Last updated
A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US Radio towers on Sandia Peak - closeup.jpg
A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US

Radio is the technology of communicating using radio waves. [1] [2] [3] Radio waves are electromagnetic waves of frequency between 3  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.


In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In radio navigation systems such as GPS and VOR, a mobile navigation instrument receives radio signals from navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless radio remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device.

The noun radio is also used to mean a broadcast radio receiver.

The existence of radio waves was first proven by German physicist Heinrich Hertz on 11 November 1886. [4] In the mid 1890s, building on techniques physicists were using to study electromagnetic waves, Guglielmo Marconi developed the first apparatus for long-distance radio communication, [5] sending a wireless Morse Code message to a recipient over a kilometer away in 1895, [6] and the first transatlantic signal on 12 December 1901. [7] The first commercial radio broadcast was transmitted on 2 November 1920, when the live returns of the Harding-Cox presidential election were broadcast by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA. [8]

The emission of radio waves is regulated by law, coordinated by the International Telecommunication Union (ITU), which allocates frequency bands in the radio spectrum for various uses.


The word "radio" is derived from the Latin word "radius", meaning "spoke of a wheel, beam of light, ray". It was first applied to communications in 1881 when, at the suggestion of French scientist Ernest Mercadier  [ fr ], Alexander Graham Bell adopted "radiophone" (meaning "radiated sound") as an alternate name for his photophone optical transmission system. [9] [10]

Following Heinrich Hertz's discovery of the existence of radio waves in 1886, the term "Hertzian waves" was initially used for this radiation. [11] The first practical radio communications systems, developed by Guglielmo Marconi in 1894–1895, transmitted telegraph signals by radio waves, [4] so radio communication was first called "wireless telegraphy". Up until about 1910 the term "wireless telegraphy" also included a variety of other experimental systems for transmitting telegraph signals without wires, including electrostatic induction, electromagnetic induction and aquatic and earth conduction, so there was a need for a more precise term referring exclusively to electromagnetic radiation. [12] [13]

The French physicist Édouard Branly, who in 1890 developed the radio wave detecting coherer, called it in French a radio-conducteur . [14] [15] The radio- prefix was later used to form additional descriptive compound and hyphenated words, especially in Europe. For example, in early 1898 the British publication The Practical Engineer included a reference to "the radiotelegraph" and "radiotelegraphy". [14] [16]

The use of "radio" as a standalone word dates back to at least 30 December 1904, when instructions issued by the British Post Office for transmitting telegrams specified that "The word 'Radio'... is sent in the Service Instructions". [14] [17] This practice was universally adopted, and the word "radio" introduced internationally, by the 1906 Berlin Radiotelegraphic Convention, which included a Service Regulation specifying that "Radiotelegrams shall show in the preamble that the service is 'Radio'". [14]

The switch to "radio" in place of "wireless" took place slowly and unevenly in the English-speaking world. Lee de Forest helped popularize the new word in the United States—in early 1907, he founded the DeForest Radio Telephone Company, and his letter in the 22 June 1907 Electrical World about the need for legal restrictions warned that "Radio chaos will certainly be the result until such stringent regulation is enforced". [18] The United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms "wireless telegraph" and "wireless telegram", by 1912 it began to promote the use of "radio" instead. The term started to become preferred by the general public in the 1920s with the introduction of broadcasting.


See History of radio, Invention of radio, Timeline of radio, History of broadcasting

Electromagnetic waves were predicted by James Clerk Maxwell in his 1873 theory of electromagnetism, now called Maxwell's equations, who proposed that a coupled oscillating electric field and magnetic field could travel through space as a wave, and proposed that light consisted of electromagnetic waves of short wavelength. On 11 November 1886, German physicist Heinrich Hertz, attempting to confirm Maxwell's theory, first observed radio waves he generated using a primitive spark gap transmitter. [4] Experiments by Hertz and physicists Jagadish Chandra Bose, Oliver Lodge, Lord Rayleigh, and Augusto Righi, among others, showed that radio waves like light demonstrated reflection, refraction, diffraction, polarization, standing waves, and traveled at the same speed as light, confirming that both light and radio waves were electromagnetic waves, differing only in frequency. [19] In 1895, Guglielmo Marconi developed the first radio communication system, using a spark gap transmitter to send Morse code over long distances. By December 1901, he had transmitted across the Atlantic ocean. [4] [5] [6] [7] Marconi and Karl Ferdinand Braun shared the 1909 Nobel Prize in Physics "for their contributions to the development of wireless telegraphy". [20]

During radio's first two decades, called the radiotelegraphy era, the primitive damped wave radio transmitters could only transmit pulses of radio waves, not the continuous waves which were needed for audio modulation, so radio was used for person-to-person commercial, diplomatic and military text messaging. Starting around 1908 industrial countries built worldwide networks of powerful transoceanic spark transmitters to exchange telegram traffic between continents and communicate with their colonies and naval fleets. During World War 1 the development of continuous wave radio transmitters, rectifying electrolytic, and crystal radio receiver detectors enabled amplitude modulation (AM) radiotelephony to be achieved by Reginald Fessenden and others, allowing sound (audio) to be transmitted. On 2 November 1920, the first commercial radio broadcast was transmitted by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA featuring live coverage of the Harding-Cox presidential election. [8]


Radio waves are radiated by electric charges undergoing acceleration. [21] [22] They are generated artificially by time varying electric currents, consisting of electrons flowing back and forth in a metal conductor called an antenna. [23] [24]

As they travel farther from the transmitting antenna, radio waves spread out so their signal strength (intensity in watts per square meter) decreases, so radio transmissions can only be received within a limited range of the transmitter, the distance depending on the transmitter power, the antenna radiation pattern, receiver sensitivity, noise level, and presence of obstructions between transmitter and receiver. An omnidirectional antenna transmits or receives radio waves in all directions, while a directional antenna or high-gain antenna transmits radio waves in a beam in a particular direction, or receives waves from only one direction. [25] [26] [27]

Radio waves travel at the speed of light in vacuum. [28] [29]

The other types of electromagnetic waves besides radio waves, infrared, visible light, ultraviolet, X-rays and gamma rays, can also carry information and be used for communication. The wide use of radio waves for telecommunication is mainly due to their desirable propagation properties stemming from their large wavelength. [24]

Radio communication

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. Signal processing system.png
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.
Comparison of AM and FM modulated radio waves Amfm3-en-de.gif
Comparison of AM and FM modulated radio waves

In radio communication systems, information is carried across space using radio waves. At the sending end, the information to be sent is converted by some type of transducer to a time-varying electrical signal called the modulation signal. [24] [30] The modulation signal may be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal consisting of a sequence of bits representing binary data from a computer. The modulation signal is applied to a radio transmitter. In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency, called the carrier wave because it serves to "carry" the information through the air. The information signal is used to modulate the carrier, varying some aspect of the carrier wave, impressing the information on the carrier. Different radio systems use different modulation methods: [31]

Many other types of modulation are also used. In some types, a carrier wave is not transmitted but just one or both modulation sidebands. [33]

The modulated carrier is amplified in the transmitter and applied to a transmitting antenna which radiates the energy as radio waves. The radio waves carry the information to the receiver location. [34] At the receiver, the radio wave induces a tiny oscillating voltage in the receiving antenna which is a weaker replica of the current in the transmitting antenna. [24] [30] This voltage is applied to the radio receiver, which amplifies the weak radio signal so it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. The modulation signal is converted by a transducer back to a human-usable form: an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. [31]

The radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter's radio waves oscillate at a different rate, in other words, each transmitter has a different frequency, measured in hertz (Hz), kilohertz (kHz), megahertz (MHz) or gigahertz (GHz). The receiving antenna typically picks up the radio signals of many transmitters. The receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. A tuned circuit (also called resonant circuit or tank circuit) acts like a resonator, similar to a tuning fork. [30] It has a natural resonant frequency at which it oscillates. The resonant frequency of the receiver's tuned circuit is adjusted by the user to the frequency of the desired radio station; this is called "tuning". The oscillating radio signal from the desired station causes the tuned circuit to resonate, oscillate in sympathy, and it passes the signal on to the rest of the receiver. Radio signals at other frequencies are blocked by the tuned circuit and not passed on. [35]


Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a component C at the carrier wave frequency
{\displaystyle f_{c}}
with the information (modulation) contained in two narrow bands of frequencies called sidebands (SB) just above and below the carrier frequency. Modulated radio signal frequency spectrum.svg
Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a component C at the carrier wave frequency with the information (modulation) contained in two narrow bands of frequencies called sidebands (SB) just above and below the carrier frequency.

A modulated radio wave, carrying an information signal, occupies a range of frequencies. The information (modulation) in a radio signal is usually concentrated in narrow frequency bands called sidebands (SB) just above and below the carrier frequency. The width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth (BW). [31] [36] For any given signal-to-noise ratio, an amount of bandwidth can carry the same amount of information (data rate in bits per second) regardless of where in the radio frequency spectrum it is located, so bandwidth is a measure of information-carrying capacity. The bandwidth required by a radio transmission depends on the data rate of the information (modulation signal) being sent, and the spectral efficiency of the modulation method used; how much data it can transmit in each kilohertz of bandwidth. Different types of information signals carried by radio have different data rates. For example, a television (video) signal has a greater data rate than an audio signal. [31] [37]

The radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. [36] [3] Each radio transmission occupies a portion of the total bandwidth available. Radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. In some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. So there is an incentive to employ technology to minimize the bandwidth used by radio services. [37]

A slow transition from analog to digital radio transmission technologies began in the late 1990s. [38] [39] Part of the reason for this is that digital modulation can often transmit more information (a greater data rate) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. Other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. [31]

Because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum (ultra-wideband) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. [37]

ITU frequency bands

The ITU arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten (10n) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. [3] [40] Each of these bands has a traditional name: [41]

Band nameAbbreviationFrequencyWavelength
low frequency
ELF3–30 Hz100,000–
10,000 km
low frequency
SLF30–300 Hz10,000 –
1,000 km
low frequency
3,000 Hz
100 km
low frequency
VLF3–30 kHz100–10 km
LF30–300 kHz10–1 km
3,000 kHz
100 m
Band nameAbbreviationFrequencyWavelength
HF3–30 MHz100–10 m
high frequency
VHF30–300 MHz10–1 m
high frequency
3,000 MHz
100–10 cm
high frequency
SHF3–30 GHz10–1 cm
high frequency
EHF30–300 GHz10–1 mm
high frequency
THF300–3,000 GHz
(0.3–3.0 THz)
1.0–0.1 mm

It can be seen that the bandwidth, the range of frequencies, contained in each band is not equal but increases exponentially as the frequency increases; each band contains ten times the bandwidth of the preceding band. [42]

The term "tremendously low frequency" (TLF) has been used for wavelengths from 1–3 Hz (300,000–100,000 km), [43] but the term has not been defined by the ITU. [41]


The airwaves are a resource shared by many users. Two radio transmitters in the same area that attempt to transmit on the same frequency will interfere with each other, causing garbled reception, so neither transmission may be received clearly. [36] Interference with radio transmissions can not only have a large economic cost, but it can also be life-threatening (for example, in the case of interference with emergency communications or air traffic control). [44] [45]

To prevent interference between different users, the emission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU), which allocates bands in the radio spectrum for different uses. [36] [3] Radio transmitters must be licensed by governments, under a variety of license classes depending on use, and are restricted to certain frequencies and power levels. In some classes, such as radio and television broadcasting stations, the transmitter is given a unique identifier consisting of a string of letters and numbers called a call sign , which must be used in all transmissions. [46] In order to adjust, maintain, or internally repair radiotelephone transmitters, individuals must hold a government license, such as the general radiotelephone operator license in the US, obtained by taking a test demonstrating adequate technical and legal knowledge of safe radio operation. [47]

Exceptions to the above rules allow the unlicensed operation by the public of low power short-range transmitters in consumer products such as cell phones, cordless phones, wireless devices, walkie-talkies, citizens band radios, wireless microphones, garage door openers, and baby monitors. In the US, these fall under Part 15 of the Federal Communications Commission (FCC) regulations. Many of these devices use the ISM bands, a series of frequency bands throughout the radio spectrum reserved for unlicensed use. Although they can be operated without a license, like all radio equipment these devices generally must be type-approved before the sale. [48]


Below are some of the most important uses of radio, organized by function.


Broadcasting is the one-way transmission of information from a transmitter to receivers belonging to a public audience. [49] Since the radio waves become weaker with distance, a broadcasting station can only be received within a limited distance of its transmitter. [50] Systems that broadcast from satellites can generally be received over an entire country or continent. Older terrestrial radio and television are paid for by commercial advertising or governments. In subscription systems like satellite television and satellite radio the customer pays a monthly fee. In these systems, the radio signal is encrypted and can only be decrypted by the receiver, which is controlled by the company and can be deactivated if the customer does not pay. [51]

Broadcasting uses several parts of the radio spectrum, depending on the type of signals transmitted and the desired target audience. Longwave and medium wave signals can give reliable coverage of areas several hundred kilometers across, but have a more limited information-carrying capacity and so work best with audio signals (speech and music), and the sound quality can be degraded by radio noise from natural and artificial sources. The shortwave bands have a greater potential range but are more subject to interference by distant stations and varying atmospheric conditions that affect reception. [52] [53]

In the very high frequency band, greater than 30 megahertz, the Earth's atmosphere has less of an effect on the range of signals, and line-of-sight propagation becomes the principal mode. These higher frequencies permit the great bandwidth required for television broadcasting. Since natural and artificial noise sources are less present at these frequencies, high-quality audio transmission is possible, using frequency modulation. [54] [55]

Audio: Radio broadcasting

Radio broadcasting means transmission of audio (sound) to radio receivers belonging to a public audience. Analog audio is the earliest form of radio broadcast. AM broadcasting began around 1920. FM broadcasting was introduced in the late 1930s with improved fidelity. A broadcast radio receiver is called a radio. Most radios can receive both AM and FM. [56]

Transmisor de bulbos AM Elcom Bauer 701 B XEQK.jpg
1100 W AM broadcasting transmitter
2008-07-28 Mast radiator.jpg
Mast radiator antenna of AM radio station
Vintage Panasonic Table Top Transistor Radio, Model R-8, AM Band, 6 Transistors, Made In Japan, Circa 1964 (49305570428).jpg
Panasonic AM radio from 1964
  • AM (amplitude modulation) – in AM, the amplitude (strength) of the radio carrier wave is varied by the audio signal. AM broadcasting, the oldest broadcasting technology, is allowed in the AM broadcast bands, between 148–283 kHz in the low frequency (LF) band for longwave broadcasts and between 526–1706 kHz in the medium frequency (MF) band for medium-wave broadcasts. [57] Because waves in these bands travel as ground waves following the terrain, AM radio stations can be received beyond the horizon at hundreds of miles distance, but AM has lower fidelity than FM. Radiated power (ERP) of AM stations in the US is usually limited to a maximum of 10 kW, although a few (clear-channel stations) are allowed to transmit at 50 kW. AM stations broadcast in monaural audio; AM stereo broadcast standards exist in most countries, but the radio industry has failed to upgrade to them, due to lack of demand. [58]
  • Shortwave broadcasting – AM broadcasting is also allowed in the shortwave bands by legacy radio stations. Since radio waves in these bands can travel intercontinental distances by reflecting off the ionosphere using skywave or "skip" propagation, shortwave is used by international stations, broadcasting to other countries. [58] [59]
KWNR Continental 816R-5B SN 247.jpg
FM broadcast transmitter of radio station KWNR, Las Vegas, with a power of 35 kW on 95.5 MHz
FM broadcasting antenna Willans Hill.jpg
FM broadcasting antenna
Klaudia 801.JPG
AM/FM boombox radio with FM whip antenna
FM car radio's interface display
  • FM (frequency modulation) – in FM the frequency of the radio carrier signal is varied slightly by the audio signal. FM broadcasting is permitted in the FM broadcast bands between about 65 and 108 MHz in the very high frequency (VHF) range. Radio waves in this band travel by line-of-sight so FM reception is limited by the visual horizon to about 30–40 mi (48–64 km), and can be blocked by hills. However it is less susceptible to interference from radio noise (RFI, sferics, static), and has higher fidelity, better frequency response, and less audio distortion than AM. In the US, radiated power (ERP) of FM stations varies from 6–100 kW. [60]
  • Digital radio involves a variety of standards and technologies for broadcasting digital radio signals over the air. Some systems, such as HD Radio and DRM, operate in the same wavebands as analog broadcasts, either as a replacement for analog stations or as a complementary service. Others, such as DAB/DAB+ and ISDB_Tsb, operate in wavebands traditionally used for television or satellite services. [61]
"Roberts" radio for DAB Portable radio receiving DAB+ transmission in UK.jpg
"Roberts" radio for DAB
  • Digital Audio Broadcasting (DAB) debuted in some countries in 1998. It transmits audio as a digital signal rather than an analog signal as AM and FM do. [62] DAB has the potential to provide higher quality sound than FM (although many stations do not choose to transmit at such high quality), has greater immunity to radio noise and interference, makes better use of scarce radio spectrum bandwidth and provides advanced user features such as electronic program guides. Its disadvantage is that it is incompatible with previous radios so that a new DAB receiver must be purchased. [63] Several nations have set dates to switch off analog FM networks in favor of DAB / DAB+, notably Norway in 2017 [64] and Switzerland in 2024. [65]
A single DAB station transmits a 1,500kHz bandwidth signal that carries from 9–12 channels of digital audio modulated by OFDM from which the listener can choose. Broadcasters can transmit a channel at a range of different bit rates, so different channels can have different audio quality. In different countries DAB stations broadcast in either Band III (174–240 MHz) or L band (1.452–1.492 GHz) in the UHF range, so like FM reception is limited by the visual horizon to about 40 miles (64 km). [66] [63]
  • Digital Radio Mondiale (DRM) is a competing digital terrestrial radio standard developed mainly by broadcasters as a higher spectral efficiency replacement for legacy AM and FM broadcasting. Mondiale means "worldwide" in French and Italian; DRM was developed in 2001, and is currently supported by 23 countries, and adopted by some European and Eastern broadcasters beginning in 2003. The DRM30 mode uses the commercial broadcast bands below 30 MHz, and is intended as a replacement for standard AM broadcast on the longwave, mediumwave, and shortwave bands. The DRM+ mode uses VHF frequencies centered around the FM broadcast band, and is intended as a replacement for FM broadcasting. It is incompatible with existing radio receivers, so it requires listeners to purchase a new DRM receiver. The modulation used is a form of OFDM called COFDM in which, up to 4 carriers are transmitted on a channel formerly occupied by a single AM or FM signal, modulated by quadrature amplitude modulation (QAM). [71] [59]
The DRM system is designed to be as compatible as possible with existing AM and FM radio transmitters, so that much of the equipment in existing radio stations can continue in use, augmented with DRM modulation equipment. [71] [59]
Volkswagen's RNS-510 receiver supports Sirius Satellite Radio. SiriusXM Display on Volkswagen's RNS-510 Receiver.png
Volkswagen's RNS-510 receiver supports Sirius Satellite Radio.

Video: Television broadcasting

Television broadcasting is the transmission of moving images by radio, which consist of sequences of still images, which are displayed on a screen on a television receiver (a "television" or TV) along with a synchronized audio (sound) channel. Television (video) signals occupy a wider bandwidth than broadcast radio (audio) signals. Analog television, the original television technology, required 6 MHz, so the television frequency bands are divided into 6 MHz channels, now called "RF channels". [74]

The current television standard, introduced beginning in 2006, is a digital format called high-definition television (HDTV), which transmits pictures at higher resolution, typically 1080 pixels high by 1920 pixels wide, at a rate of 25 or 30 frames per second. Digital television (DTV) transmission systems, which replaced older analog television in a transition beginning in 2006, use image compression and high-efficiency digital modulation such as OFDM and 8VSB to transmit HDTV video within a smaller bandwidth than the old analog channels, saving scarce radio spectrum space. Therefore, each of the 6 MHz analog RF channels now carries up to 7 DTV channels – these are called "virtual channels". Digital television receivers have different behavior in the presence of poor reception or noise than analog television, called the "digital cliff" effect. Unlike analog television, in which increasingly poor reception causes the picture quality to gradually degrade, in digital television picture quality is not affected by poor reception until, at a certain point, the receiver stops working and the screen goes black. [75] [76]

Celebro Studios Gallery.jpg
Television studio control room, Celebro Studios, London
Superturnstile Tx Muehlacker.JPG
A television broadcasting antenna
Sony KDL-40V2500 20061107.jpg
A modern flatscreen television receiver
  • Terrestrial television, over-the-air (OTA) television, or broadcast television – the oldest television technology, is the transmission of television signals from land-based television stations to television receivers (called televisions or TVs) in viewer's homes. Terrestrial television broadcasting uses the bands 41 – 88 MHz (VHF low band or Band I, carrying RF channels 1–6), 174 – 240 MHz, (VHF high band or Band III; carrying RF channels 7–13), and 470 – 614 MHz (UHF Band IV and Band V; carrying RF channels 14 and up). [77] The exact frequency boundaries vary in different countries. [78] Propagation is by line-of-sight, so reception is limited by the visual horizon. [79] In the US, the effective radiated power (ERP) of television transmitters is regulated according to height above average terrain. [80] Viewers closer to the television transmitter can use a simple "rabbit ears" dipole antenna on top of the TV, but viewers in fringe reception areas typically require an outdoor antenna mounted on the roof to get adequate reception. [79]
Berlin-neukoelln satellite-dishes 20050314 p1010596.jpg
(left) DISH Network's Super Dish 121 mounted on a rooftop. (right) A residential tower block with TV satellite dishes used by various users


Government standard frequency and time signal services operate time radio stations which continuously broadcast extremely accurate time signals produced by atomic clocks, as a reference to synchronize other clocks. [83] Examples are BPC, DCF77, JJY, MSF, RTZ, TDF, WWV, and YVTO. [84] One use is in radio clocks and watches, which include an automated receiver that periodically (usually weekly) receives and decodes the time signal and resets the watch's internal quartz clock to the correct time, thus allowing a small watch or desk clock to have the same accuracy as an atomic clock. Government time stations are declining in number because GPS satellites and the Internet Network Time Protocol (NTP) provide equally accurate time standards. [85]

Two-way voice communication

Mobile phone evolution Japan1997-2004.jpg
Cellphones typical of Japan in the early 21st century.
Bangalore Wikipedian on phone 5 closeup.jpg
Modern smartphone
Cellular phone tower shared by antennas belonging to 3 different networks.

A two-way radio is an audio transceiver, a receiver and transmitter in the same device, used for bidirectional person-to-person voice communication with other users with similar radios. An older term for this mode of communication is radiotelephony . The radio link may be half-duplex, as in a walkie-talkie, using a single radio channel in which only one radio can transmit at a time, so different users take turns talking, pressing a "push to talk" button on their radio which switches off the receiver and switches on the transmitter. Or the radio link may be full duplex, a bidirectional link using two radio channels so both people can talk at the same time, as in a cell phone. [86]

2019-07-21 - Vodafone 5G Standort Hattstedt - Detailfoto1.jpg
T-Phone 5G and T-Phone 5G Pro from Polish distribution.jpg
(left) 5G millimeter wave antenna, Germany (right) Polish 5G smartphones
Satellite phones, showing the large antennas needed to communicate with the satellite Zivile Satellitentelefone.jpg
Satellite phones, showing the large antennas needed to communicate with the satellite
Motorola SCR-536 from WW2, the first walkie-talkie Portable radio SCR536.png
Motorola SCR-536 from WW2, the first walkie-talkie
Firefighter using modern walkie-talkie Miramar Fire Department Firefighters Conduct Prescribed Burns 140612-M-RB277-066.jpg
Firefighter using modern walkie-talkie
VHF marine radio on a ship Maritime VHF Sailor type.jpg
VHF marine radio on a ship

One-way voice communication

One way, unidirectional radio transmission is called simplex .

Data communication

A laptop (with Wi-Fi module) and a typical home wireless router (on the right) connecting it to the Internet. The laptop shows its own photo Wireless network.jpg
A laptop (with Wi-Fi module) and a typical home wireless router (on the right) connecting it to the Internet. The laptop shows its own photo
Neighborhood wireless WAN router on telephone pole USI router.jpg
Neighborhood wireless WAN router on telephone pole
Parabolic antennas of microwave relay links on tower in Australia Parabolic antennas.JPG
Parabolic antennas of microwave relay links on tower in Australia
RFID tag from a DVD RFID Chip 001.JPG
RFID tag from a DVD

Space communication

Satellite Communications Center Dubna in Russia TsKS Dubna GPKS -6.jpg
Satellite Communications Center Dubna in Russia

This is radio communication between a spacecraft and an Earth-based ground station, or another spacecraft. Communication with spacecraft involves the longest transmission distances of any radio links, up to billions of kilometers for interplanetary spacecraft. In order to receive the weak signals from distant spacecraft, satellite ground stations use large parabolic "dish" antennas up to 25 metres (82 ft) in diameter and extremely sensitive receivers. High frequencies in the microwave band are used, since microwaves pass through the ionosphere without refraction, and at microwave frequencies the high-gain antennas needed to focus the radio energy into a narrow beam pointed at the receiver are small and take up a minimum of space in a satellite. Portions of the UHF, L, C, S, ku and ka band are allocated for space communication. A radio link that transmits data from the Earth's surface to a spacecraft is called an uplink, while a link that transmits data from the spacecraft to the ground is called a downlink. [125]

Communications satellite belonging to Azerbaijan Az@rbaycan peyki - VOA.jpg
Communications satellite belonging to Azerbaijan


Military air traffic controller on US Navy aircraft carrier monitors aircraft on radar screen US Navy 120208-N-TU894-022 Air-Traffic Controller 2nd Class Gregory Clemmons stands the departure position watch as Air-Traffic Controller 3rd Clas.jpg
Military air traffic controller on US Navy aircraft carrier monitors aircraft on radar screen

Radar is a radiolocation method used to locate and track aircraft, spacecraft, missiles, ships, vehicles, and also to map weather patterns and terrain. A radar set consists of a transmitter and receiver. [129] [130] The transmitter emits a narrow beam of radio waves which is swept around the surrounding space. When the beam strikes a target object, radio waves are reflected back to the receiver. The direction of the beam reveals the object's location. Since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received "echo", the range to the target can be calculated. The targets are often displayed graphically on a map display called a radar screen. Doppler radar can measure a moving object's velocity, by measuring the change in frequency of the return radio waves due to the Doppler effect. [131]

Radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with compact antennas. [130] Parabolic (dish) antennas are widely used. In most radars the transmitting antenna also serves as the receiving antenna; this is called a monostatic radar . A radar which uses separate transmitting and receiving antennas is called a bistatic radar . [132]

ASR-8 airport surveillance radar antenna. It rotates once every 4.8 seconds. The rectangular antenna on top is the secondary radar. ASR-9 Radar Antenna.jpg
ASR-8 airport surveillance radar antenna. It rotates once every 4.8 seconds. The rectangular antenna on top is the secondary radar.
Rotating marine radar antenna on a ship Rotating marine radar - rotating waveguide antenna.gif
Rotating marine radar antenna on a ship


Radiolocation is a generic term covering a variety of techniques that use radio waves to find the location of objects, or for navigation. [143]

An early iPhone with its GPS navigation app in use. HA0478-006 (6011470974).jpg
An early iPhone with its GPS navigation app in use.
A personal navigation assistant by Garmin, which uses GPS to give driving directions to a destination. Paris-PorteMolitor-GPS.jpg
A personal navigation assistant by Garmin, which uses GPS to give driving directions to a destination.
EPIRB emergency locator beacon on a ship EPIRB (1).jpg
EPIRB emergency locator beacon on a ship
Wildlife officer tracking radio-tagged mountain lion Tracking Mountain Lions.jpg
Wildlife officer tracking radio-tagged mountain lion

Remote control

US Air Force MQ-1 Predator drone flown remotely by a pilot on the ground MQ-1 Predator unmanned aircraft.jpg
US Air Force MQ-1 Predator drone flown remotely by a pilot on the ground

Radio remote control is the use of electronic control signals sent by radio waves from a transmitter to control the actions of a device at a remote location. Remote control systems may also include telemetry channels in the other direction, used to transmit real-time information on the state of the device back to the control station. Uncrewed spacecraft are an example of remote-controlled machines, controlled by commands transmitted by satellite ground stations. Most handheld remote controls used to control consumer electronics products like televisions or DVD players actually operate by infrared light rather than radio waves, so are not examples of radio remote control. A security concern with remote control systems is spoofing, in which an unauthorized person transmits an imitation of the control signal to take control of the device. [157] Examples of radio remote control:

Remote keyless entry fob for a car Automobile remote keyless entry transmitter.jpg
Remote keyless entry fob for a car
Quadcopter, a popular remote-controlled toy Md4-200.jpg
Quadcopter, a popular remote-controlled toy


Radio jamming is the deliberate radiation of radio signals designed to interfere with the reception of other radio signals. Jamming devices are called "signal suppressors" or "interference generators" or just jammers. [165]

During wartime, militaries use jamming to interfere with enemies' tactical radio communication. Since radio waves can pass beyond national borders, some totalitarian countries which practice censorship use jamming to prevent their citizens from listening to broadcasts from radio stations in other countries. Jamming is usually accomplished by a powerful transmitter which generates noise on the same frequency as the target transmitter. [166] [167]

US Federal law prohibits the nonmilitary operation or sale of any type of jamming devices, including ones that interfere with GPS, cellular, Wi-Fi and police radars. [168]

Scientific research

See also

Related Research Articles

<span class="mw-page-title-main">Microwave</span> Electromagnetic radiation with wavelengths from 1 m to 1 mm

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves, ranging from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes UHF, SHF and EHF bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.

In radio communication, a transceiver is an electronic device which is a combination of a radio transmitter and a receiver, hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. These two related functions are often combined in a single device to reduce manufacturing costs. The term is also used for other devices which can both transmit and receive through a communications channel, such as optical transceivers which transmit and receive light in optical fiber systems, and bus transceivers which transmit and receive digital data in computer data buses.

<span class="mw-page-title-main">Shortwave radio</span> Radio transmissions using wavelengths between 10 m and 100 m

Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.

<span class="mw-page-title-main">Transmitter</span> Electronic device that emits radio waves

In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.

<span class="mw-page-title-main">Intermediate frequency</span> Frequency to which a carrier wave is shifted during transmission or reception

In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.

<span class="mw-page-title-main">Radio wave</span> Type of electromagnetic radiation

Radio waves are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1mm, which is shorter than the diameter of a grain of rice. At 30 Hz the corresponding wavelength is ~10,000 kilometers, which is longer than the radius of the Earth. Wavelength of a radio wave is inversely proportional to its frequency, because its velocity is constant. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly slower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

<span class="mw-page-title-main">Ultra high frequency</span> Electromagnetic spectrum 300–3000 MHz

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.

Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.

Super high frequency (SHF) is the ITU designation for radio frequencies (RF) in the range between 3 and 30 gigahertz (GHz). This band of frequencies is also known as the centimetre band or centimetre wave as the wavelengths range from one to ten centimetres. These frequencies fall within the microwave band, so radio waves with these frequencies are called microwaves. The small wavelength of microwaves allows them to be directed in narrow beams by aperture antennas such as parabolic dishes and horn antennas, so they are used for point-to-point communication and data links and for radar. This frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave radio relay links, satellite phones, and numerous short range terrestrial data links. They are also used for heating in industrial microwave heating, medical diathermy, microwave hyperthermy to treat cancer, and to cook food in microwave ovens.

<span class="mw-page-title-main">Amateur television</span> Transmission of video in amateur radio bands

Amateur television (ATV) is the transmission of broadcast quality video and audio over the wide range of frequencies of radio waves allocated for radio amateur (Ham) use. ATV is used for non-commercial experimentation, pleasure, and public service events. Ham TV stations were on the air in many cities before commercial television stations came on the air. Various transmission standards are used, these include the broadcast transmission standards of NTSC in North America and Japan, and PAL or SECAM elsewhere, utilizing the full refresh rates of those standards. ATV includes the study of building of such transmitters and receivers, and the study of radio propagation of signals travelling between transmitting and receiving stations.

<span class="mw-page-title-main">Radio receiver</span> Device for receiving radio broadcasts

In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.

The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional boundary between the UHF and SHF bands at 3.0 GHz. The S band is used by airport surveillance radar for air traffic control, weather radar, surface ship radar, and some communications satellites, especially those satellites used by NASA to communicate with the Space Shuttle and the International Space Station. The 10 cm radar short-band ranges roughly from 1.55 to 5.2 GHz. The S band also contains the 2.4–2.483 GHz ISM band, widely used for low power unlicensed microwave devices such as cordless phones, wireless headphones (Bluetooth), wireless networking (WiFi), garage door openers, keyless vehicle locks, baby monitors as well as for medical diathermy machines and microwave ovens. India's regional satellite navigation network (IRNSS) broadcasts on 2.483778 to 2.500278 GHz.

The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU).

<span class="mw-page-title-main">Cordless telephone</span> Portable telephone that connects to a landline

A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short distance from the base station.

Earth–Moon–Earth communication (EME), also known as Moon bounce, is a radio communications technique that relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver.

A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary parts of all systems that use radio: radio and television broadcasting, cell phones, wireless networks, radar, two way radios like walkie talkies, radio navigation systems like GPS, remote entry systems, among numerous other uses.

<span class="mw-page-title-main">Wireless microphone</span> Microphone without a physical cable

A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone, it has a small, battery-powered radio transmitter in the microphone body, which transmits the audio signal from the microphone by radio waves to a nearby receiver unit, which recovers the audio. The other audio equipment is connected to the receiver unit by cable. In one type the transmitter is contained within the handheld microphone body. In another type the transmitter is contained within a separate unit called a "bodypack", usually clipped to the user's belt or concealed under their clothes. The bodypack is connected by wire to a "lavalier microphone" or "lav", a headset or earset microphone, or another wired microphone. Most bodypack designs also support a wired instrument connection. Wireless microphones are widely used in the entertainment industry, television broadcasting, and public speaking to allow public speakers, interviewers, performers, and entertainers to move about freely while using a microphone without requiring a cable attached to the microphone.

<span class="mw-page-title-main">Microwave transmission</span> Transmission of information via microwaves

Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles.

There are several uses of the 2.4 GHz ISM radio band. Interference may occur between devices operating at 2.4 GHz. This article details the different users of the 2.4 GHz band, how they cause interference to other users and how they are prone to interference from other users.


  1. "Radio". Oxford Living Dictionaries. Oxford University Press. 2019. Archived from the original on 24 March 2019. Retrieved 26 February 2019.
  2. "Definition of radio". Encyclopedia. PCMagazine website, Ziff-Davis. 2018. Retrieved 26 February 2019.
  3. 1 2 3 4 Ellingson, Steven W. (2016). Radio Systems Engineering. Cambridge University Press. pp. 1–4. ISBN   978-1316785164.
  4. 1 2 3 4 "125 Years Discovery of Electromagnetic Waves". Karlsruhe Institute of Technology. 16 May 2022. Archived from the original on 14 July 2022. Retrieved 14 July 2022.
  5. 1 2 Bondyopadhyay, Prebir K. (1995) "Guglielmo Marconi – The father of long distance radio communication – An engineer's tribute", 25th European Microwave Conference: Volume 2, pp. 879–85
  6. 1 2 "1890s – 1930s: Radio". Elon University. Archived from the original on 8 June 2022. Retrieved 14 July 2022.
  7. 1 2 Belrose, John S. (5–7 September 1995). "Radio's First Message -- Fessenden and Marconi". Institute of Electrical and Electronics Engineers . Retrieved 6 November 2022.
  8. 1 2 "History of Commercial Radio". Federal Communications Commission. 23 October 2020. Archived from the original on 1 January 2022. Retrieved 14 July 2022.
  9. "radio (n.)". Online Etymology Dictionary. Retrieved 13 July 2022.
  10. Bell, Alexander Graham (July 1881). "Production of Sound by Radiant Energy". Popular Science Monthly. pp. 329–330. [W]e have named the apparatus for the production and reproduction of sound in this way the "photophone", because an ordinary beam of light contains the rays which are operative. To avoid in future any misunderstandings upon this point, we have decided to adopt the term "radiophone", proposed by M. Mercadier, as a general term signifying the production of sound by any form of radiant energy...
  11. Manning, Trevor (2009). Microwave Radio Transmission Design Guide. Artech House. p. 2.
  12. Maver, William Jr. (1903). American Telegraphy and Encyclopedia of the Telegraph: Systems, Apparatus, Operation. New York: Maver Publishing Co. p.  333. wireless telegraphy.
  13. Steuart, William Mott; et al. (1906). Special Reports: Telephones and Telegraphs 1902. Washington D.C.: U.S. Bureau of the Census. pp. 118–119.
  14. 1 2 3 4 Thomas H. White, United States Early Radio History, Section 22
  15. Collins, A. Frederick (10 May 1902). "The Genesis of Wireless Telegraphy". Electrical World and Engineer. p. 811.
  16. "Wireless Telegraphy". The Practical Engineer. 25 February 1898. p. 174. Dr. O. J. Lodge, who preceded Marconi in making experiments in what may be called "ray" telegraphy or radiotelegraphy by a year or two, has devised a new method of sending and receiving the messages. The reader will understand that in the radiotelegraph electric waves forming the signals of the message starting from the sending instrument and travel in all directions like rays of light from a lamp, only they are invisible.
  17. "Wireless Telegraphy", The Electrical Review (London), 20 January 1905, page 108, quoting from the British Post Office's 30 December 1904 Post Office Circular.
  18. "Interference with Wireless Messages", Electrical World, 22 June 1907, page 1270.
  19. Sungook Hong (2001), Wireless: From Marconi's Black-box to the Audion, MIT Press, pp. 5–10
  20. "The Nobel Prize in Physics 1909". 2023. Archived from the original on 31 July 2023. Retrieved 31 July 2023.
  21. Kraus, John D. (1988). Antennas (2nd ed.). Tata-McGraw Hill. p. 50. ISBN   0074632191.
  22. Serway, Raymond; Faughn, Jerry; Vuille, Chris (2008). College Physics, 8th Ed. Cengage Learning. p. 714. ISBN   978-0495386933.
  23. Balanis, Constantine A. (2005). Antenna theory: Analysis and Design, 3rd Ed. John Wiley and Sons. p.  10. ISBN   978-1118585733.
  24. 1 2 3 4 Ellingson, Steven W. (2016). Radio Systems Engineering. Cambridge University Press. pp. 16–17. ISBN   978-1316785164.
  25. Visser, Hubregt J. (2012). Antenna Theory and Applications. John Wiley & Sons. ISBN   978-1119990253 . Retrieved 29 August 2022.
  26. Zainah Md Zain; Hamzah Ahmad; Dwi Pebrianti; Mahfuzah Mustafa; Nor Rul Hasma Abdullah; Rosdiyana Samad; Maziyah Mat Noh (2020). Proceedings of the 11th National Technical Seminar on Unmanned System Technology 2019: NUSYS'19. Springer Nature. p. 535. ISBN   978-9811552816. Extract of pp. 535–536
  27. "Omnidirectional Antenna - an overview | ScienceDirect Topics". Retrieved 5 September 2022.
  28. "Electromagnetic Radiation". NASA. Archived from the original on 23 May 2016. Retrieved 18 August 2022.
  29. "How far can radio waves travel in vacuum? and light waves?". Physics Stack Exchange. July 2019. Archived from the original on 18 August 2022. Retrieved 18 August 2022.
  30. 1 2 3 Brain, Marshall (7 December 2000). "How Radio Works". Retrieved 11 September 2009.
  31. 1 2 3 4 5 6 7 8 Faruque, Saleh (2016). Radio Frequency Modulation Made Easy. Springer Publishing. ISBN   978-3319412023 . Retrieved 29 August 2022.
  32. Mustafa Ergen (2009). Mobile Broadband: including WiMAX and LTE. Springer Science+Business Media. doi:10.1007/978-0-387-68192-4. ISBN   978-0387681894.
  33. Tony Dorbuck (ed.), The Radio Amateur's Handbook, Fifty-Fifth Edition, American Radio Relay League, 1977, p. 368
  34. John Avison, The World of Physics, Nelson · 2014, page 367
  35. C-W and A-M Radio Transmitters and Receivers, United States. Department of the Army – 1952, pp. 167–168
  36. 1 2 3 4 "Spectrum 101" (PDF). US National Aeronautics and Space Administration (NASA). February 2016. Archived (PDF) from the original on 11 February 2017. Retrieved 2 December 2019., p. 6
  37. 1 2 3 Pogorel, Girard; Chaduc, Jean-Marc (2010). The Radio Spectrum: Managing a Strategic Resource. Wiley). ISBN   978-0470393529 . Retrieved 29 August 2022.
  38. Norberg, Bob (27 November 2022). "Digital Radio Is Coming, But Analog Isn't Dead Yet". The Ledger . Archived from the original on 3 September 2022. Retrieved 3 September 2022.
  39. "Analogue To Digital: Radio Slow To Tune Into Transition". Financial Express . 13 October 2005. Archived from the original on 3 September 2022. Retrieved 3 September 2022.
  40. "Radio Regulations, 2016 Edition" (PDF). International Telecommunication Union. 3 November 2016. Retrieved 9 November 2019. Article 2, Section 1, p.27
  41. 1 2 Nomenclature of the frequency and wavelength bands used in telecommunications (PDF) (Report). Geneva: International Telecommunications Union. 2015. ITU-R V.431-8. Retrieved 6 April 2023.
  42. Communications-electronics Management of the Electromagnetic Spectrum (Report). Headquarters, Department of the Army. United States Department of the Army. 1973. p. 2.
  43. Duncan, Christopher; Gkountouna, Olga; Mahabir, Ron (2021). "Theoretical Applications of Magnetic Fields at Tremendously Low Frequency in Remote Sensing and Electronic Activity Classification". In Arabnia, Hamid R.; Deligiannidis, Leonidas; Shouno, Hayaru; Tinetti, Fernando G.; Tran, Quoc-Nam (eds.). Advances in Computer Vision and Computational Biology. Transactions on Computational Science and Computational Intelligence. Cham: Springer International Publishing. pp. 235–247. doi:10.1007/978-3-030-71051-4_18. ISBN   978-3030710507. S2CID   238934419.
  44. "Radio Frequency Interference Best Practices Guidebook - CISA - Feb. 2020" (PDF). Cybersecurity and Infrastructure Security Agency SAFECOM/National Council of Statewide Interoperability Coordinators. USDepartment of Homeland Security. Retrieved 29 August 2022.
  45. Mazar (Madjar), Haim (2016). Radio Spectrum Management: Policies, Regulations and Techniques. Wiley. ISBN   978-1118511794 . Retrieved 29 August 2022.
  46. "ARTICLE 19 Identification of stations" (PDF). International Telecommunication Union. Retrieved 29 August 2022.
  47. "Commercial Radio Operator Types of Licenses". Federal Communications Commission. 6 May 2016. Retrieved 29 August 2022.
  48. Dichoso, Joe (October 9, 2007). "FCC Basics of Unlicensed Transmitters" (PDF). Federal Communications Commission. Retrieved 29 August 2022.
  49. Pizzi, Skip; Jones, Graham (2014). A Broadcast Engineering Tutorial for Non-Engineers, 4th Ed. National Association of Broadcasters, Taylor and Francis. ISBN   978-0415733397.
  50. Witten, Alan Joel (2017). Handbook of Geophysics and Archaeology. Routledge. ISBN   978-1351564588 . Retrieved 30 August 2022.
  51. Bonsor, Kevin (26 September 2001). "How Satellite Radio Works". HowStuffWorks. Retrieved 30 August 2022.
  52. Gosling, William (1998). Radio Antennas and Propagation: Radio Engineering Fundamentals. Newnes. ISBN   978-0750637411 . Retrieved 30 August 2022.
  53. Griffin, B. Whitfield (2000). Radio-electronic Transmission Fundamentals. SciTech Publishing/Noble. ISBN   978-1884932137 . Retrieved 30 August 2022.
  54. Pizzi, Skip; Jones, Graham (2014). A Broadcast Engineering Tutorial for Non-Engineers. CRC Press/Focal Press. ISBN   978-1317906834 . Retrieved 30 August 2022.
  55. Perez, Reinaldo (2013). Handbook of Electromagnetic Compatibility. Academic Press. ISBN   978-1483288970 . Retrieved 30 August 2022.
  56. Green, Clarence R.; Bourque, Robert M. (1980). The Theory and Servicing of AM, FM, and FM Stereo Receivers. Prentice-Hall. p. 6.
  57. "Appendix C: Glossary" (PDF). Radio – Preparing for the Future (Report). London: Ofcom. October 2005. p. 2.
  58. 1 2 Gupta, Rakesh (2021). Education Technology in Physical Education and Sports. Audio Visual Media in Physical Education. India: Friends Publications. ISBN   978-9390649808 . Retrieved 30 August 2022.
  59. 1 2 3 Berg, Jerome S. (2008). Broadcasting on the Short Waves: 1945 to today. McFarland. ISBN   978-0786451982 . Retrieved 30 August 2022.
  60. Sterling, Christopher H.; Kieth, Michael C. (2009). Sounds of Change: A history of FM broadcasting in America. University of North Carolina Press. ISBN   978-0807877555 . Retrieved 30 August 2022.
  61. Digital Radio Guide (PDF) (Report). Switzerland: World Broadcasting Unions. 2017.
  62. Baker, William (2020). "DAB vs. FM: The differences between analog and digital radio". Radio Fidelity online magazine. Retrieved 14 September 2020.
  63. 1 2 Hoeg, Wolfgang; Lauterbach, Thomas (2004). Digital Audio Broadcasting: Principles and applications of digital radio. John Wiley & Sons. ISBN   978-0470871423 . Retrieved 30 August 2022.
  64. Revel, Timothy (10 January 2017). "Norway is first country to turn off FM radio and go digital-only". New Scientist . Retrieved 4 September 2022.
  65. McLane, Paul (30 August 2021). "Swiss FM shutdown reverts to original 2024 date". Radio World. Retrieved 4 September 2022.
  66. Trends in Radio Research: Diversity, innovation, and policies. Cambridge Scholars Publishing. 2018. p. 263.
  67. Bortzfield, Bill (27 November 2017). The state of HD Radio in Jacksonville and nationwide. WJCT Public Media (Report). Retrieved 4 September 2022.
  68. Hadfield, Marty (15 August 2016). Transmitter & programming considerations for HD Radio. RBR + TVBR ( (Report). Retrieved 4 September 2022.
  69. "Receiving NRSC‑5". 9 June 2017. Archived from the original on 20 August 2017. Retrieved 14 April 2018.
  70. Jones, Graham A.; Layer, David H.; Osenkowsky, Thomas G. (2013). NAB Engineering Handbook. National Association of Broadcasters / Taylor & Francis. pp. 558–559. ISBN   978-1136034107.
  71. 1 2 DRM System Specification (PDF) (vers. 4.2.1). Geneva, CH: European Broadcasting Union. January 2021. p. 178. ETSI ES 201 980. Retrieved 19 April 2018 via
  72. Satellite S‑band radio frequency table (Report). 15 August 2011. Retrieved 23 April 2013 via CSG Network.
  73. Bonsor, Kevin (26 September 2001). "How satellite radio works". HowStuffWorks . Retrieved 1 May 2013.
  74. Enticknap, Leo Douglas Graham (2005). Moving Image Technology: From Zoetrope to Digital. Wallflower Press (Columbia University Press). ISBN   978-1904764069 . Retrieved 31 August 2022.
  75. Starks, M. (2013). The Digital Television Revolution: Origins to Outcomes. Springer. ISBN   978-1137273345 . Retrieved 31 August 2022.
  76. Brice, Richard (2002). Newnes Guide to Digital TV. Newnes. ISBN   978-0750657211 . Retrieved 31 August 2022.
  77. Bartlet, George W., Ed. (1975). NAB Engineering Handbook, 6th Ed. Washington, D.C.: National Association of Broadcasters. p. 21.{{cite book}}: CS1 maint: multiple names: authors list (link)
  78. Lundstrom, Lars-Ingemar (2012). Understanding Digital Television: An Introduction to DVB Systems with Satellite, Cable, Broadband and Terrestrial TV Distribution. CRC Press. ISBN   978-1136032820.
  79. 1 2 Ingram, Dave (1983). Video Electronics Technology. TAB Books. ISBN   978-0830614745 . Retrieved 1 September 2022.
  80. Federal Communications Commission (Parts 20 - 39). ProStar Publications. ISBN   9781577858461.
  81. Benoit, Herve (1999). Satellite Television: Analogue and Digital Reception Techniques. Butterworth-Heinemann/Arnold. ISBN   978-0340741085 . Retrieved 1 September 2022.
  82. Long, Mark (1999). The Digital Satellite TV Handbook. Newnes. ISBN   978-0750671712 . Retrieved 1 September 2022.
  83. Weik, Martin H. (2000). "standard frequency and time signal". Computer Science and Communications Dictionary. Computer Science and Communications Dictionary. Springer. p. 1649. doi:10.1007/1-4020-0613-6_18062. ISBN   978-0792384250 . Retrieved 1 September 2022.
  84. Radio Aids to Navigation, Publication 117, Chapter 2, Radio Time Signals. Lighthouse Press. 2005. ISBN   978-1577855361 . Retrieved 1 September 2022.
  85. "What Closing A Government Radio Station Would Mean For Your Clocks". National Public Radio, Weekend Edition. Retrieved 1 September 2022.
  86. Frenzel, Louis (2017). Electronics Explained: Fundamentals for Engineers, Technicians, and Makers. Newnes. ISBN   978-0128118795 . Retrieved 2 September 2022.
  87. 1 2 Brain, Marshall; Tyson, Jeff; Layton, Julia (2018). "How Cell Phones Work". How Stuff Works. InfoSpace Holdings LLC. Retrieved 31 December 2018.
  88. Lawson, Stephen. "Ten Ways Your Smartphone Knows Where You Are". PCWorld . Retrieved 2 September 2022.
  89. Guowang Miao; Jens Zander; Ki Won Sung; Ben Slimane (2016). Fundamentals of Mobile Data Networks. Cambridge University Press. ISBN   978-1107143210.
  90. "Cellular Telephone Basics". 1 January 2006. p. 2. Archived from the original on 17 April 2012. Retrieved 2 September 2022.
  91. Brown, Sara. "5G, explained". MIT Sloan School of Management. Retrieved 2 September 2022.
  92. Osseiran, Afif; Monserrat, Jose F.; Marsch, Patrick (2016). 5G Mobile and Wireless Communications Technology. Cambridge University Press. ISBN   978-1107130098 . Retrieved 2 September 2022.
  93. Chandler, Nathan (13 February 2013). "How Satellite Phones Work". HowStuffWorks. Retrieved 2 September 2022.
  94. "Satellite Phone : Functioning/Working Of Satellite Phone". Tutorials Web. Retrieved 2 September 2022.
  95. McComb, Gordon (October 1982). "Never Miss a Call: PS Buyer's Guide to Cordless Phones". Popular Science. pp. 84–85 via Google Books.
  96. Guy, Nick (13 July 2022). "Wirecutter: The Best Cordless Phone". The New York Times. ISSN   0362-4331 . Retrieved 7 September 2022.
  97. U.S. Fire Administration (June 2016). Voice Radio Communications Guide for the Fire Service (PDF) (Report). Washington, D.C.: Federal Emergency Management Agency. pp. 33–34. Retrieved 7 September 2022.
  98. Sterling, Christopher H. (2008). Military Communications: From Ancient Times to the 21st Century. ABC-CLIO. pp. 503–504. ISBN   978-1851097326.
  99. Aeronautical Frequency Committee Manual (PDF) (Report). Aviation Spectrum Resources Inc. 2012.
  100. "Aviation Radio Bands and Frequencies". Smeter network 2011. Archived from the original on 12 February 2004. Retrieved 16 February 2011.
  101. North Atlantic Operations and Airspace Manual (PDF) (Report). ICAO European and North Atlantic Office. 28 March 2019.
  102. Van Horn, Larry. "The Military VHF/UHF Spectrum". Monitoring Times.
  103. Fletcher, Sue (2002). A Boater's Guide to VHF and GMDSS. Camden, Maine: International Marine/McGraw-Hill. ISBN   0071388028. OCLC   48674566.
  104. The ARRL Handbook for Radio Communications 2017 (94th ed.). Newington, Connecticut: American Radio Relay League. 2016. ISBN   978-1625950628. OCLC   961215964.
  105. Brain, Marshall (11 February 2021). "Radio basics: Real life examples". How radio works. How Stuff Works website. Retrieved 27 August 2022.
  106. Radiofrequency Toolkit for Environmental Health Practitioners (PDF) (Report). Vancouver, British Columbia, Canada: British Columbia Centre for Disease Control/National Collaborating Centre for Environmental Health. p. 26. ISBN   978-1926933481.
  107. "Best Baby Monitor Buying Guide". Consumer Reports. 24 April 2016. Retrieved 9 September 2022.
  108. Eargle, John (2005). "Overview of Wireless Microphone Technology". The Microphone Book (2nd ed.). Oxford: Focal Press. pp. 142–151. ISBN   978-1136118067 via Google Books.
  109. Bell, Dee Ana (1 November 2012). "Avoiding Audio Problems with Wireless Microphone Systems". TV Technology. Retrieved 10 September 2022.
  110. Vernon, Tom (28 August 2021). "Wireless Mic Industry Debates WMAS Technology". Radio World. Retrieved 10 September 2022.
  111. Lewis, Barry D.; Davis, Peter T. (2004). Wireless Networks For Dummies. John Wiley & Sons. ISBN   978-0764579776 . Retrieved 12 September 2022.
  112. 1 2 Lowe, Doug (2020). Networking For Dummies. John Wiley & Sons. ISBN   978-1119748670 . Retrieved 12 September 2022.
  113. Muller, Nathan J. (2002). Networking A to Z. McGraw-Hill Professional. pp. 45–47. ISBN   978-0071429139. Archived from the original on 24 June 2021. Retrieved 12 September 2022.
  114. Silver, H. Ward (2008). The ARRL Extra Class License Manual for Ham Radio. American Radio Relay League. ISBN   978-0872591356 . Retrieved 12 September 2022.
  115. Hillebrand, Friedhelm (2010). Short Message Service (SMS): The Creation of Personal Global Text Messaging. John Wiley & Sons. ISBN   978-0470689936 . Retrieved 12 September 2022.
  116. McGregor, Michael A.; Driscoll, Paul D.; Mcdowell, Walter (2016). Head's Broadcasting in America: A Survey of Electronic Media. Routledge. ISBN   978-1317347927 . Retrieved 12 September 2022.
  117. Radio-Electronics-Television Manufacturers Association. Engineering Department (1955). "Microwave Relay Systems for Communications". Electronic Industries Association. Retrieved 12 September 2022.
  118. Bailey, David (2003). Practical Radio Engineering and Telemetry for Industry. Elsevier. ISBN   978-0080473895 . Retrieved 12 September 2022.
  119. Arafath, Yeasin; Mazumder, Debabrata; Hassan, Rakib (2012). Automatic Meter Reading by Radio Frequency Technology. Lap Lambert Academic Publishing GmbH KG. ISBN   978-3847372219 . Retrieved 12 September 2022.
  120. Bonsor, Kevin (28 August 2001). "How E-ZPass Works". HowStuff Works. Retrieved 12 September 2022.
  121. Hunt, V. Daniel; Puglia, Albert; Puglia, Mike (2007). RFID: A Guide to Radio Frequency Identification. John Wiley & Sons. ISBN   978-0470112243 . Retrieved 12 September 2022.
  122. White, Ryan (17 December 2021). "How do submarines communicate with the outside world?". Naval Post. Retrieved 12 September 2022.
  123. "Naval Research Reviews, Vol. 27". Superintendent of Government Documents. 1974. Retrieved 12 September 2022.
  124. "Ground infrastructure". Russian Satellite Communications Company .
  125. "State-of-the-Art of Small Spacecraft Technology, 9.0 - Communications". National Aeronautics and Space Administration. 16 October 2021. Retrieved 11 September 2022.
  126. "UCS Satellite Database". Union of Concerned Scientists. 1 January 2021. Retrieved 21 May 2021.
  127. Marsten, Richard B. (2014). Communication Satellite Systems Technology. Academic Press. ISBN   978-1483276816 . Retrieved 11 September 2022.
  128. "Satellite TV-Direct Broadcast Satellite System, DBS TV". RF Wireless World. Retrieved 11 September 2022.
  129. Brain, Marshall (2020). "How radar works". How Stuff Works. Retrieved 3 September 2022.
  130. 1 2 Skolnik, Merrill (2021). "Radar". Encyclopædia Britannica online. Encyclopædia Britannica Inc. Retrieved 3 September 2022.
  131. "JetStream".
  132. Chernyak, Victor S. (1998). Fundamentals of multisite radar systems: multistatic radars and multiradar systems. CRC Press. pp. 3, 149. ISBN   9056991655.
  133. "Airport Surveillance Radar". Air traffic control, technology. US Federal Aviation Administration website. 2020. Retrieved 3 September 2022.
  134. Binns, Chris (2018). Aircraft Systems: Instruments, Communications, Navigation, and Control. Wiley. ISBN   978-1119259541 . Retrieved 11 September 2022.
  135. International Electronic Countermeasures Handbook. Artech/Horizon House. 2004. ISBN   978-1580538985 . Retrieved 11 September 2022.
  136. Bhattacharjee, Shilavadra (2021). "Marine Radars and Their Use in the Shipping Industry". Marine Insight website. Retrieved 3 September 2022.
  137. "Using and Understanding Doppler Radar". US National Weather Service website. US National Weather Service, NOAA. 2020. Retrieved 3 September 2022.
  138. Fenn, Alan J. (2007). Adaptive Antennas and Phased Arrays for Radar and Communications. Artech House. ISBN   978-1596932739 . Retrieved 11 September 2022.
  139. Teeuw, R.M. (2007). Mapping Hazardous Terrain Using Remote Sensing. Geological Society of London. ISBN   978-1862392298 . Retrieved 11 September 2022.
  140. Jol, Harry M. (2008). Ground Penetrating Radar Theory and Applications. Elsevier. ISBN   978-0080951843 . Retrieved 10 September 2022.
  141. Grosch, Theodore O. (30 June 1995). Verly, Jacques G. (ed.). "Radar sensors for automotive collision warning and avoidance". Synthetic Vision for Vehicle Guidance and Control. Society of Photo-Optical Instrumentation Engineers. 2463: 239–247. Bibcode:1995SPIE.2463..239G. doi:10.1117/12.212749. S2CID   110665898 . Retrieved 10 September 2022.
  142. Brodie, Bernard; Brodie, Fawn McKay (1973). From Crossbow to H-bomb. Indiana University Press. ISBN   0253201616 . Retrieved 10 September 2022.
  143. Sharp, Ian; Yu, Kegen (2018). Wireless Positioning: Principles and Practice, Navigation: Science and Technology. Springer. ISBN   978-9811087912 . Retrieved 10 September 2022.
  144. Teunissen, Peter; Montenbruck, Oliver (2017). Springer Handbook of Global Navigation Satellite Systems. Springer. ISBN   978-3319429281 . Retrieved 10 September 2022.
  145. El-Rabbany, Ahmed (2002). Introduction to GPS: The Global Positioning System. Artech House. ISBN   978-1580531832 . Retrieved 10 September 2022.
  146. Kiland, Taylor Baldwin; Silverstein Gray, Judy (15 July 2016). The Military GPS: Cutting Edge Global Positioning System. Enslow Publishing. ISBN   978-0766075184 . Retrieved 10 September 2022.
  147. Deltour, B.V. (August 1960). "A Guide To Nav-Com Equipment". Flying Magazine Aug 1960. Retrieved 10 September 2022.
  148. "2008 Federal Radionavigation Plan". U.S. Department of Defense. 2009. Retrieved 10 September 2022.
  149. Martin, Swayne. "How A VOR Works". Boldmethod -Digital Aviation Content. Retrieved 10 September 2022.
  150. "Non-Directional Beacon (NDB)". Systems Interface. Retrieved 10 September 2022.
  151. "How does an emergency beacon work?". CBC News. Retrieved 10 September 2022.
  152. "What is a Cospas-Sarsat Beacon?". International Cospas-Sarsat Programme. Retrieved 10 September 2022.
  153. "Scientific and Technical Aerospace Reports, Volume 23, Issue 20". NASA, Office of Scientific and Technical Information. 1985. Retrieved 10 September 2022.
  154. "An Introduction to Radio Direction Finding". defenceWeb. 8 January 2021. Retrieved 10 September 2022.
  155. Moell, Joseph D.; Curlee, Thomas N. (1987). Transmitter Hunting: Radio Direction Finding Simplified. McGraw Hill Professional. ISBN   978-0830627011 . Retrieved 10 September 2022.
  156. "Radio telemetry". Migratory Connectivity Project, Smithsonian Migratory Bird Center. Retrieved 10 September 2022.
  157. Layton, Julia (10 November 2005). "How Remote Controls Work". HowStuff Works. Retrieved 10 September 2022.
  158. Sadraey, Mohammad H. (2020). Design of Unmanned Aerial Systems. Wiley. ISBN   978-1119508694 . Retrieved 10 September 2022.
  159. Smith, Craig (2016). The Car Hacker's Handbook: A Guide for the Penetration Tester. No Starch Press. ISBN   978-1593277703 . Retrieved 10 September 2022.
  160. Pinkerton, Alasdair (15 June 2019). Radio: Making Waves in Sound. Reaktion Books. ISBN   978-1789140996 . Retrieved 9 September 2022.
  161. Biffl, Stefan; Eckhart, Matthias; Lüder, Arndt; Weippl, Edgar (2019). Security and Quality in Cyber-Physical Systems Engineering. Springer Nature. ISBN   978-3030253127 . Retrieved 9 September 2022.
  162. Boukerche, Azzedine (2008). Algorithms and Protocols for Wireless and Mobile Ad Hoc Networks. Wiley. ISBN   978-0470396377 . Retrieved 9 September 2022.
  163. Wonning, Paul R. (12 May 2021). "A Guide to the Home Electric System". Mossy Feet Books. Retrieved 9 September 2022.
  164. Chatterjee, Jyotir Moy; Kumar, Abhishek; Jain, Vishal; Rathore, Pramod Singh (2021). Internet of Things and Machine Learning in Agriculture: Technological Impacts and Challenges. Walter de Gruyter GmbH & Co KG. ISBN   978-3110691283 . Retrieved 9 September 2022.
  165. "What jamming of a wireless security system is and how to resist it | Ajax Systems Blog". Ajax Systems. Retrieved 18 January 2020.
  166. "Remedial Electronic Counter-Countermeasures Techniques". FM 24-33 — Communications Techniques: Electronic Counter-Countermeasures (Report). Department of the Army. July 1990.
  167. Varis, Tapio (1970). "The Control of Information by Jamming Radio Broadcasts". Cooperation and Conflict. 5 (3): 168–184. doi:10.1177/001083677000500303. ISSN   0010-8367. JSTOR   45083158. S2CID   145418504.
  168. "Jammer Enforcement". Federal Communications Commission. 3 March 2011. Retrieved 18 January 2020.
  169. Yeap, Kim Ho; Hirasawa, Kazuhiro (2020). Analyzing the Physics of Radio Telescopes and Radio Astronomy. IG Global. ISBN   978-1799823834 . Retrieved 9 September 2022.
  170. Joardar, Shubhendu; Claycomb, J. R. (2015). Radio Astronomy: An Introduction. Mercury Learning and Information. ISBN   978-1937585624.
  171. Chapman, Rick; Gasparovic, Richard (2022). Remote Sensing Physics: An Introduction to Observing Earth from Space. Wiley. ISBN   978-1119669074 . Retrieved 9 September 2022.
  172. Pampaloni, Paulo; Paloscia, S. (2000). Microwave Radiometry and Remote Sensing of the Earth's Surface and Atmosphere. ISBN   9067643181 . Retrieved 9 September 2022.

General references