so ive been slowly working through the Experimental Methods in RF Design book for like two years now and i finally sat down and built a regenerative receiver for the 40m band. used a jfet design i found in an old QST article, wound my own coil on a pvc form with some 26 awg i had lying around. thing actually works which honestly surprised me

my problem is the regeneration control is really touchy. i mean i can get it into oscillation fine and pull in SSB no problem but the sweet spot between just-below-oscillation and full on squealing is like a millimeter of pot travel. ive tried swapping the 100k regen pot for a 10-turn pot and it helped a little but not much. someone mentioned the tickler coupling ratio might be off — i used about a 4:1 ratio primary to tickler which i just guessed at. is there a better starting point for 40m or does it depend on the jfet im using

also running it off a 9v battery right now and wondering if a cleaner regulated supply would help at all or if thats not really where the problem is

yeah the touchy regen thing is just kind of inherent to the design honestly, but 4:1 sounds like you might have too much tickler coupling which can make it snap into oscillation really abruptly rather than sliding in smoothly. i usually start around 5:1 or even 6:1 and wind the tickler in the same direction as the main coil — if you wound it backwards you'll get positive feedback spiking way too hard

the other thing that helps a lot is putting a small series resistor in the regen control circuit, like 2.2k or so in series with the pot, so the bottom of the range isnt at true zero. gives you a little more usable travel at the useful end. some guys also swear by using a vernier dial on the pot even with a regular single turn, just slows your hand movement down mechanically

regulated supply probably wont fix the touchy problem but 9v battery voltage sag as it drains will drift your operating point so worth cleaning up anyway

what jfet are you using? i built something similar a while back with a 2N3819 and had the same snap-through issue, switched to a MPF102 and it was noticeably smoother for some reason. might be totally different in your circuit but worth trying if you have one kicking around in your junk box