Radio

Radio refers to the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. However, in general usage the term "radio" refers to the radio receiver, a device used to receive radio broadcast and programming.

Analogue audio radios are of two types, AM (Amplitude Modulation) and FM (Frequency Modulation). AM radio was dominant during the first two thirds of the 20th century and even in the 21st century remains widely used. It detects amplitude variations in the radio waves at a particular frequency, which it then amplifies to drive a loudspeaker or earphones. FM radio employs a special detector for FM signals and exhibits a phenomenon called capture, where the tuner is able to clearly receive the stronger of two stations being broadcast on the same frequency. Thus FM is able to provide high-fidelity sound over broadcast radio. Most radio sets offer both AM and FM. Earlier radios were bulky, but with the advent of solid-state transistors, they shrank and became portable. Both AM and FM portable radios were widely available. In the last decade, digital radio (especially DAB radio) has been a major innovation. This technology uses digital signals, and as such provides higher fidelity, more stations and more resistance to noise, co-channel interference and multipath.

Before the advent of TV, which is supposed to have "killed off" the radio, the radio was the dominant home entertainment medium. In the Western world, the era from the 1920s to the 1950s is seen as the Golden Age of Radio, after radio was moistly relegated to musical roles. Due to their cultural significance, radios from the classic, vintage and retro eras are well-sought after by collectors. Rare good condition fully working radios are in extreme demand, as these are seen as tributes to the Golden Age of Radio.