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A broadcast range (also listening range or listening area for
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a trans ...
, or viewing range or viewing area for
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertising, ...
) is the service area that a broadcast station or other transmission covers via
radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm ( ...
s (or possibly
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
, which is closely related). It is generally the area in which a station's
signal strength In telecommunications, particularly in radio frequency engineering, signal strength refers to the transmitter power output as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those ...
is sufficient for most receivers to decode it. However, this also depends on
interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extr ...
from other stations.


Legal definitions

The "primary service area" is the area served by a station's strongest signal. The "city-grade contour" is 70 dBμ (
decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
s relative to one microvolt per meter of signal strength) or 3.16mV/m (millivolts per meter) for FM stations in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
, according to
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdi ...
(FCC) regulations. This is also significant in
broadcast law Broadcast law is the field of law that pertains to broadcasting. These laws and regulations pertain to radio stations and TV stations, and are also considered to include closely related services like cable TV and cable radio, as well as satel ...
, in that a station must cover its
city of license In American, Canadian, and Mexican broadcasting, a city of license or community of license is the community that a radio station or television station is officially licensed to serve by that country's broadcast regulator. In North American bro ...
within this area, except for
non-commercial educational A non-commercial educational station (NCE station) is a radio station or television station that does not accept on-air advertisements ( TV ads or radio ads), as defined in the United States by the Federal Communications Commission (FCC) and was ...
and low-power stations. The legally protected range of a station extends beyond this range, out to the point where signal strength is expected to be 1mV/m for most stations in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the C ...
, though for class B1 stations it is 0.7mV/m, and as low as 0.5mV/m for full class B stations (the maximum allowed in densely populated areas of both
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world ...
and the U.S.).


Practical application

In reality,
radio propagation Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affec ...
changes along with the
weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...
and tropospheric ducting, and occasionally along with other upper-
atmospheric An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
phenomena like
sunspot Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection ...
s and even
meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extre ...
s. Thus, while a broadcasting authority might fix the range to an area with exact boundaries (defined as a series of
vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...
s), this is rarely if ever true. When a broadcast reaches well outside of its intended range due to unusual conditions,
DXing DXing is the hobby of receiving and identifying distant radio or television signals, or making two-way radio contact with distant stations in amateur radio, citizens' band radio or other two-way radio communications. Many DXers also attempt to ...
is possible. The local terrain can also play a major role in limiting broadcast range.
Mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have aris ...
s block
FM broadcast FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is ca ...
s,
AM broadcast AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmis ...
s, and TV broadcasts, and other signals in the
VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...
and especially
UHF 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 ( ...
ranges, respectively. This terrain shielding occurs when the line of sight is blocked by something through which the
radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm ( ...
s cannot pass, particularly stone. At times this may be
moot Moot may refer to: * Mootness, in American law: a point where further proceedings have lost practical significance; whereas in British law: the issue remains debatable * Moot court, an activity in many law schools where participants take part in s ...
due to weather, such as when the tall
cumulonimbus Cumulonimbus (from Latin ''cumulus'', "heaped" and ''nimbus'', "rainstorm") is a dense, towering vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. ...
clouds of a
squall line A squall line, or more accurately a quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front (which often are accomp ...
of
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...
s reflect the signal over the top, like an extremely tall
radio tower Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-ma ...
. Conversely, heavy rain may
attenuate In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable ...
the range of even local stations.
ATSC Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like th ...
digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advan ...
is affected by wind and trees (even if not surrounding the transmitter or receiver locations), apparently related to its use of 8VSB
modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...
instead of
COFDM In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital commun ...
.
AM broadcasting AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transm ...
stations have different issues, due to using the
mediumwave Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytime ...
band. Broadcast range in these stations is determined by
ground conductivity Ground conductivity refers to the electrical conductivity of the subsurface of the earth. In the International System of Units (SI) it is measured in millisiemens per meter (mS/m). Radio propagation Ground conductivity is an extremely important ...
, and the proper use and
maintenance Maintenance may refer to: Biological science * Maintenance of an organism * Maintenance respiration Non-technical maintenance * Alimony, also called ''maintenance'' in British English * Champerty and maintenance, two related legal doctri ...
of grounding radials which act as a
ground plane In electrical engineering, a ground plane is an electrically conductive surface, usually connected to electrical ground. The term has two different meanings in separate areas of electrical engineering. *In antenna theory, a ground plane is a ...
for the
mast radiator Mast, MAST or MASt may refer to: Engineering * Mast (sailing), a vertical spar on a sailing ship * Flagmast, a pole for flying a flag * Guyed mast, a structure supported by guy-wires * Mooring mast, a structure for docking an airship * Radio mas ...
s used. Skywaves reflect off the
ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays a ...
at a much greater distance above Earth's surface at night. This in turn causes mediumwave, most
shortwave Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the High frequency, high frequency band (HF), which extends from 3 to 30 MHz (10 ...
, and even
longwave In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the ...
stations to travel much further at night, which is the side of the Earth where the
solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the ...
pulls the ionosphere (and
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dy ...
) away from the
planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a yo ...
, instead of pushing toward it as on the day side. Because of this, many AM stations must cut power or go off-air at night, except for the very earliest stations still
grandfathered A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...
on clear channels. Border blaster stations in northern
Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Gua ...
also used this effect, along with very high-
power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may ...
transmitter 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 ...
s, to extend their nighttime broadcast ranges well over the US/Mexico border and across most of the United States. Various
broadcast relay station A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater (two-way radio) or complementary station (Mexico), is a broadcast transmitter which repeats (or tra ...
s can help to extend a station's area by retransmitting them on the same or another channel. What is usually called a
repeater In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some ...
in
amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency comm ...
is called a
broadcast translator A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater (two-way radio) or complementary station (Mexico), is a broadcast transmitter which repeats (or tran ...
(different channel) or booster (same channel) in American broadcasting, or the much broader category or
rebroadcaster A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater (two-way radio) or complementary station (Mexico), is a broadcast transmitter which repeats (or tran ...
s in Canadian broadcasting (which includes more than just the
low-power broadcasting Low-power broadcasting is broadcasting by a broadcast station at a low transmitter power output to a smaller service area than "full power" stations within the same region. It is often distinguished from "micropower broadcasting" (more commonly ...
used in the U.S.) Boosters are used only within the broadcast range of the parent station, and serve the same function locally as regional and national single-frequency networks do in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
. Distributed transmission has also undergone tests in the U.S., but to preserve stations'
market share Market share is the percentage of the total revenue or sales in a market that a company's business makes up. For example, if there are 50,000 units sold per year in a given industry, a company whose sales were 5,000 of those units would have a ...
in their home
media market A media market, broadcast market, media region, designated market area (DMA), television market area, or simply market is a region where the population can receive the same (or similar) television and radio station offerings, and may also incl ...
s, these will be limited to the broadcast area of a single large station.
Satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a '' broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than te ...
, which is designed for use without a dish, also uses ground repeaters in large cities due to the many obstructions their high-rise buildings cause to the many current and potential customers that are concentrated there.


Edge-of-range issues

Those at the edge of a station's broadcast range will typically notice
static Static may refer to: Places *Static Nunatak, a nunatak in Antarctica United States * Static, Kentucky and Tennessee * Static Peak, a mountain in Wyoming ** Static Peak Divide, a mountain pass near the peak Science and technology Physics *Static ...
in an analog broadcast, while
error correction In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communic ...
will keep a
digital signal A digital signal is a signal that represents data as a sequence of discrete values; at any given time it can only take on, at most, one of a finite number of values. This contrasts with an analog signal, which represents continuous values; at ...
clear until it hits the
cliff effect In telecommunications, the (digital) cliff effect or brickwall effect is a sudden loss of digital signal reception. Unlike analog signals, which gradually fade when signal strength decreases or electromagnetic interference or multipath increases ...
and suddenly disappears completely. FM stations may flip back and forth (sometimes annoyingly rapidly when moving) due to the
capture effect In a radio receiver, the capture effect, or FM capture effect, is a phenomenon associated with FM reception in which only the stronger of two signals at, or near, the same frequency or channel will be demodulated. FM phenomenon The capture ...
, while AM stations (including TV video) may overlay or fade with each other.
FM stereo FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is c ...
will tend to get static more quickly than the
monophonic Monaural or monophonic sound reproduction (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduc ...
sound due to its use of
subcarrier 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 bro ...
s, so stations may choose to extend the usable part of their range by disabling the stereo generator. Listeners can also choose to disable stereo decoding on the receiver, though loss of the stereo pilot tone causes this to happen automatically. Because this tends to turn on and off when at the threshold of reception, and the threshold is often set too low by the
manufacturer Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a r ...
's
product design Product design as a verb is to create a new product to be sold by a business to its customers. A very broad coefficient and effective generation and development of ideas through a process that leads to new products. Thus, it is a major aspect of ...
, manually disabling this when at the edge of the broadcast range prevents the annoying noisy-stereo/quiet-mono switching. The same is true of
analog TV Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog s ...
stereo and
second audio program Second audio program (SAP), also known as secondary audio programming, is an auxiliary audio channel for analog television that can be broadcast or transmitted both over-the-air and by cable television. Used mostly for audio description or oth ...
s, and even for color TV, all of which use subcarriers.
Radio reading service A radio reading service or reading service for the blind is a public service of many universities, community groups and public radio stations, where a narrator reads books, newspapers and magazines aloud for the benefit of the blind and vision-imp ...
s and other subcarrier services will also tend to suffer from dropouts sooner than the main station. Technologies are available that allow for switching to a different signal carrying the same radio program when leaving the broadcast range of a station.
Radio Data System Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identificat ...
allows for switching to a different FM or station with the same
identifier An identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of objects, where the "object" or class may be an idea, physical countable object (or class thereof), or physical mass noun, non ...
, or even to (but not necessarily from) an AM station. Satellite radio also is designed to switch seamlessly between repeaters and/or satellite when moving outside the range of one or the other.
HD Radio HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. It generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used ...
switches back to the analog signal as a fallback when the edge of the digital range is encountered, but the success of this from the listener's perspective depends on how well the station's
broadcast engineer Broadcast engineering is the field of electrical engineering, and now to some extent computer engineering and information technology, which deals with radio and television broadcasting. Audio engineering and RF engineering are also essential ...
has synchronized the two.


Digital versus analog

Digital transmissions require less power to be received clearly than analog ones. The exact figure for various modes depends on how robust the signal is made to begin with, such as modulation,
guard interval In telecommunications, guard intervals are used to ensure that distinct transmissions do not interfere with one another, or otherwise cause overlapping transmissions. These transmissions may belong to different users (as in TDMA) or to the same ...
, and
forward error correction In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...
. In each of these three factors, the caveat is that a higher
data signaling rate In telecommunication, data signaling rate (DSR), also known as gross bit rate, is the aggregate rate at which data passes a point in the transmission path of a data transmission system. # The DSR is usually expressed in bits per second. # The ...
means a
tradeoff A trade-off (or tradeoff) is a situational decision that involves diminishing or losing one quality, quantity, or property of a set or design in return for gains in other aspects. In simple terms, a tradeoff is where one thing increases, and anot ...
with reduced broadcast range. The hierarchical modulation used on DVB is a unique case, which reduces the range of the full-
definition A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional defi ...
signal, in exchange for an increase in the usable range of the lower-definition part of the video. Digital stations in North America usually are operated by the same groups as the analog side, and thus operate their own independent facilities. Because of this, the FCC requires U.S. TV stations to replicate their analog coverage with their digital signal as well. However, ATSC digital TV only requires about one-fifth the amount of power to reach the same area on the same channel as analog does. For HD Radio, the figure is only one percent of the station's analog
watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...
age, in part because it is an
in-band on-channel In-band on-channel (IBOC) is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency. The name refers to the new digital signals being broadcast in the same AM or FM band (in-band), ...
method, which uses
sideband In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal. The sidebands c ...
s that must prevent interference to
adjacent channel In broadcasting an adjacent channel is an AM, FM, or TV channel that is next to another channel. First-adjacent is immediately next to another channel, second-adjacent is two channels away, and so forth. Information on adjacent channels is u ...
s, especially for older or cheaper receivers which have insufficient sensitivity and/or
selectivity Selectivity may refer to: Psychology and behaviour * Choice, making a selection among options * Discrimination, the ability to recognize differences * Socioemotional selectivity theory, in social psychology Engineering * Selectivity (radio), a ...
. {{DEFAULTSORT:Broadcast Range Broadcast engineering Broadcast law