The BNC connector is a miniature quick-connect/disconnect radio-frequency connector for coaxial cable. It was introduced on military radio equipment in the 1940s, and has since become widely used in radio systems and as a common type of video connector. It has a twist-to-lock design, where two lugs on the female connector engage slots in the shell of the male one.
BNC is designed to maintain the characteristic impedance of the cable across the connection, and is made in 50-ohm and 75-ohm versions. It is normally used for radio-frequency signals up to about 2gigahertz and 500 volts.
Similar radio-frequency connectors differ in dimensions and attachment features, and may allow for higher voltages, higher frequencies, or three-wire connections.
History
In 1941, the US Navy used a smaller version of the threaded N connector, the Type BN (Baby N), as the UG-85/U, UG-86/U, UG-114/U and UG-115/U.
In 1943, the British introduced a ¼ inch 50 ohm coaxial cable, and companies immediately developed many connectors for it. In 1944, the US Navy called the designers together to find a single, standard design acceptable to all. Paul Neill, the inventor of the original N connector, developed a prototype connector which had a constant 50 ohm impedance at frequencies beyond 1GHz, used a bayonet fastening (faster to use than a threaded one), and was easier to manufacture and assemble. It was specified by the Bell Laboratory drawing ESL 662916, dated March 2, 1944.
In April 1944, the Navy took Neill’s design, added a C (for constant impedance) to BN to get Type BNC (Baby Neill Constant), and assigned part numbers UG 88/U to the male and UG 89/U to the female (Amphenol still makes them). The Navy issued a final drawing RE 49F 246, dated December 2, 1944.[1]
In May 1945, Octavio M. Salati of Hazeltine Corporation applied for a patent for the BNC, which was granted in January 1951.[2] In 1958, Hazeltine sued Dage Electric Company, a maker of BNC connectors, for infringement on this patent. The court found that Salati’s patent was invalid because he knew of the Navy’s BNC before his application date.[3]
Name
The US Navy used the term BNC to mean "Baby Neill Constant". The term BNC appeared in 1948 in ads for Amphenol connectors[4] together with the MIL-spec name UG-88/U.
While Paul Neill and Carl Concelman did not invent the BNC, it is often suggested that BNC means Bayonet Neill–Concelman.[5] At the time of the BNC development, Concelman worked at Danbury Knudsen and invented the C connector as an improvement to the BNC. In the late 1950s, at Amphenol, Neill and Concelman invented the TNC connector, which could mean Threaded BNC or Threaded Neill–Concelman. This may have led some to incorrectly assume that they must also have developed the BNC and created Bayonet Neill–Concelman as a backronym.
Other suggestions include Bayonet Navy Connector:[6]Bayonet N Connector, Bayonet Nut Coupling, Barrel Nut Connector, Bayonet Nipple Connector, Baby N Connector, British Naval/National Connector, and Berkeley Nucleonics Corporation.
Description
The BNC connector features two bayonet lugs on the female connector; mating is fully achieved with a quarter turn of the coupling nut. It uses an outer conductor with slots and some plastic dielectric on each gender connector. This dielectric causes increasing losses at higher frequencies. Above 4GHz, the slots may radiate signals, so the connector is usable, but not necessarily stable, up to about 11GHz. BNC connectors are made to match the characteristic impedance of cable at either 50 ohms or 75 ohms (with other impedances such as 93 ohms for ARCNET available though less common). They are usually applied for frequencies below 4GHz[5] and voltages below 500 volts.[7] The interface specifications for the BNC and many other connectors are referenced in MIL-STD-348.[8]
Usage
Rear of a video switcher with an array of BNC connectors
The BNC was originally designed for military use and has gained wide acceptance in video and RF applications up to 2GHz. BNC connectors are used with miniature-to-subminiature coaxial cable in radio, television, and other radio-frequencyelectronic equipment. They were commonly used for early computer networks, including ARCnet, the IBM PC Network, and the 10BASE2 variant of Ethernet.
The BNC connector is used for signal connections such as:
BNC tee connectors with resistive load terminators
The BNC connector is used for analog composite video and digital video interconnects 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[9] using a special power or manual tool.[10][failed verification]Wire strippers which strip outer jacket, shield braid, and inner dielectric to the correct lengths in one operation are used.[11]
Types and compatibility
BNC connectors. From left to right: 75Ω female, 75Ω male, 50Ω female, 50Ω male.
Types
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. Note that a male 50 ohm BNC has the pin larger than the one of a 75 ohm male, then it can widen the female, causing a fault connection when inserted later a 75 ohm male connector. The 50 ohm connectors are typically specified for use at frequencies up to 4GHz and the 75 ohm version up to 2GHz.
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.[7][failed verification] 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.
Compatibility
The different versions are designed to mate with each other,[7][failed verification] and 75ohm and 50ohm BNC connectors that comply with the 2007 IEC standard, IEC 61169-8,[12] will mate non-destructively. At least one manufacturer[13] claims very high reliability for the connectors' compatibility. [improper synthesis?]
At frequencies below 10MHz the impedance mismatch between a 50ohm connector or cable and a 75ohm one has negligible effects.[14] BNC connectors were thus originally made only in 50ohm 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
Rear view of a patch panel with BNC jacks in close proximity.
A BNC inserter/remover tool, also called a BNC tool, BNC extraction tool, BNC wrench, or BNC apple corer, is a tool 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 of stainless steel, and have screw driver type plastic handle grips for applying torque. Their shafts are usually double the length of a standard connector.
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.
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.[16]
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.
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
Female (left) and male (right) twin BNC connectors
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.[17] They can operate up to 100MHz and 100volts. They cannot mate with ordinary BNC connectors. An abbreviation for twinax connectors has been BNO (Huber+Suhner[de]).
Triaxial
Triaxial BNC connector
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 500V), 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.
Miniature connectors
Section through BNC and HD-BNC connectors
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
Coaxial cable, or coax, is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ; 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.
An RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range. RF connectors are typically used with coaxial cables and are designed to maintain the shielding that the coaxial design offers. Better models also minimize the change in transmission line impedance at the connection in order to reduce signal reflection and power loss. As the frequency increases, transmission line effects become more important, with small impedance variations from connectors causing the signal to reflect rather than pass through. An RF connector must not allow external signals into the circuit through electromagnetic interference and capacitive pickup.
The N connector is a threaded, weatherproof, medium-size RF connector used to join coaxial cables. It was one of the first connectors capable of carrying microwave-frequency signals, and was invented in the 1940s by Paul Neill of Bell Labs, after whom the connector is named.
The TNC connector is a threaded version of the BNC connector.
In electronics, electrical termination is the practice of ending a transmission line with a device that matches the characteristic impedance of the line. Termination prevents signals from reflecting off the end of the transmission line. Reflections at the ends of unterminated transmission lines cause distortion, which can produce ambiguous digital signal levels and misoperation of digital systems. Reflections in analog signal systems cause such effects as video ghosting, or power loss in radio transmitter transmission lines.
The F connector is a coaxial RF connector commonly used for "over the air" terrestrial television, cable television and universally for satellite television and cable modems, usually with RG-6/U cable or with RG-59/U cable.
The C connector is a type of RF connector used for terminating coaxial cable. The interface specifications for the C and many other connectors are referenced in MIL-STD-348. The connector uses two-stud bayonet-type locks. The C connector was invented by Amphenol engineer Carl Concelman. It is weatherproof without being overly bulky. The mating arrangement is similar to that of the BNC connector. It can be used up to 11 GHz, and is rated for up to 1500 volts.
SMA connectors are semi-precision coaxial RF connectors developed in the 1960s as a minimal connector interface for coaxial cable with a screw-type coupling mechanism. The connector has a 50 Ω impedance. SMA was originally designed for use from DC (0 Hz) to 12 GHz, however this has been extended over time and variants are available to 18 GHz and 26.5 GHz. There are also mechanically compatible connectors such as the K-connector which operate up to 40 GHz. The SMA connector is most commonly used in microwave systems, hand-held radio and mobile telephone antennas and, more recently, with WiFi antenna systems and USB software-defined radio dongles. It is also commonly used in radio astronomy, particularly at higher frequencies (5 GHz+).
SMB connectors are coaxial RF connectors developed in the 1960s. SMB connectors are smaller than SMA connectors.
SMC connectors are coaxial RF connectors developed in the 1960s. The interface specifications for the SMC and many other connectors are referenced in MIL-STD-348. They use a #10-32 UNF threaded interface. They offer electrical performance from direct current (DC) to 4 GHz. Some extended performance versions are rated to 10 GHz. The normally free part of a SMC connector that has a socket for the centre contact are the female connectors. The normally fixed part SMC connectors that has a pin for the centre contact are the male connectors. This is the reverse of most RF connectors. SMC jack connectors have an external thread while SMC plug connectors have the mating hex nut. The contact dimensions are identical to the snap-fit SMB. Available in 50 ohm and 75 ohm characteristic impedance, they provide an interconnect means for small form factor coaxial cables and printed circuit boards where small footprint is important.
Amphenol Corporation is an American producer of electronic and fiber optic connectors, cable and interconnect systems such as coaxial cables. Amphenol is a portmanteau from the corporation's original name, American Phenolic Corp.
RG-58/U is a type of coaxial cable often used for low-power signal and RF connections. The cable has a characteristic impedance of either 50 or 52 Ω. "RG" was originally a unit indicator for bulk RF cable in the U.S. military's Joint Electronics Type Designation System. There are several versions covering the differences in core material and shield.
The UHF connector is a name for a fairly common, but old type of threaded RF connector. The connector design was invented in the 1930s for use in the radio industry. It is a widely used standard connector for HF transmission lines on full-sized radio equipment, with BNC connectors predominating for smaller, hand-held equipment.
RG-59/U is a specific type of coaxial cable, often used for low-power video and RF signal connections. The cable has a characteristic impedance of 75 ohms, and a capacitance of around 20pF/ft (60pF/m). The 75 ohm impedance matches a dipole antenna in free space. RG was originally a unit indicator for bulk radio frequency (RF) cable in the U.S. military's Joint Electronics Type Designation System. The suffix /U means for general utility use. The number 59 was assigned sequentially. The RG unit indicator is no longer part of the JETDS system (MIL-STD-196E) and cable sold today under the RG-59 label does not necessarily meet military specifications.
The Musa connector is a type of coaxial ("coax") connector, originally developed for the manual switching of radio signals. It has a characteristic impedance of 75 Ω, and was adopted for use in the emerging television broadcast industry.
Electrical or fiber-optic connectors used by U.S. Department of Defense were originally developed in the 1930s for severe aeronautical and tactical service applications, and the Type "AN" (Army-Navy) series set the standard for modern military circular connectors. These connectors, and their evolutionary derivatives, are often called Military Standard, "MIL-STD", or (informally) "MIL-SPEC" or sometimes "MS" connectors. They are now used in aerospace, industrial, marine, and even automotive commercial applications.
A concentric twinax connector has a center pin and a cylindrical intermediate contact as compared to a dual polarized pin type.
The DIN 1.0/2.3 connector is a RF connector used for coaxial cable at microwave frequencies. They were introduced in the 1990s for telecommunication applications. They are available in 50 Ω and 75 Ω impedance and are compatible with the most widely used cable sizes. It has a push/pull lock and release feature. The DIN 1.0/2.3 is ideally suited to applications where space limitation is a factor. In broadcasting applications the 75 Ω version is used for serial digital interface video data up to maximum frequency of 4 GHz. The 50 Ω connector can be used to a maximum of 10 GHz.
Octavio M. "Tav" Salati was an American engineer, academic and educator. He served as Professor of Electrical Engineering at the University of Pennsylvania in the field of Electromagnetic Compatibility.
1 2 Thomas H. Lee, Planar microwave engineering: a practical guide to theory, measurement, and circuits, Volume 1 Cambridge University Press, p. 111 (2004). ISBN0-521-83526-7.
↑ 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 50ohm and 75ohm types, other than extremely rare (and very obvious) manufacturing faults."
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