Radios use a tuner circuit that selects a specific frequency from the wide range of radio waves picked up by the antenna. When you turn the dial or use digital buttons, you adjust a circuit that resonates at a particular frequency, effectively filtering out all others. This allows the radio to isolate and demodulate just the desired station.
An antenna is a metallic structure that transmits or receives radio waves. In a receiving radio, the antenna captures incoming radio waves and converts them into electrical signals that the radio can process. The design, length, and placement of the antenna significantly impact reception quality and range.
A crystal radio is a simple, passive AM receiver that doesn’t require a battery or power source. It uses a germanium diode (previously a galena crystal and cat's whisker) to demodulate the signal and extract the audio. It relies entirely on the energy of the received radio signal, which limits its volume and range, often requiring headphones.
Shortwave radio operates on frequencies between 1.6 MHz and 30 MHz. Unlike FM and AM, shortwave can travel very long distances—hundreds or thousands of miles—because it reflects off the ionosphere (skywave propagation). It’s widely used for international broadcasting, amateur (ham) radio, and communication in remote areas.
