Building a crystal radio using an electro magnet and a germanium diode requires several components, including a long wire antenna, high impedance headphones, and a capacitor for tuning. Germanium diodes are preferred due to their lower forward voltage compared to silicon diodes. Users have shared personal experiences of constructing crystal radios, highlighting the simplicity and battery-free operation. There is concern about the future of analog radio as the industry moves towards digital formats, potentially rendering crystal radios obsolete. Overall, the discussion emphasizes the nostalgic value and basic construction of crystal radios.