The BNC connector (initialism of "Bayonet Neill–Concelman") is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It is designed to maintain the same characteristic impedance of the cable, with 50 ohm and 75 ohm types being made. It is usually applied for video and radio frequency connections up to about 2 GHz and up to 500 volts. The connector has a twist to lock design with two lugs in the female portion of the connector engaging a slot in the shell of the male portion. The type was introduced on military radio equipment in the 1940s and has since become widely applied in radio systems, and is a common type of video connector. Similar radio-frequency connectors differ in dimensions and attachment features, and may allow for higher voltages, higher frequencies, or three-wire connections.
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 4 GHz, the slots may radiate signals, so the connector is usable, but not necessarily stable, up to about 11 GHz. 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 4 GHz[1] and voltages below 500 volts.[2] The interface specifications for the BNC and many other connectors are referenced in MIL-STD-348.[3]
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 to 2 GHz. 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[4] using a special power or manual tool.[5][failed verification]Wire strippers which strip outer jacket, shield braid, and inner dielectric to the correct lengths in one operation are used.[6]
Types and compatibility
BNC connectors. From left to right: 75 Ω female, 75 Ω male, 50 Ω female, 50 Ω 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 then 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 4 GHz and the 75 ohm version up to 2 GHz.
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.[2][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,[2][failed verification]
and a 75 ohm and a 50 ohm BNC connector which both comply with the 2007 IEC standard, IEC 61169-8,[7] will mate non-destructively. At least one manufacturer[8] claims very high reliability for the connectors' compatibility.[improper synthesis?]
At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects.[9] 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
Rear view of a patch panel with BNC jacks in close proximity.[10]
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 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.[11]
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.
Female (left) and male (right) twin BNC connectors
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.[12] 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
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 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.
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
^ abThomas 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.
^[1] 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."
