The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until 1997, North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1,2010, the majority of NTSC transmissions ended in Japan on July 24,2011, with the Japanese prefectures of Iwate and Fukushima ending the next year. In March 1941, the committee issued a standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association. Technical advancements of the side band technique allowed for the opportunity to increase the image resolution.
The NTSC selected 525 scan lines as a compromise between RCAs 441-scan line standard and Philcos and DuMonts desire to increase the number of lines to between 605 and 800. The standard recommended a frame rate of 30 frames per second, other standards in the final recommendation were an aspect ratio of 4,3, and frequency modulation for the sound signal. In January 1950, the committee was reconstituted to standardize color television, in December 1953, it unanimously approved what is now called the NTSC color television standard. The compatible color standard retained full backward compatibility with existing black-and-white television sets, Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz. These changes amounted to 0.1 percent and were tolerated by existing television receivers. The FCC had briefly approved a different color standard, starting in October 1950. However, this standard was incompatible with black-and-white broadcasts and it used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second.
CBS rescinded its system in March 1953, and the FCC replaced it on December 17,1953, with the NTSC color standard, that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by countries, including most of the Americas. With the advent of television, analog broadcasts are being phased out. Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009, low-power stations, Class A stations and translators were required to shut down by 2015. NTSC color encoding is used with the System M television signal, each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines
Super high frequency
Super high frequency is the ITU designation for radio frequencies in the range between 3 GHz and 30 GHz. This band of frequencies is known as the centimetre band or centimetre wave as the wavelengths range from one to ten centimetres. These frequencies fall within the band, so radio waves with these frequencies are called microwaves. This frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave relay links. Wireless USB technology is anticipated to use approximately one-third of this spectrum, frequencies in the SHF range are often referred to by their IEEE radar band designations, S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations. Microwaves propagate entirely by line of sight and ionospheric reflection do not occur, although in some cases they can penetrate building walls enough for useful reception, unobstructed rights of way cleared to the first Fresnel zone are usually required. Wavelengths are small enough at microwave frequencies that the antenna can be larger than a wavelength.
Therefore, they are used in point-to-point terrestrial communications links limited by the visual horizon, such high gain antennas allow frequency reuse by nearby transmitters. The size of SHF waves allows strong reflections from objects the size of automobiles and ships. Thus, the narrow beamwidths possible with high gain antennas and the low atmospheric attenuation as compared with higher frequencies make SHF the main frequencies used in radar. Attenuation and scattering by moisture in the increase with frequency. Small amounts of energy are randomly scattered by water vapor molecules in the troposphere. This is used in communications systems, operating at a few GHz. A powerful microwave beam is aimed just above the horizon, as it passes through the some of the microwaves are scattered back to Earth to a receiver beyond the horizon. Distances of 300 km can be achieved and these are mainly used for military communication. The wavelengths of SHF waves are small enough that they can be focused into narrow beams by high gain antennas from a meter to five meters in diameter.
Directive antennas at SHF frequencies are mostly aperture antennas, such as antennas, dielectric lens, slot. Large parabolic antennas can produce very narrow beams of a few degrees or less, for omnidirectional applications like wireless devices and cellphones, small dipoles or monopoles are used
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which generates a radio frequency alternating current. When a connected antenna is excited by this current, the antenna emits radio waves. The term transmitter is usually limited to equipment that generates radio waves for communication purposes, or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as ovens or diathermy equipment, are not usually called transmitters even though they often have similar circuits. The term is used more specifically to refer to a broadcast transmitter. This usage typically includes both the proper, the antenna, and often the building it is housed in. A transmitter can be a piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit is called a transceiver, the term transmitter is often abbreviated XMTR or TX in technical documents.
The purpose of most transmitters is radio communication of information over a distance, the transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is called the carrier signal. The information can be added to the carrier in several different ways, in an amplitude modulation transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation transmitter, it is added by varying the signals frequency slightly. Many other types of modulation are used, the radio signal from the transmitter is applied to the antenna, which radiates the energy as radio waves. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as phones, walkie-talkies. In more powerful transmitters, the antenna may be located on top of a building or on a tower, and connected to the transmitter by a feed line. The first primitive radio transmitters were built by German physicist Heinrich Hertz in 1887 during his investigations of radio waves.
These generated radio waves by a high voltage spark between two conductors, beginning in 1895 Guglielmo Marconi developed the first practical radio communication systems using spark transmitters. These spark-gap transmitters were used during the first three decades of radio, called the wireless telegraphy or spark era, vacuum tube transmitters took over because they were inexpensive and produced continuous waves, which could be modulated to transmit audio using amplitude modulation. This made possible commercial AM radio broadcasting, which began in about 1920, experimental television transmission had been conducted by radio stations since the late 1920s, but practical television broadcasting didnt begin until the 1940s
The International Telecommunication Union, in its International Radio Regulations, divides the world into three ITU regions for the purposes of managing the global radio spectrum. Each region has its own set of frequency allocations, the reason for defining the regions. Region 1 comprises Europe, the former Soviet Union, the western boundary is defined by Line B. Region 2 covers the Americas including Greenland, and some of the eastern Pacific Islands, the eastern boundary is defined by Line B. Region 3 contains most of non-FSU Asia east of and including Iran, the definition of the European Broadcasting Area uses some of the definitions of Region 1
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery.
Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer.
He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, usage sometimes includes Greenland and Mexico, as well as offshore islands
Digital television is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analog and channel separated signals used by analog television. Digital TV can support more than one program in the channel bandwidth. It is a service that represents the first significant evolution in television technology since color television in the 1950s. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards and this standard has been adopted in Europe, Singapore and New Zealand. Advanced Television System Committee uses eight-level vestigial sideband for terrestrial broadcasting and this standard has been adopted by six countries, United States, Mexico, South Korea, Dominican Republic and Honduras. Integrated Services Digital Broadcasting is a designed to provide good reception to fixed receivers. It utilizes OFDM and two-dimensional interleaving and it supports hierarchical transmission of up to three layers and uses MPEG-2 video and Advanced Audio Coding.
This standard has adopted in Japan and the Philippines. ISDB-T International is an adaptation of this standard using H. 264/MPEG-4 AVC that been adopted in most of South America and is being embraced by Portuguese-speaking African countries. Digital Terrestrial Multimedia Broadcasting adopts time-domain synchronous OFDM technology with a signal frame to serve as the guard interval of the OFDM block. The DTMB standard has adopted in the Peoples Republic of China, including Hong Kong. Digital TVs roots have been tied very closely to the availability of inexpensive and it wasnt until the 1990s that digital TV became a real possibility. S. Until June 1990, the Japanese MUSE standard—based on an analog system—was the front-runner among the more than 23 different technical concepts under consideration, then, an American company, General Instrument, demonstrated the feasibility of a digital television signal. This breakthrough was of significance that the FCC was persuaded to delay its decision on an ATV standard until a digitally based standard could be developed.
In March 1990, when it became clear that a standard was feasible. The new ATV standard allowed the new DTV signal to be based on new design principles. Although incompatible with the existing NTSC standard, the new DTV standard would be able to incorporate many improvements, the final standard adopted by the FCC did not require a single standard for scanning formats, aspect ratios, or lines of resolution. This outcome resulted from a dispute between the electronics industry and the computer industry over which of the two scanning processes—interlaced or progressive—is superior
The 23 centimeter,1200 MHz or 1.2 GHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use on a secondary basis. The amateur radio band is between 1240 MHz and 1300 MHz, the amateur satellite band is between 1260 MHz and 1270 MHz, and its use by satellite operations is only for up-links on a non-interference basis to other radio users. The allocations are the same in all three ITU regions, in the United Kingdom the band is between 1240 MHz and 1325 MHz. Most modes of communication used in amateur radio can be found in the 23 cm band, some of the more common modes include voice, data, EME, as well as ATV. Frequencies in the 23 cm band are harmonized by International Telecommunication Union region, CW and SSB calling frequency is 1296.2 MHz. FM simplex calling frequency is 1297.5 MHz, CW and SSB calling frequency is 1296.1 MHz. FM simplex calling frequency is 1294.5 MHz, FM Simplex Calling Frequency is 1294.0 MHz In 2008 the IARU Region-1 Cavtat Conference designated 1240.
000-1240.750 MHz as an alternative centre for narrowband activity and beacons. This is a mitigation for sharing with existing aviation radars and Primary users, or for potential issues with the European Galileo system
Amplitude modulation is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In amplitude modulation, the amplitude of the wave is varied in proportion to the waveform being transmitted. That waveform may, for instance, correspond to the sounds to be reproduced by a loudspeaker and this technique contrasts with frequency modulation, in which the frequency of the carrier signal is varied, and phase modulation, in which its phase is varied. AM was the earliest modulation method used to transmit voice by radio and it was developed during the first two decades of the 20th century beginning with Roberto Landell De Moura and Reginald Fessendens radiotelephone experiments in 1900. It remains in use today in many forms of communication, for example it is used in two way radios, VHF aircraft radio, Citizens Band Radio, and in computer modems. AM is often used to refer to mediumwave AM radio broadcasting, when it reaches its destination, the information signal is extracted from the modulated carrier by demodulation.
In amplitude modulation, the amplitude or strength of the oscillations is what is varied. For example, in AM radio communication, a continuous wave signal has its amplitude modulated by an audio waveform before transmission. The audio waveform modifies the amplitude of the wave and determines the envelope of the waveform. In the frequency domain, amplitude modulation produces a signal with power concentrated at the carrier frequency, each sideband is equal in bandwidth to that of the modulating signal, and is a mirror image of the other. Standard AM is thus sometimes called double-sideband amplitude modulation to distinguish it more sophisticated modulation methods based on AM. One disadvantage of all amplitude modulation techniques is that the receiver amplifies and detects noise, increasing the received signal to noise ratio, say, by a factor of 10, thus would require increasing the transmitter power by a factor of 10. For this reason AM broadcast is not favored for music and high fidelity broadcasting, another disadvantage of AM is that it is inefficient in power usage, at least two-thirds of the power is concentrated in the carrier signal.
The carrier signal contains none of the information being transmitted. However its presence provides a means of demodulation using envelope detection, providing a frequency. The receiver may regenerate a copy of the frequency from a greatly reduced pilot carrier to use in the demodulation process. Even with the carrier totally eliminated in double-sideband suppressed-carrier transmission, carrier regeneration is possible using a Costas phase-locked loop and this doesnt work however for single-sideband suppressed-carrier transmission, leading to the characteristic Donald Duck sound from such receivers when slightly detuned. Single sideband is used widely in amateur radio and other voice communications both due to its power efficiency and bandwidth efficiency
Low-noise block downconverter
A low-noise block downconverter is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish. Also called a block, low-noise converter, or even low-noise downconverter. The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and it receives the microwave signal from the satellite collected by the dish, amplifies it, and downconverts the block of frequencies to a lower block of intermediate frequencies. The LNB is usually a box suspended on one or more short booms, or feed arms, in front of the dish reflector. The microwave signal from the dish is picked up by a feedhorn on the LNB and is fed to a section of waveguide. One or more pins, or probes, protrude into the waveguide at right angles to the axis and act as antennas. The lower frequency IF output signal emerges from a socket on the box to which the cable connects. The LNB gets its power from the receiver or set-top box and this phantom power travels to the LNB, opposite to the signals from the LNB. A corresponding component, called a block upconverter, is used at the earth station dish to convert the band of television channels to the microwave uplink frequency.
The signal received by the LNB is extremely weak and it has to be amplified before downconversion, the low noise amplifier section of the LNB amplifies this weak signal while adding the minimum possible amount of noise to the signal. The low-noise quality of an LNB is expressed as the noise figure and this is the signal to noise ratio at the input divided by the signal to noise ratio at the output. It is typically expressed as a decibels value, the ideal LNB, effectively a perfect amplifier, would have a noise figure of 0 dB and would not add any noise to the signal. Every LNB off the line has a different noise figure because of manufacturing tolerances. Satellites use comparatively high radio frequencies to transmit their TV signals, as microwave satellite signals do not easily pass through walls, roofs, or even glass windows, it is preferable for satellite antennas to be mounted outdoors. The purpose of the LNB is to use the principle to take a block of relatively high frequencies. These lower frequencies travel through cables with much less attenuation, so there is much more signal left at the receiver end of the cable.
It is easier and cheaper to design electronic circuits to operate at these lower frequencies. The local oscillator frequency determines what block of incoming frequencies is downconverted to the expected by the receiver
Colorado is a state in the United States encompassing most of the Southern Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is part of the Western United States, the Southwestern United States, Colorado is the 8th most extensive and the 21st most populous of the 50 United States. The United States Census Bureau estimates that the population of Colorado was 5,540,545 on July 1,2016, the state was named for the Colorado River, which Spanish travelers named the Río Colorado for the ruddy silt the river carried from the mountains. The Territory of Colorado was organized on February 28,1861, Colorado is nicknamed the Centennial State because it became a state in the same year as the centennial of the United States Declaration of Independence. Colorado is noted for its landscape of mountains, high plains, canyons, rivers. Denver is the capital and the most populous city of Colorado, residents of the state are properly known as Coloradans, although the term Coloradoan has been used archaically and lives on in the title of Fort Collins newspaper, the Coloradoan.
Colorado and Utah are the states which have boundaries defined solely by lines of latitude and longitude. The summit of Mount Elbert at 14,440 feet elevation in Lake County is the highest point in Colorado, Colorado is the only U. S. state that lies entirely above 1,000 meters elevation. The point where the Arikaree River flows out of Yuma County and this point, which holds the distinction of being the highest low elevation point of any state, is higher than the high elevation points of 18 states and the District of Columbia. A little less than one half of the area of Colorado is flat, East of the Rocky Mountains are the Colorado Eastern Plains of the High Plains, the section of the Great Plains within Nebraska at elevations ranging from roughly 3,350 to 7,500 feet. The Colorado plains were mostly prairies, but they have many patches of forests, buttes. Eastern Colorado is presently covered in farmland and rangeland, along with small farming villages. Precipitation is fair, averaging from 15 to 25 inches annually, wheat, hay and oats are all typical crops, and most of the villages and towns in this region boast both a water tower and a grain elevator.
Irrigation water is available from the South Platte, the Arkansas River, and a few other streams, heavy use of ground water from wells for irrigation has caused underground water reserves to decline. As well as agriculture, eastern Colorado hosts considerable livestock, such as cattle ranches. Roughly 70% of Colorados population resides along the edge of the Rocky Mountains in the Front Range Urban Corridor between Cheyenne and Pueblo, Colorado. This region is protected from prevailing storms that blow in from the Pacific Ocean region by the high Rockies in the middle of Colorado. The Front Range includes Denver, Fort Collins, Colorado Springs, Pueblo and other townships, on the other side of the Rockies, the significant population centers in Western Colorado are the cities of Grand Junction and Montrose
The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels.
Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch.
Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
Video is an electronic medium for the recording, playback and display of moving visual media. Video systems vary greatly in the resolution of the display and refresh rate, video can be carried on a variety of media, including radio broadcast, tapes, DVDs, computer files etc. Video was originally exclusively a live technology, charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder. In 1951 the first video tape recorder captured live images from television cameras by converting the electrical impulses. Video recorders were sold for $50,000 in 1956, prices gradually dropped over the years, in 1971, Sony began selling videocassette recorder decks and tapes into the consumer market. The use of techniques in video created digital video, which allowed higher quality and, eventually. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape, the advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. PAL standards and SECAM specify 25 frame/s, while NTSC standards specify 29.97 frames, film is shot at the slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video.
The minimum frame rate to achieve a comfortable illusion of an image is about sixteen frames per second. Video can be interlaced or progressive, analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. NTSC, PAL and SECAM are interlaced formats, abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence, when displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Deinterlacing cannot, produce video quality that is equivalent to true progressive scan source material, aspect ratio describes the dimensions of video screens and video picture elements.
All popular video formats are rectilinear, and so can be described by a ratio between width and height, the screen aspect ratio of a traditional television screen is 4,3, or about 1.33,1. High definition televisions use a ratio of 16,9. The aspect ratio of a full 35 mm film frame with soundtrack is 1.375,1. Therefore, a 720 by 480 pixel NTSC DV image displayes with the 4,3 aspect ratio if the pixels are thin, the popularity of viewing video on mobile phones has led to the growth of vertical video