I have fond memories of building my first crystal radio in the 1950s, and I recently came across an old kit that was identical to the one I originally had. Restoring it brought back a flood of memories. Crystal radios were simple devices that used a demodulation scheme to receive AM radio stations. They captured minimal amounts of power from distant transmitters and efficiently converted it into sound without the need for batteries or amplifiers. The key component was the diode, which in my case was a galena crystal, although germanium diodes were later used. Tuning in stations was always an exciting experience, and I was thrilled to find that some vintage-style crystal sets are still available on sites like Etsy. I encourage others to explore the world of crystal sets and share the joy it brings.
https://www.nutsvolts.com/magazine/article/remembering-the-crystal-radio