Michigan is a state in the Great Lakes and Midwestern regions of the United States. The state's name, originates from the Ojibwe word mishigamaa, meaning "large water" or "large lake". With a population of about 10 million, Michigan is the tenth most populous of the 50 United States, with the 11th most extensive total area, is the largest state by total area east of the Mississippi River, its capital is Lansing, its largest city is Detroit. Metro Detroit is among the nation's largest metropolitan economies. Michigan is the only state to consist of two peninsulas; the Lower Peninsula is noted as shaped like a mitten. The Upper Peninsula is separated from the Lower Peninsula by the Straits of Mackinac, a five-mile channel that joins Lake Huron to Lake Michigan; the Mackinac Bridge connects the peninsulas. The state has the longest freshwater coastline of any political subdivision in the world, being bounded by four of the five Great Lakes, plus Lake Saint Clair; as a result, it is one of the leading U.
S. states for recreational boating. Michigan has 64,980 inland lakes and ponds. A person in the state is never more than six miles from a natural water source or more than 85 miles from a Great Lakes shoreline; the area was first occupied by a succession of Native American tribes over thousands of years. Inhabited by Natives, Métis, French explorers in the 17th century, it was claimed as part of New France colony. After France's defeat in the French and Indian War in 1762, the region came under British rule. Britain ceded this territory to the newly independent United States after Britain's defeat in the American Revolutionary War; the area was part of the larger Northwest Territory until 1800, when western Michigan became part of the Indiana Territory. Michigan Territory was formed in 1805, but some of the northern border with Canada was not agreed upon until after the War of 1812. Michigan was admitted into the Union in 1837 as a free one, it soon became an important center of industry and trade in the Great Lakes region and a popular immigrant destination in the late 19th and early 20th centuries.
Although Michigan developed a diverse economy, it is known as the center of the U. S. automotive industry, which developed as a major economic force in the early 20th century. It is home to the country's three major automobile companies. While sparsely populated, the Upper Peninsula is important for tourism thanks to its abundance of natural resources, while the Lower Peninsula is a center of manufacturing, agriculture and high-tech industry; when the first European explorers arrived, the most populous tribes were Algonquian peoples, which include the Anishinaabe groups of Ojibwe, Odaawaa/Odawa, the Boodewaadamii/Bodéwadmi. The three nations co-existed peacefully as part of a loose confederation called the Council of Three Fires; the Ojibwe, whose numbers are estimated to have been between 25,000 and 35,000, were the largest. The Ojibwe were established in Michigan's Upper Peninsula and northern and central Michigan, inhabited Ontario and southern Manitoba, Canada; the Ottawa lived south of the Straits of Mackinac in northern and southern Michigan, but in southern Ontario, northern Ohio and eastern Wisconsin.
The Potawatomi were in southern and western Michigan, in addition to northern and central Indiana, northern Illinois, southern Wisconsin, southern Ontario. Other Algonquian tribes in Michigan, in the south and east, were the Mascouten, the Menominee, the Miami, the Sac, the Fox; the Wyandot were an Iroquoian-speaking people in this area. French voyageurs and coureurs des bois settled in Michigan in the 17th century; the first Europeans to reach what became Michigan were those of Étienne Brûlé's expedition in 1622. The first permanent European settlement was founded in 1668 on the site where Père Jacques Marquette established Sault Ste. Marie, Michigan as a base for Catholic missions. Missionaries in 1671–75 founded outlying stations at Saint Ignace and Marquette. Jesuit missionaries were well received by the area's Indian populations, with few difficulties or hostilities. In 1679, Robert Cavelier, Sieur de la Salle built Fort Miami at present-day St. Joseph. In 1691, the French established a trading post and Fort St. Joseph along the St. Joseph River at the present-day city of Niles.
In 1701, French explorer and army officer Antoine de la Mothe Cadillac founded Fort Pontchartrain du Détroit or "Fort Pontchartrain on-the-Strait" on the strait, known as the Detroit River, between lakes Saint Clair and Erie. Cadillac had convinced King Louis XIV's chief minister, Louis Phélypeaux, Comte de Pontchartrain, that a permanent community there would strengthen French control over the upper Great Lakes and discourage British aspirations; the hundred soldiers and workers who accompanied Cadillac built a fort enclosing one arpent and named it Fort Pontchartrain. Cadillac's wife, Marie Thérèse Guyon, soon moved to Detroit, becoming one of the first European women to settle in what was considered the wilderness of Michigan; the town became a major fur-trading and shipping post. The Église de Saint-Anne was founded the same year. While the original building does not survive, the congregation remains active. Cadillac departed to serve as the French governor of Louisiana from 1710 to 1716.
French attempts to consol
Lake Superior State University
Lake Superior State University is a small public university in Sault Ste. Marie, Michigan, it is Michigan's smallest public university, with an enrollment around 3,000 students. Due to its proximity to the border, notably the twin city of Sault Ste. Marie, Ontario, LSSU has many Canadian students and maintains a close relationship with its international neighbor. In a sign of its unique situation, LSSU has the Canadian and United States flags on its campus, both Canadian and American national anthems are sung at athletic events. LSSU is known for its academic programs such as fisheries and wildlife management, engineering and the environmental sciences, teacher education, geology, business management, fire science, criminal justice, it is one of the two universities in Michigan that offers an environmental health accredited curriculum, alongside Central Michigan University. In addition, students attend for LSSU's degrees in English and creative writing, forensic sciences, recreation management, legal studies.
Lake Superior State University offers bachelor's and associate degrees, but grants a master of arts in curriculum and instruction and many certificates. The university offers joint programs with Sault College and Algoma University in Sault Ste. Marie, Ontario. LSSU has regional centers in northern Michigan in the cities of Gaylord and Petoskey. A center opened in southeast Michigan in the city of Dearborn, it is one of three Michigan public universities, a university and a community college. The area that makes up the campus of Lake Superior State University served as Fort Brady from 1894 to 1944. Lake Superior State University was established in 1946 to address the needs of returning World War II veterans and to provide educational opportunities to the people of the Eastern Upper Peninsula; the 115-acre campus includes several buildings which are listed in the National Register of Historic Places. Much of the university's upbringings can be credited to Michigan College of Mining & Technology, now known as Michigan Technological University.
The mining and technology college opened the Sault Ste. Marie Residence Center of the Michigan College of Mining & Technology, shortened to Soo Tech; the original class consisted of 272 students. The institution was renamed Lake Superior State College of Michigan Technological University in 1966; the college received autonomy from Michigan Tech. in 1970 and was known as Lake Superior State College until 1987, when the institution was granted university status. Lake Superior State University was the first college in the United States to offer an accredited four-year fire science program, continues to be one of only three universities to offer such a program; the institution is one of only three universities in the United States to offer the robotics specialization in the ABET/TAC accredited manufacturing engineering technology, electrical engineering, computer engineering, mechanical engineering bachelor of science degrees. LSSU is home to one of the best robotics educational facilities in North America.
The robotics laboratory is valued at over $3 million. The university's college radio station is WLSO, its student newspaper is The Compass. In 2010, LSSU launched its Creative Writing program, which focuses on poetry and performance writing; this program augments the twin Saults' strong artistic communities. The program's "Visiting Writer Series" brings accomplished writers to the campus to read their work and hold master classes with students and aspiring area writers. An international literary journal called Border Crossing was founded by Creative Writing faculty members at LSSU to showcase poems, short stories and essays; the journal's title references the International Border between the United States and Canada, near where LSSU sits. The English Club produces a student literary journal called Snowdrifts. Administration Building The Administration Building houses the offices of the President and Provost, as well as human resources and public safety. Arts Center The arts center is a $15 million facility which opened in 2005.
The arts center houses a 674-seat auditorium, art and dance studios and faculty offices. The Arts Center Gallery has a permanent display from the L. F. Noyes Collection of Native American and Western Art. Brady Hall This building is being used as men's freshmen housing; the building is named after Colonel Hugh Brady. Col. Brady was the first commanding officer to serve at Fort Brady. Brady Hall was built as barracks for WACS or Women's Army Corps in 1938. Brown Hall Built in the 1820s, this building served as the captain's quarters of Fort Brady. Brown Hall wasn't called by its present name until 1982 when it was named for the retired janitor, Edward J. Brown. In the 1940s, the school as well as this building became a guide for veterans of WWII. Remodeling of this hall took place in 1946. In the 1960s, Brown Hall was converted into a counseling and career center that provided academic advising, it was led by Steve Youngs and was taken on by John Truckey. It one served as the location of the School of Education, the Fine Arts Program.
It now houses the Integrated Marketing Department. Much of the known information about this building can be recovered from the LSSU KJS Library Special Collections room. CASETThe Center for Applied Science and Engineering Technology is home to the School of Engineering and Technology, as well as the School of Mathematics and Computer Science. CASET houses the LSSU Robotics
Newberry is a village in the Upper Peninsula of the U. S. state of Michigan and the county seat of Luce County. Located within McMillan Township at its southern end, it shares some administrative responsibilities with the surrounding township; the population was 1,519 at the 2010 census. The village was named in honor of John Stoughton Newberry, a U. S. Representative and industrialist from the state of Michigan. Newberry is surrounded by miles of state and national forests and is considered one of two gateways to the Tahquamenon Falls area. Newberry was designated as the moose capital of Michigan by the state legislature, in House Resolution 2002-572 and Senate Resolution 2002-259, it is home to the Newberry Correctional Facility, operating since 1996, Helen Newberry Joy Hospital. In August 2007, the Sleeper Lakes Fire burned for several weeks north of Newberry, firefighting efforts were coordinated from this village; the same was true during the Duck Lake Fire in 2012. Newberry was founded in 1882 and became the county seat when Luce County was separated from Chippewa County in 1887.
Its first courthouse was completed in 1890. Historic preservationists lost the 1970s fight to save the county's Victorian courthouse, but managed to keep the elaborate sheriff's house, now the Luce County Historical Museum. According to the United States Census Bureau, the village has a total area of 0.98 square miles, all of it land. M-28 travels west to Marquette and east to Sault Ste. Marie. M-123 runs northerly and northeasterly from Newberry to Tahquamenon Falls State Park and Paradise. Indian Trails provides daily intercity bus service between Ironwood, Michigan. Canadian National Railway provides freight rail service in the Newberry area. Luce County Airport, provides service for Newberry and surrounding communities; as of the census of 2010, there were 1,519 people, 652 households, 380 families residing in the village. The population density was 1,550.0 inhabitants per square mile. There were 796 housing units at an average density of 812.2 per square mile. The racial makeup of the village was 89.3% White, 0.4% African American, 6.3% Native American, 0.3% Asian, 0.1% Pacific Islander, 3.6% from two or more races.
Hispanic or Latino of any race were 2.8% of the population. There were 652 households of which 30.1% had children under the age of 18 living with them, 39.1% were married couples living together, 14.3% had a female householder with no husband present, 4.9% had a male householder with no wife present, 41.7% were non-families. 37.6% of all households were made up of individuals and 15.7% had someone living alone, 65 years of age or older. The average household size was 2.26 and the average family size was 2.93. The median age in the village was 41.1 years. 25.9% of residents were under the age of 18. The gender makeup of the village was 47.9% male and 52.1% female. As of the census of 2000, there were 1,686 people, 717 households, 456 families residing in the village; the population density was 2,737.1 per square mile. There were 824 housing units at an average density of 839.7 per square mile. The racial makeup of the village was 69.92% White, 19.29% African American, 4.95% Native American, 0.67% Asian, 0.04% Pacific Islander, 1.01% from other races, 4.13% from two or more races.
Hispanic or Latino of any race were 3.69% of the population. There were 717 households of which 32.6% had children under the age of 18 living with them, 46.7% were married couples living together, 12.4% had a female householder with no husband present, 36.4% were non-families. 32.5% of all households were made up of individuals and 18.0% had someone living alone, 65 years of age or older. The average household size was 2.36 and the average family size was 2.95. In the village, the population was spread out with 18.2% under the age of 18, 12.5% from 18 to 24, 39.4% from 25 to 44, 16.4% from 45 to 64, 13.6% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 181.0 males. For every 100 females age 18 and over, there were 215.7 males. The median income for a household in the village was $29,052, the median income for a family was $36,607. Males had a median income of $29,286 versus $20,956 for females; the per capita income for the village was $17,224. About 15.6% of families and 18.1% of the population were below the poverty line, including 27.5% of those under age 18 and 8.4% of those age 65 or over.
Newberry is home to Newberry High School, a part of the Tahquamenon Area school district. Newberry High School, as of the 2017-2018 school year, has a total enrollment of 205 students; the nickname of Newberry High School is the Indians and school colors include orange and black. Indians are a dated term for Native Americans. Newberry High School features a variety of varsity athletic teams. Fall sports include cross country and volleyball while winter and spring sports include wrestling, boys/girls basketball and field, softball. School rivals include St. Ignace Lasalle High School, Munising High School, Engadine High School, Sault Ste. Marie High School; the Newberry High School football team competed each year for the Little Brown Jug of the Upper Peninsula of Michigan, a rivalry game with Sault Ste. Marie dating back to 1913. Current football "trophy games" include the Battle for the Ax, played against the aforementioned Munising High School. According to the Köppen Climate Classification system, Newberry has a humid continental climate, abbreviated "Dfb" on climate
AM broadcasting is a radio broadcasting technology, which employs amplitude modulation transmissions. It was the first method developed for making audio radio transmissions, is still used worldwide for medium wave transmissions, but on the longwave and shortwave radio bands; the earliest experimental AM transmissions began in the early 1900s. However, widespread AM broadcasting was not established until the 1920s, following the development of vacuum tube receivers and transmitters. AM radio remained the dominant method of broadcasting for the next 30 years, a period called the "Golden Age of Radio", until television broadcasting became widespread in the 1950s and received most of the programming carried by radio. Subsequently, AM radio's audiences have greatly shrunk due to competition from FM radio, Digital Audio Broadcasting, satellite radio, HD radio and Internet streaming. AM transmissions are much more susceptible than FM or digital signals are to interference, have lower audio fidelity.
Thus, AM broadcasters tend to specialise in spoken-word formats, such as talk radio, all news and sports, leaving the broadcasting of music to FM and digital stations. The idea of broadcasting — the unrestricted transmission of signals to a widespread audience — dates back to the founding period of radio development though the earliest radio transmissions known as "Hertzian radiation" and "wireless telegraphy", used spark-gap transmitters that could only transmit the dots-and-dashes of Morse code. In October 1898 a London publication, The Electrician, noted that "there are rare cases where, as Dr. Lodge once expressed it, it might be advantageous to'shout' the message, spreading it broadcast to receivers in all directions". However, it was recognized that this would involve significant financial issues, as that same year The Electrician commented "did not Prof. Lodge forget that no one wants to pay for shouting to the world on a system by which it would be impossible to prevent non-subscribers from benefiting gratuitously?"On January 1, 1902, Nathan Stubblefield gave a short-range "wireless telephone" demonstration, that included broadcasting speech and music to seven locations throughout Murray, Kentucky.
However, this was transmitted using induction rather than radio signals, although Stubblefield predicted that his system would be perfected so that "it will be possible to communicate with hundreds of homes at the same time", "a single message can be sent from a central station to all parts of the United States", he was unable to overcome the inherent distance limitations of this technology. The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U. S. Navy stations. In Europe, signals transmitted from a station located on the Eiffel tower were received throughout much of Europe. In both the United States and France this led to a small market of receiver lines designed geared for jewelers who needed accurate time to set their clocks, including the Ondophone in France, the De Forest RS-100 Jewelers Time Receiver in the United States The ability to pick up time signal broadcasts, in addition to Morse code weather reports and news summaries attracted the interest of amateur radio enthusiasts.
It was recognized that, much like the telegraph had preceded the invention of the telephone, the ability to make audio radio transmissions would be a significant technical advance. Despite this knowledge, it still took two decades to perfect the technology needed to make quality audio transmissions. In addition, the telephone had been used for distributing entertainment, outside of a few "telephone newspaper" systems, most of which were established in Europe. With this in mind, most early radiotelephone development envisioned that the device would be more profitably developed as a "wireless telephone" for personal communication, or for providing links where regular telephone lines could not be run, rather than for the uncertain finances of broadcasting; the person credited as the primary early developer of AM technology is Canadian-born inventor Reginald Fessenden. The original spark-gap radio transmitters were impractical for transmitting audio, since they produced discontinuous pulses known as "damped waves".
Fessenden realized that what was needed was a new type of radio transmitter that produced steady "undamped" signals, which could be "modulated" to reflect the sounds being transmitted. Fessenden's basic approach was disclosed in U. S. Patent 706,737, which he applied for on May 29, 1901, was issued the next year, it called for the use of a high-speed alternator that generated "pure sine waves" and produced "a continuous train of radiant waves of uniform strength", or, in modern terminology, a continuous-wave transmitter. Fessenden began his research on audio transmissions while doing developmental work for the United States Weather Service on Cobb Island, Maryland; because he did not yet have a continuous-wave transmitter he worked with an experimental "high-frequency spark" transmitter, taking advantage of the fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He reported that, in the fall of 1900, he transmitted speech over a distance of about 1.6 kilometers, which appears to have been the first successful audio transmission using radio signals.
However, at this time the sound was far too distorted to be commercially practical. For a time he continued working with more sophist
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
In broadcasting and radio communications, a call sign is a unique designation for a transmitter station. In the United States of America, they are used for all FCC-licensed transmitters. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or cryptographically encoded to disguise a station's identity; the use of call signs as unique identifiers dates to the landline railroad telegraph system. Because there was only one telegraph line linking all railroad stations, there needed to be a way to address each one when sending a telegram. In order to save time, two-letter identifiers were adopted for this purpose; this pattern continued in radiotelegraph operation. These were not globally unique, so a one-letter company identifier was added. By 1912, the need to identify stations operated by multiple companies in multiple nations required an international standard. Merchant and naval vessels are assigned call signs by their national licensing authorities.
In the case of states such as Liberia or Panama, which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters. United States merchant vessels are given call signs beginning with the letters "W" or "K" while US naval ships are assigned call signs beginning with "N". Both ships and broadcast stations were assigned call signs in this series consisting of three or four letters. Ships equipped with Morse code radiotelegraphy, or life boat radio sets, Aviation ground stations, broadcast stations were given four letter call signs. Maritime coast stations on high frequency were assigned three letter call signs; as demand for both marine radio and broadcast call signs grew American-flagged vessels with radiotelephony only were given longer call signs with mixed letters and numbers. Leisure craft with VHF radios may not be assigned call signs, in which case the name of the vessel is used instead. Ships in the US still wishing to have a radio license are under FCC class SA: "Ship recreational or voluntarily equipped."
Those calls follow the land mobile format of the initial letter K or W followed by 1 or 2 letters followed by 3 or 4 numbers. U. S. Coast Guard small boats have a number, shown on both bows in which the first two digits indicate the nominal length of the boat in feet. For example, Coast Guard 47021 refers to the 21st in the series of 47-foot motor lifeboats; the call sign might be abbreviated to the final two or three numbers during operations, for example: Coast Guard zero two one. Aviation mobile stations equipped with radiotelegraphy were assigned five letter call signs.. Land Stations in Aviation were assigned four letter call signs; these call signs were phased out in the 1960s when flight radio officers were no longer required on international flights. USSR kept FRO's for the Moscow-Havana run until around 2000. All signs in aviation are derived from several different policies, depending upon the type of flight operation and whether or not the caller is in an aircraft or at a ground facility.
In most countries, unscheduled general aviation flights identify themselves using the call sign corresponding to the aircraft's registration number. In this case, the call sign is spoken using the International Civil Aviation Organization phonetic alphabet. Aircraft registration numbers internationally follow the pattern of a country prefix, followed by a unique identifier made up of letters and numbers. For example, an aircraft registered as N978CP conducting a general aviation flight would use the call sign November-niner-seven-eight-Charlie-Papa. However, in the United States a pilot of an aircraft would omit saying November, instead use the name of the aircraft manufacturer or the specific model. At times, general aviation pilots might omit additional preceding numbers and use only the last three numbers and letters; this is true at uncontrolled fields when reporting traffic pattern positions or at towered airports after establishing two-way communication with the tower controller. For example, Skyhawk eight-Charlie-Papa, left base.
In most countries, the aircraft call sign or "tail number"/"tail letters" are linked to the international radio call sign allocation table and follow a convention that aircraft radio stations receive call signs consisting of five letters. For example, all British civil aircraft have a five-letter call sign beginning with the letter G. Canadian aircraft have a call sign beginning with C–F or C–G, such as C–FABC. Wing In Ground-effect vehicles in Canada are eligible to receive C–Hxxx call signs, ultralight aircraft receive C-Ixxx call signs. In days gone by American aircraft used five letter call signs, such as KH–ABC, but they were replaced prior to World War II by the current American system of civilian aircraft call signs. Radio call signs used for communication in manned spaceflight is not formalized or regulated to the same degree as for aircraft; the three nations curren
Frequency is the number of occurrences of a repeating event per unit of time. It is referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency; the period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example: if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals, radio waves, light. For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics and radio, frequency is denoted by a Latin letter f or by the Greek letter ν or ν; the relation between the frequency and the period T of a repeating event or oscillation is given by f = 1 T.
The SI derived unit of frequency is the hertz, named after the German physicist Heinrich Hertz. One hertz means. If a TV has a refresh rate of 1 hertz the TV's screen will change its picture once a second. A previous name for this unit was cycles per second; the SI unit for period is the second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. 60 rpm equals one hertz. As a matter of convenience and slower waves, such as ocean surface waves, tend to be described by wave period rather than frequency. Short and fast waves, like audio and radio, are described by their frequency instead of period; these used conversions are listed below: Angular frequency denoted by the Greek letter ω, is defined as the rate of change of angular displacement, θ, or the rate of change of the phase of a sinusoidal waveform, or as the rate of change of the argument to the sine function: y = sin = sin = sin d θ d t = ω = 2 π f Angular frequency is measured in radians per second but, for discrete-time signals, can be expressed as radians per sampling interval, a dimensionless quantity.
Angular frequency is larger than regular frequency by a factor of 2π. Spatial frequency is analogous to temporal frequency, but the time axis is replaced by one or more spatial displacement axes. E.g.: y = sin = sin d θ d x = k Wavenumber, k, is the spatial frequency analogue of angular temporal frequency and is measured in radians per meter. In the case of more than one spatial dimension, wavenumber is a vector quantity. For periodic waves in nondispersive media, frequency has an inverse relationship to the wavelength, λ. In dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave: f = v λ. In the special case of electromagnetic waves moving through a vacuum v = c, where c is the speed of light in a vacuum, this expression becomes: f = c λ; when waves from a monochrome source travel from one medium to another, their frequency remains the same—only their wavelength and speed change. Measurement of frequency can done in the following ways, Calculating the frequency of a repeating event is accomplished by counting the number of times that event occurs within a specific time period dividing the count by the length of the time period.
For example, if 71 events occur within 15 seconds the frequency is: f = 71 15 s ≈ 4.73 Hz If the number of counts is not large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count; this is called gating error and causes an average error in the calculated frequency of Δ f = 1 2 T