Kristallradioempfängern

Kristallradios, also known as crystal radios, are simple radio receivers that do not require an external power source or batteries. They operate by harnessing the energy of radio waves themselves. The fundamental components of a crystal radio include an antenna, a tuning circuit, a detector, and an earphone. The antenna picks up radio waves, and the tuning circuit, typically consisting of a coil and a variable capacitor, allows the user to select a specific radio frequency. The detector, historically a galena crystal and a fine wire (often called a "cat's whisker"), rectifies the radio signal, separating the audio information from the carrier wave. This processed audio signal then drives a high-impedance earphone, which converts the electrical signals into sound.

The simplicity and lack of power requirements made crystal radios popular for early radio enthusiasts and in areas where electricity was unavailable. Their audio output is generally low, necessitating the use of sensitive earphones. While largely superseded by more advanced transistor and digital radios, crystal radios remain an educational tool for understanding basic radio principles and are a popular project for hobbyists and students. The term "Kristallradio" is the German word for crystal radio, reflecting the early development and widespread use of this technology across Europe.