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 made by an electronic device called a transmitter connected to an antenna. Another antenna connected to a radio receiver can pick up these waves. This simple idea lets radio be used for many different things.

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

Radio communication is used in many everyday technologies. It works in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication. In systems like GPS and VOR, radio signals help find a location by measuring how long it takes for signals to travel 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 happened in 1886. German physicist Heinrich Hertz proved that radio waves exist. Italian inventor Guglielmo Marconi built the first long-distance radio system in the 1890s. The first commercial radio broadcast was on November 2, 1920. Election results were shared with listeners by a station called KDKA. Today, international agreements help different technologies 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 by scientist Alexander Graham Bell.

After Heinrich Hertz discovered radio waves in 1886, these waves were called Hertzian waves. Early radio systems, made by Guglielmo Marconi in the 1890s, used radio waves to send telegraph messages. These were known as wireless telegraphy. Over time, the simpler word radio became common. By 1904, the British Post Office started using "Radio" in their instructions, and by 1906, an international agreement 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 started when James Clerk Maxwell showed that electricity and magnetism could travel as waves. Heinrich Hertz tested this and made radio waves.

Guglielmo Marconi was the first to use these waves to send messages far away. By 1920, radio could share live events, like election news, with many people.

Principles

Radio waves are made when electric charges move fast, like electrons going back and forth in a metal part called an antenna. These waves go through the air and can carry information far away.

Radio waves move at the speed of light in empty space and can go through many things, like walls and trees. This makes them helpful for talking to each other. They can also bend around objects and work in different weather, so we can use them for things like radio and television.

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 goes to a radio transmitter, where it changes a carrier wave. The carrier wave is a strong, steady radio signal that can travel far. By changing the carrier wave, the information travels 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 used by many people. If two radios try to use the same frequency, they can mix up each other's signals. To stop this, rules are made to control how radio waves are used. These rules are made by each country's government and a group called the International Telecommunication Union. Governments give permission for radios to send out signals and tell them which frequencies and power levels to use. Some devices, like cell phones and walkie-talkies, can be used without permission but must follow certain rules before they are sold.

Applications

Main article: Applications of radio

Radio has many uses in our daily lives. It lets us listen to music and news on the radio. It helps people talk to each other over long distances. It also sends important information, like weather updates. We use radio in technology such as radar to find objects far away and to control devices from far away.