With room for introducing many improvements, especially a better audio section, this is the most basic REGENERODYNE radio receiver circuit. A simple mixer  stage, the regenerative detector and a one stage audio amplifier triode...
In my latest version the audio module consists of a triode followed by a tetrode... in actual practice a ECL82 or 6BM8.... The power supply is on a separate chassis, and provides regulated DC to the filaments of the regenerative detector. The regenerative detector in the prototype tunes from 2.5 to 4..5 megaHertz.... With a 4 megahertz
crystal in the oscillator feeding the mixer stage, the receiver
tunes from 6.5 to 8.5 mega Hertz. Using a 6 mega Hertz
crystal the radio tunes from 8,5 to 10.5 megaHertz.
The experimental regenerative detector has to be well shielded to avoid picking up direct signals leaking from the antenna into its
basic 2.5 to 4.5 mHz tuning range.... something that can be noticed
at night... Testing many crystals to check other tuning ranges is
a lot of fun.... You may want to add an RF amplifier stage and a dual tuned bandpass input filter to further improve this marvelous little radio....