UHF television broadcasting
UHF television broadcasting is the use of ultra high frequency (UHF) radio for over-the-air transmission of television signals. UHF frequencies are used for both analog and digital television broadcasts. UHF channels are typically given higher channel numbers, like the US arrangement with VHF channels (initially) 1 to 13, and UHF channels (initially) numbered 14 to 83. Compared with an equivalent VHF television transmitter, to cover the same geographic area with a UHF transmitter requires a higher effective radiated power, implying a more powerful transmitter or a more complex antenna. However, the additional channels allow more broadcasters in a given region without causing objectionable mutual interference.
UHF broadcasting became possible due to the introduction of new high-frequency vacuum tubes developed by Philips immediately prior to the opening of World War II. These were used in experimental television receivers in the UK in the 1930s, and became widely used during the war as radar receivers. Surplus tubes flooded the market in the post-war era. At the same time, the development of color television was taking its first steps, initially based on incompatible transmission systems. The US FCC set aside a block of the then-unused and now-practical UHF frequencies for color television use. The introduction of the backward compatible NTSC standard led to these channels being released for any television use in 1952.
Early receivers were generally less efficient at UHF band reception, and the signals are also subject to more environmental interference.[1] Additionally, the signals are less susceptible to diffraction effects, which can improve reception at long range.[2] UHF generally had less clear signals, and for some markets, became the home of smaller broadcasters who were not willing to bid on the more coveted VHF allocations. These issues are greatly reduced with digital television, and today most over-the-air broadcasts take place on UHF, while VHF channels are being retired. To avoid the appearance of disappearing channels, digital broadcast systems have a virtual channel concept, allowing stations to keep their original VHF channel number while actually broadcasting on a UHF frequency.
Over time a number of former television channels in the upper UHF band have been re-designated for other uses. Channel 1 and Channel 37 were never used in the US and some other countries in order to prevent interference with radio astronomy. In 1983, the US FCC removed channels 70 through 83 and reassigned them to Land Mobile Radio System. In 2009, with the move to digital television complete in the US, channels 52 through 69 were reallocated as the 700 MHz band for cellular telephone service. In 2011, Channel 51 was removed to prevent interference with the 700 MHz band. Additionally, in 2019 the US removed channels 38 through 50 for cellular phone service. The US UHF channel map now only includes channels 14 through 36.
Canada[edit]
The first Canadian television network was publicly owned Radio-Canada, the Canadian Broadcasting Corporation. 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 American TV stations along the border.
The use of UHF to provide programming that otherwise would not be available, such as province-wide educational services (BC's Knowledge: channel, or TVOntario - the first UHF originating station in Canada), Télé-Québec, French language programming outside Québec and ethnic/multilingual television services), 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 original digital terrestrial television stations were all UHF broadcasts, although some digital broadcasts returned to VHF channels after the digital transition was completed in August 2011.[4]
Digital Audio Broadcasting, deployed on a very limited scale in Canada in 2005 and largely abandoned, 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.[5]
Ireland[edit]
In the Republic of Ireland, 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 County Longford, followed by Three Rock Mountain in South County Dublin. These sites were followed by Clermont Carn in County Louth and Holywell Hill in County Donegal in 1981. Since the analogue television switchoff on October 24, 2012, all digital terrestrial TV is on UHF only, although VHF allocations exist. The UHF band has been used in parts of Ireland for television deflector systems bringing British television signals to towns and rural areas that cannot receive these signals directly. However, since the introduction of free to air satellite transmission of UK TV channels these deflectors have largely ceased operation.
Japan[edit]
In Japan, an Independent UHF Station (ja:全国独立UHF放送協議会, Zenkoku Dokuritsu Yū-eichi-efu Hōsō Kyōgi-kai, literally National Independent UHF Broadcasting Forum) is one of a loosely knit group of free commercial 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 number of VHF broadcasters varied depending on the prefecture. For example, in the Kanto region, there were seven VHF channels available. Outside of Tokyo, Osaka, Nagoya, and Fukuoka, most prefectures had four privately owned television stations, with three of them broadcasting on UHF. Almost all prefectures had at least one privately owned VHF television station (except for Saga).
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 infomercials.
Japanese terrestrial television was converted entirely to digital UHF starting in December 2003, with all analogue television signals (both VHF and UHF) being terminated between 2010 and 2012. The analogue translators in northeastern Ishikawa Prefecture were shut down as part of a technical trial on 24 July 2010; analogue signals in the rest of that prefecture and 43 other prefectures were terminated on 24 July 2011. The analogue transmitters in the prefectures of Iwate, Miyagi, and Fukushima were switched off on 31 March 2012.
Malaysia[edit]
UHF broadcasting was used outside Kuala Lumpur and the Klang Valley by private TV station TV3 in the late 1980s, 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 1990s, 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 6 distinct UHF signals receivable by an analog TV set in the Klang Valley: Channel 27 (8TV), Channel 29 (TV3 UHF transmission), Channel 37 (NTV7), Channel 42 (TV9), Channel 55 (TV Alhijrah) and Channel 39 (WBC). Channel 35 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).
New Zealand[edit]
Refer to Australian and New Zealand television frequencies for more information.
Philippines[edit]
UHF broadcasting was introduced in the Philippines in the early 1960s when FEN Philippines began broadcasts on channel 17 in Pampanga and Zambales (as in Subic and Clark bases), and channel 43 in Bulacan and also in Metro Manila on Channel 50 until 1991 (most of its programs and newscasts are from a satellite feed directly from their U.S. military bases in Japan), at the time when Mount Pinatubo erupted and became abandoned. Commercial UHF stations began in May, 1992, as DWCP-TV on channel 21 became the first local UHF TV station in Metro Manila by the Southern Broadcasting Network as SBN-21 (then Talk TV) and commenced free programing, the second channel, DWKC-TV (on channel 31) of the Radio Mindanao Network was launched on October 31 of the same year as CTV-31 from 1992 to 2000 (then E! from 2000 to 2003 and BEAM in 2011). The third channel, DZRJ-TV (channel 29) was also launched in 1993 for the Rajah Broadcasting Network, Inc. which specializes niche programing (mostly infomercials, foreign shows and cartoons). Two more channels include DWDB-TV (channel 27) of GMA Network, Inc. (as Citynet Television from 1995 to 1999 and EMC from 1999 to 2001) and DWAC-TV (channel 23) of ABS-CBN (as Studio 23) between August 27, 1995 and October 12, 1996, as fourth and fifth UHF stations, and the sixth and the last, DWDZ-TV (channel 47) of the Associated Broadcasting Company in 1999, but it was silent in 2003. UHF channels in Metro Manila were used as an alternative to cable television which offered free programing for households in the target markets and became popular in the 1990s. Similarly, pay services were also introduced in late 1992, when DWBC-TV on channel 68 began initial transmissions as a paid UHF station offers foreign programs not shown on local TV and commencing regular service in January 1993, but it was closed down as a result from intense competition from the rival Sky Cable. From 2001 to the present, more channels were established, regional stations are established in the provinces which specialize news, public service and free programming.
With Digital TV was introduced, all UHF channels will allocate their frequencies and can be served for broadcast companies such as ABS-CBN, GMA Network and TV5, among others as the National Telecommunications Commission plans to migrate all VHF channels to digital UHF channels before December 31, 2015, though this was delayed until 2020 or 2023. Digital terrestrial television services are currently in development by the major broadcasting companies before the Implementing Rules and Regulations (IRR) will be passed by law.
South Africa[edit]
South Africa only received analog TV service in the 1970s There were four TV channels: TV1 (now SABC1), TV2 (now SABC2), TV3 (now SABC3), and later came Etv.
United Kingdom[edit]
In the UK, UHF television began in 1964 following a plan by the General Post Office 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 (both 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 modulators in devices such as domestic videocassette recorders, 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. Analogue transmissions have ceased completely since 2012 [6] after which the vacated capacity was used for additional digital television services and put into alternative use, such as mobile telecommunications or internet services.[7]
United States[edit]
The need for the UHF band[edit]
Bandwidth for television in the United States was allocated by the Federal Communications Commission (FCC) in 1937, solely in the VHF (Very High Frequency) band, across 18 channels.[8] American television broadcasting began experimentally in the 1930s with regular commercial broadcasting in cities such as New York and Chicago in 1941. Efforts at TV broadcasting on any channel were drastically curtailed once World War II began, due largely to lack of available receivers. The upper five VHF channels were removed from the FCC allocation list during the war with those frequencies re-allocated for military use, leaving thirteen channels (1 through 13) as of May 1945.[9]
The end of the war brought rapid expansion in the nascent broadcast television industry. Thirteen VHF channels was found to be insufficient to support the desired expansion of broadcast television across the United States. Interference and channel crowding in densely populated areas (such as the eastern mid-Atlantic states) was a particular problem. This bandwidth crunch was made even worse by the need to re-allocate VHF Channel 1 to land-mobile radio systems in 1948 due to radio-interference problems. To illustrate the channel crowding problem, the following cities were never allocated any VHF-TV stations at all, due to technical reasons found by the FCC: Huntsville, Alabama; Peoria, Illinois; Fort Wayne, Indiana; South Bend, Indiana, Lexington, Kentucky; Springfield, Massachusetts; Elmira, New York; Youngstown, Ohio; Scranton/Wilkes-Barre, Pennsylvania; and Yakima, Washington. Other cites were able to receive only one VHF broadcast station. The entire state of New Jersey would receive only one VHF broadcast station of its own (which was to ultimately become WNET 13 Newark). Similarly, Delaware also had only one VHF station.
Meanwhile, UHF broadcasting until 1949 was designated as experimental. In the fall of 1944, the Columbia Broadcasting System proposed 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 6 MHz channels to support the FCC's goals of a "truly nationwide and competitive service". CBS was not trying to maximize broadcast (or network) competition through freer market entry. Instead CBS's 16 MHz channels would have allowed only 27 UHF channels versus the 82 channels possible under the standard 6 MHz bandwidth. CBS Vice President 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.[9]
In October 1948, the Federal Communications Commission stopped accepting applications for new stations, a freeze expected to last "six months to a year".[8] The freeze would give the FCC and broadcasting interests time to address questions such as the allocation of additional channel frequencies, and the selection of a color television standard. At the time of the freeze, less than 100 stations were on the air, but stations already under construction would be allowed to complete work. All but one of these was on the VHF band; on December 29, 1949, KC2XAK of Bridgeport, Connecticut, became the first and only pre-1950 UHF television station to operate on a regular daily schedule. Existing FCC rules at the time of the freeze had designated 42 UHF channels, designated 14–55, between 475–890 MHz.
Freeze on new television stations (1948)[edit]
Ultimately, the question the FCC faced of how to allocate bandwidth for new television licenses would not take "months" to resolve, but several years. To newer entrants into TV broadcasting such as the American Broadcasting Company and DuMont Television Network, the need for additional TV channels in major markets was urgent.[10] For proponents of educational TV broadcasting, the difficulties in competing with commercial broadcasters for the increasingly scarce VHF channels was also a problem.[11]
Allocating more of the VHF band (30 to 300 MHz) by moving existing radio communication users away seemed to be impossible. FM radio broadcasting had already suffered a huge setback after a forced move from a 42–50 MHz allocation to an 88–108 MHz allocation in 1946.[12] This had rendered all pre-1946 FM transmitters and receivers obsolete, and there was heavy resistance to moving FM a second time. Aeronautical radio is located above 108 MHz; military aeronautical radio used 225–400 MHz. Additional public safety, commercial land-mobile, and amateur radio services had allocations in Band II. It was impractical and uneconomic to require these well-established VHF users to move to other frequencies, such as the 300 MHz – 3 GHz UHF band.
All of this made expansion of broadcast television channels into the UHF band inevitable, though the technology and broadcasting characteristics of UHF was at this time largely unproven. Even the television standard to use to broadcast on UHF was in question at the time of the 1948 FCC freeze.
With the knowledge that UHF channel allocation would be necessary to expand television coverage, and with the knowledge that by 1949 VHF television was an entrenched standard, the FCC proposed intermixture, licensing both VHF and UHF stations in a single city. Intermixture would rely on consumers rapidly adopting television sets with UHF tuning capability, and on the base assumption that a UHF television station was functionally equivalent to a VHF one. 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 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. The largest cities with the most sets in use benefitted most from VHF allocations. For example, New York City, Washington-Baltimore, Los Angeles, and San Francisco received seven VHF stations apiece, and Chicago was allocated five, with the other two of those channels going to Milwaukee, Wisconsin and Rockford, Illinois.
FCC rules published on April 11, 1952, defined the final modern-day UHF allocation of 70 channels, 14 through 83, with 6 MHz separation. It used standard NTSC standards.[13] This would allow the license freeze enacted in 1949 to end. Through the entire three-and-a-half year freeze period, KC2XAK remained the only UHF television station in regular operation.[14]
End of the license freeze (1952)[edit]
When the FCC television license freeze ended in 1952, a huge backlog of potential stations applied, many allocated to the UHF band as defined by the 1952 rules. The first commercially licensed UHF television station was WWLP in Springfield, Massachusetts;[15] however, the first commercial UHF television station on the air was KPTV, Channel 27, in Portland, Oregon, on September 18, 1952. Early in 1953, 35% of televisions sold contained a UHF tuner compliant with 1952 rules, lending hope to the idea that intermixture of UHF and VHF stations might succeed.