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Distributed Transmission System
In North American digital terrestrial television broadcasting, a distributed transmission system (DTS or DTx) 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. The signal is then simultaneously broadcast on the same frequency in different overlapping portions of the same coverage area, effectively combining many small transmitters to generate a broadcast area rivalling that of one large transmitter or to fill gaps in coverage due to terrain or localised obstacles. History While the idea of a single-frequency network of multiple transmitters broadcasting the same programming on the same channel from multiple transmitter sites is not a new concept, the ATSC digital television standard in use in North America was not designed for this mode of operation and was poorly adapted to these applications. The restrictive timing requirements and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Terrestrial Television
Digital terrestrial television (DTTV or DTT, or DTTB with "broadcasting") is a technology for terrestrial television in which land-based (terrestrial) television stations broadcast television content by radio waves to televisions in consumers' residences in a digital format. DTTV is a major technological advance over the previous analog television, and has largely replaced analog which had been in common use since the middle of the 20th century. Test broadcasts began in 1998 with the changeover to DTTV (aka Analog Switchoff (ASO), or Digital Switchover (DSO)) beginning in 2006 and is now complete in many countries. The advantages of ''digital'' terrestrial television are similar to those obtained by digitising platforms such as cable TV, satellite, and telecommunications: more efficient use of limited radio spectrum bandwidth, provision of more television channels than analog, better quality images, and potentially lower operating costs for broadcasters (after the initial up ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DVB-T
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in February, 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It is also the format widely used worldwide (including North America) for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators. Basics Rather than carrying one data carrier on a single radio frequency (RF) channel, COFDM works by splitting the digital data stream into a large number of slower digital streams, each of which digitally modulates a set of closely spaced adjacent sub-carrier frequencies. In the cas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Band I
Band I is a range of radio frequencies within the very high frequency (VHF) part of the electromagnetic spectrum. The first time there was defined "for simplicity" in Annex 1 of "Final acts of the European Broadcasting Conference in the VHF and UHF bands - Stockholm, 1961". Band I ranges from 47 to 68 MHz for the European Broadcasting Area, and from 54 to 88 MHz for the Americas and it is primarily used for television broadcasting in compliance with ITU Radio Regulations (article 1.38). With the transition to digital TV, most Band I transmitters have already been switched off. Television broadcasting usage Channel spacings vary from country to country, with spacings of 6, 7 and 8 MHz being common. In the UK, Band I was originally used by the BBC for monochrome 405-line television; likewise, the French former 455-line (1937-1939) then 441-line (1943-1956) transmitter on the Eiffel Tower in Paris, and some stations of the French monochrome 819-line system used Band I. Both 405-lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Altoona, Pennsylvania
Altoona is a city in Blair County, Pennsylvania. It is the principal city of the Altoona Metropolitan Statistical Area (MSA). The population was 43,963 at the time of the 2020 Census, making it the eighteenth most populous city in Pennsylvania. The Altoona MSA includes all of Blair County and was recorded as having a population of 122,822 at the 2020 Census, around 100,000 of whom live within a radius of the Altoona city center according to U.S. Census ZIP Code population data. This includes the adjacent boroughs of Hollidaysburg and Duncansville, adjacent townships of Logan, Allegheny, Blair, Frankstown, Antis, and Tyrone, as well as nearby boroughs of Bellwood and Newry. Having grown around the railroad industry, the city has worked to recover from industrial decline and urban decentralization experienced in recent decades. The city is home to the Altoona Curve baseball team of the Eastern League, which is the AA affiliate of the Pittsburgh Pirates Major League Baseba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johnstown, Pennsylvania
Johnstown is a city in Cambria County, Pennsylvania, United States. The population was 18,411 as of the 2020 United States Census, 2020 census. Located east of Pittsburgh, Johnstown is the principal city of the Johnstown, Pennsylvania, Metropolitan statistical area, Metropolitan Statistical Area, which includes Cambria County, Pennsylvania, Cambria County. It is also part of the Johnstown-Somerset, PA Combined Statistical Area, which includes both Cambria and Somerset County, Pennsylvania, Somerset Counties. History Johnstown was settled in 1770. The city has experienced three major floods in its history. The Johnstown Flood of May 31, 1889, occurred after the South Fork Dam collapsed upstream from the city during heavy rains. At least 2,209 people died as a result of the flood and subsequent fire that raged through the debris. Another major flood occurred in 1936. Despite a pledge by President Franklin Delano Roosevelt to make the city flood free, and subsequent work to do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
State College, Pennsylvania
State College is a home rule municipality in Centre County in the Commonwealth of Pennsylvania. It is a college town, dominated economically, culturally and demographically by the presence of the University Park campus of the Pennsylvania State University (Penn State). State College is the largest designated borough in Pennsylvania. It is the principal borough of the six municipalities that make up the State College area, the largest settlement in Centre County and one of the principal cities of the greater State College-DuBois Combined Statistical Area with a combined population of 236,577 as of the 2010 U.S. census. In the 2010 census, the borough population was 42,034 with approximately 105,000 living in the borough plus the surrounding townships often referred to locally as the "Centre Region". Many of these Centre Region communities also carry a "State College, PA" address although they are not part of the borough of State College. "Happy Valley" and "Lion Country" are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WPSX-TV
WPSU-TV (channel 3) is a PBS member television station licensed to Clearfield, Pennsylvania, United States, serving West-Central Pennsylvania. Owned by the Pennsylvania State University as part of Penn State Public Media, it is sister to NPR member WPSU (91.5 FM) and student radio station WKPS ("The Lion 90.7 FM"). The three stations share studios at Innovation Park on Penn State's University Park campus in State College. WPSU-TV's primary transmitter is located north of Clearfield in Lawrence Township, with a secondary transmitter in Pine Grove Mills, Pennsylvania. Overview WPSU-TV reaches 500,000 households in west-central and central Pennsylvania and southern New York, as well as a few households in western Pennsylvania. In many rural portions of this area, viewers need cable television to receive other stations. The station's signal is easily receivable as far away as Warren where it is carried on local cable systems instead of Erie's WQLN, Williamsport and Bradfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pennsylvania State University
The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with campuses and facilities throughout Pennsylvania. Founded in 1855 as the Farmers' High School of Pennsylvania, Penn State became the state's only Land-grant university, land-grant university in 1863. Today, Penn State is a major research university which conducts teaching, research, and public service. Its instructional mission includes undergraduate, graduate, professional and continuing education offered through resident instruction and online delivery. The University Park campus has been labeled one of the "Public Ivy, Public Ivies", a publicly funded university considered as providing a quality of education comparable to those of the Ivy League. In addition to its land-grant designation, it also participates in the sea-grant, space-grant, and sun-grant research consortia; it is on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Trade Center (1973–2001)
The original World Trade Center (WTC) was a large complex of seven buildings in the Financial District of Lower Manhattan in New York City. It opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. At the time of their completion, the Twin Towers—the original 1 World Trade Center (the North Tower) at ; and 2 World Trade Center (the South Tower) at —were the tallest buildings in the world. Other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. The complex contained of office space. The core complex was built between 1966 and 1975, at a cost of $400 million (equivalent to $3.56 billion in 2022). The idea was suggested by David Rockefeller to help stimulate urban renewal in Lower Manhattan, and his brother Nelson signed the legislation to build it. The buildings at the complex were designed by Minoru Yamasaki. In 1998, the Port Authority of New York and New Jersey decided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RF Interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares, and auroras (northern/southern lights). EMI frequently affects AM radios. It can also affect mobile phones, FM radios, and televisions, as well as observations for radio astronomy and atmospheric science. EMI can be used intentionally for radio jamming, as in electronic warfare. History Since the earliest days of radio c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflected Signal
In telecommunications, signal reflection occurs when a signal is transmitted along a transmission medium, such as a copper cable or an optical fiber. Some of the signal power may be reflected back to its origin rather than being carried all the way along the cable to the far end. This happens because imperfections in the cable cause impedance mismatches and non-linear changes in the cable characteristics. These abrupt changes in characteristics cause some of the transmitted signal to be reflected. In radio frequency (RF) practice this is often measured in a dimensionless ratio known as voltage standing wave ratio (VSWR) with a VSWR bridge. The ratio of energy bounced back depends on the impedance mismatch. Mathematically, it is defined using the reflection coefficient. Because the principles are the same, this concept is perhaps easiest to understand when considering an optical fiber. Imperfections in the glass create mirrors that reflect the light back along the fiber. Imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer. The carrier is higher in frequency than the modulation signal. In radio communication the modulated carrier is transmitted through space as a radio wave to a radio receiver. Another purpose is to transmit multiple channels of information through a single communication medium, using frequency-division multiplexing (FDM). For example in cable television which uses FDM, many carrier signals, each modulated with a different television channel, are transported through a sing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
