2. RF Preamplifier
A common gate amplifier provides reverse isolation. IMO, batteries are best suited for moors and trail. As a dedicated AC power supply enthusiast , I won’t run a regenerative receiver without this isolation to prevent my leaked signal getting 60 cycle modulated and coming back into the receiver antenna port (the cursed common mode hum thang), or perhaps, making the local Hams irate with my QRM.
Thanks to stuff like marijuana grow ops, our neighbor’s switch-mode lights, dimmers and other dumb dumbs; low band reception proves vexing in many bigger cities. I don’t want anything I’ve built adding to the radio listener interference burden.
I agree with the conclusions of regen wizard Charles Kitchin — the preamplifier should run at least 2-2.5 mA source (or emitter) current to help it avoid rectifying strong local stations. Lay the JFET flat side down on the copper board and solder the gate lead as close to the JFET plastic body as possible to squash UHF parasitic oscillations from that lead’s inductance. Further, the drain ferrite bead shown could just as easily be a low-value resistor. For example, 22 to 51 Ω.
The primary, 4 loose turns on a T68-6 = 181 nH (XL = 6.82 Ω at 6 MHz) generates enough of a magnetic field to couple the JFET output to the Q-multiplier (Q-M) tank. My circuit gives a wide range of input signal amplitude variation without too much overall gain, plus light coupling to the Q-M tank.
Above — Close up of RF preamp circuitry and Q-multiplier tank inductor. I wound the 3.34 µH inductor with 22 gauge enamel coated wire on a T68-6 toroid.
