If you haven't found it already ... here is a really interesting video to watch:https://www.youtube.com/watch?v=BupknhbDlM0
Just started watching him last week! That's quite a coincidence. He's really good at the crystal stuff.
My EE career started with Alfred Morgan... crystal sets, triodes, etc. That got me into ham radio. Wanted to know more about why things worked, so got a BSEE. Morgan is my hero. Rich