Ultra high frequency
Encyclopedia
Ultra-High Frequency designates the ITU
Radio frequency
range of electromagnetic
wave
s between 300 MHz
and 3 GHz
(3,000 MHz), also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetre
s (10 cm to 1 metre). Radio waves with frequencies above the UHF band fall into the SHF (super-high frequency) and EHF (extremely high frequency
) bands, all of which fall into the microwave
frequency range. Lower frequency signals fall into the VHF (very high frequency
) or lower bands. See Electromagnetic spectrum
and Radio spectrum
for a full listing of frequency bands.
; physical obstructions, such as mountains and buildings; and time of day all affect the signal transmission and the degradation of signal reception. All radio waves are partly absorbed by atmospheric moisture. Atmospheric absorption reduces, or attenuates
, the strength of radio signals over long distances. The effects of attenuation degradation
increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals. The ionosphere
, a layer of the Earth's atmosphere, is filled with charged particles that can reflect some radio waves. Amateur radio enthusiasts primarily use this quality of the ionosphere to help propagate lower frequency HF signals around the world: the waves are trapped, bouncing around in the upper layers of the ionosphere until they are refracted down at another point on the Earth. This is called skywave
transmission. UHF TV signals are not carried along the ionosphere but can be reflected off of the charged particles down at another point on Earth in order to reach farther than the typical line-of-sight
transmission distances; this is the skip distance
. UHF transmission and reception are enhanced or degraded by tropospheric ducting as the atmosphere warms and cools throughout the day.
The main advantage of UHF transmission is the physically short wave that is produced by the high frequency. The size of transmission and reception antennas is related to the size of the radio wave. The UHF antenna is stubby and short. Smaller and less conspicuous antennas can be used with higher frequency bands.
The major disadvantage of UHF is its limited broadcast range and reception, often called line-of-sight between the TV station's transmission antenna and customer's reception antenna, as opposed to VHF's very long broadcast range and reception, which is less restricted by line of sight.
UHF is widely used in two-way radio systems and cordless telephone
s, whose transmission and reception antennas are closely spaced. UHF signals travel over line-of-sight distances. Transmissions generated by two-way radios and cordless telephones do not travel far enough to interfere with local transmissions. Several public-safety and business communications are handled on UHF. Civilian applications, such as GMRS
, PMR446
, UHF CB
, 802.11b ("WiFi")
and the widely adapted GSM and UMTS cellular networks, also use UHF frequencies. A repeater
propagates UHF signals when a distance greater than the line of sight is required.
(SBS) on channel 28 in Sydney and Melbourne
starting in 1980, and translator stations for the Australian Broadcasting Corporation
(ABC). The UHF band is now used extensively as ABC
, SBS, commercial and public-access television
services have expanded, particularly through regional areas.
Australia also provides the UHF CB
service for general-purpose two-way communications.
. Its stations, as well as that of the first private networks (CTV
and TVA
, created in 1961), are primarily VHF. More recent third-network operators initially signing-on in the 1970s or 1980s were often relegated to UHF, or (if they were to attempt to deploy on VHF) to reduced power or stations in outlying areas. Canada's VHF spectrum was already crowded with both domestic broadcasts and numerous foreign border stations.
The use of UHF to provide programming that otherwise would not be available, such as province-wide educational services (Knowledge Channel
, TVOntario
(incidentally the first UHF station in Canada), Télé-Québec
, French language
programming (outside Québec) and ethnic/multilingual television, has therefore become common. Third networks such as Quatre-Saisons or Global
often will rely heavily on UHF stations as repeaters or as a local presence in large cities where VHF spectrum is largely already full. The handful of digital terrestrial television
stations currently on-air in Canada are also all UHF broadcasts, although some digital broadcasts will return to VHF channels vacated after the digital transition
is completed in August 2011.
Digital Audio Broadcasting
, deployed on a very limited scale in Canada in 2005, uses UHF frequencies in the L band
from 1452 to 1492 MHz. There are currently no VHF Band III
digital radio stations in Canada as, unlike in much of Europe, these frequencies are among the most popular for use by television stations.
, UHF was introduced in 1978 to augment the existing RTÉ One
VHF 625-line transmissions and to provide extra frequencies for the new RTÉ Two
channel. The first UHF transmitter site was Cairn Hill
in Co. Longford, followed by Three Rock Mountain
in South Co. Dublin. These sites were followed by Clermont Carn
in Co. Louth and Holywell Hill in Co. Donegal in 1981. Elsewhere in Ireland, both the RTÉ channels are available on VHF. Since then RTÉ have migrated nearly all their low-power relay sites to UHF. TV3 and TG4 are transmitted entirely in UHF only. When Digital Terrestrial
TV is introduced, it is intended to broadcast this on UHF only initially, although VHF allocations exist. VHF TV is likely to cease whenever the existing analogue
broadcasts are switched off. The UHF band is also used in parts of Ireland for Television deflector systems bringing British television signals to towns and rural areas that cannot receive these signals directly
terrestrial television
stations that is not a member of the major national networks keyed in Tokyo and Osaka.
Japan's original broadcasters were VHF. Although some experimental broadcasts were made as early as 1939, NHK
(founded in 1926 as a radio network modeled on the BBC) began regular VHF television broadcasting in 1953. Its two terrestrial television services (NHK General TV
and NHK Educational TV
) appear on VHF 1 and 3, respectively, in the Tokyo region. Privately owned Japanese VHF TV stations were most often built by large national newspapers with Tokyo stations exerting a large degree of control over national programming.
The independent stations broadcast in analogue UHF, unlike major networks, which were historically broadcast primarily in analogue VHF
. The loose coalition of UHF independents is operated mostly by local governments or metropolitan newspapers with less outside control. Compared with major network stations, Japan's UHF independents have more restrictive programming acquisition budgets and lower average ratings; they are also more likely to broadcast single episode or short-series UHF anime
(many of which serve to promote DVD's
or other product tie-ins) and brokered programming
such as religion
and infomercial
s.
Japanese terrestrial television
is in the process of switching entirely to digital UHF
, with all analogue television (both VHF and UHF) planned to shut down in 2011.
and the Klang Valley
by private TV station TV3
in the late 80s, with the government stations only transmitting in VHF (Bands 1 and 3) and the 450 MHz range being occupied by the ATUR cellular phone service operated by Telekom Malaysia
. The ATUR service ceased operation in the late 90s, freeing up the frequency for other uses. UHF was not commonly used in the Klang Valley until 1994 (despite TV3's signal also being available over UHF Channel 29, as TV3 transmitted over VHF Channel 12 in the Klang Valley). 1994 saw the introduction of the channel MetroVision (which ceased transmission in 1999, got bought over by TV3's parent company - System Televisyen Malaysia Berhad - and relaunched as 8TV
in 2004). This was followed by Ntv7
in 1998 (also acquired by TV3's parent company in 2005) and recently Channel 9
(which started in 2003, ceased transmission in 2005, was also acquired by TV3's parent company shortly after, and came back as TV9 in early 2006). At current count, there are 4 distinct UHF signals receivable by an analog TV set in the Klang Valley: Channel 25 (8TV), Channel 29 (TV3 UHF transmission), Channel 37 (NTV7) and Channel 39 (TV9). Channel 39 is usually allocated for VCRs, decoder units (i.e. the ASTRO and MiTV set top boxes
) and other devices that have an RF signal generator (i.e. game consoles).
to allocate sets of frequencies for 625-lined television to regions across the country, so as to accommodate four national networks with regional variations (the VHF allocations allowed for only two such networks using 405 lines). The UK UHF channels would range from 21 to 68 (later extended to 69) and regional allocations were in general grouped close together to allow for the use of aerials designed to receive a specific sub-band with greater efficiency than wider-band aerials could. Aerial manufacturers would therefore divide the band into over-lapping groups; A (channels 21-34), B (39-53), C/D (48-68) and E (39-68). The first service to use UHF was BBC2
in 1964 followed by BBC1
and ITV
(already broadcast on VHF) in 1969 and Channel 4
/S4C
in 1982. PAL
colour was introduced on UHF only in 1967 (for BBC2) and 1969 (for BBC1 & ITV).
As a consequence of achieving maximum national coverage, signals from one region would typically over-lap with that of another, which was accommodated for by allocating a different set of channels in each adjacent area, often resulting in greater choice for viewers when a network in one region aired different programmes to the neighbouring region.
Initial uptake of UHF television was very slow: Differing propagation characteristics between VHF and UHF meant new additional transmitters needed to be built, often at different locations to the then-established VHF sites, and in general with a larger number of relay stations to fill the greater number of gaps in coverage that came with the new band. This led to poor picture quality in bad coverage areas, and many years before the service achieved full national coverage. In addition to this, the only exclusively UHF service, BBC2, would run for only a few hours a day and run alternative programming for minority audiences in contrast to the more populist schedules of BBC1 and ITV. However the 1970s saw a large increase in UHF TV viewing while VHF took a significant decline: The appeal of colour, which was never introduced to VHF (despite preliminary plans to do so in the late 1950s and early 1960s) and the fall in television prices saw most households use a UHF set by the end of that decade. With the second and last VHF television service having launched in 1955, VHF TV was finally decommissioned for good in 1985 with no plans for it to return to use.
The launch of Channel 5 in 1997 added a fifth national television network to UHF, requiring deviation from the original frequency allocation plan of the early 1960s and the allocation of UHF frequencies previously not used for television (such as UK Channels 35 and 37, previously reserved for RF modulator
s in devices such as domestic videocassette recorder
s, requiring an expensive VCR re-tuning programme funded by the new network). A lack of capacity within the band to accommodate a fifth service with the complex over-lapping led to the fifth and final network having a significantly reduced national coverage compared to the other networks, with reduced picture quality in many areas and the use of wide-band aerials often required.
The launch of digital terrestrial television
in 1998 saw the continued use of UHF for television, with six multiplexes
allocated for the service, all within the UHF band. However analogue transmissions
have been planned to cease completely by 2012 after which time it is uncertain as to whether the vacated capacity will be used for additional digital television services or put into alternative use, such as mobile telecommunications or internet services.
of Bridgeport, Connecticut
, became the first UHF television station to operate on a regular daily schedule. The first commercially licensed UHF television station was WWLP
in Springfield, Massachusetts
; however, the first commercially licensed TV station on the air was KPTV
, Channel 27, in Portland, Oregon
, on September 18, 1952. This TV station used much of the equipment, including the transmitter, from KC2XAK.
American television broadcasting, which began experimentally in the 1930s with some regular commercial broadcasting in just a few cities (such as New York and Chicago) in 1941, was originally allocated (by the Federal Communication Commission - the FCC) broadcasting channels solely in the VHF (Very High Frequency) band. All VHF TV channels except channel 1 through 13
had been removed from the FCC allocation list during World War II
and those frequencies re-allocated for military use, leaving thirteen channels as of May 1945. While efforts at TV broadcasting on any channel were drastically curtailed for the duration of WW II, due largely to lack of available receivers, the post-war era would bring rapid expansion in the nascent broadcast television industry.
After VHF Channel 1 was re-allocated to land-mobile radio systems
in 1948 due to radio-interference problems, a mere one dozen TV channels remained. These were found to be not enough to serve the needs of television broadcasting as it grew nationwide during the latter 1940s and the 1950s. For example, these cities were never able to be allocated any VHF-TV stations at all, due to technical reasons found by the FCC: Fort Wayne, Indiana
, Lexington, Kentucky
, Huntsville, Alabama
, and Fresno, California
. In addition, scores more cities were able to receive only one VHF broadcast station, for example High Point, North Carolina
, Montgomery, Alabama
, Wilmington, Delaware
, Bakersfield, California
, and Santa Barbara, California
. Also, the entire state of New Jersey
would receive only one VHF broadcast station of its own (which was to ultimately become WNET
13 Newark
), leaving much of the state to be served from New York City or Philadelphia, and Delaware
has had only one VHF station. However, there was a problem with an insufficient number of TV channels being available to cover all of the United States
.
With a grand total of 106 VHF stations broadcasting by the end of the 1940s in the U.S., problems with interference between stations due to some overcrowding of stations were already becoming apparent in the densely populated areas, such as the eastern mid-Atlantic states (New York, Pennsylvania, New Jersey, Delaware, Maryland
, and Connecticut
) and Southern California
. In 1949, the Federal Communications Commission stopped accepting applications for licensing new stations (a freeze that lasted until 1952) in order to address questions such as the allocation of additional channel frequencies, and also the selection of an electronic system
for color television
.
Allocating more of the VHF band (30 to 300 MHz) by moving existing radio communication users off this band seemed to be impossible. For example, FM radio broadcasting had already suffered a huge setback after a forced move from its original 42-50 MHz allocated band to the current 88-108 MHz band in 1946 rendered all existing FM transmitters and receivers obsolete. Furthermore, several other important radio communications services use the VHF band. For example, in aeronautical radio use, a so-called "UHF radio" system for voice communications actually falls in VHF spectrum as all of its frequencies are below 300 MHz. The aeronautical radio VHF radio system, located above 108 MHz, is among the frequencies fall into the wide band that is in between Channel 6 and Channel 7 of VHF broadcast TV. Police and fire department radios, land-mobile users and two-meter amateur radio
operators also occupy VHF Band II, along with the entire FM broadcast band. It was impractical and uneconomic to require these well-established users to move to other frequencies, such as to the genuine UHF band (300 MHz-3 GHz).
The U.S. Army and Navy did not need to keep their huge wartime UHF spectrum allocation simply because they had never used most of it. That allocation had been done hastily in 1942 in the face of the emergency of a huge war of unknown duration - and with the presence of very new and poorly understood electronic technologies like radar
. In 1942, nobody knew how much bandwidth that the Army and the Navy might need for radar and for radio communications, so the Federal Government took a wise expedient: it allocated a huge amount of radio spectrum to the uniformed services for the time being, in case the service might need it. Then, it could make adjustments later.
After the War ended, and after the growth of civilian TV broadcasting in the years after the war, by 1950 expansion of TV channels into the UHF band of frequencies became inevitable. However, lots of UHF TV technology remained unproven at that time, though plenty had been learned about UHF electronics during the war, especially in the development and improvement of radar. (There are significant advantages to using shorter wavelength
s, hence higher frequencies, for radars.) Also, the question of which owners should retain the more-valuable (at that time) VHF TV channels remained hotly contested between several different competing interests.
To incumbent corporations, such as the Radio Corporation of America
and its National Broadcasting Company
subsidiary, UHF-TV and FM radio represented disruptive technologies
- competition to their existing and long-established manufacturing and broadcast interests in VHF-TV and AM radio. In the fall of 1944, Columbia Broadcasting System
pressed a high-definition black and white system on the UHF band employing 750-1,000 scanning lines that offered the possibility of higher-definition monochrome and color broadcasting, both then were precluded from the VHF band because of their bandwidth demands; more significantly, it offered the possibility for sufficient numbers of conventional 6MHz channels to support the FCC's goals of a "truly nationwide and competitive service." CBS was not trying maximize broadcast (or network) competition through freer market entry in the UHF system, but instead CBS's 16MHz channels would have allowed only 27 UHF channels versus the 82 channels possible under the standard 6MHz bandwidth. Vice President of CBS, Adrian Murphy, told the FCC: "I would say that it would be better to have two networks in color" instead of the four or more networks possible with narrower bandwidths in UHF. To newer entrants into TV broadcasting such as the DuMont Laboratories
company and its fourth-ranked DuMont Television Network
, however, the need for additional TV channels in major markets was urgent. For proponents of educational TV
broadcasting, the difficulties in competing with commercial broadcasters for the increasingly scarce VHF channels becoming a key problem.
Any attempt to pursue the objective of broadcast localism on the VHF-TV channels threatened in many regions to push the third-network TV companies such as the American Broadcasting Company
onto stations in outlying communities, if they could be accommodated on VHF channels at all.
A key question in the FCC's allocation of TV channels was hence that of intermixture. To allocate four to as many as seven VHF channels to each of the largest cities would mean forcing the smaller, intervening cities completely onto the UHF channels, while an allocation scheme that sought to assign one or two VHF channels in each smaller city would force VHF and UHF stations to compete in most markets. (Some may find it hard to believe, but the large metropolitan areas of New York City, Washington-Baltimore, Los Angeles, and San Francisco received seven VHF stations apiece, and Chicago was allocated five, with the other two possible ones going to Milwaukee and Rockford, Illinois
.)
Hopes that UHF-TV would allow dozens of television stations in every media market
were thwarted not only by poor image frequency rejection in superheterodyne receiver
s with the standard intermediate frequency
of 45.75 MHz, but also by very poor adjacent-channel rejection and channel selectivity by early tuner designs and manufactures. UHF-TV stations in the same immediate area were usually assigned by the FCC a minimum of six channels apart due to inadequate TV receiver manufacture. Technical problems with the design of vacuum tube
s for operation at high UHF frequencies were beginning to be addressed as late as 1954. These shortcomings led to "UHF taboos", which in effect limited each metropolitan area to only moderately more UHF stations than VHF ones, despite the much higher number of channels.
When the Freeze ended in 1952, the television industry exploded. It grew from the 108 pre-Freeze stations to more than 530 in 1960. These stations were established on the UHF band despite the fact it did not have near the coverage of their VHF competitors. The FCC tried solving this problem by allowing the lower powered UHF stations more power, but it did not work, VHF still had more coverage. At the same time, advertisers had caught on to this and did most of their business with VHF stations. In all, the FCC’s effort to try to intermix VHF and UHF stations in the same market had failed. While the more-established broadcasters were operating profitably on VHF channels as affiliates of the largest TV networks (at the time, NBC and CBS), most of the original UHF local stations of the 1950s soon went bankrupt, limited by the range their signals could travel, the lack of UHF tuners in most TV sets, and difficulties in finding advertisers willing to spend money on them. UHF stations fell quickly behind the VHF stations. UHF station revenues in 1953 were recorded as having a loss of $10,500,000. More stations left the air than began broadcasting and 60 percent of the industry losses were by UHF stations from 1953 to 1956.TV network affiliations were also difficult to get in many locations; the UHF stations with major-network affiliation would often lose these affiliations in favour of any viable new VHF TV station that entered the same market. Of the 82 new UHF-TV stations in the United States broadcasting as of June 1954, only 24 of them remained on the air a year later. The fraction of new TV receivers that were factory-equipped with all-channel tuners dropped from 35% in early 1953 to 9% by 1958, a drop that was only partially compensated for by field upgrades or the availability of UHF converters
for separate purchase.
The majority of the 165 UHF stations to begin telecasting between 1952 and 1959 did not survive. Under the All-Channel Receiver Act, FCC regulations by 1965 would ensure that all new TV sets sold in the U.S. had built-in UHF tuners that could receive channels 14-83. In spite of this, by 1971, there were just more than 170 full-service UHF broadcast stations nationwide.
In the United States, the UHF stations gained a reputation for being locally owned, less polished and professional, not as popular, and having weaker signal propagation than their VHF channel counterparts.
While UHF-TV has been available to American TV broadcasters since 1952, affiliates of the four major American TV network
s (NBC
, CBS
, ABC
, and DuMont
) continued to transmit their programs primarily on VHF channels wherever they were available. With the availability of the twelve VHF television channels limited by FCC spacing rules to avoid co-channel and adjacent channel
interference between TV stations in the same or nearby cities, all available VHF-TV allocations were already in use in most large TV markets by the mid-1950s.
To be more specific, two TV stations on the same channel needed to be about 160 or more miles apart, and two TV stations on adjacent channels needed to be about 60 or more miles apart. Exceptions to this rule occurred with VHF channels 4 and 5, and VHF channels 6 and 7, because there are additional "guard bands" between these two pairs that are allocated to other uses. Thus, the pair channel 4 and 5 was found in New York City, Washington, D.C., St. Louis, Los Angeles, San Francisco, and many other places. Likewise, the pair channel 6 and 7 was found in Denver and several other places.
With the most financially affluent and network-connected TV broadcasters all on VHF channels, UHF stations in major population centers of the United States were usually unable to get big TV-network affiliations (ABC, CBS, & NBC), and thus were usually either educational network or independent TV stations. Other UHF stations did for a time affiliate with less-affluent broadcast networks that didn't last very long; for example, the fourth-ranked DuMont Network, which operated from 1946 to 1956, and then went out of business. The movie UHF
, starring "Weird Al" Yankovic
and Michael Richards
, parodied the independent UHF station phenomenon.
However, there were significant cities that had few or no VHF channels allocated to them. Hence, these cities did get UHF stations that did get major network affiliations and did become financially sound businesses. Some of these stations have been located in or near state capital cities or served nearby major rural regions, such as Montgomery, Alabama
, Frankfort, Kentucky
, Dover, Delaware
, Lincoln, Nebraska
, Topeka, Kansas
, Jefferson City, Missouri
, Lansing, Michigan
, Harrisburg, Pennsylvania
, Madison, Wisconsin
, and Springfield, Missouri
. In the United States, television stations of or near state capital cities are important because they closely cover the operations of the state governments and spread the information to the residents of a wide region of the states.
TV antenna manufacturers of years ago often rated their top-of-the-line "deep-fringe" antenna models with phrases like "100 miles VHF/60 miles UHF" if the antenna included UHF reception at all. (In the practice of electrical engineering
, the frequency range in which an antenna is to be used is an important factor in its design.)
TV set manufacturers of years ago often treated UHF tuners as extra-charge optional-items until the All-Channel Receiver Act of 1964 forced their inclusion in all new TV sets as a standard. By 1964, many pioneering UHF broadcasters had already gone bankrupt. Various attempts were made by the FCC regulators to stem the tide of UHF station failures met with mixed results:
The situation was to begin to improve in the 1960s and 1970s, but progress was to be slow and difficult.
While ABC-TV and the short-lived DuMont Network, being smaller and less prosperous networks, had had a number of UHF affiliates, National Educational Television
and the later PBS
had even more.
The original SIN (Spanish International Network), which was established in 1962 as the predecessor of the modern Univision
network, was built primarily by UHF-TV broadcasters, such as charter stations KWEX-TV
, Channel 41 in San Antonio and KMEX-TV
, Channel 34, in Los Angeles
.
Ultimately, in addition to providing TV service where VHF channels simply were not possible because of the limitations on the technology, UHF-TV also became a means to obtain programming that was not being provided by the "Big Three" commercial networks. For example, there were educational services like the Public Broadcasting Service
, religious broadcasting
, and Spanish language
or multilingual broadcasting that all relied primarily on UHF channels to offer programming alternatives.
In 1970, Ted Turner
had acquired a struggling independent station on Channel 17 in Atlanta, Georgia, purchasing rerun
s of popular television shows, the Atlanta Braves
baseball team and the Atlanta Hawks
basketball team in order to provide access to entertainment for broadcast.
This station, renamed as WTBS, was uplinked in 1975 to satellite
alongside new premium channels such as HBO, gaining access to distant cable television
markets and becoming the first of various superstation
s to obtain national coverage. In 1986 Turner purchased the entire MGM
film library, and Turner Broadcasting System
's access to movie rights was to prove commercially valuable as home video
cassette rental became ubiquitous in the 1980s.
In 1986, the DuMont
owned-and-operated station
group Metromedia
was acquired by News Corporation
and used as the foundation to relaunch a fourth commercial network
, which obtained affiliation with many former big-city independent stations as Fox TV
.
While built largely from former independents and UHF stations in its early years, Fox had the large programming budgets that the original DuMont lacked. Ultimately, it was able in some markets to draw existing long-standing VHF affiliates away from established big-three networks, outbidding CBS
for National Football Conference
programming in 1994 and attracting many of that network's affiliates. Various smaller networks were created with the intent to follow in its footsteps, often assembling a fledgling network by affiliating with a disparate collection of formerly independent UHF stations that otherwise would have no network programming.
Fox launched in 1986. The film UHF
portrayed a fictional station on channel 62 in 1989. By 1994, New World Communications
was moving its established stations from CBS to Fox affiliations in multiple markets
, including WJBK-TV 2 Detroit. In many cases, this pushed CBS onto UHF; "U-62" as the new home of CBS in Detroit became CBS owned-and-operated station
WWJ-TV
in 1995, obtaining access to audiences thousands of miles distant through satellite and cable television.
The concentration of media ownership
, the proliferation of cable
and satellite television
and the digital television transition
have contributed to the quality equalization of VHF and UHF broadcasts. The distinction between UHF and VHF characteristics has declined in importance with the emergence of additional broadcast television networks (Fox
, The CW
, MyNetworkTV
, Univision
, Telemundo
and ION), and the decline of direct OTA
reception. The number of major large-city independent stations has also declined as many have joined or formed new networks.
See also DTV transition in the United States#VHF frequencies and digital television
The majority of digital TV stations currently broadcast their over-the-air signals in the UHF band, both because VHF had been already filled largely with analog TV at the time the digital facilities were built and because of severe issues with impulse noise
on digital low-VHF
channels. While virtual channel
numbering schemes routinely display channel numbers like "2.1" or "6.1" for individual North American terrestrial HDTV broadcasts, these are more often than not actually UHF signals. Many equipment vendors therefore use "HDTV antenna" or similar branding as all but synonymous to "UHF antenna".
Terrestrial digital television is based on a forward error correction
scheme, in which a channel is assumed to have a random bit error rate and additional data bits may be sent to allow these errors to be corrected at the receiver. While this error correction can work well in the UHF band where the interference consist largely of white noise
, it has largely proven inadequate on lower VHF channels where bursts of impulse noise disrupt the entire channel for short lengths of time. A short impulse-noise burst might be a minor annoyance to analog TV viewers, but due to the fixed timing and repetitive nature of analog video synchronization is usually recoverable. The same interference can prove severe enough to prevent the reliable reception of the more fragile and more highly compressed ATSC
digital television. Power limits are also lower on low-VHF; a digital UHF station may be licensed to transmit up to a megawatt of effective radiated power. Very few stations returned to VHF channels 2-6
after digital transition
was completed in 2009. At least three quarters of all full-power digital broadcasts continued to use UHF transmitters, even after transition is complete, with most of the others located on the high-VHF
channels. In some American markets, such as Syracuse, New York
, there are no full-service VHF TV stations remaining after digital transition
.
The one remaining limitation of UHF, that of a greatly reduced ability for signals to travel great distances in the presence of obstacles due to terrain, continues to adversely affect digital UHF TV reception. This limitation could potentially be overcome by the use of
DTS (Distributed Transmission Systems)
. Multiple digital UHF transmitters in carefully selected locations can be synchronized as a single-frequency network
to produce a tailored coverage area pattern rivaling that of a single full-power VHF transmitter.
While the Federal Communications Commission authorization to use DTS on anything more than an experimental basis came in November 2008, too late for sites to be acquired and transmitters built before the 2009 end of American digital transition
, it is likely that more of these distributed UHF transmission systems will be constructed alongside conventional digital broadcast translator systems in the years to come as a means to get digital and high-definition television out to a wider audience.
One notable exception to historical patterns favoring VHF broadcasters has existed in mid-size television markets within the United States that were too close to the outer fringe of the broadcast range of large-city VHF stations to qualify for their own stations on these frequencies. As no full-power VHF channels could be made available in these areas without encountering problems of interference from overlapping broadcast ranges, the Federal Communications Commission
granted some mid-sized cities only UHF licenses. With all stations (including big-three network affiliates) on UHF, all-channel receivers and antennas became commonplace locally and UHF stations signing on as early as 1954 were often able to obtain the programming and viewership needed to remain viable into the modern era.
These communities, known as UHF islands, included cities like Springfield, Massachusetts
; Fresno, California
; South Bend, Indiana
;Fort Wayne, Indiana
; and Lexington, Kentucky
. Other smaller cities found that only one VHF channel was open and any additional programming would need to be provided either by UHF, by distant stations, or by low-power broadcasting
.
A large number of very small UHF TV transmitters continue to operate with no programming or commercial identity of their own, merely retransmitting signals of existing full-power stations to a smaller area poorly covered by the main VHF signal. Such transmitters are called "translators
" rather than “stations”. The smallest, owned by local municipal-level groups or the originating TV stations, are numbered sequentially - W or K, followed by the channel number, followed by two sequentially issued letters, yielding a "translator callsign" in a generic format that appears K14AA through W69ZZ. Translators and repeaters also exist on VHF channels, but infrequently and with stringently limited power as the VHF spectrum is already crowded with full-power network stations in most regions.
The translator band
, UHF TV channels 70-83, consisted mostly of these small repeaters; it was removed from television use in 1983 with the tiny repeaters moved primarily to lower UHF channels. The 804-890 MHz band segment is now used primarily by mobile phone
s.
As improvements to originating stations signals lessen the need for these small translators in some areas, often the small transmitter facilities and their allocated frequencies would be repurposed for low-power broadcasting
; instead of repeating a distant signal, the tiny transmitter would be used to originate programming for a small local area.
and General Mobile Radio Service
use the 462 and 467 MHz areas of the UHF spectrum. There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz. These ISM band
s - open frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus - are now becoming some of the most crowded in the spectrum because they are open to everyone.
The 2.45 GHz frequency is the standard for use by microwave ovens
in residential ovens; (915 MHz is used in commercial microwave ovens) .
The spectrum from 806 MHz to 890 MHz (UHF channels 70-83) was taken away from TV broadcast services in 1983, primarily for analogue mobile telephony
. In 2009, as part of the transition from analog to digital over-the-air broadcast of television, the spectrum from 698 MHz to 806 MHz (UHF channels 52-69) was also no longer used for TV broadcasting. Channel 55, for instance, was sold to Qualcomm
for their MediaFLO
service, which is resold under various mobile telephone network brands. Some US broadcasters had been offered incentives to vacate this channel early, permitting its immediate mobile use.
The FCC
's scheduled auction for this newly available spectrum
was completed in March 2008.
Itu
Itu is an old and historic municipality in the state of São Paulo in Brazil. The population in 2009 was 157,384 and the area is 641.68 km². The elevation is 583 m. This place name comes from the Tupi language, meaning big waterfall. Itu is linked with the highway numbered the SP-75 and are flowed...
Radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
range of electromagnetic
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
s between 300 MHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
and 3 GHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
(3,000 MHz), also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetre
Decimetre
A decimetre is a unit of length in the metric system, equal to one tenth of a metre, the SI base unit of length. In simple words there are 10 cm in a decimetre....
s (10 cm to 1 metre). Radio waves with frequencies above the UHF band fall into the SHF (super-high frequency) and EHF (extremely high frequency
Extremely high frequency
Extremely high frequency is the highest radio frequency band. EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low infrared light, also referred to as terahertz radiation...
) bands, all of which fall into the microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
frequency range. Lower frequency signals fall into the VHF (very high frequency
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
) or lower bands. See Electromagnetic spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
and Radio spectrum
Radio spectrum
Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz ....
for a full listing of frequency bands.
Characteristics, advantages, and disadvantages
The point to point transmission and reception of TV and radio signals is affected by many variables. Atmospheric moisture; solar windSolar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
; physical obstructions, such as mountains and buildings; and time of day all affect the signal transmission and the degradation of signal reception. All radio waves are partly absorbed by atmospheric moisture. Atmospheric absorption reduces, or attenuates
Attenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
, the strength of radio signals over long distances. The effects of attenuation degradation
Degradation (telecommunications)
In telecommunication, degradation, which may be categorized as either "graceful" or "catastrophic", has the following meanings:#The deterioration in quality, level, or standard of performance of a functional unit....
increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals. The ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
, a layer of the Earth's atmosphere, is filled with charged particles that can reflect some radio waves. Amateur radio enthusiasts primarily use this quality of the ionosphere to help propagate lower frequency HF signals around the world: the waves are trapped, bouncing around in the upper layers of the ionosphere until they are refracted down at another point on the Earth. This is called skywave
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
transmission. UHF TV signals are not carried along the ionosphere but can be reflected off of the charged particles down at another point on Earth in order to reach farther than the typical line-of-sight
Line-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...
transmission distances; this is the skip distance
Skip distance
A skip distance is the distance a radio wave travels, usually including a hop in the ionosphere. A skip distance is a distance on the Earth's surface between the two points where radio waves from a transmitter, refracted downwards by different layers of the ionosphere, fall...
. UHF transmission and reception are enhanced or degraded by tropospheric ducting as the atmosphere warms and cools throughout the day.
The main advantage of UHF transmission is the physically short wave that is produced by the high frequency. The size of transmission and reception antennas is related to the size of the radio wave. The UHF antenna is stubby and short. Smaller and less conspicuous antennas can be used with higher frequency bands.
The major disadvantage of UHF is its limited broadcast range and reception, often called line-of-sight between the TV station's transmission antenna and customer's reception antenna, as opposed to VHF's very long broadcast range and reception, which is less restricted by line of sight.
UHF is widely used in two-way radio systems and cordless telephone
Cordless telephone
A cordless telephone or portable telephone is a telephone with a wireless handset that communicates via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station...
s, whose transmission and reception antennas are closely spaced. UHF signals travel over line-of-sight distances. Transmissions generated by two-way radios and cordless telephones do not travel far enough to interfere with local transmissions. Several public-safety and business communications are handled on UHF. Civilian applications, such as GMRS
General Mobile Radio Service
The General Mobile Radio Service is a licensed land-mobile FM UHF radio service in the United States available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members...
, PMR446
PMR446
PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...
, UHF CB
UHF CB
UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
, 802.11b ("WiFi")
IEEE 802.11
IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
and the widely adapted GSM and UMTS cellular networks, also use UHF frequencies. A repeater
Repeater
A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...
propagates UHF signals when a distance greater than the line of sight is required.
- See "Radio horizon".
Australia
In Australia, UHF was first anticipated in the mid 1970s with TV channels 27-69. The first UHF TV broadcasts in Australia were operated by Special Broadcasting ServiceSpecial Broadcasting Service
The Special Broadcasting Service is a hybrid-funded Australian public broadcasting radio and television network. The stated purpose of SBS is "to provide multilingual and multicultural radio and television services that inform, educate and entertain all Australians and, in doing so, reflect...
(SBS) on channel 28 in Sydney and Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
starting in 1980, and translator stations for the Australian Broadcasting Corporation
Australian Broadcasting Corporation
The Australian Broadcasting Corporation, commonly referred to as "the ABC" , is Australia's national public broadcaster...
(ABC). The UHF band is now used extensively as ABC
Australian Broadcasting Corporation
The Australian Broadcasting Corporation, commonly referred to as "the ABC" , is Australia's national public broadcaster...
, SBS, commercial and public-access television
Public-access television
Public-access television is a form of non-commercial mass media where ordinary people can create content television programming which is cablecast through cable TV specialty channels...
services have expanded, particularly through regional areas.
Australia also provides the UHF CB
UHF CB
UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
service for general-purpose two-way communications.
Canada
The first Canadian television network was publicly owned Radio-Canada, the Canadian Broadcasting CorporationCanadian Broadcasting Corporation
The Canadian Broadcasting Corporation, commonly known as CBC and officially as CBC/Radio-Canada, is a Canadian crown corporation that serves as the national public radio and television broadcaster...
. Its stations, as well as that of the first private networks (CTV
CTV television network
CTV Television Network is a Canadian English language television network and is owned by Bell Media. It is Canada's largest privately-owned network, and has consistently placed as Canada's top-rated network in total viewers and in key demographics since 2002, after several years trailing the rival...
and TVA
TVA (TV network)
TVA is a privately owned French language television network in Canada. The network is currently owned by Groupe TVA Inc. , a publicly traded subsidiary of Quebecor Media...
, created in 1961), are primarily VHF. More recent third-network operators initially signing-on in the 1970s or 1980s were often relegated to UHF, or (if they were to attempt to deploy on VHF) to reduced power or stations in outlying areas. Canada's VHF spectrum was already crowded with both domestic broadcasts and numerous foreign border stations.
The use of UHF to provide programming that otherwise would not be available, such as province-wide educational services (Knowledge Channel
Knowledge Channel
The Knowledge Channel is the first and only all-educational cable TV channel in the Philippines. Broadcasting 18 hours of curriculum-based programs, it is the foremost source of educational television in the country. To date, the channel is viewed by some 3 million children in 2,000 public...
, TVOntario
TVOntario
TVOntario, often referred to only as TVO , is a publicly funded, educational English-language television station and media organization in the Canadian province of Ontario. It is operated by the Ontario Educational Communications Authority, a Crown corporation owned by the Government of Ontario...
(incidentally the first UHF station in Canada), Télé-Québec
Télé-Québec
Télé-Québec is a French language public educational television network in the Canadian province of Quebec. Known legally as Société de télédiffusion du Québec , it is a provincial crown corporation owned by the Government of Quebec...
, French language
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
programming (outside Québec) and ethnic/multilingual television, has therefore become common. Third networks such as Quatre-Saisons or Global
CIII-TV
CIII-DT-41 is a television station owned by Shaw Communications that serves much of the population of the Canadian province of Ontario. It is a flagship station of the Global Television Network...
often will rely heavily on UHF stations as repeaters or as a local presence in large cities where VHF spectrum is largely already full. The handful of digital terrestrial television
Digital television in Canada
Digital television in Canada is transmitted using the ATSC standards developed for and in use in the United States. Because Canada and the U.S...
stations currently on-air in Canada are also all UHF broadcasts, although some digital broadcasts will return to VHF channels vacated after the digital transition
Digital television in Canada
Digital television in Canada is transmitted using the ATSC standards developed for and in use in the United States. Because Canada and the U.S...
is completed in August 2011.
Digital Audio Broadcasting
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
, deployed on a very limited scale in Canada in 2005, uses UHF frequencies in the L band
L band
L band refers to four different bands of the electromagnetic spectrum: 40 to 60 GHz , 1 to 2 GHz , 1565 nm to 1625 nm , and around 3.5 micrometres .-NATO L band:...
from 1452 to 1492 MHz. There are currently no VHF Band III
Band III
Band III is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band III ranges from 174 to 230 MHz, and it is primarily used for radio and television broadcasting...
digital radio stations in Canada as, unlike in much of Europe, these frequencies are among the most popular for use by television stations.
Ireland
In the Republic of IrelandRepublic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
, UHF was introduced in 1978 to augment the existing RTÉ One
RTÉ One
RTÉ One is the flagship television channel of Raidió Teilifís Éireann , and it is the most popular and most watched television channel in Ireland. It was launched as Telefís Éireann on 31 December 1961, it was renamed RTÉ Television in 1966, and it was renamed as RTÉ One upon the launch of RTÉ...
VHF 625-line transmissions and to provide extra frequencies for the new RTÉ Two
RTÉ Two
RTÉ Two is a free-to-air general entertainment channel operated by Irish state broadcaster Raidió Teilifís Éireann. RTÉ Two is available throughout the island of Ireland through digital terrestrial service Saorview, VHF and UHF bands, and is also available via satellite to Irish subscribers of...
channel. The first UHF transmitter site was Cairn Hill
Cairn Hill
A number of mountains in the British Isles have the name Cairn Hill* Cairn Hill, Northumberland in Northumberland, England* Carn Clonhugh in County Longford, Ireland which is also known as Cairn Hill* Cairn Hill, Scotland in Scotland...
in Co. Longford, followed by Three Rock Mountain
Three Rock Mountain
Three Rock Mountain is a mountain in Dun Laoghaire-Rathdown County in Ireland. It is high and forms part of the group of hills in the Dublin Mountains which comprises Two Rock, Three Rock, Kilmashogue and Tibradden Mountains. The mountain takes its name from the three groups of granite rocks at...
in South Co. Dublin. These sites were followed by Clermont Carn
Clermont Carn
Clermont Carn, variously spelt as "Clermont Cairn", "Clairmont Carn/Cairn" or other variations is a 510m high peak in the Cooley Mountains in County Louth which is also home to a main RTÉ Network Limited transmission site.-Transmitter:...
in Co. Louth and Holywell Hill in Co. Donegal in 1981. Elsewhere in Ireland, both the RTÉ channels are available on VHF. Since then RTÉ have migrated nearly all their low-power relay sites to UHF. TV3 and TG4 are transmitted entirely in UHF only. When Digital Terrestrial
Television in Ireland
Digital terrestrial television within the Republic of Ireland, known as Saorview, was launched on 27 May 2011. This service will effectively replace the current analogue terrestrial television system, which uses System I with 625 lines and the PAL colour standard, with NICAM digital stereo sound...
TV is introduced, it is intended to broadcast this on UHF only initially, although VHF allocations exist. VHF TV is likely to cease whenever the existing analogue
Analog television
Analog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...
broadcasts are switched off. The UHF band is also used in parts of Ireland for Television deflector systems bringing British television signals to towns and rural areas that cannot receive these signals directly
Japan
In Japan, an is one of a loosely knit group of free commercialCommercial broadcasting
Commercial broadcasting is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship...
terrestrial television
Terrestrial television
Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
stations that is not a member of the major national networks keyed in Tokyo and Osaka.
Japan's original broadcasters were VHF. Although some experimental broadcasts were made as early as 1939, NHK
NHK
NHK is Japan's national public broadcasting organization. NHK, which has always identified itself to its audiences by the English pronunciation of its initials, is a publicly owned corporation funded by viewers' payments of a television license fee....
(founded in 1926 as a radio network modeled on the BBC) began regular VHF television broadcasting in 1953. Its two terrestrial television services (NHK General TV
NHK General TV
is the main television service of NHK . It shows news, drama, quiz/variety shows, music, sports, anime and specials which directly compete with its commercial counterparts. It is well known for its nightly newscasts, regular documentary specials and popular historical dramas...
and NHK Educational TV
NHK Educational TV
is the second television service of NHK . It is a sister service of NHK General TV, showing programs of a more educational, cultural or intellectual nature, periodically also showing anime...
) appear on VHF 1 and 3, respectively, in the Tokyo region. Privately owned Japanese VHF TV stations were most often built by large national newspapers with Tokyo stations exerting a large degree of control over national programming.
The independent stations broadcast in analogue UHF, unlike major networks, which were historically broadcast primarily in analogue VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
. The loose coalition of UHF independents is operated mostly by local governments or metropolitan newspapers with less outside control. Compared with major network stations, Japan's UHF independents have more restrictive programming acquisition budgets and lower average ratings; they are also more likely to broadcast single episode or short-series UHF anime
UHF anime
refers to the anime broadcast by independent stations generally located in the Kanto, Chukyo and Kansai regions of Japan, who are members of the Japanese Association of Independent Television Stations . Other common names for UHF anime include and...
(many of which serve to promote DVD's
Late night anime
is a term used in Japan to denote anime television series broadcast late at night and/or in the early morning, usually between 23.00 and 4.00. Sometimes the scheduled times of such broadcasts are advertised in a format using an hour greater than 24 is a term used in Japan to denote anime...
or other product tie-ins) and brokered programming
Brokered programming
Brokered programming is a form of broadcast content in which the show's producer pays a radio or television station for air time, rather than exchanging programming for pay or the opportunity to play spot commercials...
such as religion
Religious broadcasting
Religious broadcasting refers to broadcasting by religious organizations, usually with a religious message. Many religious organizations have long recorded content such as sermons and lectures, and have moved into distributing content on their Internet websites.While this article emphasises...
and infomercial
Infomercial
Infomercials are direct response television commercials which generally include a phone number or website. There are long-form infomercials, which are typically between 15 and 30 minutes in length, and short-form infomercials, which are typically 30 seconds to 120 seconds in length. Infomercials...
s.
Japanese terrestrial television
Television in Japan
Television broadcasting in Japan started in 1939, making the country one of the first in the world with an experimental television service. In spite of that, because of the beginning of World War II in the Pacific region, this first experimentation lasted only a few months...
is in the process of switching entirely to digital UHF
Television in Japan
Television broadcasting in Japan started in 1939, making the country one of the first in the world with an experimental television service. In spite of that, because of the beginning of World War II in the Pacific region, this first experimentation lasted only a few months...
, with all analogue television (both VHF and UHF) planned to shut down in 2011.
Malaysia
UHF broadcasting was used outside Kuala LumpurKuala Lumpur
Kuala Lumpur is the capital and the second largest city in Malaysia by population. The city proper, making up an area of , has a population of 1.4 million as of 2010. Greater Kuala Lumpur, also known as the Klang Valley, is an urban agglomeration of 7.2 million...
and the Klang Valley
Klang Valley
Klang Valley is an area in Malaysia comprising Kuala Lumpur and its suburbs, and adjoining cities and towns in the state of Selangor. An alternative reference to this would be Kuala Lumpur Metropolitan Area or Greater Kuala Lumpur. It is geographically delineated by Titiwangsa Mountains to the...
by private TV station TV3
TV3 (Malaysia)
Sistem Televisyen Malaysia Berhad or TV3 began broadcasting on 1 June 1984 as Malaysia’s first commercial television station. It is part of Media Prima Berhad group of companies. It now transmits opened broadcasting business private 24-hours a day, 7 days a week since 1 January 2010...
in the late 80s, with the government stations only transmitting in VHF (Bands 1 and 3) and the 450 MHz range being occupied by the ATUR cellular phone service operated by Telekom Malaysia
Telekom Malaysia
Telekom Malaysia Berhad , DBA TM, is the largest integrated solutions provider in Malaysia, and one of Asia's leading communications companies, with a market capitalisation of RM13.9 billion and a workforce of 26,629 employees. Established as the Telecommunications Department of Malaya in 1946, it...
. The ATUR service ceased operation in the late 90s, freeing up the frequency for other uses. UHF was not commonly used in the Klang Valley until 1994 (despite TV3's signal also being available over UHF Channel 29, as TV3 transmitted over VHF Channel 12 in the Klang Valley). 1994 saw the introduction of the channel MetroVision (which ceased transmission in 1999, got bought over by TV3's parent company - System Televisyen Malaysia Berhad - and relaunched as 8TV
8TV (Malaysia)
8TV is a private Malaysian Chinese television station, previously known as MetroVision Channel 8. Metrovision closed on 1 November 1999. 8TV was officially launched on Thursday, 8 January 2004 as 8TV after being acquired by Media Prima Berhad....
in 2004). This was followed by Ntv7
Ntv7
Natseven TV Sdn Bhd or better known as ntv7 is a terrestrial television channel in Malaysia. It was launched nationwide on 7 April 1998 and was the country's third private free-to-air TV station after TV3 and Astro. Its mission is to promote a happier and more enlightened Malaysia...
in 1998 (also acquired by TV3's parent company in 2005) and recently Channel 9
TV9 (Malaysia)
TV9 is a free-to-air private television station in Malaysia. TV9 began broadcasting on 22 April 2006, as a subsidiary of Media Prima Berhad. It formerly existed as Channel 9, which began airing on 9 September 2003 and ceased transmission on 1 February 2005 due to financial difficulties faced by the...
(which started in 2003, ceased transmission in 2005, was also acquired by TV3's parent company shortly after, and came back as TV9 in early 2006). At current count, there are 4 distinct UHF signals receivable by an analog TV set in the Klang Valley: Channel 25 (8TV), Channel 29 (TV3 UHF transmission), Channel 37 (NTV7) and Channel 39 (TV9). Channel 39 is usually allocated for VCRs, decoder units (i.e. the ASTRO and MiTV set top boxes
Set-top box
A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...
) and other devices that have an RF signal generator (i.e. game consoles).
United Kingdom
In the UK, UHF television began in 1964 following a plan by the General Post OfficeGeneral Post Office
General Post Office is the name of the British postal system from 1660 until 1969.General Post Office may also refer to:* General Post Office, Perth* General Post Office, Sydney* General Post Office, Melbourne* General Post Office, Brisbane...
to allocate sets of frequencies for 625-lined television to regions across the country, so as to accommodate four national networks with regional variations (the VHF allocations allowed for only two such networks using 405 lines). The UK UHF channels would range from 21 to 68 (later extended to 69) and regional allocations were in general grouped close together to allow for the use of aerials designed to receive a specific sub-band with greater efficiency than wider-band aerials could. Aerial manufacturers would therefore divide the band into over-lapping groups; A (channels 21-34), B (39-53), C/D (48-68) and E (39-68). The first service to use UHF was BBC2
BBC Two
BBC Two is the second television channel operated by the British Broadcasting Corporation in the United Kingdom. It covers a wide range of subject matter, but tending towards more 'highbrow' programmes than the more mainstream and popular BBC One. Like the BBC's other domestic TV and radio...
in 1964 followed by BBC1
BBC One
BBC One is the flagship television channel of the British Broadcasting Corporation in the United Kingdom. It was launched on 2 November 1936 as the BBC Television Service, and was the world's first regular television service with a high level of image resolution...
and ITV
ITV
ITV is the major commercial public service TV network in the United Kingdom. Launched in 1955 under the auspices of the Independent Television Authority to provide competition to the BBC, it is also the oldest commercial network in the UK...
(already broadcast on VHF) in 1969 and Channel 4
Channel 4
Channel 4 is a British public-service television broadcaster which began working on 2 November 1982. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority , the station is now owned and operated by the Channel...
/S4C
S4C
S4C , currently branded as S4/C, is a Welsh television channel broadcast from the capital, Cardiff. The first television channel to be aimed specifically at a Welsh-speaking audience, it is the fifth oldest British television channel .The channel - initially broadcast on...
in 1982. PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
colour was introduced on UHF only in 1967 (for BBC2) and 1969 (for BBC1 & ITV).
As a consequence of achieving maximum national coverage, signals from one region would typically over-lap with that of another, which was accommodated for by allocating a different set of channels in each adjacent area, often resulting in greater choice for viewers when a network in one region aired different programmes to the neighbouring region.
Initial uptake of UHF television was very slow: Differing propagation characteristics between VHF and UHF meant new additional transmitters needed to be built, often at different locations to the then-established VHF sites, and in general with a larger number of relay stations to fill the greater number of gaps in coverage that came with the new band. This led to poor picture quality in bad coverage areas, and many years before the service achieved full national coverage. In addition to this, the only exclusively UHF service, BBC2, would run for only a few hours a day and run alternative programming for minority audiences in contrast to the more populist schedules of BBC1 and ITV. However the 1970s saw a large increase in UHF TV viewing while VHF took a significant decline: The appeal of colour, which was never introduced to VHF (despite preliminary plans to do so in the late 1950s and early 1960s) and the fall in television prices saw most households use a UHF set by the end of that decade. With the second and last VHF television service having launched in 1955, VHF TV was finally decommissioned for good in 1985 with no plans for it to return to use.
The launch of Channel 5 in 1997 added a fifth national television network to UHF, requiring deviation from the original frequency allocation plan of the early 1960s and the allocation of UHF frequencies previously not used for television (such as UK Channels 35 and 37, previously reserved for RF modulator
RF modulator
An RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
s in devices such as domestic videocassette recorder
Videocassette recorder
The videocassette recorder , is a type of electro-mechanical device that uses removable videocassettes that contain magnetic tape for recording analog audio and analog video from broadcast television so that the images and sound can be played back at a more convenient time...
s, requiring an expensive VCR re-tuning programme funded by the new network). A lack of capacity within the band to accommodate a fifth service with the complex over-lapping led to the fifth and final network having a significantly reduced national coverage compared to the other networks, with reduced picture quality in many areas and the use of wide-band aerials often required.
The launch of digital terrestrial television
Digital terrestrial television in the United Kingdom
Digital terrestrial television in the United Kingdom encompasses over 100 television, radio and interactive services broadcast via the UK's terrestrial television network and receivable with a standard television aerial...
in 1998 saw the continued use of UHF for television, with six multiplexes
Multiplex (TV)
A multiplex or mux is a group of TV channels that are mixed together for broadcast over a digital TV channel and separated out again by the receiver...
allocated for the service, all within the UHF band. However analogue transmissions
Analogue terrestrial television in the United Kingdom
Analogue terrestrial television in the United Kingdom is, traditionally, the method most people in the UK, Channel Islands and the Isle of Man used to receive television...
have been planned to cease completely by 2012 after which time it is uncertain as to whether the vacated capacity will be used for additional digital television services or put into alternative use, such as mobile telecommunications or internet services.
Television
On December 29, 1949, KC2XAKKC2XAK
KC2XAK was the world's first UHF television station. It was simply a rebroadcast/broadcast translator transmitter of New York City's WNBT , and broadcast on UHF Channel 24 in Bridgeport, Connecticut...
of Bridgeport, Connecticut
Bridgeport, Connecticut
Bridgeport is the most populous city in the U.S. state of Connecticut. Located in Fairfield County, the city had an estimated population of 144,229 at the 2010 United States Census and is the core of the Greater Bridgeport area...
, became the first UHF television station to operate on a regular daily schedule. The first commercially licensed UHF television station was WWLP
WWLP
WWLP is the NBC-affiliated television station for the Pioneer Valley of Western Massachusetts that is licensed to Springfield. It broadcasts a high definition digital signal on VHF channel 11 from a transmitter on Provin Mountain in the Feeding Hills section of Agawam. The station can also be seen...
in Springfield, Massachusetts
Springfield, Massachusetts
Springfield is the most populous city in Western New England, and the seat of Hampden County, Massachusetts, United States. Springfield sits on the eastern bank of the Connecticut River near its confluence with three rivers; the western Westfield River, the eastern Chicopee River, and the eastern...
; however, the first commercially licensed TV station on the air was KPTV
KPTV
KPTV is the Fox-affiliated television station serving the Portland, Oregon market, which includes most of the state of Oregon and portions of Southwest Washington. KPTV is owned by the Meredith Corporation in a duopoly with MyNetworkTV affiliate KPDX , with its studios located in Beaverton and...
, Channel 27, in Portland, Oregon
Portland, Oregon
Portland is a city located in the Pacific Northwest, near the confluence of the Willamette and Columbia rivers in the U.S. state of Oregon. As of the 2010 Census, it had a population of 583,776, making it the 29th most populous city in the United States...
, on September 18, 1952. This TV station used much of the equipment, including the transmitter, from KC2XAK.
American television broadcasting, which began experimentally in the 1930s with some regular commercial broadcasting in just a few cities (such as New York and Chicago) in 1941, was originally allocated (by the Federal Communication Commission - the FCC) broadcasting channels solely in the VHF (Very High Frequency) band. All VHF TV channels except channel 1 through 13
Channel 13
Channel 13 refers to several television stations:* Channel 13, Lithuania* DZTV-TV, the flagship station of the Intercontinental Broadcasting Corporation in Metro Manila, Philippines* Thirteen WNET, primary public television station of PBS in New York City...
had been removed from the FCC allocation list during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
and those frequencies re-allocated for military use, leaving thirteen channels as of May 1945. While efforts at TV broadcasting on any channel were drastically curtailed for the duration of WW II, due largely to lack of available receivers, the post-war era would bring rapid expansion in the nascent broadcast television industry.
After VHF Channel 1 was re-allocated to land-mobile radio systems
Mobile Radio
This article is about professional equipment. For mobile radios used in amateur radio, see amateur radio mobile operation. Mobile radio or mobiles refer to wireless communications systems and devices which are based on radio frequencies, and where the path of communications is movable on either...
in 1948 due to radio-interference problems, a mere one dozen TV channels remained. These were found to be not enough to serve the needs of television broadcasting as it grew nationwide during the latter 1940s and the 1950s. For example, these cities were never able to be allocated any VHF-TV stations at all, due to technical reasons found by the FCC: Fort Wayne, Indiana
Fort Wayne, Indiana
Fort Wayne is a city in the US state of Indiana and the county seat of Allen County. The population was 253,691 at the 2010 Census making it the 74th largest city in the United States and the second largest in Indiana...
, Lexington, Kentucky
Lexington, Kentucky
Lexington is the second-largest city in Kentucky and the 63rd largest in the US. Known as the "Thoroughbred City" and the "Horse Capital of the World", it is located in the heart of Kentucky's Bluegrass region...
, Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....
, and Fresno, California
Fresno, California
Fresno is a city in central California, United States, the county seat of Fresno County. As of the 2010 census, the city's population was 510,365, making it the fifth largest city in California, the largest inland city in California, and the 34th largest in the nation...
. In addition, scores more cities were able to receive only one VHF broadcast station, for example High Point, North Carolina
High Point, North Carolina
High Point is a city located in the Piedmont Triad region of North Carolina. As of 2010 the city had a total population of 104,371, according to the US Census Bureau. High Point is currently the eighth-largest municipality in North Carolina....
, Montgomery, Alabama
Montgomery, Alabama
Montgomery is the capital of the U.S. state of Alabama, and is the county seat of Montgomery County. It is located on the Alabama River southeast of the center of the state, in the Gulf Coastal Plain. As of the 2010 census, Montgomery had a population of 205,764 making it the second-largest city...
, Wilmington, Delaware
Wilmington, Delaware
Wilmington is the largest city in the state of Delaware, United States, and is located at the confluence of the Christina River and Brandywine Creek, near where the Christina flows into the Delaware River. It is the county seat of New Castle County and one of the major cities in the Delaware Valley...
, Bakersfield, California
Bakersfield, California
Bakersfield is a city near the southern end of the San Joaquin Valley in Kern County, California. It is roughly equidistant between Fresno and Los Angeles, to the north and south respectively....
, and Santa Barbara, California
Santa Barbara, California
Santa Barbara is the county seat of Santa Barbara County, California, United States. Situated on an east-west trending section of coastline, the longest such section on the West Coast of the United States, the city lies between the steeply-rising Santa Ynez Mountains and the Pacific Ocean...
. Also, the entire state of New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
would receive only one VHF broadcast station of its own (which was to ultimately become WNET
WNET
WNET, channel 13 is a non-commercial educational public television station licensed to Newark, New Jersey. With its signal covering the New York metropolitan area, WNET is a primary station of the Public Broadcasting Service and a primary provider of PBS programming...
13 Newark
Newark, New Jersey
Newark is the largest city in the American state of New Jersey, and the seat of Essex County. As of the 2010 United States Census, Newark had a population of 277,140, maintaining its status as the largest municipality in New Jersey. It is the 68th largest city in the U.S...
), leaving much of the state to be served from New York City or Philadelphia, and Delaware
Delaware
Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...
has had only one VHF station. However, there was a problem with an insufficient number of TV channels being available to cover all of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
With a grand total of 106 VHF stations broadcasting by the end of the 1940s in the U.S., problems with interference between stations due to some overcrowding of stations were already becoming apparent in the densely populated areas, such as the eastern mid-Atlantic states (New York, Pennsylvania, New Jersey, Delaware, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, and Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
) and Southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
. In 1949, the Federal Communications Commission stopped accepting applications for licensing new stations (a freeze that lasted until 1952) in order to address questions such as the allocation of additional channel frequencies, and also the selection of an electronic system
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
for color television
Color television
Color television is part of the history of television, the technology of television and practices associated with television's transmission of moving images in color video....
.
Allocating more of the VHF band (30 to 300 MHz) by moving existing radio communication users off this band seemed to be impossible. For example, FM radio broadcasting had already suffered a huge setback after a forced move from its original 42-50 MHz allocated band to the current 88-108 MHz band in 1946 rendered all existing FM transmitters and receivers obsolete. Furthermore, several other important radio communications services use the VHF band. For example, in aeronautical radio use, a so-called "UHF radio" system for voice communications actually falls in VHF spectrum as all of its frequencies are below 300 MHz. The aeronautical radio VHF radio system, located above 108 MHz, is among the frequencies fall into the wide band that is in between Channel 6 and Channel 7 of VHF broadcast TV. Police and fire department radios, land-mobile users and two-meter amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators also occupy VHF Band II, along with the entire FM broadcast band. It was impractical and uneconomic to require these well-established users to move to other frequencies, such as to the genuine UHF band (300 MHz-3 GHz).
The U.S. Army and Navy did not need to keep their huge wartime UHF spectrum allocation simply because they had never used most of it. That allocation had been done hastily in 1942 in the face of the emergency of a huge war of unknown duration - and with the presence of very new and poorly understood electronic technologies like radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
. In 1942, nobody knew how much bandwidth that the Army and the Navy might need for radar and for radio communications, so the Federal Government took a wise expedient: it allocated a huge amount of radio spectrum to the uniformed services for the time being, in case the service might need it. Then, it could make adjustments later.
After the War ended, and after the growth of civilian TV broadcasting in the years after the war, by 1950 expansion of TV channels into the UHF band of frequencies became inevitable. However, lots of UHF TV technology remained unproven at that time, though plenty had been learned about UHF electronics during the war, especially in the development and improvement of radar. (There are significant advantages to using shorter wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s, hence higher frequencies, for radars.) Also, the question of which owners should retain the more-valuable (at that time) VHF TV channels remained hotly contested between several different competing interests.
To incumbent corporations, such as the Radio Corporation of America
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
and its National Broadcasting Company
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
subsidiary, UHF-TV and FM radio represented disruptive technologies
Disruptive technology
A disruptive technology or disruptive innovation is an innovation that helps create a new market and value network, and eventually goes on to disrupt an existing market and value network , displacing an earlier technology there...
- competition to their existing and long-established manufacturing and broadcast interests in VHF-TV and AM radio. In the fall of 1944, Columbia Broadcasting System
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
pressed a high-definition black and white system on the UHF band employing 750-1,000 scanning lines that offered the possibility of higher-definition monochrome and color broadcasting, both then were precluded from the VHF band because of their bandwidth demands; more significantly, it offered the possibility for sufficient numbers of conventional 6MHz channels to support the FCC's goals of a "truly nationwide and competitive service." CBS was not trying maximize broadcast (or network) competition through freer market entry in the UHF system, but instead CBS's 16MHz channels would have allowed only 27 UHF channels versus the 82 channels possible under the standard 6MHz bandwidth. Vice President of CBS, Adrian Murphy, told the FCC: "I would say that it would be better to have two networks in color" instead of the four or more networks possible with narrower bandwidths in UHF. To newer entrants into TV broadcasting such as the DuMont Laboratories
DuMont Laboratories
DuMont Laboratories was an American television equipment manufacturer. The company was founded in 1931, by inventor Allen B. DuMont. Among the company's developments were long-lasting cathode ray tubes that would be used for television. Another product out of the lab was a DuMont invention, the...
company and its fourth-ranked DuMont Television Network
DuMont Television Network
The DuMont Television Network, also known as the DuMont Network, DuMont, Du Mont, or Dumont was one of the world's pioneer commercial television networks, rivalling NBC for the distinction of being first overall. It began operation in the United States in 1946. It was owned by DuMont...
, however, the need for additional TV channels in major markets was urgent. For proponents of educational TV
Educational television
Educational television is the use of television programs in the field of distance education. It may be in the form of individual television programs or dedicated specialty channels that is often associated with cable television in the United States as Public, educational, and government access ...
broadcasting, the difficulties in competing with commercial broadcasters for the increasingly scarce VHF channels becoming a key problem.
Any attempt to pursue the objective of broadcast localism on the VHF-TV channels threatened in many regions to push the third-network TV companies such as the American Broadcasting Company
American Broadcasting Company
The American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...
onto stations in outlying communities, if they could be accommodated on VHF channels at all.
A key question in the FCC's allocation of TV channels was hence that of intermixture. To allocate four to as many as seven VHF channels to each of the largest cities would mean forcing the smaller, intervening cities completely onto the UHF channels, while an allocation scheme that sought to assign one or two VHF channels in each smaller city would force VHF and UHF stations to compete in most markets. (Some may find it hard to believe, but the large metropolitan areas of New York City, Washington-Baltimore, Los Angeles, and San Francisco received seven VHF stations apiece, and Chicago was allocated five, with the other two possible ones going to Milwaukee and Rockford, Illinois
Rockford, Illinois
Rockford is a mid-sized city located on both banks of the Rock River in far northern Illinois. Often referred to as "The Forest City", Rockford is the county seat of Winnebago County, Illinois, USA. As reported in the 2010 U.S. census, the city was home to 152,871 people, the third most populated...
.)
Hopes that UHF-TV would allow dozens of television stations in every media market
Media market
A media market, broadcast market, media region, designated market area , Television Market Area , or simply market is a region where the population can receive the same television and radio station offerings, and may also include other types of media including newspapers and Internet content...
were thwarted not only by poor image frequency rejection in superheterodyne receiver
Superheterodyne receiver
In electronics, a superheterodyne receiver uses frequency mixing or heterodyning to convert a received signal to a fixed intermediate frequency, which can be more conveniently processed than the original radio carrier frequency...
s with the standard intermediate frequency
Intermediate frequency
In communications and electronic engineering, an intermediate frequency is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called...
of 45.75 MHz, but also by very poor adjacent-channel rejection and channel selectivity by early tuner designs and manufactures. UHF-TV stations in the same immediate area were usually assigned by the FCC a minimum of six channels apart due to inadequate TV receiver manufacture. Technical problems with the design of vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s for operation at high UHF frequencies were beginning to be addressed as late as 1954. These shortcomings led to "UHF taboos", which in effect limited each metropolitan area to only moderately more UHF stations than VHF ones, despite the much higher number of channels.
When the Freeze ended in 1952, the television industry exploded. It grew from the 108 pre-Freeze stations to more than 530 in 1960. These stations were established on the UHF band despite the fact it did not have near the coverage of their VHF competitors. The FCC tried solving this problem by allowing the lower powered UHF stations more power, but it did not work, VHF still had more coverage. At the same time, advertisers had caught on to this and did most of their business with VHF stations. In all, the FCC’s effort to try to intermix VHF and UHF stations in the same market had failed. While the more-established broadcasters were operating profitably on VHF channels as affiliates of the largest TV networks (at the time, NBC and CBS), most of the original UHF local stations of the 1950s soon went bankrupt, limited by the range their signals could travel, the lack of UHF tuners in most TV sets, and difficulties in finding advertisers willing to spend money on them. UHF stations fell quickly behind the VHF stations. UHF station revenues in 1953 were recorded as having a loss of $10,500,000. More stations left the air than began broadcasting and 60 percent of the industry losses were by UHF stations from 1953 to 1956.TV network affiliations were also difficult to get in many locations; the UHF stations with major-network affiliation would often lose these affiliations in favour of any viable new VHF TV station that entered the same market. Of the 82 new UHF-TV stations in the United States broadcasting as of June 1954, only 24 of them remained on the air a year later. The fraction of new TV receivers that were factory-equipped with all-channel tuners dropped from 35% in early 1953 to 9% by 1958, a drop that was only partially compensated for by field upgrades or the availability of UHF converters
Set-top box
A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...
for separate purchase.
The majority of the 165 UHF stations to begin telecasting between 1952 and 1959 did not survive. Under the All-Channel Receiver Act, FCC regulations by 1965 would ensure that all new TV sets sold in the U.S. had built-in UHF tuners that could receive channels 14-83. In spite of this, by 1971, there were just more than 170 full-service UHF broadcast stations nationwide.
Independent and educational stations
In the United States, the UHF stations gained a reputation for being locally owned, less polished and professional, not as popular, and having weaker signal propagation than their VHF channel counterparts.
While UHF-TV has been available to American TV broadcasters since 1952, affiliates of the four major American TV network
Television network
A television network is a telecommunications network for distribution of television program content, whereby a central operation provides programming to many television stations or pay TV providers. Until the mid-1980s, television programming in most countries of the world was dominated by a small...
s (NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
, CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
, ABC
American Broadcasting Company
The American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...
, and DuMont
DuMont Television Network
The DuMont Television Network, also known as the DuMont Network, DuMont, Du Mont, or Dumont was one of the world's pioneer commercial television networks, rivalling NBC for the distinction of being first overall. It began operation in the United States in 1946. It was owned by DuMont...
) continued to transmit their programs primarily on VHF channels wherever they were available. With the availability of the twelve VHF television channels limited by FCC spacing rules to avoid co-channel and adjacent channel
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 used in keeping stations from interfering with one...
interference between TV stations in the same or nearby cities, all available VHF-TV allocations were already in use in most large TV markets by the mid-1950s.
To be more specific, two TV stations on the same channel needed to be about 160 or more miles apart, and two TV stations on adjacent channels needed to be about 60 or more miles apart. Exceptions to this rule occurred with VHF channels 4 and 5, and VHF channels 6 and 7, because there are additional "guard bands" between these two pairs that are allocated to other uses. Thus, the pair channel 4 and 5 was found in New York City, Washington, D.C., St. Louis, Los Angeles, San Francisco, and many other places. Likewise, the pair channel 6 and 7 was found in Denver and several other places.
With the most financially affluent and network-connected TV broadcasters all on VHF channels, UHF stations in major population centers of the United States were usually unable to get big TV-network affiliations (ABC, CBS, & NBC), and thus were usually either educational network or independent TV stations. Other UHF stations did for a time affiliate with less-affluent broadcast networks that didn't last very long; for example, the fourth-ranked DuMont Network, which operated from 1946 to 1956, and then went out of business. The movie UHF
UHF (film)
UHF is a 1989 American comedy film starring "Weird Al" Yankovic, David Bowe, Fran Drescher, Victoria Jackson, Kevin McCarthy, Michael Richards, Gedde Watanabe, Billy Barty, Anthony Geary, Emo Philips and Trinidad Silva, in whose memory the film is dedicated.The title refers to Ultra High Frequency...
, starring "Weird Al" Yankovic
"Weird Al" Yankovic
Alfred Matthew "Weird Al" Yankovic is an American singer-songwriter, music producer, accordionist, actor, comedian, writer, satirist, and parodist. Yankovic is known for his humorous songs that make light of popular culture and that often parody specific songs by contemporary musical acts...
and Michael Richards
Michael Richards
Michael Anthony Richards is an American actor, comedian, writer and television producer, best known for his portrayal of the eccentric Cosmo Kramer on the television sitcom Seinfeld....
, parodied the independent UHF station phenomenon.
However, there were significant cities that had few or no VHF channels allocated to them. Hence, these cities did get UHF stations that did get major network affiliations and did become financially sound businesses. Some of these stations have been located in or near state capital cities or served nearby major rural regions, such as Montgomery, Alabama
Montgomery, Alabama
Montgomery is the capital of the U.S. state of Alabama, and is the county seat of Montgomery County. It is located on the Alabama River southeast of the center of the state, in the Gulf Coastal Plain. As of the 2010 census, Montgomery had a population of 205,764 making it the second-largest city...
, Frankfort, Kentucky
Frankfort, Kentucky
Frankfort is a city in Kentucky that serves as the state capital and the county seat of Franklin County. The population was 27,741 at the 2000 census; by population it is the 5th smallest state capital in the United States...
, Dover, Delaware
Dover, Delaware
The city of Dover is the capital and second largest city in the U.S. state of Delaware. It is also the county seat of Kent County, and the principal city of the Dover, Delaware Metropolitan Statistical Area, which encompasses all of Kent County. It is located on the St. Jones River in the Delaware...
, Lincoln, Nebraska
Lincoln, Nebraska
The City of Lincoln is the capital and the second-most populous city of the US state of Nebraska. Lincoln is also the county seat of Lancaster County and the home of the University of Nebraska. Lincoln's 2010 Census population was 258,379....
, Topeka, Kansas
Topeka, Kansas
Topeka |Kansa]]: Tó Pee Kuh) is the capital city of the U.S. state of Kansas and the county seat of Shawnee County. It is situated along the Kansas River in the central part of Shawnee County, located in northeast Kansas, in the Central United States. As of the 2010 census, the city population was...
, Jefferson City, Missouri
Jefferson City, Missouri
Jefferson City is the capital of the U.S. state of Missouri and the county seat of Cole County. Located in Callaway and Cole counties, it is the principal city of the Jefferson City metropolitan area, which encompasses the entirety of both counties. As of the 2010 census, the population was 43,079...
, Lansing, Michigan
Lansing, Michigan
Lansing is the capital of the U.S. state of Michigan. It is located mostly in Ingham County, although small portions of the city extend into Eaton County. The 2010 Census places the city's population at 114,297, making it the fifth largest city in Michigan...
, Harrisburg, Pennsylvania
Harrisburg, Pennsylvania
Harrisburg is the capital of Pennsylvania. As of the 2010 census, the city had a population of 49,528, making it the ninth largest city in Pennsylvania...
, Madison, Wisconsin
Madison, Wisconsin
Madison is the capital of the U.S. state of Wisconsin and the county seat of Dane County. It is also home to the University of Wisconsin–Madison....
, and Springfield, Missouri
Springfield, Missouri
Springfield is the third largest city in the U.S. state of Missouri and the county seat of Greene County. According to the 2010 census data, the population was 159,498, an increase of 5.2% since the 2000 census. The Springfield Metropolitan Area, population 436,712, includes the counties of...
. In the United States, television stations of or near state capital cities are important because they closely cover the operations of the state governments and spread the information to the residents of a wide region of the states.
TV antenna manufacturers of years ago often rated their top-of-the-line "deep-fringe" antenna models with phrases like "100 miles VHF/60 miles UHF" if the antenna included UHF reception at all. (In the practice of electrical engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
, the frequency range in which an antenna is to be used is an important factor in its design.)
TV set manufacturers of years ago often treated UHF tuners as extra-charge optional-items until the All-Channel Receiver Act of 1964 forced their inclusion in all new TV sets as a standard. By 1964, many pioneering UHF broadcasters had already gone bankrupt. Various attempts were made by the FCC regulators to stem the tide of UHF station failures met with mixed results:
- Limits on the number of owned-and-operated stationOwned-and-operated stationIn the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
s controlled by one corporation were raised from five stations to seven, provided that two of them were UHF stations. Both NBC-TV (WBUF 17WNED-TVWNED-TV is a Public Broadcasting Service member Public televisionstation in Buffalo, New York. Owned by the Western New York Public Broadcasting Association, it broadcasts on digital channel 43 from studios in downtown Buffalo and a transmitter located in Grand Island, New York...
BuffaloBuffalo, New YorkBuffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
, WNBC 30WVITWVIT, virtual channel 30, is the NBC owned and operated television station for the state of Connecticut, licensed to New Britain. WVIT has its offices and studios located in West Hartford, and transmitter based in Farmington, Connecticut....
HartfordHartford, ConnecticutHartford is the capital of the U.S. state of Connecticut. The seat of Hartford County until Connecticut disbanded county government in 1960, it is the second most populous city on New England's largest river, the Connecticut River. As of the 2010 Census, Hartford's population was 124,775, making...
) and CBS-TV (WHCT 18WUVNWUVN is the Connecticut affiliate for the Spanish language Univision television network. It is licensed to Hartford. Owned by Entravision, the station broadcasts its digital signal on UHF channel 46...
Hartford, WXIX 19WVTVWVTV is a television station located in Milwaukee, Wisconsin, USA and serves as Southeast Wisconsin's The CW Television Network affiliate. The station broadcasts from the Milwaukee Public Television tower on Milwaukee's northeast side with WMVS/WMVT, along with WCGV , WVTV's sister station...
Milwaukee) acquired pairs of UHF stations as an experiment in the mid-1950s, only to abandon the stations in 1958-59. Their commercial network programming soon returned to VHF channel affiliates. WBUF's allocation on channel 17 was donated to the public-TV broadcaster WNED-TV, which now broadcasts as a Public Broadcasting ServicePublic Broadcasting ServiceThe Public Broadcasting Service is an American non-profit public broadcasting television network with 354 member TV stations in the United States which hold collective ownership. Its headquarters is in Arlington, Virginia....
station.
- The UHF television impact policy (1960–1988) allowed applications for new VHF TV stations to be opposed in cases where licensure could lead to the economic failure of an existing UHF TV broadcaster.
- The secondary affiliation rule (1971–1995) prohibited a network entering a market with two existing VHF TV network affiliates and one UHF independent TV station from placing its programs on a secondary basis on one or both VHF stations without offering them to the UHF station.
- Limits on UHF effective radiated power, originally very restrictive, were relaxed. A UHF TV station could be licensed for up to five megawatts of carrier power, unlike VHF TV stations, which were limited to 100 (Channels 2-6) or 316 kilowatts of carrier power (Channels 7-13) depending on their channel.
- More recent limits on station ownership are based on the combined percentage of the American population (originally 35% maximum, now increased to 45%) reached by one group of stations under common ownership. A UHF discount, by which only half of the audience of a UHF station would be counted against these limits, would ultimately allow groups such as PAX to reach the majority of the American audience using owned-and-operated UHF stations.
The situation was to begin to improve in the 1960s and 1970s, but progress was to be slow and difficult.
While ABC-TV and the short-lived DuMont Network, being smaller and less prosperous networks, had had a number of UHF affiliates, National Educational Television
National Educational Television
National Educational Television was an American non-commercial educational public television network in the United States from May 16, 1954 to October 4, 1970...
and the later PBS
Public Broadcasting Service
The Public Broadcasting Service is an American non-profit public broadcasting television network with 354 member TV stations in the United States which hold collective ownership. Its headquarters is in Arlington, Virginia....
had even more.
The original SIN (Spanish International Network), which was established in 1962 as the predecessor of the modern Univision
Univision
Univision is a Spanish-language television network in the United States. It has the largest audience of Spanish language television viewers according to Nielsen ratings. Randy Falco, COO, has been in charge of the company since the departure of Univision Communications president and CEO Joe Uva...
network, was built primarily by UHF-TV broadcasters, such as charter stations KWEX-TV
KWEX-TV
KWEX-DT, channel 41, is the local Univisión owned and operated station in San Antonio, Texas. The station is the first commercially-based Spanish language television station in the United States.- History :...
, Channel 41 in San Antonio and KMEX-TV
KMEX-TV
KMEX-DT, "Univisión 34 Los Angeles", is the Univision owned-and-operated station in Los Angeles and the network's flagship station for the West Coast. KMEX, first broadcast in 1962, opened the way for other Spanish-language stations and networks in the United States...
, Channel 34, in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
.
Ultimately, in addition to providing TV service where VHF channels simply were not possible because of the limitations on the technology, UHF-TV also became a means to obtain programming that was not being provided by the "Big Three" commercial networks. For example, there were educational services like the Public Broadcasting Service
Public Broadcasting Service
The Public Broadcasting Service is an American non-profit public broadcasting television network with 354 member TV stations in the United States which hold collective ownership. Its headquarters is in Arlington, Virginia....
, religious broadcasting
Religious broadcasting
Religious broadcasting refers to broadcasting by religious organizations, usually with a religious message. Many religious organizations have long recorded content such as sermons and lectures, and have moved into distributing content on their Internet websites.While this article emphasises...
, and Spanish language
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
or multilingual broadcasting that all relied primarily on UHF channels to offer programming alternatives.
Fourth networks, satellite and cable television
In 1970, Ted Turner
Ted Turner
Robert Edward "Ted" Turner III is an American media mogul and philanthropist. As a businessman, he is known as founder of the cable news network CNN, the first dedicated 24-hour cable news channel. In addition, he founded WTBS, which pioneered the superstation concept in cable television...
had acquired a struggling independent station on Channel 17 in Atlanta, Georgia, purchasing rerun
Rerun
A rerun or repeat is a re-airing of an episode of a radio or television broadcast. The invention of the rerun is generally credited to Desi Arnaz. There are two types of reruns—those that occur during a hiatus, and those that occur when a program is syndicated. Reruns can also be, as the...
s of popular television shows, the Atlanta Braves
Atlanta Braves
The Atlanta Braves are a professional baseball club based in Atlanta, Georgia. The Braves are a member of the Eastern Division of Major League Baseball's National League. The Braves have played in Turner Field since 1997....
baseball team and the Atlanta Hawks
Atlanta Hawks
The Atlanta Hawks are an American professional basketball team based in Atlanta, Georgia. They are part of the Southeast Division of the Eastern Conference in the National Basketball Association .-The first years:...
basketball team in order to provide access to entertainment for broadcast.
This station, renamed as WTBS, was uplinked in 1975 to satellite
Satellite television
Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...
alongside new premium channels such as HBO, gaining access to distant cable television
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
markets and becoming the first of various superstation
Superstation
Superstation in United States television can have several meanings. In its most precise meaning, a superstation is defined by the Federal Communications Commission as "A television broadcast station, other than a network station, licensed by the FCC that is secondarily transmitted by a satellite...
s to obtain national coverage. In 1986 Turner purchased the entire MGM
Metro-Goldwyn-Mayer
Metro-Goldwyn-Mayer Inc. is an American media company, involved primarily in the production and distribution of films and television programs. MGM was founded in 1924 when the entertainment entrepreneur Marcus Loew gained control of Metro Pictures, Goldwyn Pictures Corporation and Louis B. Mayer...
film library, and Turner Broadcasting System
Turner Broadcasting System
Turner Broadcasting System, Inc. is the Time Warner subsidiary managing the collection of cable networks and properties started and acquired by Robert Edward "Ted" Turner starting in the mid-1970s. The company has its headquarters in the CNN Center in Atlanta, Georgia. TBS, Inc...
's access to movie rights was to prove commercially valuable as home video
Home video
Home video is a blanket term used for pre-recorded media that is either sold or rented/hired for home cinema entertainment. The term originates from the VHS/Betamax era but has carried over into current optical disc formats like DVD and Blu-ray Disc and, to a lesser extent, into methods of digital...
cassette rental became ubiquitous in the 1980s.
In 1986, the DuMont
DuMont Television Network
The DuMont Television Network, also known as the DuMont Network, DuMont, Du Mont, or Dumont was one of the world's pioneer commercial television networks, rivalling NBC for the distinction of being first overall. It began operation in the United States in 1946. It was owned by DuMont...
owned-and-operated station
Owned-and-operated station
In the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
group Metromedia
Metromedia
Metromedia was a media company that owned radio and television stations in the United States from 1956 to 1986 and owned Orion Pictures from 1986-1997.- Overview :...
was acquired by News Corporation
News Corporation
News Corporation or News Corp. is an American multinational media conglomerate. It is the world's second-largest media conglomerate as of 2011 in terms of revenue, and the world's third largest in entertainment as of 2009, although the BBC remains the world's largest broadcaster...
and used as the foundation to relaunch a fourth commercial network
Fourth television network
In American television terminology, a fourth network is a reference to a fourth broadcast television network, as opposed to the Big Three television networks that dominated US TV from the 1950s to the 1990s: ABC, CBS, and NBC....
, which obtained affiliation with many former big-city independent stations as Fox TV
Fox Broadcasting Company
Fox Broadcasting Company, commonly referred to as Fox Network or simply Fox , is an American commercial broadcasting television network owned by Fox Entertainment Group, part of Rupert Murdoch's News Corporation. Launched on October 9, 1986, Fox was the highest-rated broadcast network in the...
.
While built largely from former independents and UHF stations in its early years, Fox had the large programming budgets that the original DuMont lacked. Ultimately, it was able in some markets to draw existing long-standing VHF affiliates away from established big-three networks, outbidding CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
for National Football Conference
National Football Conference
The National Football Conference is one of the two conferences of the National Football League . This conference and its counterpart, the American Football Conference , currently contain 16 teams each, making up the 32 teams of the NFL.-Current teams:Since 2002, the NFC has comprised 16 teams,...
programming in 1994 and attracting many of that network's affiliates. Various smaller networks were created with the intent to follow in its footsteps, often assembling a fledgling network by affiliating with a disparate collection of formerly independent UHF stations that otherwise would have no network programming.
Fox launched in 1986. The film UHF
UHF (film)
UHF is a 1989 American comedy film starring "Weird Al" Yankovic, David Bowe, Fran Drescher, Victoria Jackson, Kevin McCarthy, Michael Richards, Gedde Watanabe, Billy Barty, Anthony Geary, Emo Philips and Trinidad Silva, in whose memory the film is dedicated.The title refers to Ultra High Frequency...
portrayed a fictional station on channel 62 in 1989. By 1994, New World Communications
New World Communications
New World Pictures was an independent motion picture and television production company, and later television station owner in the United States from the late 1980s to the mid-1990s...
was moving its established stations from CBS to Fox affiliations in multiple markets
Fox affiliate switches of 1994
The United States television network affiliate switches of 1994 were a series of events resulting from a multi-million dollar deal between Fox Broadcasting Company, known commonly as Fox, and New World Communications, an owner of several VHF television stations affiliated with major networks,...
, including WJBK-TV 2 Detroit. In many cases, this pushed CBS onto UHF; "U-62" as the new home of CBS in Detroit became CBS owned-and-operated station
Owned-and-operated station
In the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
WWJ-TV
WWJ-TV
WWJ-TV, virtual channel 62 , is the CBS-owned and operated television station in Detroit, Michigan. It is co-owned with Detroit's CW station, WKBD-TV , and the two stations share a studio in Southfield, Michigan, a Detroit suburb....
in 1995, obtaining access to audiences thousands of miles distant through satellite and cable television.
The concentration of media ownership
Concentration of media ownership
Concentration of media ownership refers to a process whereby progressively fewer individuals or organizations control increasing shares of the mass media...
, the proliferation of cable
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
and satellite television
Satellite television
Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...
and the digital television transition
Digital television transition
The digital television transition is the process in which analog television broadcasting is converted to and replaced by digital television. This primarily involves both TV stations and over-the-air viewers; however it also involves content providers like TV networks, and cable television...
have contributed to the quality equalization of VHF and UHF broadcasts. The distinction between UHF and VHF characteristics has declined in importance with the emergence of additional broadcast television networks (Fox
Fox Broadcasting Company
Fox Broadcasting Company, commonly referred to as Fox Network or simply Fox , is an American commercial broadcasting television network owned by Fox Entertainment Group, part of Rupert Murdoch's News Corporation. Launched on October 9, 1986, Fox was the highest-rated broadcast network in the...
, The CW
The CW Television Network
The CW Television Network is a television network in the United States launched at the beginning of the 2006–2007 television season. It is a joint venture between CBS Corporation, the former owners of United Paramount Network , and Time Warner's Warner Bros., former majority owner of The WB...
, MyNetworkTV
MyNetworkTV
MyNetworkTV is a television broadcast syndication service in the United States, owned by the Fox Entertainment Group, a division of News Corporation...
, Univision
Univision
Univision is a Spanish-language television network in the United States. It has the largest audience of Spanish language television viewers according to Nielsen ratings. Randy Falco, COO, has been in charge of the company since the departure of Univision Communications president and CEO Joe Uva...
, Telemundo
Telemundo
Telemundo is an American television network that broadcasts in Spanish. The network is the second-largest Spanish-language content producer in the world, and the second-largest Spanish-language network in the United States, behind Univision....
and ION), and the decline of direct OTA
Terrestrial television
Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
reception. The number of major large-city independent stations has also declined as many have joined or formed new networks.
Digital television
See also DTV transition in the United States#VHF frequencies and digital television
The majority of digital TV stations currently broadcast their over-the-air signals in the UHF band, both because VHF had been already filled largely with analog TV at the time the digital facilities were built and because of severe issues with impulse noise
Impulse noise (audio)
Impulse noise is a category of noise which includes unwanted, almost instantaneous sharp sounds . Noises of the kind are usually caused by electromagnetic interference, scratches on the recording disks, and ill synchronization in digital recording and communication...
on digital low-VHF
Band I
Band I is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band I ranges from 47 to 88 MHz, and it is primarily used for radio and television broadcasting....
channels. While virtual channel
Virtual channel
In telecommunications, a logical channel number , also known as virtual channel, is a channel designation which differs from that of the actual radio channel on which the signal travels....
numbering schemes routinely display channel numbers like "2.1" or "6.1" for individual North American terrestrial HDTV broadcasts, these are more often than not actually UHF signals. Many equipment vendors therefore use "HDTV antenna" or similar branding as all but synonymous to "UHF antenna".
Terrestrial digital television is based on a forward error correction
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
scheme, in which a channel is assumed to have a random bit error rate and additional data bits may be sent to allow these errors to be corrected at the receiver. While this error correction can work well in the UHF band where the interference consist largely of white noise
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...
, it has largely proven inadequate on lower VHF channels where bursts of impulse noise disrupt the entire channel for short lengths of time. A short impulse-noise burst might be a minor annoyance to analog TV viewers, but due to the fixed timing and repetitive nature of analog video synchronization is usually recoverable. The same interference can prove severe enough to prevent the reliable reception of the more fragile and more highly compressed ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
digital television. Power limits are also lower on low-VHF; a digital UHF station may be licensed to transmit up to a megawatt of effective radiated power. Very few stations returned to VHF channels 2-6
Band I
Band I is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band I ranges from 47 to 88 MHz, and it is primarily used for radio and television broadcasting....
after digital transition
DTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
was completed in 2009. At least three quarters of all full-power digital broadcasts continued to use UHF transmitters, even after transition is complete, with most of the others located on the high-VHF
Band III
Band III is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band III ranges from 174 to 230 MHz, and it is primarily used for radio and television broadcasting...
channels. In some American markets, such as Syracuse, New York
Syracuse, New York
Syracuse is a city in and the county seat of Onondaga County, New York, United States, the largest U.S. city with the name "Syracuse", and the fifth most populous city in the state. At the 2010 census, the city population was 145,170, and its metropolitan area had a population of 742,603...
, there are no full-service VHF TV stations remaining after digital transition
DTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
.
The one remaining limitation of UHF, that of a greatly reduced ability for signals to travel great distances in the presence of obstacles due to terrain, continues to adversely affect digital UHF TV reception. This limitation could potentially be overcome by the use of
DTS (Distributed Transmission Systems)
Distributed transmission system
In North American digital terrestrial television broadcasting, a distributed transmission system is a form of single-frequency network in which a single broadcast signal is fed via microwave, landline, or communications satellite to multiple synchronised terrestrial radio transmitter sites...
. Multiple digital UHF transmitters in carefully selected locations can be synchronized as a single-frequency network
Single-frequency network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.-Overview:...
to produce a tailored coverage area pattern rivaling that of a single full-power VHF transmitter.
While the Federal Communications Commission authorization to use DTS on anything more than an experimental basis came in November 2008, too late for sites to be acquired and transmitters built before the 2009 end of American digital transition
DTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
, it is likely that more of these distributed UHF transmission systems will be constructed alongside conventional digital broadcast translator systems in the years to come as a means to get digital and high-definition television out to a wider audience.
UHF islands
One notable exception to historical patterns favoring VHF broadcasters has existed in mid-size television markets within the United States that were too close to the outer fringe of the broadcast range of large-city VHF stations to qualify for their own stations on these frequencies. As no full-power VHF channels could be made available in these areas without encountering problems of interference from overlapping broadcast ranges, the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
granted some mid-sized cities only UHF licenses. With all stations (including big-three network affiliates) on UHF, all-channel receivers and antennas became commonplace locally and UHF stations signing on as early as 1954 were often able to obtain the programming and viewership needed to remain viable into the modern era.
These communities, known as UHF islands, included cities like Springfield, Massachusetts
Springfield, Massachusetts
Springfield is the most populous city in Western New England, and the seat of Hampden County, Massachusetts, United States. Springfield sits on the eastern bank of the Connecticut River near its confluence with three rivers; the western Westfield River, the eastern Chicopee River, and the eastern...
; Fresno, California
Fresno, California
Fresno is a city in central California, United States, the county seat of Fresno County. As of the 2010 census, the city's population was 510,365, making it the fifth largest city in California, the largest inland city in California, and the 34th largest in the nation...
; South Bend, Indiana
South Bend, Indiana
The city of South Bend is the county seat of St. Joseph County, Indiana, United States, on the St. Joseph River near its southernmost bend, from which it derives its name. As of the 2010 Census, the city had a total of 101,168 residents; its Metropolitan Statistical Area had a population of 316,663...
;Fort Wayne, Indiana
Fort Wayne, Indiana
Fort Wayne is a city in the US state of Indiana and the county seat of Allen County. The population was 253,691 at the 2010 Census making it the 74th largest city in the United States and the second largest in Indiana...
; and Lexington, Kentucky
Lexington, Kentucky
Lexington is the second-largest city in Kentucky and the 63rd largest in the US. Known as the "Thoroughbred City" and the "Horse Capital of the World", it is located in the heart of Kentucky's Bluegrass region...
. Other smaller cities found that only one VHF channel was open and any additional programming would need to be provided either by UHF, by distant stations, or by low-power broadcasting
Low-power broadcasting
Low-power broadcasting is electronic broadcasting at very low power and low cost, to a small community area.The terms "low-power broadcasting" and "micropower broadcasting" should not be used interchangeably, because the markets are not the same...
.
Broadcast translators and low-power television
A large number of very small UHF TV transmitters continue to operate with no programming or commercial identity of their own, merely retransmitting signals of existing full-power stations to a smaller area poorly covered by the main VHF signal. Such transmitters are called "translators
Broadcast relay station
A broadcast relay station, relay transmitter, broadcast translator , rebroadcaster , or repeater is a broadcast transmitter which relays, repeats, or reflects the signal of another radio station or television station, usually to an area not covered by the signal of the originating station...
" rather than “stations”. The smallest, owned by local municipal-level groups or the originating TV stations, are numbered sequentially - W or K, followed by the channel number, followed by two sequentially issued letters, yielding a "translator callsign" in a generic format that appears K14AA through W69ZZ. Translators and repeaters also exist on VHF channels, but infrequently and with stringently limited power as the VHF spectrum is already crowded with full-power network stations in most regions.
The translator band
Broadcast relay station
A broadcast relay station, relay transmitter, broadcast translator , rebroadcaster , or repeater is a broadcast transmitter which relays, repeats, or reflects the signal of another radio station or television station, usually to an area not covered by the signal of the originating station...
, UHF TV channels 70-83, consisted mostly of these small repeaters; it was removed from television use in 1983 with the tiny repeaters moved primarily to lower UHF channels. The 804-890 MHz band segment is now used primarily by mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s.
As improvements to originating stations signals lessen the need for these small translators in some areas, often the small transmitter facilities and their allocated frequencies would be repurposed for low-power broadcasting
Low-power broadcasting
Low-power broadcasting is electronic broadcasting at very low power and low cost, to a small community area.The terms "low-power broadcasting" and "micropower broadcasting" should not be used interchangeably, because the markets are not the same...
; instead of repeating a distant signal, the tiny transmitter would be used to originate programming for a small local area.
Radio, mobile and non-broadcast applications
The Family Radio ServiceFamily Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
and General Mobile Radio Service
General Mobile Radio Service
The General Mobile Radio Service is a licensed land-mobile FM UHF radio service in the United States available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members...
use the 462 and 467 MHz areas of the UHF spectrum. There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz. These ISM band
ISM band
The industrial, scientific and medical radio bands are radio bands reserved internationally for the use of radio frequency energy for industrial, scientific and medical purposes other than communications....
s - open frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus - are now becoming some of the most crowded in the spectrum because they are open to everyone.
The 2.45 GHz frequency is the standard for use by microwave ovens
Microwave oven
A microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...
in residential ovens; (915 MHz is used in commercial microwave ovens) .
The spectrum from 806 MHz to 890 MHz (UHF channels 70-83) was taken away from TV broadcast services in 1983, primarily for analogue mobile telephony
Advanced Mobile Phone System
Advanced Mobile Phone System was an analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983, Israel in 1986, and Australia in 1987. It was the primary analog mobile phone system in North America through the 1980s and into the 2000s...
. In 2009, as part of the transition from analog to digital over-the-air broadcast of television, the spectrum from 698 MHz to 806 MHz (UHF channels 52-69) was also no longer used for TV broadcasting. Channel 55, for instance, was sold to Qualcomm
Qualcomm
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
for their MediaFLO
MediaFLO
MediaFLO is a technology developed by Qualcomm for transmitting audio, video and data to portable devices such as mobile phones and personal televisions, used for mobile television...
service, which is resold under various mobile telephone network brands. Some US broadcasters had been offered incentives to vacate this channel early, permitting its immediate mobile use.
The FCC
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
's scheduled auction for this newly available spectrum
United States 2008 wireless spectrum auction
The United States 700 MHz FCC wireless spectrum auction, officially known as Auction 73, was started by the Federal Communications Commission on January 24, 2008 for the rights to operate the 700 MHz frequency band in the United States...
was completed in March 2008.
Australia
- UHF CB Australia - UHF CB News, Information & Repeater Locations. UHF CB Australia Supporting and expanding the UHF CB network
- UHF Citizens BandUHF CBUHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
: 300- 3000MHz
Canada
- 470-806 MHz: Terrestrial televisionTerrestrial televisionTerrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
(with select channels in the 700 MHz band left vacant) - 1452-1492 MHz: Digital Audio BroadcastingDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
(L bandL bandL band refers to four different bands of the electromagnetic spectrum: 40 to 60 GHz , 1 to 2 GHz , 1565 nm to 1625 nm , and around 3.5 micrometres .-NATO L band:...
) - Many other frequency assignments for Canada and Mexico are similar to their US counterparts
United Kingdom
- 380–395 MHz: Terrestrial Trunked RadioTerrestrial Trunked RadioTerrestrial Trunked Radio is a professional mobile radio and two-way transceiver specification...
(TETRA) service for emergency use - 430–440 MHz: Amateur radio (ham - 70 cm band)
- 457–464 MHz: Scanning telemetry and telecontrol, assigned mostly to the water, gas, and electricity industries
- 606–614 MHz: Radio microphones and radio-astronomy
- 470–862 MHz: TV channels 21–69 (channel 36 used for radar, channel 38 used for radio astronomy, channel 69 used for licenced and licence exempt wireless microphones, channels 31-40 and 63-68 to be released and may be made available for other uses by Ofcom. Public consultation due December 2006)
- 1240–1316 MHz: Amateur radio (ham - 23 cm band)
- 1880–1900 MHz: DECTDigital Enhanced Cordless TelecommunicationsDigital Enhanced Cordless Telecommunications , usually known by the acronym DECT, is a digital communication standard, which is primarily used for creating cordless phone systems...
Cordless telephoneCordless telephoneA cordless telephone or portable telephone is a telephone with a wireless handset that communicates via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station... - 2310–2450 MHz: Amateur radio (ham - 13 cm band)
United States
A brief summary of some UHF frequency use:- 225–420 MHz: Government use, including meteorologyMeteorologyMeteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
, military aviation, and federal two-way use - 420–450 MHz: Government radiolocation and amateur radioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
(70 cm band) - 433 MHz: Short range consumer devices including automotive, alarm systems, home automation, temperature sensors
- 450–470 MHz: UHF business band, General Mobile Radio ServiceGeneral Mobile Radio ServiceThe General Mobile Radio Service is a licensed land-mobile FM UHF radio service in the United States available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members...
, and Family Radio ServiceFamily Radio ServiceThe Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
2-way "walkie-talkies", public safety - 470–512 MHz: TV channels 14–20 (also shared for land mobile 2-way radio use in some areas)
- 512–698 MHz: TV channels 21–51 (channel 37 used for radio astronomyRadio astronomyRadio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
) - 698–806 MHz: Was auctioned in March 2008;United States 2008 wireless spectrum auctionThe United States 700 MHz FCC wireless spectrum auction, officially known as Auction 73, was started by the Federal Communications Commission on January 24, 2008 for the rights to operate the 700 MHz frequency band in the United States...
bidders got full use after the transition to digital TVDigital televisionDigital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
was completed on June 12, 2009 (formerly UHF TV channels 52–69) - 806–824 MHz: Public safety and commercial 2-way (formerly TV channels 70–72)
- 824–851 MHz: Cellular A & B franchises, terminal (mobile phone) (formerly TV channels 73–77)
- 851–869 MHz: Public safety and commercial 2-way (formerly TV channels 77–80)
- 869–896 MHz: Cellular A & B franchises, base station (formerly TV channels 80–83)
- 902–928 MHz: ISM bandISM bandThe industrial, scientific and medical radio bands are radio bands reserved internationally for the use of radio frequency energy for industrial, scientific and medical purposes other than communications....
, amateur radio (33 cm band), cordless phones and stereo, radio-frequency identification, datalinks - 929–930 MHz: Pagers
- 931–932 MHz: Pagers
- 935–941 MHz: Commercial 2-way radio
- 941–960 MHz: Mixed studio-transmitter links, SCADA, other.
- 960–1215 MHz: Aeronautical Radionavigation
- 1240–1300 MHz: Amateur radio (23 cm band)
- 1452–1492 MHz: Military use (therefore not available for Digital Audio BroadcastingDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
, unlike Canada/Europe) - 1710–1755 MHz: AWSAdvanced Wireless ServicesAWS-1 or UMTS band IV, is a wireless telecommunications spectrum band used for mobile voice and data services, video, and messaging. AWS-1 is used in the United States and Canada...
mobile phone uplink (UL) Operating Band - 1850–1910 MHz: PCS mobile phone—order is A, D, B, E, F, C blocks. A, B, C = 15 MHz; D, E, F = 5 MHz
- 1920–1930 MHz: DECTDigital Enhanced Cordless TelecommunicationsDigital Enhanced Cordless Telecommunications , usually known by the acronym DECT, is a digital communication standard, which is primarily used for creating cordless phone systems...
Cordless telephoneCordless telephoneA cordless telephone or portable telephone is a telephone with a wireless handset that communicates via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station... - 1930–1990 MHz: PCS base stations—order is A, D, B, E, F, C blocks. A, B, C = 15 MHz; D, E, F = 5 MHz
- 2110–2155 MHz: AWSAdvanced Wireless ServicesAWS-1 or UMTS band IV, is a wireless telecommunications spectrum band used for mobile voice and data services, video, and messaging. AWS-1 is used in the United States and Canada...
mobile phone downlink (DL) Operating Band - 2300–2310 MHz: Amateur radio (13 cm band, lower segment)
- 2310–2360 MHz: Satellite radioSatellite radioSatellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...
(SiriusSirius Satellite RadioSirius Satellite Radio is a satellite radio service operating in North America, owned by Sirius XM Radio.Headquartered in New York City, with smaller studios in Los Angeles and Memphis, Sirius was officially launched on July 1, 2002 and currently provides 69 streams of music and 65 streams of...
and XMXM Satellite RadioXM Satellite Radio is one of two satellite radio services in the United States and Canada, operated by Sirius XM Radio. It provides pay-for-service radio, analogous to cable television. Its service includes 73 different music channels, 39 news, sports, talk and entertainment channels, 21 regional...
) - 2390–2450 MHz: Amateur radio (13 cm band, upper segment)
- 2400–2483.5 MHz: ISMISM bandThe industrial, scientific and medical radio bands are radio bands reserved internationally for the use of radio frequency energy for industrial, scientific and medical purposes other than communications....
, IEEE 802.11IEEE 802.11IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
, 802.11b, 802.11g, 802.11n Wireless LANLänLän and lääni refer to the administrative divisions used in Sweden and previously in Finland. The provinces of Finland were abolished on January 1, 2010....
, IEEE 802.15.4-2006, BluetoothBluetoothBluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
, Radio-controlled aircraftRadio-controlled aircraftA radio-controlled aircraft is controlled remotely by a hand-held transmitter and a receiver within the craft...
, Microwave ovenMicrowave ovenA microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...
, ZigBeeZigBeeZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on an IEEE 802 standard for personal area networks. Applications include wireless light switches, electrical meters with in-home-displays, and other consumer and industrial...
See also
- All-Channel Receiver Act
- Australasian television frequenciesAustralasian television frequencies-What led to the differences:What are the important underlining circumstances that led to the different allocations?* Universally the VHF low band channels of , 1, 2, and 3 were allocated on an ad-hoc basis in Australia and NZ without any trans-Tasman coordination.* Australia decided against...
- BluetoothBluetoothBluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
- Broadcast television systems
- Channel 37Channel 37Channel 37 is an unused television channel in countries using the M and N broadcast television system standards. Channel 37 occupies a band of UHF frequencies from 608 to 614 MHz, frequencies that are particularly important to radio astronomy...
- Digital Audio BroadcastingDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
and its regional implementationsRegional implementations of DABThe radio technology known as Digital Audio Broadcasting , and its TV sibling, Digital Multimedia Broadcasting, is being operated in several regions worldwide, either in the form of full commercial services, or as feasibility studies... - Digital terrestrial televisionDigital terrestrial televisionDigital terrestrial television is the technological evolution of broadcast television and advance from analog television, which broadcasts land-based signals...
- Knife-edge effectKnife-edge effectIn electromagnetic wave propagation, the knife-edge effect or edge diffraction is a redirection by diffraction of a portion of the incident radiation that strikes a well-defined obstacle such as a mountain range or the edge of a building....
- L-band
- North American broadcastNorth American broadcast television frequenciesThe North American broadcast television frequencies are on designated television channels numbered 2 through 69, approximately between 54 and 806 MHz. Traditionally, the frequencies are divided into two sections, the very high frequency band and the ultra high frequency band. The VHF band is...
and cable television frequenciesNorth American cable television frequenciesIn North American cable TV networks, the radio frequencies used to carry signals to the customer are allocated to standardarized channel numbers listed in the CEA standard 542. Cable channel frequencies are generally different from off-air broadcast frequencies... - Television channel frequenciesTelevision channel frequenciesThe following tables show the frequencies assigned to broadcast television channels in various regions of the world, along with the ITU letter designator for the system used. The frequencies shown are for the video and audio carriers. The channel itself occupies several megahertz of bandwidth....
- Terrestrial televisionTerrestrial televisionTerrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
- Thing (listening device)Thing (listening device)The Thing, also known as the Great Seal bug, was one of the first covert listening devices to use passive techniques to transmit an audio signal...
- UHF CBUHF CBUHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
- Very high frequencyVery high frequencyVery high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
- Wi-FiWi-FiWi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
External links
- U.S. cable television channel frequencies
- TVTower.com - Commercial Television Frequencies
- Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).