Radio spectrum
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The radio spectrum is the part of the
electromagnetic spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...
with frequencies from 3  Hz to 3,000 
GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
(3  THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in
telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...
. 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 The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...
(ITU). Different parts of the radio spectrum are allocated by the ITU for different radio transmission technologies and applications; some 40 radiocommunication services are defined in the ITU's Radio Regulations (RR). In some cases, parts of the radio spectrum are sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations). Ranges of allocated frequencies are often referred to by their provisioned use (for example, cellular spectrum or television spectrum). 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 utilize it more effectively is driving modern telecommunications innovations such as trunked radio systems, spread spectrum, ultra-wideband, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio.


Limits

The
frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
boundaries of the radio spectrum are a matter of convention in physics and are somewhat arbitrary. Since radio waves are the lowest frequency category of
electromagnetic wave In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ...
s, there is no lower limit to the frequency of radio waves.Radio waves are defined by the ITU as: "electromagnetic waves of frequencies arbitrarily lower than 3000 GHz, propagated in space without artificial guide", Radio waves are defined by the ITU as: "electromagnetic waves of frequencies arbitrarily lower than 3000 GHz, propagated in space without artificial guide". At the high frequency end the radio spectrum is bounded by the
infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
band. The boundary between radio waves and infrared waves is defined at different frequencies in different scientific fields. The terahertz band, from 300 gigahertz to 3 terahertz, can be considered either as microwaves or infrared. It is the highest band categorized as radio waves by the
International Telecommunication Union The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...
. but spectroscopic scientists consider these frequencies part of the far infrared and mid infrared bands. Because it is a fixed resource, the ''practical'' limits and basic physical considerations of the radio spectrum, the frequencies which are useful for
radio communication Radio is the technology of telecommunication, communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...
, are determined by technological limitations which are impossible to overcome. So although the radio spectrum is becoming increasingly congested, there is no possible way to add additional frequency bandwidth outside of that currently in use. The lowest frequencies used for radio communication are limited by the increasing size of transmitting antennas required. The size of antenna required to radiate radio power efficiently increases in proportion to
wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
or inversely with frequency. Below about 10 kHz (a wavelength of 30 km), elevated wire antennas kilometers in diameter are required, so very few radio systems use frequencies below this. A second limit is the decreasing bandwidth available at low frequencies, which limits the data rate that can be transmitted. Below about 30 kHz, audio modulation is impractical and only slow baud rate data communication is used. The lowest frequencies that have been used for radio communication are around 80 Hz, in ELF submarine communications systems built by a few nations' navies to communicate with their submerged submarines hundreds of meters underwater. These employ huge ground dipole antennas 20–60 km long excited by megawatts of transmitter power, and transmit data at an extremely slow rate of about 1 bit per minute (17 millibits per second, or about 5 minutes per character). The highest frequencies useful for radio communication are limited by the absorption of microwave energy by the atmosphere. As frequency increases above 30 GHz (the beginning of the millimeter wave band), atmospheric gases absorb increasing amounts of power, so the power in a beam of radio waves decreases exponentially with distance from the transmitting antenna. At 30 GHz, useful communication is limited to about 1 km, but as frequency increases the range at which the waves can be received decreases. In the terahertz band above 300 GHz, the radio waves are attenuated to zero within a few meters due to the absorption of electromagnetic radiation by the atmosphere (mainly due to
ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
,
water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
and
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
), which is so great that it is essentially opaque to
electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...
emissions, until it becomes transparent again near the
near-infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
and optical window frequency ranges.


Bands

A radio band is a small
frequency band Spectral bands are regions of a given spectrum, having a specific range of wavelengths or frequencies. Most often, it refers to electromagnetic bands, regions of the electromagnetic spectrum. More generally, spectral bands may also be means in ...
(a contiguous section of the range of the radio spectrum) in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands. For example, broadcasting, mobile radio, or navigation devices, will be allocated in non-overlapping ranges of frequencies.


Band plan

For each radio band, the ITU has a band plan (or frequency plan) which dictates how it is to be used and shared, to avoid interference and to set protocol for the compatibility of
transmitter In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna (radio), antenna with the purpose of sig ...
s and receivers. Each frequency plan defines the frequency range to be included, how channels are to be defined, and what will be carried on those channels. Typical definitions set forth in a frequency plan are: * numbering scheme – which channel numbers or letters (if any) will be assigned * center frequencies – how far apart the carrier wave for each channel will be * bandwidth and/or deviation – how wide each channel will be * spectral mask – how extraneous
signal A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In ...
s will be attenuated by frequency *
modulation Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...
– what type will be used or are permissible *content – what types of information are allowed, such as audio or
video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...
, analog or digital *
licensing A license (American English) or licence ( Commonwealth English) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another par ...
– what the procedure will be to obtain a
broadcast license A broadcast license is a type of spectrum license granting the licensee permission to use a portion of the radio frequency spectrum in a given geographical area for broadcasting purposes. The licenses generally include restrictions, which va ...


ITU

The actual authorized frequency bands are defined by the ITU and the local regulating agencies like the US
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...
(FCC) and voluntary best practices help avoid interference. As a matter of convention, the ITU divides the radio spectrum into 12 bands, each beginning at a
wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
which is a power of ten (10''n'') metres, with corresponding frequency of 3×108−''n'' 
hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
, and each covering a decade of frequency or wavelength. Each of these bands has a traditional name. For example, the term '' high frequency'' (HF) designates the wavelength range from 100 to 10 metres, corresponding to a frequency range of 3 to 30 MHz. This is just a symbol and is not related to allocation; the ITU further divides each band into subbands allocated to different services. Above 300 GHz, the absorption of
electromagnetic radiation In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength ...
by Earth's atmosphere is so great that the atmosphere is effectively opaque, until it becomes transparent again in the
near-infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
and optical window frequency ranges. These ''ITU radio bands'' are defined in the ITU Radio Regulations. Article 2, provision No. 2.1 states that "the radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table".ITU Radio Regulations, Volume 1, Article 2; Edition of 2020. Available online at The table originated with a recommendation of the fourth CCIR meeting, held in Bucharest in 1937, and was approved by the International Radio Conference held at Atlantic City, NJ in 1947. The idea to give each band a number, in which the number is the logarithm of the approximate geometric mean of the upper and lower band limits in Hz, originated with B. C. Fleming-Williams, who suggested it in a letter to the editor of ''Wireless Engineer'' in 1942. For example, the approximate geometric mean of band 7 is 10 MHz, or 107 Hz. The band name "tremendously low frequency" (TLF) has been used for frequency and wavelength of 1–3 Hz , 300,000–100,000 km (1000 Mm), but the term has not been defined by the ITU.


IEEE radar bands

Frequency bands in the
microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
range are designated by letters. This convention began around World War II with military designations for frequencies used in
radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
, which was the first application of microwaves. There are several incompatible naming systems for microwave bands, and even within a given system the exact frequency range designated by a letter may vary somewhat between different application areas. One widely used standard is the ''IEEE radar bands'' established by the US
Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is an American 501(c)(3) public charity professional organization for electrical engineering, electronics engineering, and other related disciplines. The IEEE has a corporate office ...
.


EU,

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...
, US ECM frequency designations


Waveguide frequency bands


Comparison of radio band designation standards

A frequency of 1–3 Hz has been called TLF but the term has not been defined by the ITU.


Applications


Broadcasting

Broadcast frequencies: * Longwave AM Radio = 148.5 kHz – 283.5 kHz (LF) * Mediumwave AM Radio = 520 kHz – 1700 kHz (MF) * Shortwave AM Radio = 3 MHz – 30 MHz (HF) Designations for television and FM radio broadcast frequencies vary between countries, see Television channel frequencies and FM broadcast band. Since VHF and UHF frequencies are desirable for many uses in urban areas, in North America some parts of the former television broadcasting band have been reassigned to
cellular phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This radi ...
and various land mobile communications systems. Even within the allocation still dedicated to television, TV-band devices use channels without local broadcasters. The Apex band in the United States was a pre-WWII allocation for VHF audio broadcasting; it was made obsolete after the introduction of FM broadcasting.


Air band

Airband refers to VHF frequencies 108 to 137 MHz, used for navigation and voice communication with aircraft. Trans-oceanic aircraft also carry HF radio and satellite transceivers.


Marine band

The greatest incentive for development of radio was the need to communicate with ships out of visual range of shore. From the very early days of radio, large oceangoing vessels carried powerful long-wave and medium-wave transmitters. High-frequency allocations are still designated for ships, although satellite systems have taken over some of the safety applications previously served by 500 kHz and other frequencies. 2182 kHz is a medium-wave frequency still used for marine emergency communication. Marine VHF radio is used in coastal waters and relatively short-range communication between vessels and to shore stations. Radios are channelized, with different channels used for different purposes; marine Channel 16 is used for calling and emergencies.


Amateur radio frequencies

Amateur radio frequency allocations vary around the world. Several bands are common for amateurs worldwide, usually in the HF part of the spectrum. Other bands are national or regional allocations only due to differing allocations for other services, especially in the VHF and UHF parts of the radio spectrum.


Citizens' band and personal radio services

Citizens' band radio is allocated in many countries, using channelized radios in the upper HF part of the spectrum (around 27 MHz). It is used for personal, small business and hobby purposes. Other frequency allocations are used for similar services in different jurisdictions, for example UHF CB is allocated in Australia. A wide range of personal radio services exist around the world, usually emphasizing short-range communication between individuals or for small businesses, simplified license requirements or in some countries covered by a class license, and usually FM transceivers using around 1 watt or less.


Industrial, scientific, medical

The ISM bands were initially reserved for non-communications uses of RF energy, such as
microwave oven A microwave oven, or simply microwave, is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces Dipole#Molecular dipoles, polar molecules in the food to rotate and ...
s, radio-frequency heating, and similar purposes. However, in recent years the largest use of these bands has been by short-range low-power communications systems, since users do not have to hold a radio operator's license.
Cordless telephone 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 ...
s, wireless computer networks,
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is li ...
devices, and
garage door opener A garage door opener is a motorized device that opens and closes a garage door controlled by switches on the garage wall. Most also include a handheld radio remote control carried by the owner, which can be used to open and close the door from ...
s all use the ISM bands. ISM devices do not have regulatory protection against interference from other users of the band.


Land mobile bands

Bands of frequencies, especially in the VHF and UHF parts of the spectrum, are allocated for communication between fixed base stations and land mobile vehicle-mounted or portable transceivers. In the United States these services are informally known as business band radio. See also Professional mobile radio. Police radio and other public safety services such as fire departments and ambulances are generally found in the VHF and UHF parts of the spectrum. Trunking systems are often used to make most efficient use of the limited number of frequencies available. The demand for mobile telephone service has led to large blocks of radio spectrum allocated to
cellular frequencies Cellular frequencies are the sets of frequency ranges within the ultra high frequency band that have been frequency assignment, assigned for cellular-compatible mobile devices, such as mobile phones, to connect to cellular networks.Guowang Miao, ...
.


Radio control

Reliable radio control uses bands dedicated to the purpose. Radio-controlled toys may use portions of unlicensed spectrum in the 27 MHz or 49 MHz bands, but more costly aircraft, boat, or land vehicle models use dedicated radio control frequencies near 72 MHz to avoid interference by unlicensed uses. The 21st century has seen a move to 2.4 GHz spread spectrum RC control systems. Licensed
amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...
operators use portions of the 6-meter band in North America. Industrial remote control of cranes or railway locomotives use assigned frequencies that vary by area.


Radar

Radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
applications use relatively high power pulse transmitters and sensitive receivers, so radar is operated on bands not used for other purposes. Most radar bands are in the
microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
part of the spectrum, although certain important applications for
meteorology Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agricultur ...
make use of powerful transmitters in the UHF band.


See also


Notes


References

*ITU-R Recommendation V.431
Nomenclature of the frequency and wavelength bands used in telecommunications
International Telecommunication Union The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...
, Geneva. *IEEE Standard 521-2002: Standard Letter Designations for Radar-Frequency Bands *AFR 55-44/AR 105-86/OPNAVINST 3430.9A/MCO 3430.1, 27 October 1964 superseded by AFR 55-44/AR 105-86/OPNAVINST 3430.1A/MCO 3430.1A, 6 December 1978: Performing Electronic Countermeasures in the United States and Canada, Attachment 1,ECM Frequency Authorizations.


External links


UnwantedEmissions.com
A reference to radio spectrum allocations.

European Commission policy. {{Authority control