RF connectors constitute a transmission system where both inner and outer conductors align along the same axis, supported by insulation, to facilitate connections between various subsystems within a communication system or to convey signals between different components. Primarily employed for transmitting RF signals, they also offer robust shielding capabilities, with certain models effectively mitigating impedance variations at connection points. With a diverse range of types available, this article will provide a detailed overview of BNC connectors.

BNC Connector Summary

The BNC connector is one of the most common RF connectors, characterized by its small size and quick-connect bayonet-style design, widely used in applications with frequencies below 4GHz.

Origin of the BNC Connector

The BNC connector, named after its inventors Paul Neill and Carl Concelman, stands for Bayonet Nut Connector, a name that vividly describes its appearance and the bayonet locking mechanism it employs. Neill, who previously worked at Bell Labs and invented the N connector, and Concelman, who worked at Amphenol and invented the C connector, collaborated on its development.

The foundation of the BNC connector's development is primarily attributed to the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering at the University of Pennsylvania. While working at Hazeltine Electronics Corporation in 1945, he applied for a patent for a coaxial cable connector designed to minimize wave reflections/losses. The patent was granted in 1951.

BNC straight male connector with crimp/solder attachment, 0.195 inches

The BNC connector is widely utilized in wireless communication systems, television, testing equipment, and RF electronics, with early computer networks also employing BNC connectors. The signal frequency range supported by BNC connectors spans from 0 to 4 GHz, although utilizing specialized high-quality versions designed for this frequency allows operation at frequencies as high as 12 GHz. BNC connectors are available in two characteristic impedance variants: 50 ohms and 75 ohms, with the 50-ohm variant being more popular.

Performance of BNC Connectors

For low-frequency and DC circuits, virtually any standard connector can transmit current through mechanical linkage. However, radio frequency requirements necessitate minimizing impedance variations in connections to avoid reflections and impedance mismatch-induced wave destruction.

BNC connectors are constant impedance connectors, meaning their characteristic impedance remains consistent throughout the connection, equivalent to the characteristic impedance of coaxial cables. As radio frequency signals propagate along coaxial cables, encountering no impedance variation when passing through BNC connectors, they exhibit fewer reflections and lower losses, rendering BNC connectors an ideal choice for RF applications.

BNC Male Right Angle Connector, Crimp/Solder Accessories

BNC connectors can handle up to 4 GHz, but they are typically utilized for voltages and frequencies below 500V and 3 GHz, respectively. The following features are generally shared by all BNC connectors, although they may vary depending on the manufacturer. Taking the Pasternack product EZ-240-SM-X as an example, its performance specifications are showcased.

The Structure and Applications of BNC Connectors

BNC Connector Construction and Applications

There are numerous formats available for BNC connectors. In addition to plugs and sockets, other RF components such as attenuators and adapters can also be used in conjunction with them.

In addition to possessing the necessary impedance, BNC plugs also adhere to specific coaxial cable formats. Consequently, all internal components are compatible with the coaxial cable being used. Thus, the BNC plug for the cable to be used must be specified. While there is some flexibility, it is advisable to select the appropriate cable format.

The most common types of connectors are straight connectors and right-angle connectors. Right-angle connectors are particularly suitable for situations where the cable must exit the connector neatly or in environments with limited space. Unfortunately, right-angle connectors incur slightly higher losses compared to straight connectors. For most applications, this may not pose a significant issue, but there might be a slight variation when operating close to the frequency limits of the connector.

12G SDI 75 ohm BNC right-angle female connector, panel mount.

BNC connectors find their most widespread applications in RF and video functions, including testing equipment, nuclear instrumentation, aviation electronics, radio antennas, and serial digital interface video signals.

In commercial video equipment, BNC connectors can replace RCA connectors for transmitting composite video signals. Typically, one BNC connector is needed to connect consumer electronics with RCA jacks to commercial video equipment. Additionally, BNC connectors are extensively used in recording studios for transmitting timing signals, enabling synchronization among various digital recording devices.

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