Radio
Radio is the technology of
In radio communication, used in
The existence of radio waves was first proven by German physicist
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.
Etymology
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 , Alexander Graham Bell adopted "radiophone" (meaning "radiated sound") as an alternate name for his photophone optical transmission system.[9][10]
Following
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.
History
During radio's first two decades, called the
Technology
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
Radio waves travel at the speed of light in vacuum.[28][29]
The other types of
Radio communication
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
- AM (amplitude modulation) – in an AM transmitter, the amplitude (strength) of the radio carrier wave is varied by the modulation signal;[31]: 3
- FM (frequency modulation) – in an FM transmitter, the frequency of the radio carrier wave is varied by the modulation signal;[31]: 33
- FSK (frequency-shift keying) – used in wireless digital devices to transmit digital signals, the frequency of the carrier wave is shifted between frequencies.[31]: 58
- OFDM (digital audio broadcasting (DAB) to transmit digital data using a minimum of radio spectrum bandwidth. It has higher spectral efficiency and more resistance to fading than AM or FM. In OFDM, multiple radio carrier waves closely spaced in frequency are transmitted within the radio channel, with each carrier modulated with bits from the incoming bitstream so multiple bits are being sent simultaneously, in parallel. At the receiver, the carriers are demodulated and the bits are combined in the proper order into one bitstream.[32]
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
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
Bandwidth
A modulated radio wave, carrying an information signal, occupies a range of
The
A slow transition from
Because it is a fixed resource which is in demand by an increasing number of users, the
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 name Abbreviation Frequency Wavelength Extremely
low frequencyELF 3–30 Hz 100,000–
10,000 kmSuper
low frequencySLF 30–300 Hz 10,000 –
1,000 kmUltra
low frequencyULF 300–
3,000 Hz1,000–
100 kmVery
low frequencyVLF 3–30 kHz 100–10 km Low
frequencyLF 30–300 kHz 10–1 km Medium
frequencyMF 300–
3,000 kHz1,000–
100 m
Band name Abbreviation Frequency Wavelength High
frequencyHF 3–30 MHz 100–10 m Very
high frequencyVHF 30–300 MHz 10–1 m Ultra
high frequencyUHF 300–
3,000 MHz100–10 cm Super
high frequencySHF 3–30 GHz 10–1 cm Extremely
high frequencyEHF 30–300 GHz 10–1 mm Tremendously
high frequencyTHF 300–3,000 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] though the term has not been defined by the ITU.[41]
Regulation
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.
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,
Applications
Below are some of the most important uses of radio, organized by function.
Broadcasting
Broadcasting uses several parts of the radio spectrum, depending on the type of signals transmitted and the desired target audience.
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]
- AM (
- 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]
- FM (
- 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]
- 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 1,500 kHz 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]
- audio data compression algorithm.[70]
- 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]
Video: Television broadcasting
The current television standard, introduced beginning in 2006, is a digital format called
- fringe reception areas typically require an outdoor antenna mounted on the roof to get adequate reception.[79]
- geostationary orbit 22,200 miles (35,700 km) above the Earth's equator transmits many channels (up to 900) modulated on a 12.2 to 12.7 GHz Ku band microwave downlink signal to a rooftop satellite dish antenna on the subscriber's residence. The microwave signal is converted to a lower intermediate frequency at the dish and conducted into the building by a coaxial cable to a set-top box connected to the subscriber's TV, where it is demodulated and displayed. The subscriber pays a monthly fee.[81][82]
Time
Government
Two-way voice communication
A
- millimeter wave band, around 28 and 39 GHz. Since these frequencies have a shorter range than previous cellphone bands, the cells will be smaller than the cells in previous cellular networks which could be many miles across. Millimeter-wave cells will only be a few blocks long, and instead of a cell base station and antenna tower, they will have many small antennas attached to utility poles and buildings.[91][92]
- cell towers. They are more expensive than cell phones; but their advantage is that, unlike a cell phone which is limited to areas covered by cell towers, satphones can be used over most or all of the geographical area of the Earth. In order for the phone to communicate with a satellite using a small omnidirectional antenna, first-generation systems use satellites in low Earth orbit, about 400–700 miles (640–1,100 km) above the surface. With an orbital period of about 100 minutes, a satellite can only be in view of a phone for about 4 – 15 minutes, so the call is "handed off" to another satellite when one passes beyond the local horizon. Therefore, large numbers of satellites, about 40 to 70, are required to ensure that at least one satellite is in view continuously from each point on Earth. Other satphone systems use satellites in geostationary orbit in which only a few satellites are needed, but these cannot be used at high latitudes because of terrestrial interference.[93][94]
- landline telephone in which the handset is portable and communicates with the rest of the phone by a short-range full duplex radio link, instead of being attached by a cord. Both the handset and the base station have low-power radio transceivers that handle the short-range bidirectional radio link.[95] As of 2022[update], cordless phones in most nations use the DECT transmission standard.[96]
- CB, FRS, GMRS, and MURS. Modern digital systems, called trunked radio systems, have a digital channel management system using a control channel that automatically assigns frequency channels to user groups.[97]
- Walkie-talkie – a battery-powered portable handheld half-duplex two-way radio, used in land mobile radio systems.[98]
- air corridors a VHF-AM system using channels between 108 and 137 MHz in the VHF band is used. This system has a typical transmission range of 200 miles (320 km) for aircraft flying at cruising altitude.[99][100] For flights in more remote areas, such as transoceanic airline flights, aircraft use the HF band or channels on the Inmarsat or Iridium satphone satellites.[101] Military aircraft also use a dedicated UHF-AM band from 225.0 to 399.95 MHz.[102]
- full-duplex, to be compatible with the telephone network, to allow users to make telephone calls through a marine operator.[103]
- radiotelegraphy.[104]
One-way voice communication
One way, unidirectional radio transmission is called
- Baby monitor – a crib-side appliance for parents of infants that transmits the baby's sounds to a receiver carried by the parent, so they can monitor the baby while they are in other parts of the house.[105] The wavebands used vary by region, but analog baby monitors generally transmit with low power in the 16, 9.3–49.9 or 900 MHz wavebands, and digital systems in the 2.4 GHz waveband.[106] Many baby monitors have duplex channels so the parent can talk to the baby, and cameras to show video of the baby.[107]
Data communication
- VoIP), audio, and video content (called streaming media). Security is more of an issue for wireless networks than for wired networks since anyone nearby with a wireless modem can access the signal and attempt to log in. The radio signals of wireless networks are encrypted using WPA.[111]
- ISM bands with OFDM (orthogonal frequency-division multiplexing) modulation to transmit data at high rates. The transmitters in Wi-Fi modems are limited to a radiated power of 200 mW to 1 watt, depending on country. They have a maximum indoor range of about 150 ft (50 m) on 2.4 GHz and 50 ft (20 m) on 5 GHz.[112]
- cell towers; satellite internet access; and lower frequencies in the UHF band, which have a longer range than Wi-Fi frequencies. Since WWAN networks are much more expensive and complicated to administer than Wi-Fi networks, their use so far has generally been limited to private networks operated by large corporations.[112]
- ISM band. This allows Bluetooth networks to operate in the presence of noise, other wireless devices and other Bluetooth networks using the same frequencies, since the chance of another device attempting to transmit on the same frequency at the same time as the Bluetooth modem is low. In the case of such a "collision", the Bluetooth modem just retransmits the data packet on another frequency.[113]
- data packets are exchanged between computer-controlled radio modems (transmitter/receivers) called nodes, which may be separated by miles, and maybe mobile. Each node only communicates with neighboring nodes, so packets of data are passed from node to node until they reach their destination using the X.25 network protocol. Packet radio systems are used to a limited degree by commercial telecommunications companies and by the amateur radio community.[114]
- Short Message Service (SMS) which transmits using spare bandwidth on the control radio channel used by cell phones to handle background functions like dialing and cell handoffs. Due to technical limitations of the channel, text messages are limited to 160 alphanumeric characters.[115]
- microwaves to another dish antenna and receiver. Since the antennas must be in line-of-sight, distances are limited by the visual horizon to 30–40 miles (48–64 km). Microwave links are used for private business data, wide area computer networks (WANs), and by telephone companies to transmit long-distance phone calls and television signals between cities.[116][117]
- Telemetry – automated one-way (simplex) transmission of measurements and operation data from a remote process or device to a receiver for monitoring. Telemetry is used for in-flight monitoring of missiles, drones, satellites, and weather balloon radiosondes, sending scientific data back to Earth from interplanetary spacecraft, communicating with electronic biomedical sensors implanted in the human body, and well logging. Multiple channels of data are often transmitted using frequency-division multiplexing or time-division multiplexing.[118] Telemetry is starting to be used in consumer applications such as:
- water meters, and gas meters that, when triggered by an interrogation signal, transmit their readings by radio to a utility reader vehicle at the curb, to eliminate the need for an employee to go on the customer's property to manually read the meter.[119]
- Electronic toll collection – on toll roads, an alternative to manual collection of tolls at a toll booth, in which a transponder in a vehicle, when triggered by a roadside transmitter, transmits a signal to a roadside receiver to register the vehicle's use of the road, enabling the owner to be billed for the toll.[120]
- ISM bands and have a short range. Active tags, powered by a battery, are larger but can transmit a stronger signal, giving them a range of hundreds of meters.[121]
- Submarine communication – When submerged, submarines are cut off from all ordinary radio communication with their military command authorities by the conductive seawater. However radio waves of low enough frequencies, in the VLF (30 to 3 kHz) and ELF (below 3 kHz) bands are able to penetrate seawater. Navies operate large shore transmitting stations with power output in the megawatt range to transmit encrypted messages to their submarines in the world's oceans. Due to the small bandwidth, these systems cannot transmit voice, only text messages at a slow data rate. The communication channel is one-way, since the long antennas needed to transmit VLF or ELF waves cannot fit on a submarine. VLF transmitters use miles long wire antennas like umbrella antennas. A few nations use ELF transmitters operating around 80 Hz, which can communicate with submarines at lower depths. These use even larger antennas called ground dipoles, consisting of two ground (Earth) connections 23–60 km (14–37 mi) apart, linked by overhead transmission lines to a power plant transmitter.[122][123]
Space communication
This is radio communication between a
- satellite ground station a microwave transmitter and large satellite dish antenna transmit a microwave uplink beam to the satellite. The uplink signal carries many channels of telecommunications traffic, such as long-distance telephone calls, television programs, and internet signals, using a technique called frequency-division multiplexing (FDM). On the satellite, a transponder receives the signal, translates it to a different downlink frequency to avoid interfering with the uplink signal, and retransmits it down to another ground station, which may be widely separated from the first. There the downlink signal is demodulated and the telecommunications traffic it carries is sent to its local destinations through landlines. Communication satellites typically have several dozen transponders on different frequencies, which are leased by different users.[127]
- Direct broadcast satellite – a geostationary communication satellite that transmits retail programming directly to receivers in subscriber's homes and vehicles on Earth, in satellite radio and TV systems. It uses a higher transmitter power than other communication satellites, to allow the signal to be received by consumers with a small unobtrusive antenna. For example, satellite television uses downlink frequencies from 12.2 to 12.7 GHz in the ku band transmitted at 100 to 250 watts, which can be received by relatively small 43–80 cm (17–31 in) satellite dishes mounted on the outside of buildings.[128]
Radar
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
- Terminal Radar Approach Control), where air traffic controllers direct the aircraft by radio to maintain safe aircraft separation.[133]
- Secondary surveillance radar – Aircraft carry radar transponders, transceivers which when triggered by the incoming radar signal transmit a return microwave signal. This causes the aircraft to show up more strongly on the radar screen. The radar which triggers the transponder and receives the return beam, usually mounted on top of the primary radar dish, is called the secondary surveillance radar. Since radar cannot measure an aircraft's altitude with any accuracy, the transponder also transmits back the aircraft's altitude measured by its altimeter, and an ID number identifying the aircraft, which is displayed on the radar screen.[134]
- Electronic countermeasures (ECM) – Military defensive electronic systems designed to degrade enemy radar effectiveness, or deceive it with false information, to prevent enemies from locating local forces. It often consists of powerful microwave transmitters that can mimic enemy radar signals to create false target indications on the enemy radar screens.[135]
- Marine radar – an S or X band radar on ships used to detect nearby ships and obstructions like bridges.[136] A rotating antenna sweeps a vertical fan-shaped beam of microwaves around the water surface surrounding the craft out to the horizon.
- Doppler shift.[137]
- Phased-array radar – a radar set that uses a phased array, a computer-controlled antenna that can steer the radar beam quickly to point in different directions without moving the antenna. Phased-array radars were developed by the military to track fast-moving missiles and aircraft. They are widely used in military equipment and are now spreading to civilian applications.[138]
- Synthetic aperture radar (SAR) – a specialized airborne radar set that produces a high-resolution map of ground terrain. The radar is mounted on an aircraft or spacecraft and the radar antenna radiates a beam of radio waves sideways at right angles to the direction of motion, toward the ground. In processing the return radar signal, the motion of the vehicle is used to simulate a large antenna, giving the radar a higher resolution.[139]
- Ground-penetrating radar – a specialized radar instrument that is rolled along the ground surface in a cart and transmits a beam of radio waves into the ground, producing an image of subsurface objects. Frequencies from 100 MHz to a few GHz are used. Since radio waves cannot penetrate very far into earth, the depth of GPR is limited to about 50 feet.[140]
- LIDAR system on an automobile or vehicle that detects if the vehicle is about to collide with an object and applies the brakes to prevent the collision.[141]
- Radar fuze – a detonator for an aerial bomb which uses a radar altimeter to measure the height of the bomb above the ground as it falls and detonates it at a certain altitude.[142]
Radiolocation
Radiolocation is a generic term covering a variety of techniques that use radio waves to find the location of objects, or for navigation.[143]
- Radio beacon – a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. The locations of beacons are plotted on navigational maps used by aircraft and ships.[147]
- callsign consisting of one to 3 Morse code letters as an identifier.[150]
- GPS receiver, and broadcast to rescue teams their exact location within 20 meters.[151]
- Doppler frequency shift of the radio waves due to the relative motion of the transmitter and the satellite, and quickly transmit the information to the appropriate local first responder organizations, which perform the search and rescue.[152][153]
- bearing of a radio signal, to determine the location of the transmitter. The location of a terrestrial transmitter can be determined by simple triangulation from bearings taken by two RDF stations separated geographically, as the point where the two bearing lines cross, this is called a "fix". Military forces use RDF to locate enemy forces by their tactical radio transmissions, counterintelligence services use it to locate clandestine transmitters used by espionage agents, and governments use it to locate unlicensed transmitters or interference sources. Older RDF receivers used rotatable loop antennas, the antenna is rotated until the radio signal strength is weakest, indicating the transmitter is in one of the antenna's two nulls. The nulls are used since they are sharper than the antenna's lobes (maxima). More modern receivers use phased array antennas which have a much greater angular resolution.[154][155]
- GPS receivers which record and transmit a log of the animal's location.[156]
Remote control
Radio remote control is the use of electronic
- automatic pilot systems that maintain stable flight and only require manual control to change directions.[158]
- key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. When a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. The fob must be close to the vehicle, typically within 5 to 20 meters. North America and Japan use a frequency of 315 MHz, while Europe uses 433.92 and 868 MHz. Some models can also remotely start the engine, to warm up the car. A security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ("code grabber") to record the radio signal during opening, which can later be replayed to open the door. To prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. To prevent thieves from simulating the pseudorandom generator to calculate the next key, the radio signal is also encrypted.[159]
- Garage door opener – a short-range handheld transmitter which can open or close a building's electrically operated garage door from outside, so the owner can open the door upon arrival, and close it after departure. When a button is pressed the control transmits a coded FSK radio signal to a receiver in the opener, raising or lowering the door. Modern openers use 310, 315 or 390 MHz. To prevent a thief using a replay attack, modern openers use a rolling code system.[160][161]
- PCM or FSK.[162]
- Wireless doorbell – A residential doorbell that uses wireless technology to eliminate the need to run wires through the building walls. It consists of a doorbell button beside the door containing a small battery powered transmitter. When the doorbell is pressed it sends a signal to a receiver inside the house with a speaker that sounds chimes to indicate someone is at the door. They usually use the 2.4 GHz ISM band. The frequency channel used can usually be changed by the owner in case another nearby doorbell is using the same channel.[163][164]
Jamming
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
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
- Remote sensing – in radio, remote sensing is the reception of electromagnetic waves radiated by natural objects or the atmosphere for scientific research. All warm objects emit microwaves and the spectrum emitted can be used to determine temperature. Microwave radiometers are used in meteorology and earth sciences to determine temperature of the atmosphere and earth surface, as well as chemical reactions in the atmosphere.[171][172]
See also
- Outline of radio
- Electromagnetic radiation and health
- List of radios – List of specific models of radios
- Radio quiet zone
References
- ^ "Radio". Oxford Living Dictionaries. Oxford University Press. 2019. Archived from the original on 24 March 2019. Retrieved 26 February 2019.
- ^ "Definition of radio". Encyclopedia. PCMagazine website, Ziff-Davis. 2018. Retrieved 26 February 2019.
- ^ ISBN 978-1316785164.
- ^ a b c d "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.
- ^ a b 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
- ^ a b "1890s – 1930s: Radio". Elon University. Archived from the original on 8 June 2022. Retrieved 14 July 2022.
- ^ a b Belrose, John S. (5–7 September 1995). "Radio's First Message -- Fessenden and Marconi". Institute of Electrical and Electronics Engineers. Retrieved 6 November 2022.
- ^ a b "History of Commercial Radio". Federal Communications Commission. 23 October 2020. Archived from the original on 1 January 2022. Retrieved 14 July 2022.
- ^ "radio (n.)". Online Etymology Dictionary. Retrieved 13 July 2022.
- ^ 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...
- ^ Manning, Trevor (2009). Microwave Radio Transmission Design Guide. Artech House. p. 2.
- ^ Maver, William Jr. (1903). American Telegraphy and Encyclopedia of the Telegraph: Systems, Apparatus, Operation. New York: Maver Publishing Co. p. 333.
wireless telegraphy.
- ^ Steuart, William Mott; et al. (1906). Special Reports: Telephones and Telegraphs 1902. Washington D.C.: U.S. Bureau of the Census. pp. 118–119.
- ^ a b c d https://earlyradiohistory.us/sec022.htm Thomas H. White, United States Early Radio History, Section 22
- ^ Collins, A. Frederick (10 May 1902). "The Genesis of Wireless Telegraphy". Electrical World and Engineer. p. 811.
- ^ "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.
- ^ "Wireless Telegraphy", The Electrical Review (London), 20 January 1905, page 108, quoting from the British Post Office's 30 December 1904 Post Office Circular.
- ^ "Interference with Wireless Messages", Electrical World, 22 June 1907, page 1270.
- ^ Sungook Hong (2001), Wireless: From Marconi's Black-box to the Audion, MIT Press, pp. 5–10
- NobelPrize.org. 2023. Archivedfrom the original on 31 July 2023. Retrieved 31 July 2023.
- ISBN 0074632191.
- ISBN 978-0495386933.
- ISBN 978-1118585733.
- ^ ISBN 978-1316785164.
- ISBN 978-1119990253. Retrieved 29 August 2022.
- ^ "Omnidirectional Antenna - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 5 September 2022.
- ^ "Electromagnetic Radiation". NASA. Archived from the original on 23 May 2016. Retrieved 18 August 2022.
- Physics Stack Exchange. July 2019. Archivedfrom the original on 18 August 2022. Retrieved 18 August 2022.
- ^ a b c Brain, Marshall (7 December 2000). "How Radio Works". HowStuffWorks.com. Retrieved 11 September 2009.
- ^ ISBN 978-3319412023. Retrieved 29 August 2022.
- ISBN 978-0387681894.
- ^ Tony Dorbuck (ed.), The Radio Amateur's Handbook, Fifty-Fifth Edition, American Radio Relay League, 1977, p. 368
- ^ John Avison, The World of Physics, Nelson · 2014, page 367
- ^ C-W and A-M Radio Transmitters and Receivers, United States. Department of the Army – 1952, pp. 167–168
- ^ a b c d "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
- ^ ISBN 978-0470393529. Retrieved 29 August 2022.
- ^ 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.
- ^ "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.
- ^ "Radio Regulations, 2016 Edition" (PDF). International Telecommunication Union. 3 November 2016. Retrieved 9 November 2019. Article 2, Section 1, p.27
- ^ a b 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.
- ^ Communications-electronics Management of the Electromagnetic Spectrum (Report). Headquarters, Department of the Army. United States Department of the Army. 1973. p. 2.
- S2CID 238934419.
- ^ "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.
- ISBN 978-1118511794. Retrieved 29 August 2022.
- ^ "ARTICLE 19 Identification of stations" (PDF). International Telecommunication Union. Retrieved 29 August 2022.
- ^ "Commercial Radio Operator Types of Licenses". Federal Communications Commission. 6 May 2016. Retrieved 29 August 2022.
- ^ Dichoso, Joe (October 9, 2007). "FCC Basics of Unlicensed Transmitters" (PDF). Federal Communications Commission. Retrieved 29 August 2022.
- ISBN 978-0415733397.
- ISBN 978-1351564588. Retrieved 30 August 2022.
- ^ Bonsor, Kevin (26 September 2001). "How Satellite Radio Works". howstuffworks.com. HowStuffWorks. Retrieved 30 August 2022.
- ISBN 978-0750637411. Retrieved 30 August 2022.
- ISBN 978-1884932137. Retrieved 30 August 2022.
- ISBN 978-1317906834. Retrieved 30 August 2022.
- ISBN 978-1483288970. Retrieved 30 August 2022.
- ^ Green, Clarence R.; Bourque, Robert M. (1980). The Theory and Servicing of AM, FM, and FM Stereo Receivers. Prentice-Hall. p. 6.
- ^ "Appendix C: Glossary" (PDF). Radio – Preparing for the Future (Report). London: Ofcom. October 2005. p. 2.
- ^ ISBN 978-9390649808. Retrieved 30 August 2022.
- ^ ISBN 978-0786451982. Retrieved 30 August 2022.
- ISBN 978-0807877555. Retrieved 30 August 2022.
- ^ Digital Radio Guide (PDF) (Report). Switzerland: World Broadcasting Unions. 2017.
- ^ Baker, William (2020). "DAB vs. FM: The differences between analog and digital radio". Radio Fidelity online magazine. Retrieved 14 September 2020.
- ^ ISBN 978-0470871423. Retrieved 30 August 2022.
- ^ Revel, Timothy (10 January 2017). "Norway is first country to turn off FM radio and go digital-only". New Scientist. Retrieved 4 September 2022.
- ^ McLane, Paul (30 August 2021). "Swiss FM shutdown reverts to original 2024 date". Radio World. Retrieved 4 September 2022.
- ^ Trends in Radio Research: Diversity, innovation, and policies. Cambridge Scholars Publishing. 2018. p. 263.
- ^ Bortzfield, Bill (27 November 2017). The state of HD Radio in Jacksonville and nationwide. WJCT Public Media (Report). Retrieved 4 September 2022.
- ^ Hadfield, Marty (15 August 2016). Transmitter & programming considerations for HD Radio. RBR + TVBR (rbr.com) (Report). Retrieved 4 September 2022.
- ^ "Receiving NRSC‑5". theori.io. 9 June 2017. Archived from the original on 20 August 2017. Retrieved 14 April 2018.
- ISBN 978-1136034107.
- ^ a b 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 ETSI.org.
- ^ Satellite S‑band radio frequency table (Report). 15 August 2011. Retrieved 23 April 2013 – via CSG Network.
- ^ Bonsor, Kevin (26 September 2001). "How satellite radio works". HowStuffWorks. Retrieved 1 May 2013.
- ISBN 978-1904764069. Retrieved 31 August 2022.
- ISBN 978-1137273345. Retrieved 31 August 2022.
- ISBN 978-0750657211. Retrieved 31 August 2022.
- ^ 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) - ISBN 978-1136032820.
- ^ ISBN 978-0830614745. Retrieved 1 September 2022.
- ISBN 9781577858461.
- ISBN 978-0340741085. Retrieved 1 September 2022.
- ISBN 978-0750671712. Retrieved 1 September 2022.
- ISBN 978-0792384250. Retrieved 1 September 2022.
- ^ "What Closing A Government Radio Station Would Mean For Your Clocks". National Public Radio, Weekend Edition. Retrieved 1 September 2022.
- ISBN 978-0128118795. Retrieved 2 September 2022.
- ^ a b Brain, Marshall; Tyson, Jeff; Layton, Julia (2018). "How Cell Phones Work". How Stuff Works. InfoSpace Holdings LLC. Retrieved 31 December 2018.
- PCWorld. Retrieved 2 September 2022.
- ISBN 978-1107143210.
- ^ "Cellular Telephone Basics". Privateline.com. 1 January 2006. p. 2. Archived from the original on 17 April 2012. Retrieved 2 September 2022.
- ^ Brown, Sara. "5G, explained". mitsloan.mit.edu. MIT Sloan School of Management. Retrieved 2 September 2022.
- ISBN 978-1107130098. Retrieved 2 September 2022.
- ^ Chandler, Nathan (13 February 2013). "How Satellite Phones Work". howstuffworks.com. HowStuffWorks. Retrieved 2 September 2022.
- ^ "Satellite Phone : Functioning/Working Of Satellite Phone". tutorialsweb.com. Tutorials Web. Retrieved 2 September 2022.
- ^ McComb, Gordon (October 1982). "Never Miss a Call: PS Buyer's Guide to Cordless Phones". Popular Science. pp. 84–85 – via Google Books.
- ISSN 0362-4331. Retrieved 7 September 2022.
- ^ 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.
- ISBN 978-1851097326.
- ^ Aeronautical Frequency Committee Manual (PDF) (Report). Aviation Spectrum Resources Inc. 2012.
- ^ "Aviation Radio Bands and Frequencies". Smeter network 2011. Archived from the original on 12 February 2004. Retrieved 16 February 2011.
- ^ North Atlantic Operations and Airspace Manual (PDF) (Report). ICAO European and North Atlantic Office. 28 March 2019.
- ^ Van Horn, Larry. "The Military VHF/UHF Spectrum". Monitoring Times.
- OCLC 48674566.
- OCLC 961215964.
- ^ Brain, Marshall (11 February 2021). "Radio basics: Real life examples". How radio works. How Stuff Works website. Retrieved 27 August 2022.
- ISBN 978-1926933481.
- ^ "Best Baby Monitor Buying Guide". Consumer Reports. 24 April 2016. Retrieved 9 September 2022.
- ISBN 978-1136118067– via Google Books.
- ^ Bell, Dee Ana (1 November 2012). "Avoiding Audio Problems with Wireless Microphone Systems". TV Technology. Retrieved 10 September 2022.
- ^ Vernon, Tom (28 August 2021). "Wireless Mic Industry Debates WMAS Technology". Radio World. Retrieved 10 September 2022.
- ISBN 978-0764579776. Retrieved 12 September 2022.
- ^ ISBN 978-1119748670. Retrieved 12 September 2022.
- ISBN 978-0071429139. Archivedfrom the original on 24 June 2021. Retrieved 12 September 2022.
- ISBN 978-0872591356. Retrieved 12 September 2022.
- ISBN 978-0470689936. Retrieved 12 September 2022.
- ISBN 978-1317347927. Retrieved 12 September 2022.
- ^ Radio-Electronics-Television Manufacturers Association. Engineering Department (1955). "Microwave Relay Systems for Communications". Electronic Industries Association. Retrieved 12 September 2022.
- ISBN 978-0080473895. Retrieved 12 September 2022.
- ISBN 978-3847372219. Retrieved 12 September 2022.
- ^ Bonsor, Kevin (28 August 2001). "How E-ZPass Works". howstuffworks.com. HowStuff Works. Retrieved 12 September 2022.
- ISBN 978-0470112243. Retrieved 12 September 2022.
- ^ White, Ryan (17 December 2021). "How do submarines communicate with the outside world?". navalpost.com. Naval Post. Retrieved 12 September 2022.
- ^ "Naval Research Reviews, Vol. 27". Superintendent of Government Documents. 1974. Retrieved 12 September 2022.
- ^ "Ground infrastructure". Russian Satellite Communications Company.
- ^ "State-of-the-Art of Small Spacecraft Technology, 9.0 - Communications". nasa.gov. National Aeronautics and Space Administration. 16 October 2021. Retrieved 11 September 2022.
- ^ "UCS Satellite Database". Union of Concerned Scientists. 1 January 2021. Retrieved 21 May 2021.
- ISBN 978-1483276816. Retrieved 11 September 2022.
- ^ "Satellite TV-Direct Broadcast Satellite System, DBS TV". rfwireless-world.com. RF Wireless World. Retrieved 11 September 2022.
- ^ Brain, Marshall (2020). "How radar works". How Stuff Works. Retrieved 3 September 2022.
- ^ a b Skolnik, Merrill (2021). "Radar". Encyclopædia Britannica online. Encyclopædia Britannica Inc. Retrieved 3 September 2022.
- ^ "JetStream". www.noaa.gov.
- ISBN 9056991655.
- ^ "Airport Surveillance Radar". Air traffic control, technology. US Federal Aviation Administration website. 2020. Retrieved 3 September 2022.
- ISBN 978-1119259541. Retrieved 11 September 2022.
- ISBN 978-1580538985. Retrieved 11 September 2022.
- ^ Bhattacharjee, Shilavadra (2021). "Marine Radars and Their Use in the Shipping Industry". Marine Insight website. Retrieved 3 September 2022.
- ^ "Using and Understanding Doppler Radar". US National Weather Service website. US National Weather Service, NOAA. 2020. Retrieved 3 September 2022.
- ISBN 978-1596932739. Retrieved 11 September 2022.
- ISBN 978-1862392298. Retrieved 11 September 2022.
- ISBN 978-0080951843. Retrieved 10 September 2022.
- S2CID 110665898. Retrieved 10 September 2022.
- ISBN 0253201616. Retrieved 10 September 2022.
- ISBN 978-9811087912. Retrieved 10 September 2022.
- ISBN 978-3319429281. Retrieved 10 September 2022.
- ISBN 978-1580531832. Retrieved 10 September 2022.
- ISBN 978-0766075184. Retrieved 10 September 2022.
- ^ Deltour, B.V. (August 1960). "A Guide To Nav-Com Equipment". Flying Magazine Aug 1960. Retrieved 10 September 2022.
- ^ "2008 Federal Radionavigation Plan". U.S. Department of Defense. 2009. Retrieved 10 September 2022.
- ^ Martin, Swayne. "How A VOR Works". boldmethod.com. Boldmethod -Digital Aviation Content. Retrieved 10 September 2022.
- ^ "Non-Directional Beacon (NDB)". systemsinterface.com. Systems Interface. Retrieved 10 September 2022.
- ^ "How does an emergency beacon work?". cbc.ca. CBC News. Retrieved 10 September 2022.
- ^ "What is a Cospas-Sarsat Beacon?". cospas-sarsat.int. International Cospas-Sarsat Programme. Retrieved 10 September 2022.
- ^ "Scientific and Technical Aerospace Reports, Volume 23, Issue 20". NASA, Office of Scientific and Technical Information. 1985. Retrieved 10 September 2022.
- ^ "An Introduction to Radio Direction Finding". defenceweb.co.za. defenceWeb. 8 January 2021. Retrieved 10 September 2022.
- ISBN 978-0830627011. Retrieved 10 September 2022.
- ^ "Radio telemetry". Migratory Connectivity Project, Smithsonian Migratory Bird Center. Retrieved 10 September 2022.
- ^ Layton, Julia (10 November 2005). "How Remote Controls Work". HowStuff Works. Retrieved 10 September 2022.
- ISBN 978-1119508694. Retrieved 10 September 2022.
- ISBN 978-1593277703. Retrieved 10 September 2022.
- ISBN 978-1789140996. Retrieved 9 September 2022.
- ISBN 978-3030253127. Retrieved 9 September 2022.
- ISBN 978-0470396377. Retrieved 9 September 2022.
- ^ Wonning, Paul R. (12 May 2021). "A Guide to the Home Electric System". Mossy Feet Books. Retrieved 9 September 2022.
- ISBN 978-3110691283. Retrieved 9 September 2022.
- ^ "What jamming of a wireless security system is and how to resist it | Ajax Systems Blog". Ajax Systems. Retrieved 18 January 2020.
- ^ "Remedial Electronic Counter-Countermeasures Techniques". FM 24-33 — Communications Techniques: Electronic Counter-Countermeasures (Report). Department of the Army. July 1990.
- S2CID 145418504.
- ^ "Jammer Enforcement". Federal Communications Commission. 3 March 2011. Retrieved 18 January 2020.
- ISBN 978-1799823834. Retrieved 9 September 2022.
- ISBN 978-1937585624.
- ISBN 978-1119669074. Retrieved 9 September 2022.
- ISBN 9067643181. Retrieved 9 September 2022.
General references
- Basic Radio Principles and Technology – Elsevier Science
- The Electronics of Radio – Cambridge University Press
- Radio Systems Engineering – Cambridge University Press
- Radio-Electronic Transmission Fundamentals – SciTech Publishing
- Analog Electronics, Analog Circuitry Explained – Elsevier Science