More Regen Radio Designs
Some regenerative radio circuit designs based on the "noisy regen" circuit.
Noisy Regen circuit with a sensitive AM detector circuit based on a current mirror. You can add a decoupling capacitor (100n) between the collector and emitter of Q3 though that may cause audio instability. C2 is optional at higher frequencies (>3MHz.) A disadvantage of the circuit is the low input impedance of Q1 loads the tuned circuit L1 C1 and the tuned circuit is directly connected to a number of semiconductor junctions reducing frequency stability and SSB reception clarity.
A slightly preferred version, though an exact current mirror match between Q3 and Q4 is off the table.
An Armstrong oscillator version of the Noisy Regen circuit that solves impedance matching and other problems.
A Vackar oscillator version that allows the same easy band switching as the original Noisy Regen circuit.
C1 and C2 are optional, removing C1 reduces the chances of any RC constant unwanted audio oscillation but technically is a slightly negative choice. Depending on the bandwidth of the following audio amplifier stage C2 can be omitted, or you could directly replace R4 with headphones.