1.
Amateur radio operator
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As a component of their license, amateur radio operators are assigned a call sign that they use to identify themselves during communication. There are about three million amateur radio operators worldwide, amateur radio operators are also known as radio amateurs or hams. The term ham as a nickname for radio operators originated in a pejorative usage by operators in commercial and professional radio communities. The word was adopted by amateur radio operators. Few governments maintain detailed demographic statistics of their radio operator populations. The majority of radio operators worldwide reside in Japan, the United States, Thailand, South Korea. The top five countries by percentage of the population are Japan, Slovenia, Taiwan, South Korea, only the governments of Yemen and North Korea currently prohibit their citizens from becoming amateur radio operators. In some countries, acquiring an amateur license is difficult because of the bureaucratic processes or fees that place access to a license out of reach for most citizens. Most nations permit foreign nationals to earn an amateur radio license, in the vast majority of countries, the population of amateur radio operators is predominantly male. In China 12% of amateur operators are women, whilst in the United States is it approximately 15%. The Young Ladies Radio League is an organization of female amateur radio operators. A male amateur radio operator can be referred to as an OM, a female amateur radio operator can be referred to as a YL, from the abbreviation used for young lady, regardless of the operators age. Sometimes the wife of a ham operator is called a YF, although these codes are derived from English language abbreviations, their use is common among amateur radio operators worldwide. Incidentally, the most common language heard in the HF amateur bands is English, in most countries there is no minimum age requirement to earn an amateur radio license and become an amateur radio operator. Although the number of radio operators in many countries increases from year to year. In some countries, the age is over 80 years old. The World Wide Young Contesters organization promotes youth involvement, particularly amongst Europeans, a strong tie also exists between the amateur radio community and the Scouting movement to introduce radio technology to youth. WOSMs annual Jamboree On The Air is Scoutings largest activity, with a half million Scouts, when referring to a person, the phrase Silent Key and its abbreviation SK indicates an amateur radio operator who is deceased
2.
Radio
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When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form, Radio systems need a transmitter to modulate some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation. Radio systems also need an antenna to convert electric currents into radio waves, an antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected, the electromagnetic wave is intercepted by a tuned receiving antenna. Radio frequencies occupy the range from a 3 kHz to 300 GHz, a radio communication system sends signals by radio. The term radio is derived from the Latin word radius, meaning spoke of a wheel, beam of light, however, this invention would not be widely adopted. The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world, the United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram, the term started to become preferred by the general public in the 1920s with the introduction of broadcasting. Radio systems used for communication have the following elements, with more than 100 years of development, each process is implemented by a wide range of methods, specialised for different communications purposes. Each system contains a transmitter, This consists of a source of electrical energy, the transmitter contains a system to modulate some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle such as amplitude, frequency, phase. Amplitude modulation of a carrier wave works by varying the strength of the signal in proportion to the information being sent. For example, changes in the strength can be used to reflect the sounds to be reproduced by a speaker. It was the used for the first audio radio transmissions. Frequency modulation varies the frequency of the carrier, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. FM has the capture effect whereby a receiver only receives the strongest signal, Digital data can be sent by shifting the carriers frequency among a set of discrete values, a technique known as frequency-shift keying. FM is commonly used at Very high frequency radio frequencies for high-fidelity broadcasts of music, analog TV sound is also broadcast using FM. Angle modulation alters the phase of the carrier wave to transmit a signal
3.
Amateur radio station
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An amateur radio station is a radio station designed to provide radiocommunications in the amateur radio service for an amateur radio operator. Radio amateurs build and operate several types of radio stations, including fixed ground stations, mobile stations, space stations. A slang term used for an amateur stations location is the shack, named after the small enclosures added to the upperworks of naval ships to hold early radio equipment. See also An amateur radio station established in a permanent structure with equipment that is not intended for operation is referred to as a fixed station. This is the most common form of radio station, and can be found in homes, schools. A typical fixed station is equipped with a transceiver and one or more antennas, fixed stations might also be equipped with amplifiers, antenna rotators, SWR meters, and other station accessories. Fixed stations are powered from the AC mains electrical supply available in the building. Some equipment in fixed stations may run off low voltage DC instead of AC, some fixed stations are equipped with auxiliary sources of power, such as electrical generators or batteries for use in emergencies. An amateur radio station installed in a vehicle is referred to as a mobile station, a typical mobile station is equipped with a transceiver, one or more antennas, and a microphone. The transceiver may be designed for installation in vehicles. Most antennas used in mobile stations are omnidirectional, few mobile stations are equipped to communicate with Morse code or digital modes. Most mobile stations are designed to be operated by the operator while driving. Most transceivers installed in vehicles are designed to run on 12-16 VDC, a specialized form of mobile station used for competition in a VHF amateur radio contest in North America is called a rover station. While it may not be a requirement, many mobile stations will append a /M to end of their call sign while operating to identify themselves to other stations as a mobile station. Rover station operating in a VHF contest will append a /R to the end of their call sign, maritime mobile stations are mobile stations installed in a watercraft, usually an ocean-going vessel. When in international waters, these stations are operated under the authority of the flag under which the vessel is registered. In addition to the requirements of amateur radio, operation of maritime mobile stations also requires the permission of the captain of the vessel. Maritime mobile stations append a /MM to end of their call sign, aeronautical mobile stations are mobile stations installed in an aircraft
4.
AM broadcasting
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AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a signal and is still widely used today. Commercial and public AM broadcasting is authorized in the wave band worldwide. Commercial AM broadcasting developed from amateur broadcasts around 1920, and was the commercially important form of radio broadcasting until FM broadcasting began after World War II. This period is known as the Golden Age of Radio, today, AM competes with FM, as well as with various digital radio broadcasting services distributed from terrestrial and satellite transmitters. AM broadcasting was the first broadcasting technology invented, the technology of amplitude modulation radio transmission was developed between 1900 and 1920. This was used for private communication and message traffic, such as telegrams. The entrepreneurs who developed AM radiotelephone transmission did not anticipate broadcasting voice, the term broadcasting, borrowed from agriculture, was applied to this new activity around 1920. Prior to 1920 there was no concept of broadcasting, or that radio listeners could be a market for entertainment. Although there were a number of broadcasts during this period. True radio broadcasting didnt begin until around 1920, when it sprang up spontaneously among amateur stations, AM remained the dominant method of broadcasting for the next 30 years, a period called the Golden Age of Radio, until FM broadcasting started to become widespread in the 1950s. AM remains a popular, profitable entertainment medium today and the dominant form of broadcasting in some such as Australia. The first AM voice transmission was made by Canadian researcher Reginald Fessenden on 23 December 1900, Fessenden is a significant figure in the development of AM radio. He helped develop one of the first – the Alexanderson alternator, the first practical continuous wave AM transmitters were based on versions of the Poulsen arc transmitter invented in 1903, and the huge, expensive Alexanderson alternator, developed 1906–1910. The modifications necessary to transmit AM were clumsy and resulted in low audio quality. Modulation was usually accomplished by a carbon microphone inserted directly in the antenna wire, the limited power handling ability of the microphone severely limited the power of the first radiotelephones, in powerful transmitters water-cooled microphones had to be used. At the receiving end, the crystal radio receivers then in use could not drive loudspeakers, only earphones. The discovery in 1912 of the ability of the Audion vacuum tube, invented in 1906 by Lee De Forest
5.
FM broadcasting
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FM broadcasting is a method of radio broadcasting using frequency modulation technology. Invented in 1933 by American engineer Edwin Armstrong, it is used worldwide to provide high-fidelity sound over broadcast radio, FM broadcasting is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. FM radio stations use the VHF frequencies, the term FM band describes the frequency band in a given country which is dedicated to FM broadcasting. Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. Usually 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions, In the former Soviet republics, and some former Eastern Bloc countries, assigned frequencies are at intervals of 30 kHz. This band, sometimes referred to as the OIRT band, is slowly being phased out in many countries, in those countries the 87. 5–108.0 MHz band is referred to as the CCIR band. In Japan, the band 76–95 MHz is used, the frequency of an FM broadcast station is usually an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines, in some parts of Europe, Greenland and Africa, only even multiples are used. In the UK odd or even are used, in Italy, multiples of 50 kHz are used. There are other unusual and obsolete FM broadcasting standards in countries, including 1,10,30,74,500. Random noise has a triangular spectral distribution in an FM system and this can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver. Reducing the high frequencies in the receiver also reduces the high-frequency noise. These processes of boosting and then reducing certain frequencies are known as pre-emphasis and de-emphasis, the amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used, in the Americas and South Korea,75 µs is used. This applies to both mono and stereo transmissions, for stereo, pre-emphasis is applied to the left and right channels before multiplexing. They cannot be pre-emphasized as much because it would cause excessive deviation of the FM carrier, systems more modern than FM broadcasting tend to use either programme-dependent variable pre-emphasis, e. g. dbx in the BTSC TV sound system, or none at all. Long before FM stereo transmission was considered, FM multiplexing of other types of audio level information was experimented with. Edwin Armstrong who invented FM was the first to experiment with multiplexing and these original FM multiplex subcarriers were amplitude modulated
6.
Television
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Television or TV is a telecommunication medium used for transmitting moving images in monochrome, or in color, and in two or three dimensions and sound. The term can refer to a set, a television program. Television is a medium for entertainment, education, news, politics, gossip. Television became available in experimental forms in the late 1920s. After World War II, a form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses. During the 1950s, television was the medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US, for many reasons, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions greatly increased in popularity, another development was the move from standard-definition television to high-definition television, which provides a resolution that is substantially higher. HDTV may be transmitted in various formats, 1080p, 1080i, in 2013, 79% of the worlds households owned a television set. Most TV sets sold in the 2000s were flat-panel, mainly LEDs, major manufacturers announced the discontinuation of CRT, DLP, plasma, and even fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are gradually expected to be replaced by OLEDs, also, major manufacturers have announced that they will increasingly produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s, Television signals were initially distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by cable or optical fiber, satellite systems and. Until the early 2000s, these were transmitted as analog signals, a standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is correctly called a video monitor rather than a television, the word television comes from Ancient Greek τῆλε, meaning far, and Latin visio, meaning sight. The Anglicised version of the term is first attested in 1907 and it was. formed in English or borrowed from French télévision. In the 19th century and early 20th century, other. proposals for the name of a technology for sending pictures over distance were telephote. The abbreviation TV is from 1948, the use of the term to mean a television set dates from 1941
7.
Shortwave radio
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Shortwave radio is radio transmission using shortwave frequencies, generally 1. 6–30 MHz, just above the medium wave AM broadcast band. Radio waves in this band can be reflected or refracted from a layer of charged atoms in the atmosphere called the ionosphere. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances and this is called skywave or skip propagation. Shortwave radio is used for broadcasting of voice and music to listeners over very large areas. It is also used for military radar, diplomatic communication. The widest popular definition of the frequency interval is the ITU Region 1 definition, and is the span 1. 6–30 MHz, just above the medium wave band. In reality, the definition of the frequency band is a mess. The broadcast medium wave band now extends above the 200 m/1500 kHz limit, early radio telegraphy had used long wave transmissions. The drawbacks to this included a very limited spectrum available for long distance communication. It was also difficult to beam the radio wave directionally with long wave, prior to the 1920s, the shortwave frequencies above 1.5 MHz were regarded as useless for long distance communication and were designated in many countries for amateur use. Franklin rigged up an antenna at Poldhu Wireless Station, Cornwall. In June and July 1923, wireless transmissions were completed during nights on 97 meters from Poldhu to Marconis yacht Elettra in the Cape Verde Islands, in September 1924, Marconi transmitted daytime and nighttime on 32 meters from Poldhu to his yacht in Beirut. Franklin went on to refine the directional transmission, by inventing the curtain array aerial system, the UK-to-Canada shortwave Beam Wireless Service went into commercial operation on 25 October 1926. Beam Wireless Services from the UK to Australia, South Africa, Shortwave communications began to grow rapidly in the 1920s, similar to the internet in the late 20th century. Shortwave also ended the need for investments in massive longwave wireless stations. The cable companies began to lose large sums of money in 1927, the British government convened the Imperial Wireless and Cable Conference in 1928 to examine the situation that had arisen as a result of the competition of Beam Wireless with the Cable Services. The name of the company was changed to Cable and Wireless Ltd. in 1934, long-distance cables had a resurgence beginning in 1956 with the laying of TAT-1 across the Atlantic Ocean, the first voice frequency cable on this route. This provided 36 high quality telephone channels and was followed by even higher capacity cables all around the world
8.
Postcard
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A postcard or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope. Shapes other than rectangular may also be used, there are novelty exceptions, such as wood postcards, made of thin wood, and copper postcards sold in the Copper Country of the U. S. state of Michigan, and coconut postcards from tropical islands. In some places, one can send a postcard for a lower fee than for a letter, stamp collectors distinguish between postcards and postal cards. While a postcard is usually printed by a company, individual or organization. The worlds oldest postcard was sent in 1840 to the writer Theodore Hook from Fulham in London, the study and collecting of postcards is termed deltiology. Cards with messages had been created and posted by individuals since the beginning of postal services. The earliest known picture postcard was a design on card, posted in Fulham in London by the writer Theodore Hook to himself in 1840. He probably created and posted the card to himself as a joke on the postal service, since the image is a caricature of workers in the post office. In 2002 the postcard sold for a record £31,750, in Britain, postcards without images were issued by the Post Office in 1870, and were printed with a stamp as part of the design, which was included in the price of purchase. These cards came in two sizes, the larger size was found to be slightly too large for ease of handling, and was soon withdrawn in favour of cards 13mm shorter. The first known printed picture postcard, with an image on one side, was created in France in 1870 at Camp Conlie by Léon Besnardeau, Conlie was a training camp for soldiers in the Franco-Prussian war. While these are certainly the first known picture postcards, there was no space for stamps, in the following year the first known picture postcard in which the image functioned as a souvenir was sent from Vienna. The first advertising card appeared in 1872 in Great Britain and the first German card appeared in 1874, Cards showing images increased in number during the 1880s. Images of the newly built Eiffel Tower in 1889 and 1890 gave impetus to the postcard, Early postcards often showcased photography of nude women. These were commonly known as French postcards, due to the number of them produced in France. The first American postcard was developed in 1873 by the Morgan Envelope Factory of Springfield and these first postcards depicted the Interstate Industrial Exposition that took place in Chicago. Later in 1873, Post Master John Creswell introduced the first pre-stamped Postal Cards, Postcards were made because people were looking for an easier way to send quick notes. The first postcard to be printed as a souvenir in the United States was created in 1893 to advertise the Worlds Columbian Exposition in Chicago, initially, the United States government prohibited private companies from calling their cards postcards, so they were known as souvenir cards
9.
Postal mail
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The mail or post is a system for physically transporting documents and other small packages, or, the postcards, letters, and parcels themselves. A postal service can be private or public, though many governments place restrictions on private systems, since the mid-19th century national postal systems have generally been established as government monopolies with a fee on the article prepaid. Proof of payment is often in the form of adhesive postage stamps, modern private postal systems are typically distinguished from national postal agencies by the names courier or delivery service. Postal authorities often have other than transporting letters. In some countries, a postal, telegraph and telephone service oversees the system, in addition to telephone. Some countries postal systems allow for savings accounts and handle applications for passports, the Universal Postal Union, established in 1874, includes 192 member countries and sets the rules for international mail exchanges. The word mail comes from the Medieval English word male, referring to a bag or pack. It was spelled that way until the 17th century, and is distinct from the word male, the French have a similar word, malle for a trunk or large box, and mála is the Irish term for a bag. In the 17th century, the mail began to appear as a reference for a bag that contained letters. Over the next hundred years the word began to be applied strictly to the letters themselves. The U. S. Postal Service delivers the mail, the term email first appeared in the 1970s. The term snail-mail is a retronym to distinguish it from the quicker email, various dates have been given for its first use. Post is derived from Medieval French poste, which stems from the past participle of the Latin verb ponere. The practice of communication by written documents carried by an intermediary from one person or place to another almost certainly dates back nearly to the invention of writing, however, development of formal postal systems occurred much later. The earliest surviving piece of mail is also Egyptian, dating to 255 BC, the first credible claim for the development of a real postal system comes from Ancient Persia, but the point of invention remains in question. He also negotiated with neighbouring countries to do the same and had built from the city of Post in Western Iran all the way up to the city of Hakha in the East. Other writers credit his successor Darius I of Persia, other sources claim much earlier dates for an Assyrian postal system, with credit given to Hammurabi and Sargon II. Mail may not have been the mission of this postal service
