UHF television broadcasting
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 issues are greatly reduced with digital television, and today most over-the-air broadcasts take place on UHF, while VHF channels are being retired.
Conductors, normally metal wires or rods, are cut to a length so that the desired radio signal will create a standing wave of electrical current within them.
These openings are the spaces between any metal in the area, including lines of nails or screws in the roof and walls, electrical wiring, and the frames of doors and windows.
Moving from VHF to UHF is a much more expensive proposition, generally requiring all new equipment, and a dramatic increase in power in order to maintain the same service area.
Stations making the transition generally acquired a second channel allocation in the upper UHF region to test their new equipment, and then moved into the low-UHF or high-VHF once the conversion period was over.
More recent third-network operators that initially signed 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.
[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.
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.
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).
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).
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.
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.
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.
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).
[7] 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.
Efforts at TV broadcasting on any channel were drastically curtailed once World War II began, due largely to lack of available receivers.
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.
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".
[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.
Ultimately, the question the FCC faced of how to allocate bandwidth for new television licenses would not take "months" to resolve, but several years.
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.
[14] 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.
[20] In the United States, UHF stations gained a reputation for local ownership, nonprofessional operations, small audiences and weak signal propagation.
These included Montgomery, Alabama; Frankfort, Kentucky; Dover, Delaware; Lincoln, Nebraska; Topeka, Kansas; Jefferson City, Missouri; Lansing, Michigan; Harrisburg, Pennsylvania; Madison, Wisconsin; and Springfield, Illinois.
This station, renamed WTBS, was uplinked in 1976 to satellite alongside new premium channels such as HBO, gaining access to distant cable television markets and becoming the first of various superstations to obtain national coverage.
Turner Broadcasting System's access to movie rights proved commercially valuable as home video cassette rental became ubiquitous in the 1980s.
The same interference can prove severe enough to prevent the reliable reception of the more fragile and more highly compressed[citation needed] ATSC digital television.
Other smaller cities such as Madison, Wisconsin; Bakersfield, California; Fresno, California; Fort Myers, Florida; Mankato, Minnesota; Watertown, New York; Erie, Pennsylvania; Columbia, South Carolina; and Harrisburg, Pennsylvania only received one VHF license, meaning that any additional programming would need to be provided either by UHF, by distant stations, or by low-power broadcasting.
