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BNC connector: Definition and Types

BNC Connector

Definition of BNC connector

The BNC connector (an initialism of “Bayonet Neill–Concelman”) may be a miniature quick connect/disconnect frequency connector used for coax.

BNC connector: Definition and Types

Description

The interface specifications for the BNC and lots of other connectors are referenced in MIL-STD-348. It features two bayonet lugs on the feminine connector; mating is fully achieved with 1 / 4 turn of the coupling nut. BNC connectors are used with miniature to subminiature coax in radio, television, and other radio-frequency equipment.

The BNC was commonly used for early computer networks, including ARCnet, the IBM PC Network, and therefore the 10BASE2 variant of Ethernet. They are usually applied for frequencies below 4 GHz and voltages below 500 volts.

Types

BNC connectors are most ordinarily made ohm versions, matched to be used with cables of an equivalent characteristic impedance. The 75-ohm types can sometimes be recognized by the reduced or absent dielectric within the mating ends but this is often by no means reliable. There was a proposal within the early 1970s for the dielectric material to be colored red in 75-ohm connectors, and while this is often occasionally implemented, it didn’t become standard.

The 75-ohm connector is dimensionally slightly different from the 50-ohm variant, but the 2 nevertheless are often made to mate. The 50-ohm connectors are typically specified to be used at frequencies up to 4 GHz and therefore the 75-ohm version up to 2 GHz.

A 95-ohm variant is employed within the aerospace sector, but rarely elsewhere. It is used with 95-ohm connections for glass displays on some aircraft.

BNC connector: Definition and Types


Video and the DS3 Telco headquarters applications use 75-ohm BNC connectors and 50-ohm connectors are used for data and RF. Many VHF receivers used 75-ohm antenna inputs, in order that they often used 75 ohm BNC connectors.
Reverse-polarity BNC (RP-BNC) may be a variation of the BNC specification which reverses the polarity of the interface.

In a connector of this sort, the feminine contact normally found during a jack is typically within the plug, while the male contact normally found during a plug is in the jack. This guarantees reverse polarity interface connectors don’t cope with the standard interface connectors. The SHV connector can also be a high-voltage BNC variant that uses reverse polarity configuration.

Smaller versions of the BNC connector i.e. High-density BNC and Mini BNC are manufactured by Amphenol. While retaining the electrical characteristics of the primary specification, they have smaller footprints giving a far better packing density on circuit boards and equipment backplanes.

These connectors have a 75-ohm impedance which makes them suitable for HD video applications.

Compatibility

The different versions are designed to deal with each other, and a 75 ohm and a 50 ohm BNC connector which both suits the 2007 IEC standard, IEC 60169-8, will mate non-destructively. At least 1 manufacturer claims very high reliability for the connector’s compatibility.

At frequencies that are below 10 MHz, the impedance will 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, to be used with any impedance of the cable. Above this frequency, however, the mismatch becomes progressively more significant and may cause signal reflections.

BNC connector: Definition and Types


SHV and MHV connectors (for high voltages)

Safe High Voltage (SHV) Miniature High Voltage (MHV) connectors are suitable for all high voltage applications up to five kV DC or 3.5 kV RMS. The SHV connector uses reverse polarity configuration.

In a connector of this sort, the feminine contact normally found during a jack is typically within the plug, while the male contact normally found during a plug is in the jack. This ensures that reverse polarity interface connectors don’t mate with standard interface connectors.

The MHV connectors are easily mistaken for BNC type and may be made to mate with them by brute force. These connectors provide safer handling: center contacts are well recessed to prevent shock hazards in an unmated condition. All inner contacts are fully captivated and can withstand axial forces of 100 N minimum. When mating a connector pair the outer conductor contact is formed before the inner conductor contacts.

TNC connectors

A threaded version of the BNC connector referred to as the TNC connector is additionally available. The connector features a 50 Ω impedance and operates best within the 0–11 GHz frequency spectrum. It has better performance than the BNC connector at the microwave frequencies.

Twin BNC connectors use the same bayonet latching shell as a BNC connector. They contain two independent contact points: one is male and one is called female, allowing the connection of a 78 ohm or 95-ohm shielded differential pair like RG-108A. They can also operate up to 100 volts and 100 MHz. They cannot mate with ordinary BNC connectors.

Twinax connectors feature keyway polarization to ensure system integrity and prevent signals from being mixed, making them ideal for computer network applications.

Triaxial

Triaxial (or Triax) connectors are a variant of BNC that carry a sign and guard also as the ground conductor. Triax connectors are utilized in applications where maximum RF shielding and minimum noise radiation is required.

These are utilized in sensitive electronic measurement systems, like those made by Keithley Instruments. triaxial connectors include a three-lug arrangement so that to rule out an accidental forced mating with a BNC connector. Adaptors exist to permit some interconnection possibilities between triaxial and BNC connectors.