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Aquitaine

Aquitaine (,, ; Aquitània ; Akitania; Poitevin-Saintongeais: Aguiéne), archaic Guyenne or Guienne (Guiana), is a historical region of Southwestern France and a former administrative region. Since 1 January 2016 it has been part of the administrative region of Nouvelle-Aquitaine. It is situated in the southwest corner of metropolitan France, along the Atlantic Ocean and the Pyrenees mountain range on the border with Spain; for most of its written history Bordeaux has been a vital port and administrative centre. It is composed of the five departments of Dordogne, Lot-et-Garonne, Pyrénées-Atlantiques, Landes and Gironde. Gallia Aquitania was established by the Romans in ancient times and in the Middle Ages, Aquitaine was a kingdom and a duchy, whose boundaries fluctuated considerably.

Ancient history
There are traces of human settlement by prehistoric peoples, especially in the Périgord, but the earliest attested inhabitants in the south-west were the Aquitani, who were not considered Celtic people, but more akin to the Iberians (see Gallia Aquitania). Although a number of different languages and dialects were in use in the area during ancient times, it is most likely that the prevailing language of Aquitaine during the late pre-historic to Roman period was an early form of the Basque language. This has been demonstrated by various Aquitanian names and words that were recorded by the Romans, and which are currently easily readable as Basque. Whether this Aquitanian language (Proto-Basque) was a remnant of a Vasconic language group that once extended much farther, or it was generally limited to the Aquitaine/Basque region is not known. One reason the language of Aquitaine is important is because Basque is the last surviving non-Indo-European language in western Europe and it has had some effect on the languages around it, including Spanish and, to a lesser extent, French.

The original Aquitania (named after the inhabitants) at the time of Caesar's conquest of Gaul included the area bounded by the river Garonne, the Pyrenees and the Atlantic Ocean. The name may stem from Latin 'aqua', maybe derived from the town "Aquae Augustae", "Aquae Tarbellicae" or just "Aquis" (Dax, Akize in modern Basque) or as a more general geographical feature. Under Augustus' Roman rule, from 27 BCE the province of Aquitania was further stretched to the north to the river Loire, thus including proper Gaul tribes along with old Aquitani south of the Garonne (cf. Novempopulania and Gascony) within the same region.

In 392, the Roman imperial provinces were restructured as Aquitania Prima (north-east), Aquitania Secunda (centre) and Aquitania Tertia, better known as Novempopulania in the south-west.

Early Middle Ages
Accounts of Aquitania during the Early Middle Ages are imprecise, but there was much unrest. The Visigoths were called into Gaul as foederati, legalizing their status within the Empire. Eventually they established themselves as the de facto rulers in south-west Gaul as central Roman rule collapsed. Visigoths established their capital in Toulouse, but their tenure on Aquitaine was feeble. In 507, they were expelled south to Hispania after their defeat in the Battle of Vouillé by the Franks, who became the new rulers in the area to the south of the Loire.

The Roman Aquitania Tertia remained in place as Novempopulania, where a duke was appointed to hold a grip over the Basques (Vascones/Wascones, rendered Gascons in English). These dukes were quite detached from central Frankish overlordship, sometimes governing as independent rulers with strong ties to their kinsmen south of the Pyrenees. As of 660, the foundations for an independent Aquitaine/Vasconia polity were established by the duke Felix of Aquitaine, a magnate (potente(m)) from Toulouse, probably of Gallo-Roman stock. Despite its nominal submission to the Merovingians, the ethnic make-up of the new Aquitanian realm was not Frankish, but Gallo-Roman north of the Garonne and in main towns and Basque, especially south of the Garonne.

A united Basque-Aquitanian realm reached its heyday under Odo the Great's rule. In 721, the Aquitanian duke fended Umayyad troops (Sarracens) off at Toulouse, but in 732 (or 733, according to Roger Collins), an Umayyad expedition commanded by Abdul Rahman Al Ghafiqi defeated Odo next to Bordeaux, and went on to loot its way up to Poitiers. Odo was required to pledge allegiance to the Frankish Charles Martel in exchange for help against the advancing Arab forces. Basque-Aquitanian self-rule temporarily came to a halt, definitely in 768 after the assassination of Waifer.

In 781, Charlemagne decided to proclaim his son Louis King of Aquitaine within the Carolingian Empire, ruling over a realm comprising the Duchy of Aquitaine and the Duchy of Vasconia. He suppressed various Basque (Gascon) uprisings, even venturing into the lands of Pamplona past the Pyrenees after ravaging Gascony, with a view to imposing his authority also in the Vasconia to south of Pyrenees. According to his biography, he achieved everything he wanted and after staying overnight in Pamplona, on his way back his army was attacked in Roncevaux in 812, but narrowly escaped an engagement at the Pyrenean passes.

Seguin (Sihiminus), count of Bordeaux and Duke of Vasconia, seemed to have attempted a detachment from the Frankish central authority on Charlemagne's death. The new emperor Louis the Pious reacted by removing him from his capacity, which stirred the Basques into rebellion. The king in turn sent his troops to the territory, obtaining their submission in two campaigns and killing the duke, while his family crossed the Pyrenees and continued to foment risings against Frankish power. In 824, the 2nd Battle of Roncevaux took place, in which counts Aeblus and Aznar, Frankish vassals from the Duchy of Vasconia sent by the new King of Aquitaine, Pepin, were captured by the joint forces of Iñigo Arista and the Banu Qasi.

Before Pepin's death, emperor Louis had appointed a new king in 832, his son Charles the Bald, while the Aquitanian lords elected Pepin II as king. This struggle for control of the kingdom led to a constant period of war between Charles, loyal to his father and the Carolingian power, and Pepin II, who relied more on the support of Basque and Aquitanian lords.

Ethnic make-up in the Early Middle Ages
Despite the early conquest of southern Gaul by the Franks after the Battle of Vouillé in 507, the Frankish element was feeble south of the Loire, where Gothic and Gallo-Roman Law prevailed and a small Frankish settlement took place. However scarce, some Frankish population and nobles settled down in regions like Albigeois, Carcassonne (on the fringes of Septimania), Toulouse, and Provence and Lower Rhone (the last two not in Aquitaine). After the death of the king Dagobert I, the Merovingian tenure south of the Loire became largely nominal, with the actual power being in the hands of autonomous regional leaders and counts. The Franks may have become largely assimilated to the preponderant Gallo-Roman culture by the 8th century, but their names were well in use by the ruling class, like Odo. Still, in the Battle of Toulouse, the Aquitanian duke Odo was said to be leading an army of Aquitanians and Franks.

On the other hand, the Franks did not mix with the Basques, keeping separate paths. In the periods before and after the Muslim thrust, the Basques are often cited in several accounts stirring against Frankish attempts to subdue Aquitaine (stretching up to Toulouse) and Vasconia, pointing to a not preponderant but clearly significant Basque presence in the former too. Recorded evidence points to their deployment across Aquitaine in a military capacity as a mainstay of the Duke's forces. 'Romans' are cited as living in the cities of Aquitaine, as opposed to the Franks (mid 8th century).

Aquitaine after the Treaty of Verdun
After the 843 Treaty of Verdun, the defeat of Pepin II and the death of Charles the Bald, the Kingdom of Aquitaine (subsumed in West Francia) ceased to have any relevance and the title of King of Aquitaine took on a nominal value. In 1058, the Duchy of Vasconia (Gascony) and Aquitaine merged under the rule of William VIII, Duke of Aquitaine.

The title "Duke of Aquitaine" was held by the counts of Poitiers from the 10th to the 12th century.

English Aquitaine
Aquitaine passed to France in 1137 when the duchess Eleanor of Aquitaine married Louis VII of France, but their marriage was annulled in 1152. When Eleanor's new husband became King Henry II of England in 1154, the area became an English possession, and a cornerstone of the Angevin Empire. Aquitaine remained English until the end of the Hundred Years' War in 1453, when it was annexed by France.

During the three hundred years that the region was ruled by the Kings of England, links between Aquitaine and England strengthened, with large quantities of wine produced in southwestern France being exported to London, Southampton, and other English ports. In fact, so much wine and other produce was being exported to London and sold that by the start of the Hundred Years' War the profits from Aquitaine were the principal source of the English King's income per annum.

After the Hundred Years' War
The region served as a stronghold for the Protestant Huguenots during the 16th and 17th centuries, who suffered persecution at the hands of the French Catholics. The Huguenots called upon the English crown for assistance against forces led by Cardinal Richelieu.

From the 13th century until the French Revolution, Aquitaine was usually known as Guyenne.

Demographics
Aquitaine consists of 3,150,890 inhabitants, equivalent to 6% of the total French population.

The region of Aquitaine forms the 6th most populated region in France.

Language
French is the official language of the region. Many residents also have some knowledge of Basque, of a variety of Occitan (Gascon, Limousin, or Languedocien), or of the Poitevin-Saintongeais dialect of French.

In 2005, 78,000 children were learning Occitan as a second language in state schools and 2,000 were enrolled in Occitan-medium private schools.

Basque speakers number about 73,000, concentrated in the far south of the region:
 * Labourd: 37% of the population (38,600 bilingual, 24,000 able to read and understand)
 * Lower Navarre and Soule: 76% of the population (28,000 bilingual, 7,000 able to read and understand)

Important cities
Bordeaux is the largest city in Aquitaine. It is a port city on the Garonne River in the Gironde department. It is the capital of Aquitaine, as well as the prefecture of the Gironde department. Bordeaux is famous for its wine industry. Apart from Bordeaux, there are also other important cities in Aquitaine.

 * Bordeaux
 * Pau
 * Mérignac
 * Pessac
 * Bayonne
 * Périgueux
 * Talence
 * Anglet
 * Agen
 * Mont-de-Marsan
 * Dax

Sport
The region is home to many successful sports teams. In particular worth mentioning are:

Football
 * FC Girondins de Bordeaux, one of France's most successful association football teams.
 * Pau FC
 * FC Libourne-Saint-Seurin

Rugby union is particularly popular in the region. Clubs include:
 * SU Agen
 * Aviron Bayonnais
 * Biarritz Olympique, runners-up in the 2005–6 Heineken Cup.
 * Union Bordeaux-Bègles
 * Section Paloise
 * Stade Montois
 * US Dax

Basketball
 * Élan Béarnais Pau-Orthez one of the most successful French basketball clubs

Bull-fighting is also popular in the region.

Major surfing championships regularly take place on Aquitaine's coast.

title: Aquitaine


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East Anglia

East Anglia is an area in the East of England. It comprises the counties of Norfolk and Suffolk and Cambridgeshire, with Essex also included in some definitions. The name derives from the Anglo-Saxon kingdom of the East Angles, a people whose name originated in Anglia, in what is now Northern Germany.

Area
Definitions of what constitutes East Anglia vary. The Kingdom of East Anglia, established by Anglo-Saxons in the 6th century, originally consisted of the modern counties of Norfolk and Suffolk and expanded west into at least part of Cambridgeshire, typically the northernmost parts known as The Fens. The contemporary NUTS 2 statistical unit of East Anglia comprises Norfolk, Suffolk and Cambridgeshire (including the City of Peterborough unitary authority). Those three counties have formed the Roman Catholic Diocese of East Anglia since 1976, and were the subject of a possible government devolution package in 2016.

Essex has sometimes been included in definitions of East Anglia, including by the London Society of East Anglians. Although the Kingdom of Essex to the south was a separate element of the Heptarchy of Anglo-Saxon England and did not identify as Angles but Saxons, many people in Essex today still consider themselves to be East Anglian. For example, Colchester United F.C. is one of the clubs competing for the informal football title Pride of Anglia, but not Southend United F.C. from further south in the county. Culturally, north Essex has much more in common with Suffolk and the rest of East Anglia due to its similar rural landscape, when compared to the south which is much more urban given its proximity to London. However, the county of Essex by itself forms a NUTS 2 statistical unit in the East of England region. Other definitions of the area have been used or proposed over the years. For example, the Redcliffe-Maud Report in 1969, which followed the Royal Commission on the Reform of Local Government, recommended the creation of eight provinces in England. The proposed East Anglia province would have included northern Essex, southern Lincolnshire and a small part of Northamptonshire as well as Cambridgeshire, Norfolk and Suffolk.

Places described as the "gateway" to East Anglia include the Cambridgeshire towns of Ely and St Neots (traditionally in Huntingdonshire).

East Anglian cities Peterborough and Cambridge have consistently been on the U.K.'s fastest growing cities in both population and economy. Compared to the rest of the U.K., East Anglia alongside the East of England has the fastest growth by population in the country.

The largest city and urban area in East Anglia is Peterborough with an urban population of 215,673 and a total population of 217,705 as of Census 2021.

History
The kingdom of East Anglia initially consisted of Norfolk and Suffolk, but the Isle of Ely also became part of it upon the marriage of East Anglian princess Æthelthryth. It was formed around 520 by merging the North and South Folk, Angles who had settled in the former lands of the Iceni during the previous century, and it was one of the Anglo-Saxon kingdoms of the heptarchy as defined in the 12th-century writings of Henry of Huntingdon. East Anglia has been cited by a number of scholars as being a region where settlement of continental Germanic speakers was particularly early and dense,  possibly following a depopulation in the fourth century.

A 2016 study found that modern East Anglians share a strong genetic affinity with early medieval skeletons, but differ substantially from Iron Age and Roman era ones, which are more similar to the Welsh. This was taken to support a major influence of the Anglian migrations on the genetic makeup of East Anglia. In a 2022 study by Joscha Gretzinger et al., the populations of Norfolk and Suffolk were found to be the group with the lowest amount of Iron Age/Roman period British Isles-related ancestry, with only about 11-17.5% of their ancestry being derived from that group, while having one of the highest amounts of Continental North European (43.8-50.7%), and the highest amount of Continental West European (32.2-43.1%) ancestry in all of England.

East Anglia was the most powerful of the Anglo-Saxon kingdoms of England for a brief period following a victory over the rival kingdom of Northumbria around 616, and its King Rædwald was Bretwalda (overlord of the Anglo-Saxon kingdoms). However, this did not last; the Mercians defeated it twice over the next 40 years, and East Anglia continued to weaken in relation to the other kingdoms. Offa of Mercia finally had king Æthelberht killed in 794 and took control of the kingdom himself. Independence was temporarily restored by rebellion in 825, but the Danes killed King Edmund on 20 November 869 and captured the kingdom. Edward the Elder incorporated East Anglia into the Kingdom of England, and it later became an earldom.

Parts of East Anglia remained marshland until the 17th century drainage of the Fens, despite some earlier engineering work during the Roman occupation. The alluvial land was converted into wide swaths of productive arable land by a series of systematic drainage projects, mainly using drains and river diversions along the lines of Dutch practice. In the 1630s, thousands of Puritan families from East Anglia emigrated to New England in America, taking much East Anglian culture with them that can still be traced today. East Anglia based much of its earnings on wool, textiles, and arable farming and was a rich area of England until the Industrial Revolution caused a manufacturing and development shift to the Midlands and the North.

During the Second World War, the Royal Air Force and the United States Army Air Force constructed many airbases in East Anglia for the heavy bomber fleets of the Combined Bomber Offensive against German-occupied Europe. East Anglia was ideally suited to airfield construction, as it includes large areas of open, level terrain and is close to mainland Europe. Many of the airfields can still be seen today, particularly from aerial photographs, and a few remain in use, the most prominent being Norwich International Airport. Pillboxes were erected in 1940 to help defend the nation against invasion, and they can also be found throughout the area at strategic points. Similarly, but from the Napoleonic Wars, a number of Martello towers can be found along the coast.

Geography
East Anglia is bordered to the north and east by the North Sea, to the south by the estuaries of the rivers Orwell and Stour, and shares an undefined land border to the west with the rest of England. Much of northern East Anglia is flat, low-lying and marshy (such as the Fens of Cambridgeshire and Norfolk), although the extensive drainage projects of the past centuries and very low rainfall actually make East Anglia the driest area of England. Inland, much of the rest of Suffolk and Norfolk is gently undulating, with glacial moraine ridges providing some areas of steeper relief. The highest point in Norfolk is the 103 m Beacon Hill; the supposed flatness of Norfolk is noted in literature, including Noël Coward's Private Lives – "Very flat, Norfolk".

On the north-west corner East Anglia is bordered by a bay known as The Wash, where owing to deposits of sediment and land reclamation, the coastline has altered markedly within historical times; several towns once on the coast of the Wash (notably King's Lynn) are now some distance inland. Conversely, over to the east on the coast exposed to the North Sea the coastline is subject to rapid erosion and has shifted inland significantly since historic times.

Major rivers include the River Nene and Suffolk's Stour, running through country beloved of the painter John Constable. The River Cam is a tributary of the Great Ouse and gives its name to Cambridge, whilst Norwich sits on the River Yare and River Wensum. The River Orwell flows through Ipswich and has its mouth, along with the Stour at Felixstowe. The Norfolk and Suffolk Broads form a network of waterways between Norwich and the coast and are popular for recreational boating. The Ouse flows into the Wash at King's Lynn.

Major urban areas in East Anglia include the cities of Norwich, Cambridge and Peterborough, and the town of Ipswich. Other towns and cities include Bury St Edmunds, Ely, Lowestoft, Great Yarmouth and King's Lynn. Much of the area is still rural in nature with many villages surrounded by a mixture of breckland, fens, broads and agricultural land.

East Anglia was once covered in extensive forests dating back thousands of years. Recent studies have revealed that around 4,000 years ago, the East Anglian Fens were home to a vast yew forest. This discovery was made through the analysis of over 400 well-preserved yew tree trunks, known as 'bog oaks', which were unearthed by farmers during deep ploughing. These ancient yews thrived between approximately 5,200 and 4,200 years ago, indicating that a dense native woodland, including oak and yew, covered the Fens during that period. Research suggests that the reason for its sudden collapse approx. 4,200 years ago was a sudden and dramatic rise in the North Sea which flooded the fens, covering the landscape in salt and killing all the trees. Over time, much of East Anglia's ancient woodland was cleared for agriculture and other human activities. By the time of the Domesday Book in 1086, only about 15% of England was woodland or wood-pasture. The agricultural areas of East Anglia saw some of the most dramatic declines in woodland cover. By 1870, woodland cover in England had fallen below 5%. Despite the extensive clearance, some ancient woodlands still survive in East Anglia. These are typically defined as areas of woodland that have persisted since 1600 in England. Notable examples in East Anglia include Thetford Forest, the largest lowland pine forest in Britain, Hainault Forest in Essex, home to approx. 4,000 ancient hornbeam pollards, and The Thicks in Staverton, with about 4,000 ancient oak pollards.

Climate
The climate of East Anglia is generally dry and mild. Temperatures range from an average of 1–10 °C in the winter to 12–25 °C in the summer, although it is not uncommon for daily temperatures to fall and rise significantly outside these averages. Although water plays a significant role in the Fenland and Broadland landscapes, the area is among the driest in the United Kingdom and during the summer months, tinder-dry conditions are frequently experienced, occasionally resulting in field and heath fires. Many areas receive less than 700 mm of rainfall a year and this is fairly evenly distributed throughout the year. Sunshine totals tend to be higher towards the coastal areas.

Transport

Transport in East Anglia consists of an extensive road and rail network. Main A roads, such as the A12 and A47 link the area to the rest of the UK, and the A14 links the Midlands to the Port of Felixstowe. This is the busiest container port in the UK, dealing with over 40% of UK container traffic and is a major gateway port into the country. There is very little motorway within East Anglia.

The East Anglia franchise covers many of the railways in the region. Rail links include the Great Eastern Main Line from Norwich to London Liverpool Street and the West Anglia Main Line connecting Cambridge to London. Sections of the East Coast Main Line run through the area and Peterborough is an important interchange on this line. The area is linked to the Midlands and north-west England by rail and has a number of local rail services, such as the Bittern Line from Norwich to Sheringham.

East Anglia is ideal for cycling and National Cycle Route 1 passes through it. Cambridge has the largest proportion of its residents in the UK cycling to work with 25% commuting by bicycle. The city is also home to the Cambridgeshire Guided Busway, which at 13.3 miles (21.4 km) was the longest stretch of guided bus-way in the world when it opened in 2011.

The only major commercial airport is Norwich Airport, although London Stansted Airport, the fourth busiest passenger airport in the UK, lies just south of Cambridge in north-west Essex.

Universities
The University of Cambridge, established at the start of the 13th century and in the town of the same name, is East Anglia's best-known institution of higher learning and is among the oldest and most famous universities in the world. Other institutions include the University of East Anglia (in Norwich), University of Essex, Norwich University of the Arts, Anglia Ruskin University (based in Cambridge), University of Suffolk (based in Ipswich) and University Centre Peterborough.

Enterprise zones
Great Yarmouth and Lowestoft Enterprise Zone, an enterprise zone initiated by New Anglia Local Enterprise Partnership, was announced in 2011 and launched in April 2012. It includes six sites with a total area of 121 ha, which have attracted a number of energy-related businesses. The sites are Beacon Park and South Denes in Great Yarmouth, Mobbs Way, Riverside Road and South Lowestoft Industrial Estate in Lowestoft and Ellough Business Park in Ellough near Beccles. There is also an enterprise zone in Cambridgeshire, Alconbury Enterprise Campus in Huntingdon.

Symbols and culture
A shield of three golden crowns, placed two above one, on a blue background has been used as a symbol of East Anglia for centuries. The coat of arms was ascribed by medieval heralds to the Anglo-Saxon Kingdom of East Anglia and the Wuffingas dynasty which ruled it. The arms are effectively identical to the coat of arms of Sweden.

The three crowns appear, carved in stone, on the baptismal font (c. 1400) in the parish church of Saxmundham, and on the 15th-century porch of Woolpit church, both in Suffolk. They also appear in local heraldry and form part of the arms of the diocese of Ely and the arms of the borough of Bury St Edmunds, where the crowns are shown pierced with arrows to represent the martyrdom of Edmund the Martyr, the last king of East Anglia. Other users of the arms include the former Isle of Ely County Council, the Borough of Colchester and the University of East Anglia. The flag of Cambridgeshire (adopted in 2015) includes the three gold crowns on a blue field.

The East Anglian flag, as it is known today, superimposes the three crowns in a blue shield on a St George's cross. It was proposed by George Henry Langham and adopted in 1902 by the London Society of East Anglians (established in 1896).

East Anglia features heavily in English literature, notably in Noël Coward's Private Lives and the history of its waterways and drainage forms the backdrop to Graham Swift's novel Waterland. The area also figures in works by L.P. Hartley, Arthur Ransome, Dorothy L. Sayers, and M.R. James, who grew up in Suffolk and who chose the area as the setting for several of his best-known ghost stories, "A Warning to the Curious" and "'Oh, Whistle, and I'll Come to You, My Lad'" among them.

"Suffolk pink" and similar pastel colours of whitewash are commonly seen on houses in Suffolk, Norfolk and their neighbouring counties.

Tourism
East Anglia has holiday resorts that range from the traditional coastal towns of Felixstowe and Lowestoft in Suffolk and Great Yarmouth and Hunstanton in Norfolk, to towns like Aldeburgh and Southwold in Suffolk. Other tourist attractions include historic towns and cities like Bury St Edmunds, Cambridge and Ely as well as areas such as Constable Country, the Broads and the North Norfolk coast.

Politics
The Conservative Party is dominant in East Anglia. In the 2024 United Kingdom local elections, the Conservatives suffered heavy losses. In the 2019 election, twelve councillors – all Conservative – were returned unopposed to Fenland District Council, which topped the Electoral Reform Society's list of 'rotten boroughs'.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: East Anglia


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Coaxial cable

RG-59.jpg flexible coaxial cable composed of: 1.

2. Outer plastic sheath

3. Woven copper shield

4. Inner dielectric insulator

5. Copper core ]]

Coaxial cable, or coax (pronounced ), is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric (insulating material); many coaxial cables also have a protective outer sheath or jacket. The term coaxial refers to the inner conductor and the outer shield sharing a geometric axis.

Coaxial cable is a type of transmission line, used to carry high-frequency electrical signals with low losses. It is used in such applications as telephone trunk lines, broadband internet networking cables, high-speed computer data busses, cable television signals, and connecting radio transmitters and receivers to their antennas. It differs from other shielded cables because the dimensions of the cable and connectors are controlled to give a precise, constant conductor spacing, which is needed for it to function efficiently as a transmission line.

Coaxial cable was used in the first (1858) and following transatlantic cable installations, but its theory was not described until 1880 by English physicist, engineer, and mathematician Oliver Heaviside, who patented the design in that year (British patent No. 1,407).

Applications
Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers to their antennas, computer network (e.g., Ethernet) connections, digital audio (S/PDIF), and distribution of cable television signals. One advantage of coaxial over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference.

Description
Coaxial cable conducts electrical signals using an inner conductor (usually a solid copper, stranded copper or copper-plated steel wire) surrounded by an insulating layer and all enclosed by a shield, typically one to four layers of woven metallic braid and metallic tape. The cable is protected by an outer insulating jacket. Normally, the outside of the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor. When using differential signaling, coaxial cable provides an advantage of equal push-pull currents on the inner conductor and inside of the outer conductor that restrict the signal's electric and magnetic fields to the dielectric, with little leakage outside the shield. Further, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable, if unequal currents are filtered out at the receiving end of the line. This property makes coaxial cable a good choice both for carrying weak signals that cannot tolerate interference from the environment, and for stronger electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits. Larger diameter cables and cables with multiple shields have less leakage.

Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, and computer and instrumentation data connections.

The characteristic impedance of the cable ($Z_{0}$) is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. In radio frequency systems, where the cable length is comparable to the wavelength of the signals transmitted, a uniform cable characteristic impedance is important to minimize loss. The source and load impedances are chosen to match the impedance of the cable to ensure maximum power transfer and minimum standing wave ratio. Other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield quality.

Construction
Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, and cost. The inner conductor might be solid or stranded; stranded is more flexible. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is often used as an inner conductor for cable used in the cable TV industry.

The insulator surrounding the inner conductor may be solid plastic, a foam plastic, or air with spacers supporting the inner wire. The properties of the dielectric insulator determine some of the electrical properties of the cable. A common choice is a solid polyethylene (PE) insulator, used in lower-loss cables. Solid Teflon (PTFE) is also used as an insulator, and exclusively in plenum-rated cables. Some coaxial lines use air (or some other gas) and have spacers to keep the inner conductor from touching the shield.

Many conventional coaxial cables use braided copper wire forming the shield. This allows the cable to be flexible, but it also means there are gaps in the shield layer, and the inner dimension of the shield varies slightly because the braid cannot be flat. Sometimes the braid is silver-plated. For better shield performance, some cables have a double-layer shield. The shield might be just two braids, but it is more common now to have a thin foil shield covered by a wire braid. Some cables may invest in more than two shield layers, such as "quad-shield", which uses four alternating layers of foil and braid. Other shield designs sacrifice flexibility for better performance; some shields are a solid metal tube. Those cables cannot be bent sharply, as the shield will kink, causing losses in the cable. When a foil shield is used a small wire conductor incorporated into the foil makes soldering the shield termination easier.

For high-power radio-frequency transmission up to about 1 GHz, coaxial cable with a solid copper outer conductor is available in sizes of 0.25 inch upward. The outer conductor is corrugated like a bellows to permit flexibility and the inner conductor is held in position by a plastic spiral to approximate an air dielectric. One brand name for such cable is Heliax.

Coaxial cables require an internal structure of an insulating (dielectric) material to maintain the spacing between the center conductor and shield. The dielectric losses increase in this order: Ideal dielectric (no loss), vacuum, air, polytetrafluoroethylene (PTFE), polyethylene foam, and solid polyethylene. An inhomogeneous dielectric needs to be compensated by a non-circular conductor to avoid current hot-spots.

While many cables have a solid dielectric, many others have a foam dielectric that contains as much air or other gas as possible to reduce the losses by allowing the use of a larger diameter center conductor. Foam coax will have about 15% less attenuation but some types of foam dielectric can absorb moisture—especially at its many surfaces—in humid environments, significantly increasing the loss. Supports shaped like stars or spokes are even better but more expensive and very susceptible to moisture infiltration. Still more expensive were the air-spaced coaxials used for some inter-city communications in the mid-20th century. The center conductor was suspended by polyethylene discs every few centimeters. In some low-loss coaxial cables such as the RG-62 type, the inner conductor is supported by a spiral strand of polyethylene, so that an air space exists between most of the conductor and the inside of the jacket. The lower dielectric constant of air allows for a greater inner diameter at the same impedance and a greater outer diameter at the same cutoff frequency, lowering ohmic losses. Inner conductors are sometimes silver-plated to smooth the surface and reduce losses due to skin effect. A rough surface extends the current path and concentrates the current at peaks, thus increasing ohmic loss.

The insulating jacket can be made from many materials. A common choice is PVC, but some applications may require fire-resistant materials. Outdoor applications may require the jacket to resist ultraviolet light, oxidation, rodent damage, or direct burial. Flooded coaxial cables use a water-blocking gel to protect the cable from water infiltration through minor cuts in the jacket. For internal chassis connections the insulating jacket may be omitted.

Signal propagation
Twin-lead transmission lines have the property that the electromagnetic wave propagating down the line extends into the space surrounding the parallel wires. These lines have low loss, but also have undesirable characteristics. They cannot be bent, tightly twisted, or otherwise shaped without changing their characteristic impedance, causing reflection of the signal back toward the source. They also cannot be buried or run along or attached to anything conductive, as the extended fields will induce currents in the nearby conductors causing unwanted radiation and detuning of the line. Standoff insulators are used to keep them away from parallel metal surfaces. Coaxial lines largely solve this problem by confining virtually all of the electromagnetic wave to the area inside the cable. Coaxial lines can therefore be bent and moderately twisted without negative effects, and they can be strapped to conductive supports without inducing unwanted currents in them, so long as provisions are made to ensure differential signalling push-pull currents in the cable.

In radio-frequency applications up to a few gigahertz, the wave propagates primarily in the transverse electric magnetic (TEM) mode, which means that the electric and magnetic fields are both perpendicular to the direction of propagation. However, above a certain cutoff frequency, transverse electric (TE) or transverse magnetic (TM) modes can also propagate, as they do in a hollow waveguide. It is usually undesirable to transmit signals above the cutoff frequency, since it may cause multiple modes with different phase velocities to propagate, interfering with each other. The outer diameter is roughly inversely proportional to the cutoff frequency. A propagating surface-wave mode that only involves the central conductor also exists, but is effectively suppressed in coaxial cable of conventional geometry and common impedance. Electric field lines for this TM mode have a longitudinal component and require line lengths of a half-wavelength or longer.

Coaxial cable may be viewed as a type of waveguide. Power is transmitted through the radial electric field and the circumferential magnetic field in the TEM mode. This is the dominant mode from zero frequency (DC) to an upper limit determined by the electrical dimensions of the cable.

Connectors
Coaxial connectors are designed to maintain a coaxial form across the connection and have the same impedance as the attached cable. Connectors are usually plated with high-conductivity metals such as silver or tarnish-resistant gold. Due to the skin effect, the RF signal is only carried by the plating at higher frequencies and does not penetrate to the connector body. Silver however tarnishes quickly and the silver sulfide that is produced is poorly conductive, degrading connector performance, making silver a poor choice for this application.

Important parameters
Coaxial cable is a particular kind of transmission line, so the circuit models developed for general transmission lines are appropriate. See Telegrapher's equation.

Physical parameters
In the following section, these symbols are used:

 * Length of the cable, $$\ \ell ~.$$
 * Outside diameter of inner conductor, $$\ d ~.$$
 * Inside diameter of the shield, $$\ D ~.$$
 * Dielectric constant of the insulator, $$\ \epsilon ~.$$ The dielectric constant is often quoted as the relative dielectric constant $$\ \epsilon_\mathsf{r}\ $$ referred to the dielectric constant of free space $$\ \epsilon_\mathsf{o}\ :$$ $$\ \epsilon = \epsilon_\mathsf{r}\ \epsilon_\mathsf{o} ~.$$ When the insulator is a mixture of different dielectric materials (e.g., polyethylene foam is a mixture of polyethylene and air), then the term effective dielectric constant $$\ \epsilon_\mathsf{eff}\ $$ is often used.
 * Magnetic permeability of the insulator, $$\ \mu ~.$$ Permeability is often quoted as the relative permeability $$\ \mu_\mathsf{r}\ $$ referred to the permeability of free space $$\ \mu_\mathsf{o}\ :$$ $$\ \mu = \mu_\mathsf{r}\ \mu_\mathsf{o} ~.$$ The relative permeability will almost always be $1$.

Fundamental electrical parameters

 * Shunt capacitance per unit length, in farads per metre.
 * $$ C = \frac{2 \pi \epsilon}{\ \ln\left(\frac{\ D\ }{d} \right)\ } = \frac{2 \pi \epsilon_\mathsf{o} \epsilon_\mathsf{r} }{\ \ln\left(\frac{\ D\ }{d} \right)\ } $$

 * Series inductance per unit length, in henries per metre, considering the central conductor to be a thin hollow cylinder (due to skin effect).
 * $$ L = \frac{\mu}{\ 2 \pi\ }\ \ln\left(\frac{\ D\ }{d} \right)= \frac{\ \mu_\mathsf{o} \mu_\mathsf{r}\ }{ 2 \pi}\ \ln\left( \frac{\ D\ }{d} \right) $$

 * Series resistance per unit length, in ohms per metre. The resistance per unit length is just the resistance of inner conductor and the shield at low frequencies. At higher frequencies, skin effect increases the effective resistance by confining the conduction to a thin layer of each conductor.
 * Shunt conductance per unit length, in siemens per metre. The shunt conductance is usually very small because insulators with good dielectric properties are used (a very low loss tangent). At high frequencies, a dielectric can have a significant resistive loss.

Derived electrical parameters

 * Characteristic impedance in ohms (Ω). The complex impedance $Z$$o$ of an infinite length of transmission line is:

 * $$ Z_\mathsf{o} = \sqrt{\frac{R + sL\ }{G + sC\ }\ } $$
 * Where $R$ is the resistance per unit length, $L$ is the inductance per unit length, $G$ is the conductance per unit length of the dielectric, $C$ is the capacitance per unit length, and $s = jω = j2πf$ is the frequency. The "per unit length" dimensions cancel out in the impedance formula.
 * At DC the two reactive terms are zero, so the impedance is real-valued, and is extremely high. It looks like
 * $$ Z_\mathsf{DC} = \sqrt{\frac{\ R\ }{G}\ } ~.$$
 * With increasing frequency, the reactive components take effect and the impedance of the line is complex-valued. At very low frequencies (audio range, of interest to telephone systems) $G$ is typically much smaller than $sC$, so the impedance at low frequencies is
 * $$ Z_\mathsf{Low Freq} \approx \sqrt{\frac{R}{\ sC\ }\ }\ ,$$
 * which has a phase value of -45 degrees.
 * At higher frequencies, the reactive terms usually dominate $R$ and $G$, and the cable impedance again becomes real-valued. That value is $Z_{o}$, the characteristic impedance of the cable:
 * $$ Z_\mathsf{o} = \sqrt{\frac{sL}{\ sC\ }\ }= \sqrt{\frac{L}{\ C\ }\ } ~.$$
 * Assuming the dielectric properties of the material inside the cable do not vary appreciably over the operating range of the cable, the characteristic impedance is frequency independent above about five times the shield cutoff frequency. For typical coaxial cables, the shield cutoff frequency is 600 Hz (for RG-6A) to 2,000 Hz (for RG-58C).
 * The parameters $L$ and $C$ are determined from the ratio of the inner ($d$) and outer ($D$) diameters and the dielectric constant ($ε$). The characteristic impedance is given by
 * $$ Z_\mathsf{o} = \frac{1}{\ 2\pi\ }\sqrt{\frac{\mu}{\ \epsilon\ }\ }\ \ln\left( \frac{D}{\ d\ } \right) \approx \frac{\ 59.96\ \mathsf{\Omega}\ }{\sqrt{\epsilon_\mathsf{r}\ } } \ln\left( \frac{D}{\ d\ } \right)  \approx \frac{\ 138\ \mathsf{\Omega}\ }{\sqrt{\epsilon_\mathsf{r}\ } } \log_{10}\left( \frac{D}{\ d\ } \right) ~.$$

 * Attenuation (loss) per unit length, in decibels per meter. This is dependent on the loss in the dielectric material filling the cable, and resistive losses in the center conductor and outer shield. These losses are frequency dependent, the losses becoming higher as the frequency increases. Skin effect losses in the conductors can be reduced by increasing the diameter of the cable. A cable with twice the diameter will have half the skin effect resistance. Ignoring dielectric and other losses, the larger cable would halve the dB/meter loss. In designing a system, engineers consider not only the loss in the cable but also the loss in the connectors.
 * Velocity of propagation, in meters per second. The velocity of propagation depends on the dielectric constant and permeability (which is usually $1$).
 * $$ v = \frac{1}{\ \sqrt{\epsilon \mu\ }\ } = \frac{c}{\ \sqrt{\epsilon_\mathsf{r} \mu_\mathsf{r}\ } \ } $$

 * Single-mode band. In coaxial cable, the dominant mode (the mode with the lowest cutoff frequency) is the TEM mode, which has a cutoff frequency of zero; it propagates all the way down to DC. The mode with the next lowest cutoff is the TE$11$ mode. This mode has one 'wave' (two reversals of polarity) in going around the circumference of the cable. To a good approximation, the condition for the TE$11$ mode to propagate is that the wavelength in the dielectric is no longer than the average circumference of the insulator; that is that the frequency is at least
 * $$f_\mathsf{c} \approx \frac{1}{\ \pi \left( \frac{D + d}{2} \right) \sqrt{\mu \epsilon\ } } = \frac{ c }{\ \pi \left(\frac{D + d}{2}\right) \sqrt{\mu_\mathsf{r} \epsilon_\mathsf{r}\ } } ~.$$
 * Hence, the cable is single-mode from DC up to this frequency, and might in practice be used up to 90% of this frequency.

 * Peak Voltage. The peak voltage is set by the breakdown voltage of the insulator.:
 * $$ V_\mathsf{p} =\ E_\mathsf{d} \ \frac{d}{2}\ \ln \left( \frac{\ D\ }{d} \right) $$
 * where
 * $V$$p$ is the peak voltage
 * $E$$d$ is the insulator's breakdown voltage in volts per meter
 * $d$ is the inner diameter in meters
 * $D$ is the outer diameter in meters
 * The calculated peak voltage is often reduced by a safety factor.

Choice of impedance
The best coaxial cable impedances were experimentally determined at Bell Laboratories in 1929 to be 77 Ω for low-attenuation, 60 Ω for high-voltage, and 30 Ω for high-power. For a coaxial cable with air dielectric and a shield of a given inner diameter, the attenuation is minimized by choosing the diameter of the inner conductor to give a characteristic impedance of 76.7 Ω. When more common dielectrics are considered, the lowest insertion loss impedance drops down to a value between 52 and 64 Ω. Maximum power handling is achieved at 30 Ω.

The approximate impedance required to match a centre-fed dipole antenna in free space (i.e., a dipole without ground reflections) is 73 Ω, so 75 Ω coax was commonly used for connecting shortwave antennas to receivers. These typically involve such low levels of RF power that power-handling and high-voltage breakdown characteristics are unimportant when compared to attenuation. Likewise with CATV, although many broadcast TV installations and CATV headends use 300 Ω folded dipole antennas to receive off-the-air signals, 75 Ω coax makes a convenient 4:1 balun transformer for these as well as possessing low attenuation.

The arithmetic mean between 30 Ω and 77 Ω is 53.5 Ω; the geometric mean is 48 Ω. The selection of 50 Ω as a compromise between power-handling capability and attenuation is in general cited as the reason for the number. 50 Ω also works out tolerably well because it corresponds approximately to the feedpoint impedance of a half-wave dipole, mounted approximately a half-wave above "normal" ground (ideally 73 Ω, but reduced for low-hanging horizontal wires).

RG-62 is a 93 Ω coaxial cable originally used in mainframe computer networks in the 1970s and early 1980s (it was the cable used to connect IBM 3270 terminals to IBM 3274/3174 terminal cluster controllers). Later, some manufacturers of LAN equipment, such as Datapoint for ARCNET, adopted RG-62 as their coaxial cable standard. The cable has the lowest capacitance per unit-length when compared to other coaxial cables of similar size.

All of the components of a coaxial system should have the same impedance to avoid internal reflections at connections between components (see Impedance matching). Such reflections may cause signal attenuation. They introduce standing waves, which increase losses and can even result in cable dielectric breakdown with high-power transmission. In analog video or TV systems, reflections cause ghosting in the image; multiple reflections may cause the original signal to be followed by more than one echo. If a coaxial cable is open (not connected at the end), the termination has nearly infinite resistance, which causes reflections. If the coaxial cable is short-circuited, the termination resistance is nearly zero, which causes reflections with the opposite polarity. Reflections will be nearly eliminated if the coaxial cable is terminated in a pure resistance equal to its impedance.

Signal leakage
Signal leakage is the passage of electromagnetic fields through the shield of a cable and occurs in both directions. Ingress is the passage of an outside signal into the cable and can result in noise and disruption of the desired signal. Egress is the passage of signal intended to remain within the cable into the outside world and can result in a weaker signal at the end of the cable and radio frequency interference to nearby devices. Severe leakage usually results from improperly installed connectors or faults in the cable shield.

For example, in the United States, signal leakage from cable television systems is regulated by the FCC, since cable signals use the same frequencies as aeronautical and radionavigation bands. CATV operators may also choose to monitor their networks for leakage to prevent ingress. Outside signals entering the cable can cause unwanted noise and picture ghosting. Excessive noise can overwhelm the signal, making it useless. In-channel ingress can be digitally removed by ingress cancellation.

An ideal shield would be a perfect conductor with no holes, gaps, or bumps connected to a perfect ground. However, a smooth solid highly conductive shield would be heavy, inflexible, and expensive. Such coax is used for straight-line feeds to commercial radio broadcast towers. More economical cables must make compromises between shield efficacy, flexibility, and cost, such as the corrugated surface of flexible hardline, flexible braid, or foil shields. Since shields cannot be perfect conductors, current flowing on the inside of the shield produces an electromagnetic field on the outer surface of the shield.

Consider the skin effect. The magnitude of an alternating current in a conductor decays exponentially with distance beneath the surface, with the depth of penetration being proportional to the square root of the resistivity. This means that, in a shield of finite thickness, some small amount of current will still be flowing on the opposite surface of the conductor. With a perfect conductor (i.e., zero resistivity), all of the current would flow at the surface, with no penetration into and through the conductor. Real cables have a shield made of an imperfect, although usually very good, conductor, so there must always be some leakage.

The gaps or holes, allow some of the electromagnetic field to penetrate to the other side. For example, braided shields have many small gaps. The gaps are smaller when using a foil (solid metal) shield, but there is still a seam running the length of the cable. Foil becomes increasingly rigid with increasing thickness, so a thin foil layer is often surrounded by a layer of braided metal, which offers greater flexibility for a given cross-section.

Signal leakage can be severe if there is poor contact at the interface to connectors at either end of the cable or if there is a break in the shield.

To greatly reduce signal leakage into or out of the cable, by a factor of 1000, or even 10,000, superscreened cables are often used in critical applications, such as for neutron flux counters in nuclear reactors.

Superscreened cables for nuclear use are defined in IEC 96-4-1, 1990, however as there have been long gaps in the construction of nuclear power stations in Europe, many existing installations are using superscreened cables to the UK standard AESS(TRG) 71181 which is referenced in IEC 61917.

Ground loops
A continuous current, even if small, along the imperfect shield of a coaxial cable can cause visible or audible interference. In CATV systems distributing analog signals the potential difference between the coaxial network and the electrical grounding system of a house can cause a visible "hum bar" in the picture. This appears as a wide horizontal distortion bar in the picture that scrolls slowly upward. Such differences in potential can be reduced by proper bonding to a common ground at the house. See ground loop.

Noise
External fields create a voltage across the inductance of the outside of the outer conductor between sender and receiver. The effect is less when there are several parallel cables, as this reduces the inductance and, therefore, the voltage. Because the outer conductor carries the reference potential for the signal on the inner conductor, the receiving circuit measures the wrong voltage.

Transformer effect
The transformer effect is sometimes used to mitigate the effect of currents induced in the shield. The inner and outer conductors form the primary and secondary winding of the transformer, and the effect is enhanced in some high-quality cables that have an outer layer of mu-metal. Because of this 1:1 transformer, the aforementioned voltage across the outer conductor is transformed onto the inner conductor so that the two voltages can be cancelled by the receiver. Many senders and receivers have means to reduce the leakage even further. They increase the transformer effect by passing the whole cable through a ferrite core one or more times.

Common mode current and radiation
Common mode current occurs when stray currents in the shield flow in the same direction as the current in the center conductor, causing the coax to radiate. They are the opposite of the desired "push-pull" differential signalling currents, where the signal currents on the inner and outer conductor are equal and opposite.

Most of the shield effect in coax results from opposing currents in the center conductor and shield creating opposite magnetic fields that cancel, and thus do not radiate. The same effect helps ladder line. However, ladder line is extremely sensitive to surrounding metal objects, which can enter the fields before they completely cancel. Coax does not have this problem, since the field is enclosed in the shield. However, it is still possible for a field to form between the shield and other connected objects, such as the antenna the coax feeds. The current formed by the field between the antenna and the coax shield would flow in the same direction as the current in the center conductor, and thus not be canceled. Energy would radiate from the coax itself, affecting the radiation pattern of the antenna. With sufficient power, this could be a hazard to people near the cable. A properly placed and properly sized balun can prevent common-mode radiation in coax. An isolating transformer or blocking capacitor can be used to couple a coaxial cable to equipment, where it is desirable to pass radio-frequency signals but to block direct current or low-frequency power.

Higher impedance at audio frequencies
The characteristic impedance formula above is a good approximation at radio frequencies however for frequencies below 100 kHz (such as audio) it becomes important to use the complete telegrapher's equation:

 * $$Z_\text{o} = \sqrt{ \frac{R + j\omega L}{G + j\omega C}\ }$$

Applying this formula to typical 75 ohm coax we find the measured impedance across the audio spectrum will range from ~150 ohms to ~5K ohms, much higher than nominal. The velocity of propagation also slows considerably. Thus we can expect coax cable impedances to be consistent at RF frequencies but variable across audio frequencies. This effect was manifested when trying to send a plain voice signal across the transatlantic telegraph cable, with poor results.

Standards
Most coaxial cables have a characteristic impedance of either 50, 52, 75, or 93 Ω. The RF industry uses standard type-names for coaxial cables. Thanks to television, RG-6 is the most commonly used coaxial cable for home use, and the majority of connections outside Europe are by F connectors.

A series of standard types of coaxial cable were specified for military uses, in the form "RG-#" or "RG-#/U". They date from World War II and were listed in MIL-HDBK-216 published in 1962. These designations are now obsolete. The RG designation stands for Radio Guide; the U designation stands for Universal. The current military standard is MIL-SPEC MIL-C-17. MIL-C-17 numbers, such as "M17/75-RG214", are given for military cables and manufacturer's catalog numbers for civilian applications. However, the RG-series designations were so common for generations that they are still used, although critical users should be aware that since the handbook is withdrawn there is no standard to guarantee the electrical and physical characteristics of a cable described as "RG-# type". The RG designators are mostly used to identify compatible connectors that fit the inner conductor, dielectric, and jacket dimensions of the old RG-series cables.

Dielectric material codes

 * FPE is foamed polyethylene
 * PE is solid polyethylene
 * PF is polyethylene foam
 * PTFE is polytetrafluoroethylene;
 * ASP is air space polyethylene

VF is the Velocity Factor; it is determined by the effective $$\epsilon_r$$ and $$\mu_r$$

 * VF for solid PE is about 0.66
 * VF for foam PE is about 0.78 to 0.88
 * VF for air is about 1.00
 * VF for solid PTFE is about 0.70
 * VF for foam PTFE is about 0.84

There are also other designation schemes for coaxial cables such as the URM, CT, BT, RA, PSF and WF series.

Uses
Short coaxial cables are commonly used to connect home video equipment, in ham radio setups, and in Nuclear Instrumentation Modules. While formerly common for implementing computer networks, in particular Ethernet ("thick" 10BASE5 and "thin" 10BASE2), twisted pair cables have replaced them in most applications except in the consumer cable modem market for broadband Internet access.

Long distance coaxial cable was used in the 20th century to connect radio networks, television networks, and long-distance telephone networks though this has largely been superseded by later methods (fibre optics, T1/E1, satellite).

Shorter coaxials still carry cable television signals to the majority of television receivers, and this purpose consumes the majority of coaxial cable production. In 1980s and early 1990s coaxial cable was also used in computer networking, most prominently in Ethernet networks, where it was later in late 1990s to early 2000s replaced by UTP cables in North America and STP cables in Western Europe, both with 8P8C modular connectors.

Micro coaxial cables are used in a range of consumer devices, military equipment, and also in ultrasound scanning equipment.

The most common impedances that are widely used are 50 or 52 ohms and 75 ohms, although other impedances are available for specific applications. The 50 / 52 ohm cables are widely used for industrial and commercial two-way radio frequency applications (including radio, and telecommunications), although 75 ohms is commonly used for broadcast television and radio.

Coaxial cable is often used to carry signals from an antenna to a receiver. In many cases, the same cable carries power toward the antenna, to power a preamplifier. In some cases, a single cable carries unidirectional power and bidirectional data/signals, as in DiSEqC.

Hard line

Larger varieties of hardline may have a center conductor that is constructed from either rigid or corrugated copper tubing. The dielectric in hard line may consist of polyethylene foam, air, or a pressurized gas such as nitrogen or desiccated air (dried air). In gas-charged lines, hard plastics such as nylon are used as spacers to separate the inner and outer conductors. The addition of these gases into the dielectric space reduces moisture contamination, provides a stable dielectric constant, and provides a reduced risk of internal arcing. Gas-filled hardlines are usually used on high-power RF transmitters such as television or radio broadcasting, military transmitters, and high-power amateur radio applications but may also be used on some critical lower-power applications such as those in the microwave bands. However, in the microwave region, waveguide is more often used than hard line for transmitter-to-antenna, or antenna-to-receiver applications. The various shields used in hard line also differ; some forms use rigid tubing, or pipe, while others may use a corrugated tubing, which makes bending easier, as well as reduces kinking when the cable is bent to conform. Smaller varieties of hard line may be used internally in some high-frequency applications, in particular in equipment within the microwave range, to reduce interference between stages of the device.

Radiating
Radiating or leaky cable is another form of coaxial cable which is constructed in a similar fashion to hard line, however it is constructed with tuned slots cut into the shield. These slots are tuned to the specific RF wavelength of operation or tuned to a specific radio frequency band. This type of cable is to provide a tuned bi-directional "desired" leakage effect between transmitter and receiver. It is often used in elevator shafts, US Navy Ships, underground transportation tunnels and in other areas where an antenna is not feasible. One example of this type of cable is Radiax (CommScope).

RG-6
RG-6 is available in four different types designed for various applications. In addition, the core may be copper clad steel (CCS) or bare solid copper (BC). "Plain" or "house" RG-6 is designed for indoor or external house wiring. "Flooded" cable is infused with water-blocking gel for use in underground conduit or direct burial. "Messenger" may contain some waterproofing but is distinguished by the addition of a steel messenger wire along its length to carry the tension involved in an aerial drop from a utility pole. "Plenum" cabling is expensive and comes with a special Teflon-based outer jacket designed for use in ventilation ducts to meet fire codes. It was developed since the plastics used as the outer jacket and inner insulation in many "Plain" or "house" cabling gives off poisonous gas when burned.

Triaxial cable
Triaxial cable or triax is coaxial cable with a third layer of shielding, insulation and sheathing. The outer shield, which is earthed (grounded), protects the inner shield from electromagnetic interference from outside sources.

Semi-rigid
Semi-rigid cable is a coaxial form using a solid copper outer sheath. This type of coax offers superior screening compared to cables with a braided outer conductor, especially at higher frequencies. The major disadvantage is that the cable, as its name implies, is not very flexible, and is not intended to be flexed after initial forming. (See )

Conformable cable is a flexible reformable alternative to semi-rigid coaxial cable used where flexibility is required. Conformable cable can be stripped and formed by hand without the need for specialized tools, similar to standard coaxial cable.

Rigid line
Rigid line is a coaxial line formed by two copper tubes maintained concentric every other meter using PTFE-supports. Rigid lines cannot be bent, so they often need elbows. Interconnection with rigid line is done with an inner bullet/inner support and a flange or connection kit. Typically, rigid lines are connected using standardised EIA RF Connectors whose bullet and flange sizes match the standard line diameters. For each outer diameter, either 75 or 50 ohm inner tubes can be obtained. Rigid line is commonly used indoors for interconnection between high-power transmitters and other RF-components, but more rugged rigid line with weatherproof flanges is used outdoors on antenna masts, etc. In the interests of saving weight and costs, on masts and similar structures the outer line is often aluminium, and special care must be taken to prevent corrosion. With a flange connector, it is also possible to go from rigid line to hard line. Many broadcasting antennas and antenna splitters use the flanged rigid line interface even when connecting to flexible coaxial cables and hard line. Rigid line is produced in a number of different sizes:

Interference and troubleshooting
Coaxial cable insulation may degrade, requiring replacement of the cable, especially if it has been exposed to the elements on a continuous basis. The shield is normally grounded, and if even a single thread of the braid or filament of foil touches the center conductor, the signal will be shorted causing significant or total signal loss. This most often occurs at improperly installed end connectors and splices. Also, the connector or splice must be properly attached to the shield, as this provides the path to ground for the interfering signal.

Despite being shielded, interference can occur on coaxial cable lines. Susceptibility to interference has little relationship to broad cable type designations (e.g. RG-59, RG-6) but is strongly related to the composition and configuration of the cable's shielding. For cable television, with frequencies extending well into the UHF range, a foil shield is normally provided, and will provide total coverage as well as high effectiveness against high-frequency interference. Foil shielding is ordinarily accompanied by a tinned copper or aluminum braid shield, with anywhere from 60 to 95% coverage. The braid is important to shield effectiveness because (1) it is more effective than foil at preventing low-frequency interference, (2) it provides higher conductivity to ground than foil, and (3) it makes attaching a connector easier and more reliable. "Quad-shield" cable, using two low-coverage aluminum braid shields and two layers of foil, is often used in situations involving troublesome interference, but is less effective than a single layer of foil and single high-coverage copper braid shield such as is found on broadcast-quality precision video cable.

In the United States and some other countries, cable television distribution systems use extensive networks of outdoor coaxial cable, often with in-line distribution amplifiers. Leakage of signals into and out of cable TV systems can cause interference to cable subscribers and to over-the-air radio services using the same frequencies as those of the cable system.

History

 * 1858 — Coaxial cable used in first (1858) transatlantic cable.
 * 1880 — Coaxial cable patented in England by Oliver Heaviside, patent no. 1,407.
 * 1884 — Siemens & Halske patent coaxial cable in Germany (Patent No. 28,978, 27 March 1884).
 * 1894 — Nikola Tesla (U.S. Patent 514,167)
 * 1929 — First modern coaxial cable patented by Lloyd Espenschied and Herman Affel of AT&T's Bell Telephone Laboratories.
 * 1936 — First closed circuit transmission of TV pictures on coaxial cable, from the 1936 Summer Olympics in Berlin to Leipzig.
 * 1936 — Underwater coaxial cable installed between Apollo Bay, near Melbourne, Australia, and Stanley, Tasmania. The 300 km cable can carry one 8.5-kHz broadcast channel and seven telephone channels.
 * 1936 — AT&T installs experimental coaxial telephone and television cable between New York and Philadelphia, with automatic booster stations every 10 mi. Completed in December, it can transmit 240 telephone calls simultaneously.
 * 1936 — Coaxial cable laid by the General Post Office (now BT) between London and Birmingham, providing 40 telephone channels.
 * 1941 — First commercial use in US by AT&T, between Minneapolis, Minnesota and Stevens Point, Wisconsin. L1 system with capacity of one TV channel or 480 telephone circuits.
 * 1949 — On January 11, eight stations on the US East Coast and seven Midwestern stations are linked via a long-distance coaxial cable.
 * 1956 — First transatlantic telephone coaxial cable laid, TAT-1.

 * 1962 — 960 km Sydney–Melbourne co-axial cable commissioned, carrying 3 x 1,260 simultaneous telephone connections, and-or simultaneous inter-city television transmission.

title: Coaxial cable