# BNC connector
The BNC connector (Bayonet Neill–Concelman) is a miniature radio-frequency coaxial connector with a bayonet locking mechanism, standardized with a 6.5 mm (0.256 in) inner diameter of the outer conductor and used for quick connect/disconnect of low-power coaxial lines in instrumentation, video, and telecommunications.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [2](https://webstore.iec.ch/en/publication/4753)
| Key fact | Detail |
|---|---|
| Full name | Bayonet Neill–Concelman, after Paul Neill of Bell Labs and Carl Concelman of Amphenol[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [3](https://www.amphenolrf.com/en-us/assets/file/4065861575/) |
| Coupling | Two-stud bayonet lock; mating is achieved with a quarter turn of the coupling nut[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [3](https://www.amphenolrf.com/en-us/assets/file/4065861575/) |
| Impedance | 50 Ω standard; 75 Ω versions widely used for video[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) |
| Frequency limit | About 4 GHz for standard designs, because the bayonet slots begin to radiate above that; 75 Ω designs commonly support up to 2 GHz[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) |
| Interface size | Inner diameter of outer conductor 6.5 mm (0.256 in), per IEC 61169-8[2](https://webstore.iec.ch/en/publication/4753) |
| Typical uses | Oscilloscopes and test equipment, UHF radio, broadcast video (SDI), CCTV and CATV, early 10BASE2 Ethernet[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [4](https://www.ti.com/lit/ug/snla188/snla188.pdf?ts=1779833382223) |
| Key standards | IEC 61169-8 (international) and MIL-C-39012 (US military)[2](https://webstore.iec.ch/en/publication/4753) • [5](https://www.commscope.com/globalassets/digizuite/2418-design-fundamentals-for-high-bandwidth-bnc-connectors-wp-111203-en.pdf?r=1) |
## Design and coupling
A BNC connection joins a male plug and a female jack, each a two-conductor coaxial interface: a center contact carries the signal, and the outer shell and sleeve carry the return, which in many applications is grounded.[6](https://patents.justia.com/patent/6517359) The female side carries two diametrically opposed engagement pins that extend radially outward from its sleeve; the male side has a locking collar with a pair of slots. When the collar is rotated, the pins ride in the slots and the two halves are drawn together and locked.[6](https://patents.justia.com/patent/6517359) In the common plug construction, a pin in the female receptacle engages a ramped circumferential groove in the male bayonet sleeve, so rotation pulls the receptacle and connector snugly together, with a concave spring washer inside the rear of the sleeve providing biasing force.[7](https://patents.google.com/patent/US6857891)
The bayonet mechanism is the connector's defining practical feature: it mates with only a quarter turn of the coupling nut, giving tactile feedback and a positive lock, which is why BNC remains favored on test benches where cables are connected and removed frequently.[3](https://www.amphenolrf.com/en-us/assets/file/4065861575/) • [8](https://www.amphenolrf.com/connectors/hd-bnc-connectors.html) The trade-off is mechanical: a bayonet resists vibration less well than a threaded coupling, which is why the threaded TNC variant exists for mobile and outdoor radio use.[9](https://placapcb.com/blog/tipos-conectores-coaxiales-guia-bnc-sma-n-tnc-fakra)
## History
The BNC descends from two WWII-era connectors. Wartime radar created the need for frequency-dependent connector performance, and Paul Neill, an engineer at [Bell Labs](https://www.edgepedia.org/bell-labs), is credited with the first performance-driven connector, the threaded type N. Shortly afterward, Karl Concelman, an engineer at IPC, the predecessor of Amphenol RF, developed the type C, a bayonet-coupled connector with a Teflon dielectric interface. Many later connectors, including the BNC, were derived from these two.[7](https://patents.google.com/patent/US6857891) Amphenol RF describes the BNC as developed in the late 1940s as a miniature version of the type C connector, named for Amphenol engineer Carl Concelman together with Neill.[3](https://www.amphenolrf.com/en-us/assets/file/4065861575/)
An earlier design underlies the name. Octavio M. Salati filed a US patent application for an electrical connector for coaxial transmission lines on May 19, 1945, and the patent, US 2,540,012, was granted on January 30, 1951.[10](https://patents.google.com/patent/US2540012A/en) The BNC is accordingly considered an iterative improvement of Salati's design rather than an entirely new invention.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) Salati's patent addressed a problem that still defines BNC design: reflections occur wherever the connector's characteristic impedance differs from that of the transmission line, and his goal was a small, sturdy connector that avoided such reflections while withstanding voltages of several thousand volts.[10](https://patents.google.com/patent/US2540012A/en)
The threaded TNC variant, essentially a BNC with threads instead of a bayonet, is credited to General RF Fittings (GRFF), the predecessor of SV Microwave.[7](https://patents.google.com/patent/US6857891)
## Electrical characteristics
Standard BNC connectors are 50 Ω, and 75 Ω versions are also commonplace; both impedances are provided for in the original military specification, MIL-C-39012, which governs all the interface dimensions but leaves insulator material and crimp details to the manufacturer.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [5](https://www.commscope.com/globalassets/digizuite/2418-design-fundamentals-for-high-bandwidth-bnc-connectors-wp-111203-en.pdf?r=1) The two versions are intermateable without restrictions, because the interface dimensions are shared; however, within those standardized mating-face dimensions a perfect 75 Ω characteristic impedance cannot be realized, so 75 Ω performance depends on internal design choices such as the center pin crimp diameter and the insulator.[11](https://www.amphenolrf.com/en-us/assets/file/4065861576/) • [5](https://www.commscope.com/globalassets/digizuite/2418-design-fundamentals-for-high-bandwidth-bnc-connectors-wp-111203-en.pdf?r=1)
The frequency ceiling comes from the coupling geometry itself. Above about 4 GHz, the slots in the BNC interface begin to radiate, imposing a hard limit on the series' operating range.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) Representative manufacturer specifications for a crimp-type BNC jack give DC to 4 GHz for the 50 Ω version, DC to 1 GHz for the 75 Ω version, a working voltage of 500 VRMS maximum for both, and a maximum VSWR (voltage standing wave ratio, a measure of reflected signal) of 1.3.[12](https://www.bojiang.com.tw/en/product/456.html)
In serial digital video, the BNC's non-precision impedance was long a known limitation. [Digital video](https://www.edgepedia.org/digital-video) standards tolerate both the 50 Ω and 75 Ω versions within a fairly wide return-loss specification of ±15 dB, equivalent to a 52 Ω to 107 Ω range in a 75 Ω system; this was acceptable for signals with rise times of 500 ps to 1.5 ns, but high-definition serial links with rise times under 270 ps made the limitation more pronounced, prompting manufacturers to produce 75 Ω BNCs with good return loss above 2 GHz.[4](https://www.ti.com/lit/ug/snla188/snla188.pdf?ts=1779833382223)
## Standards
The international sectional specification is IEC 61169-8:2007, which covers RF coaxial connectors with an inner diameter of the outer conductor of 6.5 mm (0.256 in) with bayonet lock and 50 Ω characteristic impedance, intended for low-power, quick connect/disconnect applications.[2](https://webstore.iec.ch/en/publication/4753) It superseded IEC 60169-8:1978, whose 1997 amendment added informative interface dimensions allowing 75 Ω BNC connectors to mate with the 50 Ω connectors of the standard in a non-destructive manner.[13](https://cdn.standards.iteh.ai/samples/1523/3eb88f9b8998420dbd4cbde52e2ed20f/IEC-60169-8-1978-AMD2-1997.pdf) In the United States, MIL-C-39012 is the specification used by every major connector manufacturer for both 50 Ω and 75 Ω BNCs; it fixes the interface dimensions, including the 0.053 inch (±0.001) male center pin at the interface point, but does not specify insulator material, size, shape, or crimp dimensions.[5](https://www.commscope.com/globalassets/digizuite/2418-design-fundamentals-for-high-bandwidth-bnc-connectors-wp-111203-en.pdf?r=1)
## Applications
The 75 Ω version serves analog and digital video transmission, including MATV building distribution, CCTV, and CATV.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) Serial digital video systems in broadcast have employed BNC connectors since the analog era, and the connector remains the standard interface for SDI equipment.[4](https://www.ti.com/lit/ug/snla188/snla188.pdf?ts=1779833382223) BNC is also the common connector for coupling low-voltage signals to measurement instruments such as oscilloscopes.[14](https://patents.google.com/patent/US7114956B2/en)
A practical rule when mixing connector families in one RF system is that the connector with the lowest frequency range sets the frequency range of the whole system; [Rohde & Schwarz](https://www.edgepedia.org/rohde-and-schwarz)'s guidance lists BNC at 4 GHz, well below SMA at 12 GHz or TNC at 15 GHz.[15](https://www.wainwright-filters.com/blog/content/uploads/2020/04/Guide-to-Selecting-Handling-Coaxial-Connectors.pdf)
## Variants
Beyond the TNC threaded version, manufacturers have produced higher-density and higher-frequency derivatives. Amphenol's HD-BNC keeps the push-and-turn bayonet interface but delivers true 50 Ω and 75 Ω performance in a footprint four times smaller than a traditional BNC, with 12 G 75 Ω products supporting 4K-SDI and ultra-high-definition video.[8](https://www.amphenolrf.com/connectors/hd-bnc-connectors.html) Standard 75 Ω BNC products have also been extended upward: 12G-SDI broadcast solutions specify BNC connectors operating from DC to 12 GHz with return loss of at least 30 dB from DC to 6 GHz, and Belden sells a 12 GHz Series 7 75 Ω BNC connector meeting SMPTE 2082-1 return-loss requirements.[16](https://www.amphenolrf.com/zh-cn/assets/file/4067456701/) • [17](https://www.belden.com/products/connectors/coaxial-connectors/standard-and-micro-bnc-connectors/4794rbuhd1-b50) Other variants include reverse-polarity BNCs, which swap the male and female center conductors to prevent accidental mating of incompatible technologies, and isolated connectors with a non-metallic insulating shell, designed so that a damaged shell on an instrument such as an oscilloscope can be replaced by the user without opening the housing.[1](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc) • [14](https://patents.google.com/patent/US7114956B2/en)
## References
1. [BNC, Powertec Information Portal](https://portal.powertec.com.au/equipment/rf-communications/rf-connectors/rf-connector-series/bnc)
2. [IEC 61169-8:2007, Radio-frequency connectors – Part 8, IEC](https://webstore.iec.ch/en/publication/4753)
3. [Amphenol RF BNC coaxial connectors datasheet](https://www.amphenolrf.com/en-us/assets/file/4065861575/)
4. [Broadcast Video Owner's Manual, Texas Instruments / National Semiconductor](https://www.ti.com/lit/ug/snla188/snla188.pdf?ts=1779833382223)
5. [Design fundamentals for high-bandwidth BNC connectors, CommScope white paper](https://www.commscope.com/globalassets/digizuite/2418-design-fundamentals-for-high-bandwidth-bnc-connectors-wp-111203-en.pdf?r=1)
6. [US Patent 6,517,359, System and method for mating electrical connections, Justia](https://patents.justia.com/patent/6517359)
7. [US Patent 6,857,891 B1, High frequency coaxial connector, Google Patents](https://patents.google.com/patent/US6857891)
8. [HD-BNC Connectors, Amphenol RF](https://www.amphenolrf.com/connectors/hd-bnc-connectors.html)
9. [Tipos de Conectores Coaxiales: Guía Técnica, WellPCB España](https://placapcb.com/blog/tipos-conectores-coaxiales-guia-bnc-sma-n-tnc-fakra)
10. [US Patent 2,540,012 A, Electrical connector, Octavio M. Salati, Google Patents](https://patents.google.com/patent/US2540012A/en)
11. [BNC Coaxial Connectors, Amphenol RF](https://www.amphenolrf.com/en-us/assets/file/4065861576/)
12. [BNC Jack RF Coaxial connector, crimp type, Bo-Jiang](https://www.bojiang.com.tw/en/product/456.html)
13. [IEC 60169-8:1978/AMD2:1997, Annex A, iTeh Standards preview](https://cdn.standards.iteh.ai/samples/1523/3eb88f9b8998420dbd4cbde52e2ed20f/IEC-60169-8-1978-AMD2-1997.pdf)
14. [US Patent 7,114,956 B2, Isolated BNC connector with replaceable bayonet shell, Google Patents](https://patents.google.com/patent/US7114956B2/en)
15. [Guidance on Selecting and Handling Coaxial RF Connectors, Rohde & Schwarz](https://www.wainwright-filters.com/blog/content/uploads/2020/04/Guide-to-Selecting-Handling-Coaxial-Connectors.pdf)
16. [12G SDI Broadcast Solutions, Amphenol RF](https://www.amphenolrf.com/zh-cn/assets/file/4067456701/)
17. [12 GHz Series 7 BNC Connector 4794RBUHD1 B50, Belden](https://www.belden.com/products/connectors/coaxial-connectors/standard-and-micro-bnc-connectors/4794rbuhd1-b50)
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*Topic: Encyclopedia › Technology and the built world › Communications and everyday technology › Broadcast engineering and radio equipment › Broadcast antennas and RF systems › RF connectors, switches, and ancillary components*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license