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Hilversum

Hilversum

Image:Loudspeaker.png Hilversum is a municipality and a town in the Netherlands. Located in the region called "'t Gooi", it is the largest town in that area. It is surrounded by heathland, woods, meadows, lakes, and smaller villages.

The town Hilversum

Hilversum lies some 30 km south-east of Amsterdam and 25 km north of Utrecht. The town is often called "media city" as it is the principal centre for radio and television broadcasting in the Netherlands. Radio Netherlands, heard worldwide via shortwave radio since the 1920s, is based here. Hilversum is home to an extensive complex of audio and television studios belonging to the national broadcast production company NOB, as well as to the studios and offices of all the Dutch public broadcasting organizations and many commercial TV production companies too. Hilversum is also known for its architecturally important "Raadhuis" or town hall, designed by Willem Dudok (1884-1974). The town has three railway stations: Hilversum Noord, Hilversum Centraal and Hilversum Sportpark, as well as a small airport a few km to the south.

History

Hilversum started out as nothing but a big slab of land used for agriculture. Around 900 it started to form, but it wasn't until 1305 that the first official mention of Hilversum ("Hilfershem") was made. At this point in time, it was a part of Laren, the oldest town in the Gooi area. Laren Some believe that Hilversum was built by the Belgians when they fled from the Spanish troops, but some official documents clearly define that the area now called Hilversum was used as nothing but farmland to provide Amsterdam with food. In March 1424, Hilversum received its most coveted official independent status. This caused some growth in the town, which was still nothing but an agricultural hovel. In 1725 and 1766, big fires destroyed most of the town, levelling parts of the old townhouse and the church next to it. Hilversum started to become a media city when the Philips company established a radio factory there. In 1964, the inhabitant count reached a record high - over 103,000 people were living there. At the moment it fluctuates around 84,000. In 2002, contested Dutch politician Pim Fortuyn was assassinated at Hilversum Media Park after just having finished a radio interview. Hilversum has three libraries (two of which will be closing next year), two swimming pools (Helmond Sport and De Lieberg), a number of sporting halls and several shopping centres (such as Hilvershof, Kerkelanden, Riebeeck-Gallerij, Severijn, and Chatham). In the region the city centre is known as 'het dorp' which means 'the village'.

External links

- [http://www.hilversum.nl/ Official Community Information]
- [http://www.ehhv.nl/ Hilversum Airport]
- [http://www.mediapark.nl/ Hilversum Media Park] Category:North Holland Category:Cities in the Netherlands

Municipality

A municipality or "general-purpose district" (compare with: "special-purpose district") is an administrative local area generally composed of a clearly defined territory and commonly referring to a city, town, or village government. Municipalities are not necessarily the same as townships. In most countries, this is the smallest administrative subdivision that has its own democratically elected representative leadership. In several European countries, municipalities as second level entities are referred to as communes.

Municipalities as second level entities

- In Australia, a municipality is a city, or shire and is a subdivision of a state
- In Austria, a municipality (Gemeinde) is part of a district (Bezirk), which is in turn part of a state (Bundesland).
- In Belgium, a municipality (gemeente/commune) is part of a province (provincie/province)
- In Bosnia and Herzegovina, a municipality (općina or opština) is
- part of a canton (kanton)
- a subdivision (grouped in regions)
- In Brazil, a municipality (município) is part of a state (estado)
- In Canada, a municipality is a city, town, township, county, or regional municipality which has been incorporated by statute by the legislatures of the Provinces and territories of Canada. It is also a specific designation for certain municipalities in Quebec and Ontario.
- In Chile, a municipality (comuna) is part of a province (provincia)
- In Croatia, a municipality (općina) is part of a county (županija)
- In Denmark, a municipality (kommune) is part of a county (amt)
- In Finland, a municipality (kunta/kommun) is part of a province (lääni/län)
- In France, a municipality (commune) is part of a department (département)
- In Germany, a municipality (Gemeinde) is part of a district (Kreis). Larger entities of the same level are named town (Stadt).
- In Greece, a municipality is either an urban demoi or rural koinotetes which is then part of a prefecture (nomos) and then a larger region known as a periphery.
- In Italy, a municipality (comune) is part of a province (provincia) which is part of a region (regione).
- In Japan, any government other than the Japanese national government is called a municipality.
- In Mexico, a municipality (municipio) is a subdivision of a state (estado) and a borogh (delegación) is a subdivision of the Federal District (see municipalities of Mexico and Boroughs of the Mexican Federal District).
- In the Netherlands, a municipality (gemeente) is part of a province (provincie).
- Every part of mainland New Zealand is part of either a "city" (mostly urban) or a "district" (mostly rural). The term "municipality" has become rare in New Zealand since about 1979 and has no legal status.
- In Norway, a municipality (kommune) is part of a county (fylke)
- In the Philippines, a municipality (bayan) is part of a province (lalawigan) and is composed of barangays.
- In Poland, a municipality (commune) (gmina) is a part of a county (powiat).
- In Portugal, a municipality (município) is subdivision of a district (distritos).
- In Puerto Rico, a municipality (municipio) is a city. Each municipality has an elected mayor.
- In Romania, a municipality (municipiu) is a town or a city ranked by law at this level. See Municipality in Romania for more information.
- In Serbia, a municipality (opština) is part of a county (okrug)
- In South Africa, municipalities are subdivisions of a province, and are ranked by size. In descending order: metropolitan, district, local.
- In Sweden, a municipality (kommun) is part of a county (län).
- In Switzerland, a municipality (commune/Gemeinde/comune) is part of a canton (canton/Kanton/cantone) and defined by cantonal law.
- In the United States, the entities that have status as a municipality vary from state to state. Cities, towns, boroughs, or villages are common terms for municipalities. Townships, counties, and parishes are not generally considered to be municipalities, although there are exceptions. In some states, towns have a non-municipal status similar to townships.

First level entities and other forms of municipalities

- In the People's Republic of China, a municipality (直辖市 in pinyin: zhíxiéshì) is a city with equal status to a province: Beijing, Tianjin, Shanghai, and Chongqing (see Municipality of China)
- In the Republic of China on Taiwan, a municipality (直轄市 in Wade-Giles: chi-hsia-shih) is a city with equal status to a province: Taipei and Kaohsiung. (see Municipality of China)
- In Portugal, a municipality (município/concelho) is the primary local administrative unit. Although it is a part of a district (distrito) for certain national administrative purposes, the municipality is not subordinate to the district and decentralization is doing away with the districts. A municipality contains one or more freguesias.
- In Puerto Rico, there are no first order administrative divisions, and the municipalities (municipio) serves as second-order, but first level, administrative divisions.
- In Montenegro, a municipality (opština) is the topmost regional division
- Municipalities of Libya, some very large.
- In Slovenia, a municipality (občina) is the primary local administrative unit. There are 193 of them, 11 of which have a special "Urban" status with additional autonomy.
- In Spain, a municipality (município) is the primary local administrative unit. It is a part of a province (provincia) for all national administrative purposes. A municipality contains one or more parroquias. In the Galiza region, the municipalities are called concellos.

Town

There is no universal, standard definition of the word town. This is mostly due to the evolution of the English language as an amalgamation of words from many other languages. "City" and "village" came into English from Latin via French. "Town" and "borough" (also "burrow," "burgh," "bury," etc.) are native English and Scottish words.

Etymology of the word and use around the world

In Old English and Old Scots, "Town" (or "toun," "ton," etc.) originally meant a fortified municipality, whereas a borough was not fortified. But that distinction did not last long, and "Edina Burgh" or "Edinburgh" - modernly called a "city" - was a fortified "town" from its founding. In American English, a town is usually a municipal corporation that is smaller than a city but larger than a village. In some cases, "town" is an alternate name for "city" or "village" (especially a larger village). Sometimes, the word "town" is short for "township." In general, towns can be differentiated from townships, villages, or hamlets on the basis of their economic character, in that most of a town's population will tend to derive their living from manufacturing industry, commerce, and public service rather than primary industry such as agriculture or related activities. A place's population size is not a reliable determinant of urban character. In many areas of the world, as in India at least until recent times, a large village might contain several times as many people as a small town. The modern phenomena of extensive suburban growth, satellite urban development, and migration of city-dwellers to villages have further complicated the definition of towns, creating communities urban in their economic and cultural characteristics but lacking other characteristics of urban localities. Some forms of non-rural settlement, such as temporary mining locations, may be clearly non-rural, but have at best a questionable claim to be called a town. The distinction between a town and a city similarly depends on the approach adopted: a city may strictly be an administrative entity which has been granted that designation by law, but in informal usage, the term is also used to denote an urban locality of a particular size or importance: whereas a medieval city may have possessed as few as 10,000 inhabitants, today some consider an urban place of fewer than 100,000 as a town, even though there are many officially designated cities that are very much smaller than that.

Australia

In Australia, the status of a town is formally applied in only a few states. Most states do define cities, and towns are commonly understood to be those centres of population not formally declared to be cities and usually with a population in excess of about 250 people. The creation and delimitation of Local Government Areas is the responsibility of the state and territory Governments. In all states and the Northern Territory each incorporated area has an official status. The various LGA status types currently in use are:
- New South Wales: Cities (C) and Areas (A)
- Victoria: Cities (C), Rural Cities (RC), Boroughs (B) and Shires (S)
- Queensland: Cities (C), Shires (S), Towns (T) and Island Councils (IC)
- South Australia: Cities (C), Rural Cities (RC), Municipalities/Municipal Councils (M), District Councils (DC), Regional Councils (RegC) and Aboriginal Councils (AC)
- Western Australia: Cities (C), Towns (T) and Shires (S)
- Tasmania: Cities (C) and Municipalities (M)
- Northern Territory: Cities (C), Towns (T), Community Government Councils (CGC) and Shires (S).

Reference

- [http://www.abs.gov.au/Ausstats/abs@.nsf/0/9f0b5791ed98061fca256f1900128409?OpenDocument Australian Bureau of Statistics: Australian Standard Geographical Classification (ASGC) 2005]

England and Wales

In England and Wales, the status of a city is reserved for places that have a Royal Charter entitling them to the name, traditionally associated with the possession of a cathedral. Some large municipalities are legally boroughs but not cities, whereas some cities are quite small — St. David's for instance. It is often thought that towns with bishops' seats rank automatically as cities: however, Chelmsford remains a town despite being the seat of the Diocese of Chelmsford. St. Asaph, which is the seat of the Diocese of St. Asaph, is another such town. Within Greater London, there are two cities, each with its own cathedral - the City of London (St. Paul's Cathedral; Anglican) and the City of Westminster (Westminster Cathedral; also Anglican). Historically, a town was generally distinguished from a village by having a regular market or fair. Not all towns were boroughs. There are some English villages (e.g. Kidlington, Oxfordshire) larger than some small towns (e.g. Middleham, North Yorkshire). The word town can also be used as a general term for urban areas, including cities. In this usage, a city is a type of town — a large one, with a certain status. For example, London is a city, but is sometimes referred to as "London town" (the "City of London" is the nucleus informally known as the "Square Mile"). Also, going from the suburbs to central London is to "go into town".

Germany

Germans do not differentiate between city and town. The German word for both is "Stadt" as it is in many other languages that do not make any difference between the Anglo-Saxon concepts. A town with more than 100,000 inhabitants is called a Großstadt, which is the most adequate equivalence for city.

The United States

City of London In the United States of America, the meaning of the term town varies from state to state. In some states, a town is an incorporated municipality, that is, one with a charter received from the state, similar to a city. Typically, municipalities are classed as cities, towns or boroughs, or villages in decreasing order of size, although not all states have all three levels. Many states do not use the term "town" for incorporated municipalities. In some states, for example Wisconsin, "town" is used in the same way that civil township is used in elsewhere. In other states, such as Michigan, the term "town" has no official meaning and is simply used informally to refer to a populated place, whether incorporated or not. In the six New England states, a town is a municipality, and in these states, in practice a more important unit than the county. In Connecticut and Rhode Island, in fact, counties only exist as map divisions and have no legal functions; in the other four states, counties are primarily judicial districts, with other functions primarily in New Hampshire and Vermont. In all six, towns perform functions that in most states would be county functions. The defining feature of a New England town, as opposed to a city, is that a town meeting and a board of selectmen serve as the main form of government for a town, while cities are run by a mayor and a city council. For example, Brookline, Massachusetts is a town, even though it is fairly urban, because of its form of government. In New York, a town is similarly a subdivision of the county, but with less importance than in New England. Of some importance is the fact that, in New York, a town provides a closer level of governance than its enclosing county, providing almost all municipal services to unincorporated areas, called hamlets and selected services to incorporated areas, called villages. In New York, a town typically contains a number of such hamlets and villages. However, due to the independent nature of Incorporated Villages, they may exist in two towns or even two counties. Everyone in New York State who does not live in an Indian reservation or a city lives in a town and possibly in one of the town's hamlets or villages. (Some other states have similar entities called townships.) In New York, "town" is essentially short for "township." In Virginia, a town is an incorporated municipality similar to a city (though with a smaller required minimum population), but while cities are by Virginia law independent of counties, towns are contained within a county. In California (where the term "village" is not used), "town" is simply another word for "city" (especially a "general law city", as distinct from a "charter city").

External links

- [http://www.open-site.org/Regional Open-Site Regional] — Contains information about towns in numerous countries. als:Stadt ja:村落 simple:Town

Heathland

Heaths are anthropogenic habitats found primarily in northern and western Europe, where they have been created by thousands of years of human clearance of natural forest vegetation by grazing and burning on mainly infertile acidic soils. They subdivide into two broad categories depending on climate, with true heathland developing in warm, dry conditions, and moorland developing in cooler, wetter conditions. As they have developed over a long period, a unique assemblage of plants and animals has adapted to thrive in these habitats. Modern techniques of agriculture now threaten much of this habitat, by ploughing, fertilising and planting with arable crops, or conversion to commercial forestry plantations. Heathlands are also threatened by forest growth as a result of the discontinuation of traditional farming techniques such as grazing and burning that kept the cultural landscapes intact. Some are also threatened by urban sprawl.

Heathland

urban sprawl). Purple flowers of Calluna vulgaris and yellow flowers of Ulex gallii]] Heathland is a lowland habitat, and is favoured where climatic conditions are typically warm and dry, particularly in summer, and soils acidic, of low fertility, and often sandy and very free-draining; bogs do occur where drainage is poor, but are usually only small in extent. It is dominated by low shrubs, 0.2-2 m tall, particularly heather (Calluna vulgaris), heath (Erica species) and gorse (Ulex species). It is noted for the brilliant colours when these species flower in late summer (see photo, left). The habitat is maintained artificially by a combination of grazing and periodic burning, or (rarely) mowing; if not so maintained, it is rapidly re-colonised by forest, mainly of pine (Pinus species) and Silver birch (Betula pendula). Heathlands have a very typical associated bird fauna, notably Montagu's Harrier, Eurasian Hobby, European Nightjar, Wood Lark, Tree Pipit, European Stonechat and Dartford Warbler; where there are scattered trees, Green Woodpecker is also characteristic. Some reptiles are also largely confined to healthland, notably the Sand Lizard and the Smooth Snake, and one amphibian, the Natterjack Toad. It is also an excellent habitat for ants with many species being restricted entirely to it. One of the biggest heathlands is the Lüneburger Heide in northern Germany. Other notable heaths include large parts of the New Forest and the Breckland in southern and eastern England respectively, and the Veluwe in the Netherlands, and smaller areas in Dorset, Devon and Surrey in southern England. Heathland habitats are also found in parts of Denmark, France, Spain and along the Norwegian coastline.

Moorland

Spain Upland moorland habitats occur mainly in northern and western Britain and Ireland, and are similar in also often being dominated by heather, but differ from typical heathland in being colder and much wetter, often with extensive bogs, giving rise to a different mix of associated fauna, such as Red Grouse, Hen Harrier, Merlin, Golden Plover, Curlew, Sky Lark, Meadow Pipit, Whinchat, Ring Ouzel and Twite. Reptiles are fewer due to the cooler conditions, with only the Common Viper being frequent. When moorland is overgrazed by excessive numbers of sheep or deer, most of the heather is lost, being replaced by coarse, unpalatable grasses and bracken, with a greatly reduced fauna. Notable areas of upland moorland in Britain include Bodmin Moor, Dartmoor, Exmoor, the Dark Peak, the North York Moors, the Forest of Bowland, the Lake District, the Pennines, Mid Wales, and the Southern Uplands of Scotland and the Scottish Highlands. In more northerly latitudes, moorland is also found in lowland areas in the Scottish Highlands, Iceland and Norway; in the far north where trees do not grow naturally, moorland grades into natural tundra.

External links

- [http://www.countryside.gov.uk/WiderWelcome/NCAF/NCAF4_4.asp The Countryside Agency] information on types of open land Category: Landforms

Meadow

"Meadow" can refer to a number of things:
- A meadow, a tract of grassland, either in its natural state or used as pasture or for growing hay, a large paddock. See also heath (habitat).
- A water-meadow is an area of flat land by a river or stream that is subject to flooding.
- The Meadows, a park in Edinburgh.
- Henry Meadows of Wolverhampton, England, who were suppliers of engines to the British motor industry.
- Meadow, an open source programming project. ja:Meadow

Lake

A Lake is a body of water surrounded by land. The majority of lakes are fresh water, and most lie in the northern hemisphere at higher latitudes. Large lakes are sometimes referred to as "inland seas" and small seas are sometimes referred to as lakes. The term lake is also used to describe a feature such as Lake Eyre, which is dry most of the time but becomes filled under seasonal conditions of heavy rainfall. Many lakes are artificial and are constructed for hydro-electric power supply, recreation (swimming, wind surfing,...), water supply, etc. Finland is known as The Land of the Thousands Lakes (actually there are 187,888 lakes in Finland, 60,000 of them are big ones) and Minnesota is known as The Land of Ten Thousand Lakes. The Great Lakes of North America originated in the ice age. Over 60% of the world's lakes are in Canada; this is because of the deranged drainage system that dominates the country.

Origin of natural lakes

Most lakes are young, as the natural results of erosion will tend to wear away one of the basin sides containing the lake. There are a number of natural processes that can form lakes. A recent tectonic uplift of a mountain range can create bowl-shaped depressions that accumulate water and form lakes. The advance and retreat of glaciers can scrape depressions in the surface where lakes accumulate. Such lakes are common in Scandinavia, Siberia and Canada. Lakes can also form by means of landslides or by glacial blockages. An example of the latter occurred during the last ice age in the state of Washington, when a huge lake formed behind a glacial flow. When the ice retreated, the result was an immense flood that created the Dry Falls Monument at Sun Lakes, Washington. Saline lakes can form where there is no natural outlet or the water evaporates rapidly, and the drainage surface of the water table has a higher than normal salt content. Examples of salt lakes include the Great Salt Lake, the Caspian Sea and the Dead Sea. Small, crescent-shaped lakes called oxbow lakes can form in river valleys as the result of meandering. The slow-moving river forms a sinuous shape as the outer side of bends is torn away more rapidly than the inner side. Eventually a horseshoe bend is formed and the river cuts through the narrow neck. This gap now forms the main passage for the river and the ends of the bend become silted up. Lake Vostok is an under-ice lake in Antarctica, possibly the largest in the world. The pressure from ice and the internal chemical composition means that if the lake were drilled into, it may result in a fissure and spraying in the same manner as a shaken can of soda. Some lakes, like Lake Baikal and Lake Tanganyika are volcanic in origin, and lie on geological fault lines. The Crater Lake in Oregon is a lake located within the caldera of an extinct volcano. Some lakes come into existence as a result of sinkhole activity.

Characteristics

The change in level of a lake is controlled by the difference between the sources of inflow and outflow, compared to the total volume of the lake. The significant input sources are precipitation onto the lake; runoff carried by streams and channels from the lake's catchment area; groundwater channels and aquifers, and man-made sources from outside the catchment area. Output sources are evaporation from the lake; surface and groundwater flows, and any extraction of lake water by humans. As climate conditions and human water requirements vary, these will create fluctuations in the lake level. Lakes can be categorized on the basis of their richness of nutrients, which typically effects plant growth. Nutrient poor lakes are said to be oligotrophic, and are generally clear, having a low concentration of plant life. Mesotropic lakes have good clarity and an average level of nutrients. Eutrophic lakes are enriched with nutrients, resulting in good plant growth and possible algal blooms. A hypertrophic lake is a water body that has been highly enriched with nutrients. These lakes typically have poor clarity and are subject to algal blooms. Lakes typically reach this condition due to human activities, such as heavy use of fertilizers in the lake catchment area. Such lakes are of little use, and have a poor ecosystem.

Types of lakes

A periglacial lake is one in which part of its margin is formed by an ice sheet, ice cap or glacier, the ice having obstructed the natural drainage of the land. A subglacial lake is one which is permanently covered by ice. They can occur under glaciers and ice caps or ice sheets. There are many such lakes, but Lake Vostok in Antarctica is by far the largest. The are kept liquid because the overlying ice acts as a thermal insulator retaining energy introduced to its underside by friction, water percolating through crevasses, by the pressure from the mass of the ice sheet above or by geothermal heating below. Because of the unusual relationship between water's temperature and its density, the water in lakes in temperate climates mixes twice a year. Fresh water is most dense at about 4 degrees Celsius. When the temperature of the water at the surface of a lake reaches the temperature at which water is most dense all the water in the lake can mix, bringing oxygen starved water up from the depths, and bringing oxygen down to decomposing sediments. When the density of surface water differs from that of the deeper water there is a marked barrier layer, the thermocline, that prevents mixing. Deep Temperate lakes can maintain a reservoir of cold water year-round. The reservoir of deep, cold water allows cities to tap that reservoir for deep lake water cooling. Since the water of deep tropical lakes never reaches the temperature where water reaches its maximum density, there is no process that makes the water mix. The deeper layer becomes oxygen starved, and can become saturated with carbon dioxide, and possibly other gases, like sulfur dioxide, if there is even a trace of volcanic activity. Exceptional events, like earthquakes or landslides, which do cause mixing, that brings up the deep layers, can release a vast cloud of toxic gas. The amount of gas that can be dissolved in water is pressure related. As the water surfaces, and the pressure drops, a vast amount of gas cab comes out of solution. Under these circumstances even carbon dioxide is toxic. Carbon dioxide is heavier than air, and the released carbon dioxide flows down the river valley.

Artificial lakes

A reservoir (French: réservoir) is an artificial lake created by flooding land behind a dam. Some of the world's largest lakes are reservoirs. Artificial lakes can also be made deliberately by digging one or by flooding an open-pit mine.

Abiotic and biotic limnology

mine Limnology divides lakes in three zones: littoral zone, which is a sloped area that is close to land; open-water zone, where sunlight is abundant; and deep-water zone, where little sunlight can reach. The depth which light can reach in lakes depends on the density and motion of particles. These particles can be sedimentary or biological in origin and are responsible for the color of the water. Decaying plant matter for instance is responsible for a yellow or brown color, while algae result in greenish water. In very shallow water bodies, iron oxides make water reddish brown. Biological particles are algae and detritus. A sediment particle is in suspension if its weight is less than the random turbidity forces acting upon it. The turbidity is a decisive factor in the transparency of the water. Bottom-dwelling detritivorous fish are responsible for turbid waters, because they stir the mud in search for food. Piscivorous fish eat plant-eating (planktonivorous) fish, thus increasing the number of algae (see aquatic trophic cascade). The light depth or transparency is measured by using a Secchi disk. This is a 20 cm disk with alternating white and black quadrants. The depth at which the disk is no longer visible, is the Secchi depth, and is a measure for transparency. It is commonly used to test eutrophication. A lake moderates the surrounding region's temperature and climate because water has a very high specific heat capacity (4186). In the daytime, the lake can cool the land beside it with local winds, resulting in a sea breeze; in the night, it can warm it, forming a land breeze.

How lakes disappear

A lake may be infilled with deposited sediment, and gradually, the lake becomes a wetland, such as a swamp or marsh. An important difference exists between lowland and highland lakes: lowland lakes are more placid, are less rocky/more sedimentary, have a less sloping bottom, and generally contain more plant life. Large water plants (typically reeds) accelerate this closing process significantly because they trap sediment. Turbid lakes, and lakes with much plant-eating fish, tend to disappear slower. A "disappearing" lake (barely noticeable on a human timescale) typically has a water's edge with extensive plant mats. They become a new habitat for other plants (like peat moss, when conditions are right) and animals, many of which are very rare. Gradually, the lake closes, and young peat may form, forming a fen. In lowland river valleys (allowing the river to meander), the presence of peat is explained by the closing of historical oxbow lakes. In the very last stages of succession, more trees would grow in, eventually turning the wetland into a forest. Some lakes can also disappear seasonally; they are called Intermittent lakes and are typical of karstic terrain. A prime example of this is Lake Cerknica in Slovenia. On June 3, 2005 in Bolotnikovo, Russia, a lake called White Lake vanished in a short period of time (minutes). News sources reported government officials theorized that this strange phenomena may have been caused by a shift on soil underneath the lake which drained water to channels leading to Oka River. Neusiedler See, located in Austria and Hungary, dried up several times for a of number years during the past centuries. As of 2005, it is again rapidly losing water, giving rise to the fear that it will be completely dried up by 2010.

Extraterrestrial lakes

At present the surface of the planet Mars is too cold to permit pooling of liquid water on the surface. However geologic evidence appears to confirm that ancient lakes once formed on the surface. It is also possible that volcanic activity on Mars will occasionally melt the subsurface ice, forming large lakes. Under current conditions this water will quickly evaporate or freeze unless insulated in some manner, such as by a coating of volcanic ash. Jupiter's small moon Io is volcanically active due to tidal stresses, and as a result sulfur deposits have accumulated on the surface. Some photographs taken during the Galileo mission appear to show lakes of liquid sulfur on the surface. There are dark basaltic plains on the Moon, similar to lunar maria but smaller, that are called lacus (singular lacus, Latin for "lake"). They were once thought by early astronomers to be literal lakes.

Notable lakes

- The largest lake in the world by surface area is the Caspian Sea. With a surface area of 394,299 sq. km., it has a surface area greater than the next six largest lakes combined.
- The largest freshwater lake, and second largest lake altogether is Lake Superior with a surface area of 82,414 sq. km. It is also the largest lake in North America and is a part of the Great Lakes.
- The deepest lake is Lake Baikal in Siberia, with a bottom at 1,741 m (5,712 ft.) and is the world's largest freshwater lake by volume.
- The highest navigable lake is lake Titicaca, at 3821 m above sea level. It is also the second largest lake in South America.
- The world's highest lake is Lhagba Pool in Tibet at 6,368 m.
- The world's lowest lake is the Dead Sea, at 396 m (1,302 ft.) below sea level. It is also the lake with the highest salt concentration.
- The largest freshwater-lake island is Manitoulin Island on Lake Huron, with a surface area of 2,766 square km.
- The largest lake located on an island is Nettilling Lake on Baffin Island.
- Lake Toba on the island of Sumatra is located in what is probably the largest resurgent caldera on Earth.
- The largest freshwater lake in Europe is Lake Balaton, followed by Lake Geneva.
- Lake Victoria is the largest lake in Africa. It is a part of the Great Lakes of Africa.
- Lake Maracaibo is the largest lake in South America. Lake Titicaca is the largest freshwater lake in South America.
- The largest lake located completely within the boundaries of a single city is Lake Wanapitei in the city of Greater Sudbury, Ontario, Canada. Before the current city boundaries came into effect in 2001, this status was held by Lake Ramsey, also in Sudbury.
- Saimaa is the largest lake in Finland (the land of 187,888 lakes).

External links

- [http://www.highestlake.com/ Lists of the highest lakes in the US and the world]
- [http://www.mlswa.org/lkclassif1.htm Lake Classification Systems]
- [http://www.uklakes.net/ UKLakes Database]
- [http://www.midwestlakes.org/ Midwest Lakes Policy Center] Category:Bodies of water Category:Landforms ko:호수 ja:湖 simple:Lake th:ทะเลสาบ

Village

:For a list of references which "The Village" could refer to, see The Village A village is a human settlement commonly found in rural areas. It is usually larger than a hamlet and smaller than a town or city. Villages have been the normal unit of community living in most areas of the world throughout its history, up until the Industrial revolution and the ongoing process of urbanization. In many U.S. states, a village is a type of municipal government (see below).

Traditional villages

Although many types and organizational patterns of village life have existed, the typical village was small, consisting of perhaps 5 to 30 families. Homes were situated together for sociability and defense, and land surrounding the living quarters was farmed.

England

In England the main historical distinction between a hamlet and a village is that the latter will have a church, and will therefore usually have been the worship centre of a parish. A village was traditionally distinguished from a town in that a village lacked a regular agricultural market, although today such markets are uncommon even in settlements which clearly are towns. Due to the vagueness of this definition, there is some question as to which is the largest village in England.

United States

Incorporated villages

In twenty U.S. states, the term "village" refers to a specific form of incorporated municipal government, similar to a city but with less authority and geographic scope. However, this is a generality; in many states, there are villages that are an order of magnitude larger than the smallest cities in the state. The distinction is not necessarily based on population, but on the relative powers granted to the different types of municipalities and correspondingly, different obligations to provide specific services to residents. In some states such as New York, Wisconsin, or Michigan, a village is an incorporated municipality, usually, but not always, within a single town or civil township. Residents pay taxes to the village and town or township and may vote in elections for both as well. In some cases, the village may be coterminous with the town or township. There are also many villages which span the boundaries of more than one town or township, and some villages may even straddle county borders. There is no limit to the population of a village in New York. (Hempstead, the largest village in the state, has 55,000 residents, making it more populous than many of the state's cities); however, villages in the state may not exceed five square miles (13 km²) in area. The state of Wisconsin has similar status for villages. The largest village is Menomonee Falls, which has over 25,000 residents. Michigan also has no set population limit for villages and there are many villages that are larger than cities in the state. Villages in Ohio are almost always legally separate from any townships that they may have been incorporated from (there are exceptions, such as Chagrin Falls, where the township includes the entirety of the village). They have no area limitations, but must reincorporate as cities if they grow to over 5,000 in population. Villages have the same home-rule rights as cities with fewer of the responsibilities. Unlike cities, they have the option of being either a "statutory village" and running their governments according to state law (with a six-member council serving four-year terms and a mayor who votes only to break ties) or being a "charter village" and writing a charter to run their government as they see fit. :See Political subdivisions of New York State#Village Village (Oregon)

Unincorporated villages

In many states, the term "village" is used to refer to a relatively small unincorporated community, similar to a hamlet in New York state. This informal usage may be found even in states that have villages as an incorporated municipality, although such usage might be considered incorrect and confusing.

External links

Village types:
- [http://www.pygmies.info/camps.html African Pygmies Villages] ja:村 th:หมู่บ้าน

Utrecht (city)

:There is also Utrecht, South Africa Utrecht is a municipality and the capital city of the Dutch province of Utrecht. It is the fourth largest city of the Netherlands.

Population centres

- The city of Utrecht (population: 244,000)
- Vleuten-De Meern (population: 26,000)
- De Meern
- Vleuten
- Haarzuilens (population: 500) Vleuten-De Meern was a separate municipality until 2001, which included the village of Haarzuilens. Population data are approximations as of early 2004.

The city of Utrecht

2004 Utrecht is famous for the Dom Tower of Utrecht and the canal structure in the inner city. It is the center of the Dutch railroad network and the location of the head office of the Nederlandse Spoorwegen (Dutch Railways), which is the largest brick building in the Netherlands (the "UFO" gracing its facade stems from an art program in 2000). A large indoor shopping center called Hoog Catharijne is located between the central railway station and the city center. The corridors have been considered public places like streets, and the main route from station to city center is therefore open all night. Over the next 20 years (counting from 2004), parts of Hoog Catharijne will disappear in connection with the [http://www2.utrecht.nl/smartsite.dws?id=4537 Aanpak Stationsgebied] scheme. Parts of the city's network of canals, which were filled to create the shopping center and central station area, are being recreated. Utrecht University is the largest university of The Netherlands. Utrecht is also home to the FC Utrecht football club, which plays in Stadium Nieuw Galgenwaard.

History

The origin of the city was the erection of a Roman fortification (castellum) around AD 47. It was built at the river Rhine, which followed a more northern route than it does now and was the border of the Roman Empire. The name of the place was Traiectum, which means fordable place. During the ages around 500 Romans were encamped here. Near the fort there was a settlement with artisans, traders and soldiers' women and children. In the middle of the 2nd century Germanic peoples regularly invaded the territories that Romans had conquered from them, and around 270 the Romans left Utrecht. About the period 270-500 little is known. In the 6th century Utrecht came under the influence of the Franks. During the Middle Ages Utrecht was the most important city of the Northern Netherlands. Willibrordus is usually considered to be its first bishop. In 695 he was appointed archbishop of the Frisians and in 703 or 704 Pepin II of Herstal gave him Utrecht as see for his missionary activities further north. Utrecht received city rights in 1122. Later the bishops of Utrecht exercised as prince-bishops worldly power not only in the province of Utrecht (Nedersticht) but also further to the northeast. The Veluwe soon became part of Gelre but Overijssel remained the Oversticht. In 1528 the wordly power over both Neder- and Oversticht was transferred to Charles V, Holy Roman Emperor, who became the Lord of the 17 Netherlands (the current Benelux plus the 'Nord' of France). 17 Netherlands, 1945]] In 1579 the northern seven provinces of these Low Countries signed the Union of Utrecht. They decided to join forces against Spanish rule. The Union of Utrecht is seen as the beginning of the Dutch Republic. In 1580 this predominantly Protestant state abolished the bishoprics, including the one in Utrecht, which had become an archiepiscopal see in 1559. Only in 1853 was the see reinstated. The Treaty of Utrecht in 1713 settled the War of the Spanish Succession. Its most lasting result was the cession by Spain of Gibraltar to Great Britain. In 1843, a railway that connected Utrecht with Amsterdam was opened. After that, Utrecht gradually became the centre of the Dutch railway network. During World War II, Utrecht was held by the Germans until the general German surrender of the Netherlands on May 5, 1945. Canadian troops entered the city on May 7, 1945. Since World War II, the city has grown considerably when new neighbourhoods such as Kanaleneiland, Hoograven, Lunetten, and (recently) Leidsche Rijn were built.

Education

Utrecht University is the largest university of The Netherlands (26.787 students as of 2004). The university is based in the inner city and in the Uithof campus area, on the east of the city. It's the 41th best university in the world, according to Shanghai Jiaotong University's [http://ed.sjtu.edu.cn/ranking.htm university ranking] in 2005. Utrecht is also home to two other large institutions of higher education: the HvU University of Professional Education Utrecht (30,000 students), and the HKU Utrecht School of the Arts (3,000 students).

Transport

The public transport network of Utrecht includes:
- The Utrecht Centraal railway station (NS (dutch railways) internal abbreviation:ut), which is a main node of the Dutch railway network and also serves as a major regional bus station. There are three minor railway stations in Utrecht: Utrecht Overvecht (uto), Utrecht Lunetten (utl), and Utrecht Terwijde (utt). Additionally, at least three new railway stations are planned.
- Local GVU buses, including a high-quality bus line to the Uithof university district to the east of the city, served by bi-articulated buses.
- Regional Connexxion buses
- BBA buses to and from the region northwest of the city, and to Breda and Oosterhout (Interliner).
- A light-rail (sneltram in Dutch) line which runs from the Utrecht Centraal station, through the neighbourhoods of Lombok and Kanaleneiland, to Nieuwegein and IJsselstein. This line is also operated by Connexxion. Utrecht also has a harbour on the Amsterdam-Rhine Canal, which is connected to the Rhine river. The CTU container terminal has a capacity of 80,000 containers a year. In 2003, the port facilitated the transport of four million tons of cargo; mostly sand, gravel, fertilizer, and fodder.

Museums

- [http://www.aamu.nl/ Aboriginal Art Museum]
- [http://www.centraalmuseum.nl/ Centraal Museum] (arts and municipal history)
- [http://www.catharijneconvent.nl/ Museum Catharijneconvent] (history of Christian culture and arts in the Netherlands)
- [http://www.museumspeelklok.nl/ National museum 'From musical clock to street organ'] (several centuries of mechanical musical instruments)
- [http://www.spoorwegmuseum.nl/engels/algemeen Railroad museum] (history of Dutch railroad)
- [http://www.museum.uu.nl/ University museum] (see Utrecht University) Utrecht University

Famous people from Utrecht

- Pope Adrian VI
- Louis Andriessen (composer)
- Marco van Basten (soccer player)
- Dick Bruna (writer, illustrator)
- C.H.D. Buys Ballot (meteorologist)
- Theo van Doesburg (painter, artist)
- Anton Reinhard Falck (politician and lawyer)
- Anton Geesink (Olympic judo champion)
- Gerhard van Honthorst (painter)
- Trijn van de Leemput (local female hero of the Eighty Years' War)
- Gerrit Rietveld (designer, architect)
- Tineke Schouten (comedian, singer, actor)
- Wesley Sneijder (soccer player)
- Herman van Veen (comedian, singer)
- Jochem Uytdehaage (ice skater)
- Henk Westbroek (singer, DJ, local politician, bar owner)
- Jan Wouters (soccer player)

External links

- [http://www.utrecht.nl/ Official website of the city]
- [http://www.aartsbisdom.nl/ Official website of the archdiocese]
- Maps:
- [http://www.utrecht.nl/vgi/zoek.cfm?straatnaam=Domplein_(_Utrecht_)&xco=136775.243&yco=455868.011&schaal=1200 City map]
- [http://geocement.esrinl.com/viewer.htm Map of the whole province, but showing about equal detail]
- [http://www.gvu.nl/(kp5a3i45wb3yycbzgyvywpfo)/lijnnetkaart.aspx?baseID=2&subID=51 GVU line map of bus routes (does not show lines of other companies)]
- [http://www.plattegronden.nl/gemeentevleuten-demeern/ Map of the western part of the municipality ]
- [http://members.lycos.nl/ovhome/ut151202.jpg Overview of the bus station] (southern part, for regional buses, as opposed to city buses at the north side)
- [http://www.busesintl.com/May_2003.htm Article on the Busway Program] (bus route between the station and the Uithof)
- [http://www.antonenmarieke.demon.nl/panoramas.html Panorama photography in the center of the city] Category:Utrecht Category:Cities in the Netherlands Category:Cities on the Rhine ja:ユトレヒト

Mediaş

Mediaş (Hungarian: Medgyes, German: Mediasch) is a town in Romania. It is located in the heart of Transylvania, on the valley of Târnava Mare river in the Sibiu County. It has a population of 62,750. There has been a settlement at the town's location since prehistoric times.

External links

- Find out more about Mediaş and see pictures from [http://www.therealtransylvania.com/journeys.html#5 Mediaş]
- http://www.primariamedias.ro/en/istorie1.htm Category:Cities in Romania Category:Municipalities in Romania Category:Sibiu

Radio

Radio is the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of light.

Radio waves

Radio waves are a form of electromagnetic radiation, created whenever a charged object (e.g. an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to a few hundred gigahertz. Other types of electromagnetic radiation, with frequencies above the RF range are infrared, visible light, ultraviolet, X-rays and gamma rays. Since the energy of an individual photon of radio frequency is too low to remove an electron from an atom, radio waves are classified as non-ionizing radiation.

non-ionizing radiation
Radio transmission diagram and electromagnetic waves.

Electromagnetic radiation travels (propagates) by means of oscillating electromagnetic fields that pass through the air and the vacuum of space equally well, and does not require a medium of transport (such as the aether). When radio waves pass an electrical conductor, the oscillating electric or magnetic field (depending on the shape of the conductor) induces an alternating current and voltage in the conductor. This can be transformed into audio or other signals that carry information. Although the word 'radio' is used to describe this phenomenon, the transmissions which we know as television, radio, radar, and cell phone are all classed as radio frequency emissions.

History and invention

The identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. The controversy over who invented the radio, with the benefit of hindsight, can be broken down as follows: :Q1: Who invented 'wireless transmission of data' (spark-gap radio)? :A1: Alexander Popov, Guglielmo Marconi, Nikola Tesla (possibly in that order). :Q2: Who invented amplitude-modulated (AM) radio, so that more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of the spectrum)? :A2: Reginald Fessenden _{[http://www.invent.org/hall_of_fame/59.html]} and Lee de Forest. :Q3: Who invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics? :A3: Edwin H. Armstrong and Lee de Forest. Early radios ran the entire power of the transmitter through a carbon microphone. While some early radios used some type of amplification through electric current or battery, through the mid 1920s the most common type of receiver was the crystal set. In the 1920s, amplifying vacuum tubes revolutionized both radio receivers and transmitters.

Discovery and development

The theoretical basis of the propagation of electromagnetic waves was first described in 1873 by James Clerk Maxwell in his paper to the Royal Society A dynamical theory of the electromagnetic field, which followed his work between 1861 and 1865. In 1878 David E. Hughes was the first to transmit and receive radio waves when he noticed that his induction balance caused noise in the receiver of his homemade telephone. He demonstrated his discovery to the Royal Society in 1880 but was told it was merely induction. It was Heinrich Rudolf Hertz who, between 1886 and 1888, first validated Maxwell's theory through experiment, demonstrating that radio radiation had all the properties of waves (now called Hertzian waves), and discovering that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. William Henry Ward was issued on April 30, 1872. Mahlon Loomis was issued on July 30, 1872. Landell de Moura, a Brazilian priest and scientist, conducted experiments after 1893 (but at least by 1894). He did not publicize his achievement until 1900. Claims have been made that Nathan Stubblefield invented radio before either Tesla or Marconi, but his device seems to have worked by induction transmission rather than radio transmission.

Wireless age

In 1893 in St. Louis, Missouri, Tesla made devices for his experiments with the electricity. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of their work. [http://www.ieee-virtual-museum.org/collection/people.php?taid=&id=1234597&lid=1] They contained all the elements that were later incorporated into radio systems before the development of the vacuum tube. He initially experimented with magnetic receivers, unlike the coherers used by Marconi and other early experimenters. [http://www.teslasociety.com/teslarec.pdf]. Tesla is usually considered the first to apply the mechanism of electrical conduction to wireless practices. On 19 August 1894, British physicist Sir Oliver Lodge demonstrated the reception of Morse code signalling using radio waves using a detecting device called a coherer, a tube filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884. Edouard Branly of France and Popov of Russia later produced improved versions of the coherer. Alexander Popov, who was the first to develop a practical communication system based on the coherer, is usually considered to have been the inventor of radio. In 1894 he built a coherer and presented it to the Russian Physical and Chemical Society on May 7 1895 [http://www.ieee.org/organizations/history_center/milestones_photos/popov.html]. In March 1896, he effected transmission of radio waves between different campus buildings in Saint Petersburg, but didn't care to apply for a patent. The Indian physicist, Jagdish Chandra Bose, during the years 1894-1900, performed pioneering research on radio waves and created waves as short as 5 mm. [http://www.ieee-virtual-museum.org/collection/people.php?taid=&id=1234735&lid=1] In November 1894 J.C. Bose ignited gunpowder and rang a bell at a distance using electromagnetic waves, confirming that communication signals can be sent without using wires. But he was not interested in patenting his work too. In 1896 Marconi was awarded what is sometimes recognised as the world's first patent for radio with British Patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for. In 1897 he established the world's first radio station on the Isle of Wight, England. The same year in the U.S., some key developments in radio's early history were created and patented by Tesla. The U.S. Patent Office reversed its decision in 1904, awarding Marconi a patent for the invention of radio, possibly influenced by Marconi's financial backers in the States, who included Thomas Edison and Andrew Carnegie. Some believe this was made for financial reasons, allowing the U.S. government to avoid having to pay the royalties that were being claimed by Tesla for use of his patents. In 1909, Marconi, with Karl Ferdinand Braun, was also awarded the Nobel Prize in Physics for "contributions to the development of wireless telegraphy". However, Tesla's patent (number 645576) was reinstated in 1943 by the U.S. Supreme Court, shortly after his death. This decision was based on the fact that prior art existed before the establishment of Marconi's patent. Some believe the decision was also made for financial reasons, to allow the U.S. government to avoid having to pay damages that were being claimed by the Marconi Company for use of its patents during World War I.

"Wireless" factories and vacuum tubes

Marconi opened the world's first "wireless" factory in Hall Street, Chelmsford, England in 1898, employing around 50 people. Around 1900, Tesla opened the Wardenclyffe Tower facility and advertised services. By 1903, the tower structure neared completion. Various theories exist on how Tesla intended to achieve the goals of this wireless system (reportedly, a 200 kW system). Tesla claimed that Wardenclyffe, as part of a World System of transmitters, would have allowed secure multichannel transceiving of information, universal navigation, time synchronization, and a global location system. The next great invention was the vacuum tube detector, invented by a team of Westinghouse engineers. On Christmas Eve, 1906, Reginald Fessenden (using his heterodyne principle) transmitted the first radio audio broadcast in history from Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible. The world's first radio news program was broadcast August 31, 1920 by station 8MK in Detroit, Michigan. The world's first regular wireless broadcasts for entertainment commenced in 1922 from the Marconi Research Centre at Writtle near Chelmsford, England.

20th century

Developments in the early 20th century (1900-1959):
- Aircraft used commercial AM radio stations for navigation. This continued through the early 1960s when VOR systems finally became widespread (though AM stations are still marked on U.S. aviation charts).
- In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes.
- Radio was used to transmit pictures visible as television as early as the 1920s. Standard analog transmissions started in North America and Europe in the 1940s.
- In 1954, Regency introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5V Battery". Developments in the latter half of the 20th century (1960-1999):
- In 1960, Sony introduced their first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was durable, because there were no tubes to burn out. Over the next twenty years, transistors displaced tubes almost completely except for very high power, or very high frequency, uses.
- In 1963 color television was commercially transmitted, and the first (radio) communication satellite, TELSTAR, was launched.
- In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links.
- In the 1970s, LORAN became the premier radio navigation system. Soon, the U.S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987.
- In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software radio that could become a different radio on the fly by changing software.
- Digital transmissions began to be applied to broadcasting in the late 1990s.

Uses of radio

software radio software radio Many of radio's early uses were maritime, for sending telegraphic messages using Morse code between ships and land. One of the earliest users included the Japanese Navy scouting the Russian fleet during the Battle of Tsushima in 1905. One of the most memorable uses of marine telegraphy was during the sinking of the RMS Titanic in 1912, including communications between operators on the sinking ship and nearby vessels, and communications to shore stations listing the survivors. Radio was used to pass on orders and communications between armies and navies on both sides in World War I; Germany used radio communications for diplomatic messages once its submarine cables were cut by the British. The United States passed on President Woodrow Wilson's Fourteen Points to Germany via radio during the war. Broadcasting began to become feasible in the 1920s, with the widespread introduction of radio receivers, particularly in Europe and the United States. Besides broadcasting, point-to-point broadcasting, including telephone messages and relays of radio programs, became widespread in the 1920s and 1930s. Another use of radio in the pre-war years was the development of detecting and locating aircraft and ships by the use of radar (RAdio Detecting And Ranging). Today, radio takes many forms, including wireless networks, mobile communications of all types, as well as radio broadcasting. Read more about radio's history. Before the advent of television, commercial radio broadcasts included not only news and music, but dramas, comedies, variety shows, and many other forms of entertainment. Radio was unique among dramatic presentation that it used only sound. For more, see radio programming. There are a number of uses of radio:

Audio

- AM broadcast radio sends music and voice in the Medium Frequency (MF—0.300 MHz to 3 MHz) radio spectrum. AM radio uses amplitude modulation, in which louder sounds at the microphone causes wider fluctuations in the transmitter power while the transmitter frequency remains unchanged. Transmissions are affected by static because lightning and other sources of radio add their radio waves to the ones from the transmitter.
- FM broadcast radio sends music and voice, with higher fidelity than AM radio. In frequency modulation, louder sounds at the microphone cause the transmitter frequency to fluctuate farther, the transmitter power stays constant. FM is transmitted in the Very High Frequency (VHF—30 MHz to 300 MHz) radio spectrum. FM requires more radio frequency space than AM and there are more frequencies available at higher frequencies, so there can be more stations, each sending more information. Another effect is that shorter VHF radio waves act more like light, travelling in straight lines, hence the reception range is generally limited to about 50-100 miles. During unusual upper atmospheric conditions, FM signals are occasionally reflected back towards the Earth by the ionosphere, resulting in Long distance FM reception. FM receivers are subject to the capture effect, which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.
- FM Subcarrier services are secondary signals transmitted "piggyback" along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as reading services for the blind, background music or stereo sound signals. In some extremely crowded metropolitan areas, the subchannel program might be an alternate foreign language radio program for various ethnic groups. Subcarriers can also transmit digital data, such as station identification, the current song's name, web addresses, or stock quotes. In some countries, FM radios automatically retune themselves to the same channel in a different district by using sub-bands.
- Aviation voice radios use VHF AM. AM is used so that multiple stations on the same channel can be received. (Use of FM would result in stronger stations blocking out reception of weaker stations due to FM's capture effect). Aircraft fly high enough that their transmitters can be received hundreds of miles (kilometres) away, even though they are using VHF.
- Marine voice radios can use AM in the shortwave High Frequency (HF—3 MHz to 30 MHz) radio spectrum for very long ranges or narrowband FM in the VHF spectrum for much shorter ranges.
- Government, police, fire and commercial voice services use narrowband FM on special frequencies. Fidelity is sacrificed to use a smaller range of radio frequencies, usually five kilohertz of deviation (5 thousand cycles per second), rather than the 75 used by FM broadcasts and 25 used by TV sound.
- Civil and military HF (high frequency) voice services use shortwave radio to contact ships at sea, aircraft and isolated settlements. Most use single sideband voice (SSB), which uses less bandwidth than AM. SSB sounds like ducks quacking on an AM radio. Viewed as a graph of frequency versus power, an AM signal shows power where the frequencies of the voice add and subtract with the main radio frequency. SSB cuts the bandwidth in half by suppressing the carrier and (usually) lower sideband. This also makes the transmitter about three times more powerful, because it doesn't need to transmit the unused carrier and sideband.
- TETRA, Terrestrial Trunked Radio is a digital cell phone system for military, police and ambulances.
- Commercial services such as XM and Sirius offer digital Satellite radio.

Telephony

- Cell phones transmit to a local cell transmitter/receiver site, which connects to the public service telephone network through an optic fiber or microwave radio. When the phone leaves the cell radio's area, the central computer switches the phone to a new cell. Cell phones originally used FM, but now most use various digital encodings.
- Satellite phones come in two types: INMARSAT and Iridium. Both types provide world-wide coverage. INMARSAT uses geosynchronous satellites, with aimed high-gain antennas on the vehicles. Iridium provides cell phones, except the cells are satellites in orbit.

Video

- Television sends the picture as AM, and the sound as FM, on the same radio signal.
- Digital television encodes three bits as eight strengths of AM signal. The bits are sent out-of-order to reduce the effect of bursts of radio noise. A Reed-Solomon error correction code lets the receiver detect and correct errors in the data. Although any data could be sent, the standard is to use MPEG-2 for video, and five CD-quality (44.1 kHz) audio channels (center, left, right, left-back and right back). With all this, it takes only half the bandwidth of an analog TV signal because the video data is compressed.

Navigation

- All satellite navigation systems use satellites with precision clocks. The satellite transmits its position, and the time of the transmission. The receiver listens to four satellites, and can figure its position as being on a line that is tangent to a spherical shell around each satellite, determined by the time-of-flight of the radio signals from the satellite. A computer in the receiver does the math.
- Loran systems also used time-of-flight radio signals, but from radio stations on the ground.
- VOR systems (used by aircraft), have a antenna array that transmits two signals simultaneously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuring the difference in phase of these two signals, an aircraft can determine its bearing from the station. An aircraft can get readings from two VORs, and locate its position at the intersection of the two beams.
- Radio direction-finding is the oldest form of radio navigation. Before 1960 navigators used movable loop antennas to locate commercial AM stations near cities. In some cases they used marine radiolocation beacons, which share a range of frequencies just above AM radio with amateur radio operators.

Radar

- Radar detects things at a distance by bouncing radio waves off them. The delay caused by the echo measures the distance. The direction of the beam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface.
- Navigational radars scan a wide area two to four times per minute. They use very short waves that reflect from earth and stone. They are common on commercial ships and long-distance commercial aircraft
- General purpose radars generally use navigational radar frequencies, but modulate and polarize the pulse so the receiver can determine the type of surface of the reflector. The best general-purpose radars distinguish the rain of heavy storms, as well as land and vehicles. Some can superimpose sonar data and map data from GPS position.
- Search radars scan a wide area with pulses of short radio waves. They usually scan the area two to four times a minute. Sometimes search radars use the doppler effect to separate moving vehicles from clutter.
- Targeting radars use the same principle as search radar but scan a much smaller area far more often, usually several times a second or more.
- Weather radars resemble search radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weather radar use the doppler to measure wind speeds.

Emergency services

- emergency position-indicating rescue beacons (EPIRBs), emergency locating transmitters or personal locator beacons are small radio transmitters that satellites can use to locate a person or vehicle needing rescue. Their purpose is to help rescue people in the first day, when survival is most likely. There are several types, with widely-varying performance.

Data (digital radio)

- The oldest form of digital broadcast was spark gap telegraphy, used by pioneers such as Marconi. By pressing the key, the operator could send messages in Morse code by energizing a rotating commutating spark gap. The rotating commutator produced a tone in the receiver, where a simple spark gap would produce a hiss, indistinguishable from static. Spark gap transmitters are now illegal, because their transmissions span several hundred megahertz. This is very wasteful of both radio frequencies and power.
- The next advance was continuous wave telegraphy, or CW, in which a pure radio frequency, produced by a vacuum tube electronic oscillator was switched on and off by a key. A receiver with a local oscillator would "heterodyne" with the pure radio frequency, creating a whistle-like audio tone. CW uses less than 100Hz of bandwidth. CW is still used, these days primarily by amateur radio operators (hams). Strictly, on-off keying of a carrier should be known as "Interrupted Continuous Wave" or ICW.
- Radio teletypes usually operate on short-wave (HF) and are much loved by the military because they create written information without a skilled operator. They send a bit as one of two tones. Groups of five or seven bits become a character printed by a teletype. From about 1925 to 1975, radio teletype was how most commercial messages were sent to less developed countries. These are still used by the military and weather services.
- Aircraft use a 1200 Baud radioteletype service over VHF to send their ID, altitude and position, and get gate and connecting-flight data.
- Microwave dishes on satellites, telephone exchanges and TV stations usually use quadrature amplitude modulation (QAM). QAM sends data by changing both the phase and the amplitude of the radio signal. Engineers like QAM because it packs the most bits into a radio signal. Usually the bits are sent in "frames" that repeat. A special bit pattern is used to locate the beginning of a frame.
- Systems that need reliability, or that share their frequency with other services may use "corrected orthogonal frequency-division multiplexing" or COFDM. COFDM breaks a digital signal into as many as several hundred slower subchannels. The digital signal is often sent as QAM on the subchannels. Modern COFDM systems use a small computer to make and decode the signal with digital signal processing, which is more flexible and far less expensive than older systems that implemented separate electronic channels. COFDM resists fading and ghosting because the narrow-channel QAM signals can be sent slowly. An adaptive system, or one that sends error-correction codes can also resist interference, because most interference can affect only a few of the QAM channels. COFDM is used for WiFi, some cell phones, Digital Radio Mondiale, Eureka 147, and many other local area network, digital TV and radio standards.
- Most new radio systems are digital, see also:Digital TV, Satellite Radio, Digital Audio Broadcasting.

Heating

Radio-frequency energy generated for heating of objects is generally not intended to radiate outside of the generating equipment, to prevent interferance with other radio signals.
- Microwave ovens use intense radio waves to heat food. (Note: It is a common misconception that the radio waves are tuned to the resonant frequency of water molecules. The microwave frequencies used are actually about a factor of 10 below the resonant frequency.)
- Diathermy equipment is used in surgery for sealing of blood vessels.
- Induction furnaces are used for melting metal for casting.

Mechanical Force

- Tractor beams: Radio waves exert small electrostatic and magnetic forces. These are enough to perform station-keeping in microgravity environments.
- Conceptually, Spacecraft propulsion: Radiation pressure from intense radio waves has been proposed as a propulsion method for an interstellar probe called Starwisp. Since the waves are long, the probe could be a very light-weight metal mesh, and thus achieve higher accelerations than if it were a solar sail.

Other

solar sail
- Amateur radio is a hobby where enthusiasts who purchase or build their own equipment and use radio for their own enjoyment. They may also provide an emergency and public-service radio service. This has been of great use, saving lives in many instances. Radio amateurs are able to use frequencies in a large number of narrow bands throughout the radio spectrum. Radio amateurs use all forms of encoding, including obsolete and experimental ones. Several forms of radio were pioneered by radio amateurs and later became commercially important, including FM, single-sideband AM, digital packet radio and satellite repeaters.
- Personal radio services such as Citizens' Band Radio, Family Radio Service, Multi-Use Radio Service and others exist in North America to provide simple, (usually) short range communication for individuals and small groups, without the overhead of licensing. Similar services exist in other parts of the world.
- Wireless energy transfer: A number of schemes have been proposed that transmit power using microwaves, and the technique has been demonstrated. (See Microwave power transmission). These schemes include, for example, solar power stations in orbit beaming energy down to terrestrial users.
- Radio remote control: Use of radio waves to transmit control data to a remote object as in some early forms of guided missile, some early TV remotes and a range of model boats, cars and aeroplanes. Large industrial remote-controlled equipment such as cranes and switching locomotives now usually use digital radio techniques to ensure safety and reliability.