Been playing around with crystal radios lately. I have a loose coupled radio that consists of a pre-selector tuned circuit, a detector with a 1N34 germanium detector than can be switched out to allow external detectors to be used with the tuning circuits. Lastly, I have a wave trap tuned circuit that can be used to null out strong adjacent signals that might otherwise swamp the desired signal. These three modules are all built up in separate boxes and just placed near each other to couple together as strongly or weekly as desired by just varying the distance between them.
Now I am playing around with point contact semiconductors. This one is galena though I have some iron pyrite I would like to try as well.
I have built a few "fox-hole" receivers using the old blue double edge razor blades and a pencil but never got a chance to play around with point contact rectifiers made from minerals until now. Should be fun.