cents each so this is my go to MOSFET. I think a 2N7002 would be a close match. Anyway as you can see I used a transformer with three windings.
I adjusted the coils a little to see how it effected the circuit.
I think a pot across the feed back coil would be a good option.
You can see the coil on the gate is 1 millihenry. I wound a piece of wire about 24" long on a core (blue) and it was 1.8 millihenry. Putting a pot across the feedback coil would allow adjusting the circuit with a toroid core coil. So the original question, is it doable? The answer would be found by trying it.
This circuit would only require the input tank to be adjustable. The quench circuit could be fix tuned and the feedback could be adjusted with a pot.
EDIT:
The blue coil frequency response is up to 1Mhz.
The jfet has intrinsic diode between gate and source, so as oscillations build up in jfet circuit, oscillation stops. The mosfet has no such diode, so mosfets can't be used as direct replacement in jfet circuit. Compare senstivity of your mosfet/jfet circuits. The RF noise spectrum of oscillator has particular shape that coincides with best sensitivity.
ReplyDelete