A voice beyond the room.

Two kinds of wave

The sound from a radio’s speaker is a mechanical vibration in the air. The signal arriving at its antenna is an electromagnetic wave. The receiver selects a signal and recovers the audio information; the speaker turns an electrical signal into sound.

What AM and FM mean

In amplitude modulation, or AM, audio information changes the amplitude of a carrier wave. In frequency modulation, or FM, it changes the carrier’s frequency. Your receiver demodulates that changing signal to recover the programme.

Listening together

The BBC began daily transmissions from London’s 2LO studio on 14 November 1922. Broadcast radio made a shared appointment out of sound: people in different homes could hear the same performance or bulletin at the same time.

Different routes to your radio

Analogue broadcasts, digital broadcasts and internet streams deliver audio in different ways. Internet radio uses a network connection rather than reception of a local broadcast signal. A device labelled “digital” is not automatically able to receive every service: check its supported formats and your local coverage.

The pleasure of a familiar voice

Sometimes the fascination is technical. Sometimes it is the voice that keeps you company while you make tea, work in the shed or drive home. Radio’s history is a history of inventions and of small daily rituals.