Regen Receiver 3.5-7.5MHz PCB kit and controls. AM/CW/SSB. Kit by Spectrum.

This version is for 3.5-7.5MHz. The circuit uses a field effect transistor as an infinite impedance detector which is fed from a tuned circuit coupled to a Q multiplier circuit. When the Q multiplier is close to oscillation it considerably enhances the sensitivity of the radio for the reception ofamplitude modulated signals.

eBay