Radio

Radio is the technology of communicating using radio waves. Radio waves are a type of electromagnetic wave with frequencies between 3 hertz (Hz) and 300 gigahertz (GHz). These waves are created by an electronic device called a transmitter connected to an antenna, and they can be picked up by another antenna connected to a radio receiver. This basic idea allows radio to work for many different purposes.

An antenna farm hosting various radio antennas on Sandia Peak near Albuquerque, New Mexico, United States

Radio communication is used in many everyday technologies, including radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication. In systems like GPS and VOR, radio signals help determine a location by measuring the time it takes for signals to arrive from known points. Radio also powers remote controls for devices such as drones, garage door openers, and keyless entry systems.

The discovery of radio waves dates back to 1886, when German physicist Heinrich Hertz proved their existence. Building on this, Italian inventor Guglielmo Marconi created the first long-distance radio communication system in the 1890s. The first commercial radio broadcast happened on November 2, 1920, when election results were shared with listeners via a station called KDKA. Today, the use of radio waves is managed by international agreements to make sure different technologies can share the airwaves safely.

Etymology

The word radio comes from the Latin word radius, meaning "spoke of a wheel" or "ray of light." It was first used in communications in 1881 when scientist Alexander Graham Bell used the term radiophone for his optical transmission system.

After Heinrich Hertz discovered radio waves in 1886, these waves were called Hertzian waves. Early radio systems, created by Guglielmo Marconi in the 1890s, used radio waves to send telegraph messages, and were known as wireless telegraphy. Over time, the simpler term radio became common. By 1904, the British Post Office began using "Radio" in their instructions, and by 1906, an international agreement officially used the word radio. The term became popular in the 1920s when radio broadcasting began.

History

Main article: History of radio

Further information: Invention of radio, Timeline of radio, and History of broadcasting

Radio technology began with the work of James Clerk Maxwell, who predicted that waves of electricity and magnetism could travel through space. Later, Heinrich Hertz confirmed this by creating and detecting radio waves in experiments.

Guglielmo Marconi was the first to use radio waves for communication, sending messages over long distances. By 1920, radio had advanced enough to broadcast live events, such as election results, to many listeners.

Principles

Radio waves are created when electric charges move quickly, such as electrons flowing back and forth in a metal conductor called an antenna. These waves travel through the air and can carry information over distances.

Radio waves move at the speed of light in a vacuum and can pass through many materials, like walls and trees, which makes them useful for communication. Unlike other types of waves, radio waves can bend around objects and travel through different weather conditions, allowing us to use them for things like radio and television broadcasts.

Communication systems

Radio communication. Information such as sound is converted by a transducer, such as a microphone, to an electrical signal, which modulates a radio wave produced by the transmitter. A receiver intercepts the radio wave and extracts the information-bearing modulation signal, which is converted back to a human usable form with another transducer, such as a loudspeaker.

In radio communication, information travels through space using radio waves. At the sending end, the information — like sound from a microphone, images from a video camera, or data from a computer — is changed into an electrical signal. This signal is sent to a radio transmitter, where it changes a carrier wave. The carrier wave is like a strong, steady radio signal that can travel far. By changing the carrier wave, the information is carried along with it.

At the receiving end, special equipment picks up these radio waves and turns them back into the original information, whether it is sound, images, or data. Each radio station uses a different frequency, so they don’t interfere with each other. This way, many stations can broadcast at the same time without mixing up their signals.

Band name	Abbreviation	Frequency	Wavelength
Extremely low frequency	ELF	3–30 Hz	100,000–10,000 km
Super low frequency	SLF	30–300 Hz	10,000–1,000 km
Ultra low frequency	ULF	300–3,000 Hz	1,000–100 km
Very low frequency	VLF	3–30 kHz	100–10 km
Low frequency	LF	30–300 kHz	10–1 km
Medium frequency	MF	300–3,000 kHz	1,000–100 m

Band name	Abbreviation	Frequency	Wavelength
High frequency	HF	3–30 MHz	100–10 m
Very high frequency	VHF	30–300 MHz	10–1 m
Ultra high frequency	UHF	300–3,000 MHz	100–10 cm
Super high frequency	SHF	3–30 GHz	10–1 cm
Extremely high frequency	EHF	30–300 GHz	10–1 mm
Tremendously high frequency	THF	300–3,000 GHz (0.3–3.0 THz)	1.0–0.1 mm

Regulation

The airwaves are shared by many users, and if two radio transmitters try to use the same frequency, they can interfere with each other. To prevent this, the use of radio waves is regulated by national laws and an international body called the International Telecommunication Union. Governments license radio transmitters and assign them specific frequencies and power levels to avoid interference. Some devices, like cell phones and walkie-talkies, can be used without a license but must meet certain standards before they are sold.

Applications

Main article: Applications of radio

Radio is used in many ways in everyday life. It helps us listen to music and news on the radio, allows people to talk to each other over long distances, and sends important information like weather updates. It is also used in technology such as radar to detect objects far away and to control devices from a distance.