Male 50 ohm BNC connector
|Type||RF coaxial connector|
|Designer||Paul Neill, Carl Concelman, & Octavio M. Salati|
|Passband||Typically 0–4 GHz|
The BNC (Bayonet Neill–Concelman) connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It features two bayonet lugs on the female connector; mating is fully achieved with a quarter turn of the coupling nut. BNC connectors are used with miniature-to-subminiature coaxial cable in radio, television, and other radio-frequencyelectronic equipment, test instruments, and video signals. The BNC was commonly used for early computer networks, including ARCnet, the IBM PC Network, and the 10BASE2 variant of Ethernet. BNC connectors are made to match the characteristic impedance of cable at either 50 ohms or 75 ohms. They are usually applied for frequencies below 4 GHz and voltages below 500 volts.
Similar connectors using the bayonet connection principle exist, and a threaded connector is also available. United States military standard MIL-PRF-39012 entitled Connectors, Coaxial, Radio Frequency, General Specification for (formerly MIL-C-39012) covers the general requirements and tests for radio frequency connectors used with flexible cables and certain other types of coaxial transmission lines in military, aerospace, and spaceflight applications.
The BNC was originally designed for military use and has gained wide acceptance in video and RF applications to 2 GHz. The BNC uses a slotted outer conductor and some plastic dielectric on each gender connector. This dielectric causes increasing losses at higher frequencies. Above 4 GHz, the slots may radiate signals, so the connector is usable, but not necessarily stable up to about 11 GHz. Both 50 ohm and 75 ohm versions are available. The BNC connector is used for signal connections such as:
The BNC connector is used for composite video on commercial video devices. Consumer electronics devices with RCA connector jacks can be used with BNC-only commercial video equipment by inserting an adapter. BNC connectors were commonly used on 10base2 thin Ethernet network cables and network cards. BNC connections can also be found in recording studios. Digital recording equipment uses the connection for synchronization of various components via the transmission of word clock timing signals.
Typically the male connector is fitted to a cable, and the female to a panel on equipment. Cable connectors are often designed to be fitted by crimping using a special power or manual tool.Wire strippers which strip outer jacket, shield braid, and inner dielectric to the correct lengths in one operation are used.
The connector was named the BNC (for BayonetNeill–Concelman) after its bayonet mount locking mechanism and its inventors, Paul Neill and Carl Concelman. Neill worked at Bell Labs and also invented the N connector; Concelman worked at Amphenol and also invented the C connector. A backronym has been mistakenly applied to it: British Naval Connector. Another common incorrectly attributed origin is Berkeley Nucleonics Corporation.
The basis for the development of the BNC connector was largely the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering of the University of Pennsylvania. In 1945, while working at Hazeltine Electronics Corporation, he filed a patent for a connector for coaxial cables that would minimize wave reflection/loss. The patent was granted in 1951.
Types and compatibility
BNC connectors are most commonly made in 50 and 75 ohm versions, matched for use with cables of the same characteristic impedance. The 75 ohm types can sometimes be recognized by the reduced or absent dielectric in the mating ends but this is by no means reliable. There was a proposal in the early 1970s for the dielectric material to be coloured red in 75 ohm connectors, and while this is occasionally implemented, it did not become standard. The 75 ohm connector is dimensionally slightly different from the 50 ohm variant, but the two nevertheless can be made to mate. The 50 ohm connectors are typically specified for use at frequencies up to 4 GHz and the 75 ohm version up to 2 GHz. A 95 ohm variant is used within the aerospace sector, but rarely elsewhere. It is used with the 95 ohm video connections for glass cockpit displays on some aircraft.
Video (particularly HD video signals) and DS3 Telco central office applications primarily use 75 ohm BNC connectors, whereas 50 ohm connectors are used for data and RF. Many VHF receivers used 75 ohm antenna inputs, so they often used 75 ohm BNC connectors.
Reverse-polarity BNC (RP-BNC) is a variation of the BNC specification which reverses the polarity of the interface. In a connector of this type, the female contact normally found in a jack is usually in the plug, while the male contact normally found in a plug is in the jack. This ensures that reverse polarity interface connectors do not mate with standard interface connectors. The SHV connector is a high-voltage BNC variant that uses this reverse polarity configuration.
Smaller versions of the BNC connector, called Mini BNC and High Density BNC (HD BNC), are manufactured by Amphenol. While retaining the electrical characteristics of the original specification, they have smaller footprints giving a higher packing density on circuit boards and equipment backplanes. These connectors have true 75 ohm impedance making them suitable for HD video applications.
The different versions are designed to mate with each other, and a 75 ohm and a 50 ohm BNC connector which both comply with the 2007 IEC standard, IEC 60169-8, will mate non-destructively. At least one manufacturer claims very high reliability for the connectors' compatibility.
At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects. BNC connectors were thus originally made only in 50 ohm versions, for use with any impedance of cable. Above this frequency, however, the mismatch becomes progressively more significant and can lead to signal reflections.
BNC inserter/remover tool
A BNC inserter/remover tool also called a BNC tool, BNC extraction tool, BNC wrench, or BNC apple corer, is used to insert or remove BNC connectors in high density or hard-to-reach locations, such as densely wired patch panels in broadcast facilities like central apparatus rooms.
BNC tools are usually light weight, made with stainless steel, and have screw driver type plastic handle grips for applying torque. Their shafts are usually double the length of a standard screw driver.
They help to safely, efficiently and quickly connect and disconnect BNC connectors in jack fields. BNC tools facilitate access and minimize the risk of accidentally disconnecting nearby connectors.
Main article: RF connector
Main article: SR connector
In the USSR, BNC connectors were copied as SR connectors. As a result of recalculating from imperial to metric measurements their dimensions differ slightly from those of BNC. They are however generally interchangeable with them, sometimes with force applied.
TNC (Threaded Neill–Concelman)
Main article: TNC connector
A threaded version of the BNC connector, known as the TNC connector (for Threaded Neill-Concelman) is also available. It has superior performance to the BNC connector at microwave frequencies.
Twin BNC or twinax
Twin BNC (also known as twinax) connectors use the same bayonet latching shell as an ordinary BNC connector but contain two independent contact points (one male and one female), allowing the connection of a 78 ohm or 95 ohm shielded differential pair such as RG-108A. They can operate up to 100 MHz and 100 volts. They cannot mate with ordinary BNC connectors. An abbreviation for twinax connectors has been BNO (Sühner).
Triaxial (also known as triax) connectors are a variant on BNC that carry a signal and guard as well as ground conductor. These are used in sensitive electronic measurement systems. Early triaxial connectors were designed with just an extra inner conductor, but later triaxial connectors also include a three-lug arrangement to rule out an accidental forced mating with a BNC connector. Adaptors exist to allow some interconnection possibilities between triaxial and BNC connectors. The triaxial may also be known as a Trompeter connection.
For higher voltages (above 500 V), MHV and SHV connectors are typically used. MHV connectors are easily mistaken for BNC type, and can be made to mate with them by brute force. The SHV connector was developed as a safer alternative, it will not mate with ordinary BNC connectors and the inner conductor is much harder to accidentally contact.
BNC connectors are commonly used in electronics, but in some applications they are being replaced by LEMO 00 miniature connectors which allow for significantly higher densities. In video broadcast industry, the DIN 1.0/2.3 and the HD-BNC connector are used for higher density products
- ^ abThomas H. Lee, Planar microwave engineering: a practical guide to theory, measurement, and circuits, Volume 1 Cambridge University Press, p. 111 (2004). ISBN 0-521-83526-7.
- ^ abcBNC Connector specifications, Amphenol Connex
- ^Typical crimp BNC connector
- ^Typical manual crimp tool for fitting BNC and other coaxial connectors to cables
- ^Typical coax one-operation stripper
- ^"Extended Definition: BNC connector". Webster's Online Dictionary. Archived from the original on 17 November 2006. Retrieved 13 June 2013.
- ^Electrical connector. US Patent 2,540,012 by Octavio M. Salati
- ^webstore.iec.ch Radio-frequency connectors - Part 8: Sectional specification - RF coaxial connectors with inner diameter of outer conductor 6,5 mm (0,256 in) with bayonet lock - Characteristic impedance 50 Ω (type BNC)
- ^Canford. "In over 15 years and many million BNC connectors we have no first hand experience of incompatibility between 50 ohm and 75 ohm types, other than extremely rare (and very obvious) manufacturing faults."
- ^BNC Connectors, The Canford Group
- ^Trompeter Product Catelog(PDF). Trompeter. p. 51. Retrieved 24 January 2015.
- ^E-Base Interactive. "Twin BNC connector series". Amphenol RF. Retrieved 26 November 2011.
Ever since the beginning of the current global economic crisis, the focus of both critical analysis and public odium has been speculative capital. In the populist narrative, it was the breathtaking shenanigans of the banks in an atmosphere of deregulation that led to the economic collapse. The “financial economy,” characterized as parasitic and bad, was contrasted to the “real economy,” which was said to produce real goods and real value. Resources flowed into speculative activities in finance, resulting in a loss of dynamism in the real economy and eventually leading to credit cutoff at the height of the crisis, causing bankruptcies and massive layoffs.
Vampire Squid versus Corporate Galahad?
The principal villain in this narrative is Goldman Sachs. The image of this Wall Street denizen has been etched in the public mind by Matt Taibbi’s description of it as “a great vampire squid wrapped around the face of humanity, relentlessly jamming its blood funnel into anything that smells like money.”
In this account, the old nemesis of the progressive analysts, the transnational corporation (TNC), slips quietly into the background. Indeed, it is seen as part of the real economy, as the commonly used term “non-financial corporation” implies. In contrast to the investment banks that create fictitious products like derivatives, TNCs are said to create real products like Apple’s nifty iPads and iPhones. While Goldman Sachs is pictured as a vampire squid, Apple is depicted as a corporate Galahad that can be relied on to deliver the consumer’s wildest desires. In one survey, 56 percent of Americans associated nothing negative with Apple.
A recent two-part series in the New York Times on Apple, however, reminds us that transnational corporations and their practice of outsourcing jobs are front-and-center when it comes to the current economic crisis. And it is not only “smokestack” corporations like GM and Boeing that have massively shifted work from the United States to cheap labor havens abroad, but also those involved in the knowledge industry. Indeed, the highest proportion of firms with an offshoring strategy belongs to the information technology and software development industries. But while HP and Dell have become associated with outsourcing, Apple’s prowess at turning out products that capture the popular imagination has kept it from being tainted with the image of being a labor exporter.
Apple and Outsourcing
Apple earned over $400,000 in profit per employee in 2011, more than Goldman Sachs or Exxon. Yet in the last few years, it has created few jobs in its home base and prime market, the United States. According to the Times account, “Apple employs 43,000 people in the United States and 20,000 overseas, a small fraction of the over 400,000 American workers at General Motors in the 1950s, or the hundreds of thousands at General Electric in the 1980s. Many more people work for Apple’s contractors: an additional 700,000 people engineer, build and assemble iPads, iPhones and Apple’s other products. But almost none of them work in the United States. Instead, they work for foreign companies in Asia, Europe and elsewhere, at factories that almost all electronics designers rely upon to build their wares. “
The genesis of the financial crisis, in fact, cannot be separated from the strategic moves of “real economy” actors like Apple [and] their readiness to leave their home base and home market.
The genesis of the financial crisis, in fact, cannot be separated from the strategic moves of “real economy” actors like Apple. Their readiness to leave their home base and home market was one of the central causes of the crisis. The creation of credit was the central link between this trend in the real economy and the dynamics of finance. Before we examine this link, however, it is important to review some facts about outsourcing.
It is estimated that 8 million U.S. manufacturing jobs were eliminated between June 1979 and December 2009. One report describes the grim process of deindustrialization: “Long before the banking collapse of 2008, such important U.S. industries as machine tools, consumer electronics, auto parts, appliances, furniture, telecommunications equipment, and many others that had once dominated the global marketplace suffered their own economic collapse. Manufacturing employment dropped to 11.7 million in October 2009, a loss of 5.5 million or 32 percent of all manufacturing jobs since October 2000. The last time fewer than 12 million people worked in the manufacturing sector was in 1941. In October 2009, more people were officially unemployed (15.7 million) than were working in manufacturing.”
Outsourcing and Stagnation in the Real Economy
This decimation of the manufacturing sector, which involved the elimination a massive number of well-paying manufacturing jobs, played a central role in the stagnation of income, wages, and purchasing power in the United States. In the three decades prior to the crash of 2008, Robert Reich notes, the wages of the typical American hardly increased, and actually dropped in the 2000s.
This stagnation of income posed a threat to both business and the state. To the first, the slow growth of demand would translate into overproduction and, thus, diminished profits in the corporations’ key market. To the state, it posed the specter of rising social conflict and instability.
The threat of a stagnant market was thwarted—temporarily—by the private sector via a massive increase in credit creation by banks, who lowered lending standards and hooked millions of consumers into multiple credit cards, with a great deal of the funds lent sourced from China and other capital-exporting Asian economies. Credit kept consumption up and fueled the boom in the 1990s and the middle of the first decade of the 21st century.
Washington tried to ward off political resentment by adopting a strategy of “populist credit expansion,” that is, making easy credit for housing available for low-income groups via Freddie Mac and Fannie Mae. Political stability was not the only outcome of this approach; it was accompanied by greater profitability for speculative capital. As Raghuram Rajan writes, “As more money from the government flooded into financing or supporting low income housing, the private sector joined the party. After all, they could do the math, and they understood that the political compulsions behind government actions would not disappear quickly. With agency support, subprime mortgages would be liquid, and low-cost housing would increase in price. Low risk and high return—what more could the private sector desire?”
The Apple-China Connection
Co-opting the masses with credit expansion collapsed with the financial implosion of 2008. Today, millions of Americans are both without jobs and in terrible debt. But, as the continuing high unemployment rate indicates, the export of jobs continues unabated, and China remains the favored destination.
Apple's march to market supremacy has been accomplished at tremendous cost to both American and Chinese workers.
Part of the reason South China retains its primacy as an investment site is that Chinese suppliers, with subsidies from the state, have established an unbeatable supply chain of contiguous factories, radically bringing down transport costs, enabling rapid assembly of an iPad or iPhone, and thus satisfying customers in a highly competitive market in record time.
Steve Jobs, the legendary founder of Apple, played a key role in creating this system. Apple executives recount his wanting a glass screen for the iPhone that could not be scratched, and his wanting it in “six weeks.” After one executive left that meeting, says the Times, he booked a flight to China. “If Mr. Jobs wanted perfect,” he recalled, “there was nowhere else to go. “
Mastery of the economics of the supply chain is, however, only one of the reasons Jobs and Apple favored China. The central reason continued to be cheap labor that is disciplined by the state. What emerges in the Times account about Apple’s practices is that, despite its protestations about being a socially responsible firm, Apple bargains hard, allowing its contractors “only the slimmest of profits.” Thus, “suppliers often try to cut corners, replace expensive chemicals with less costly alternatives, or push their employees to work faster and longer. “The only way you make money working for Apple is figuring out how to do things more efficiently or cheaper,” said an executive at one company that helped bring the iPad to market. “And then they’ll come back the next year, and force a 10 percent price cut.” Not surprisingly, a number of Apple suppliers have been plagued with accidents, including explosions, since, as one former Apple executive put it, “If you squeeze margins, you’re forcing them to cut safety.”
The consequences of severe cost-cutting have not only been accidents but also protests by workers. Some of them took the tragic route of suicide, such as those that occurred in 2009 and 2010 at Foxconn, a notorious, gigantic corporate contractor, while others resorted to spontaneous labor actions that were put down forcefully by management and the state.
Apple’s products are top of the line, distinguished by their superior design, engineering, and personality or “soul.” But the company’s march to market supremacy has been accomplished at tremendous cost to both American and Chinese workers. The iPad and iPhone are engineering masterpieces. But these commodities are not simply material. They also incarnate the social relations of production. They are the expression of the marriage between a demanding enterprise that has become the cutting edge corporation of our time and what Slavoj Zizek has called today’s “ideal capitalist state”: China, with the freedom it offers capital along with its unparalleled capacity to discipline labor. One cannot but agree with Jared Bernstein, a former White House economic adviser, when he told the Times, “If it’s [the Apple system] the pinnacle of capitalism, we should be worried.”