The HamBone

The essence of a "Gennie" is positive feedback of RF to a tuned circuit, where it can be tuned once more to improve selectivity and gain.
The feedback is often provided by a coil inductively coupled to the tuned circuit, often just a simple LC tank.

Here is another approach to providing feedback with a capacitor tap. Cool, huh?
For a full description try: https://techlib.com/electronics/regen.html

Here's a variant on the ticklerless theme:

Can you see why R1 controls RF gain? This circuit should be able to tune more than the 2:1 of the previous post, and might lend itself to simple single coils for different ranges -or why not a switched tapped coil?
There's much more about this radio at http://www.electroniq.net/radio-frequen ... eiver.html

OMG, here's another with a very similar approach. P1 controls regen, similarly to R1 in the previous example. The feedback now comes from a tapped coil.
A full description is at https://rustybolt.info/wordpress/?p=12120