Bayonet Neill-Concelman connectors, or BNC connectors, are a type of radio frequency cable fitted onto coaxial cables, and send audio and video signals. BNC connectors were first introduced as a component of military-grade radio equipment, debuting in the 1940s. However, since they’re incredibly useful for transmitting audio and video signals, their usage has widely expanded past the scope of military-grade equipment. Let’s look at the current status and use of BNC connectors, especially in professional and military A/V settings.
Anatomy of the BNC Connector
BNC connectors are a type of connector for a coaxial cable that features a female connector with two bayonet lugs. Therefore, you must quarter-turn the coupling nut on the female connector to mate the male and female connectors. Further, BNC connectors have a slotted outer conductor and plastic dielectric present on both gender connectors. However, some BNC connectors may have reduced or no dielectric present, especially the 75-ohm configuration of the connector.
BNC connectors maintain a characteristic impedance of 50 or 75 ohms. However, other characteristic impedance ratings, like 93 ohms, are available for alternate use cases of the BNC connector. But these additional ratings are less common than the 50 and 75-impedances.
We typically use BNC connectors for audio or video signals projecting at 4GHz or lower and running at 500 volts or less. However, the cable can handle up to 11GHz, albeit suffering severe stability issues over 4GHz. Some cables can only handle up to 2GHz.
BNC Connectors: Uses
BNC connectors first debuted on the market for use in military-grade radio frequency electronics. However, these connectors have been embraced and accepted and used in the audio/video community for their stability and versatile use cases within the A/V model. Most cables are only stable up to 2GHz but remain widely applicable for transmitting audio and video frequencies.
You can also use BNC connectors to connect miniature-to-subminiature coaxial cables in television, radio, and other consumer, commercial, and military-grade radio-frequency electronic equipment. For example, one of the most common uses of BNC connectors is video switchers in television studios. BNC connectors also saw use in early computer networking, including early networks like the IBM PC Network, ARCnet, and the 10BASE2 configuration of ethernet connections.
Additionally, we currently use BNC connectors in the following industries and use cases:
- Analog interface signals
- Serial digital interface video signals
- Radio antennas
- Avionics (aerospace electronics)
- Nuclear instruments
- Test equipment
BNC connectors are also commonly used in composite cables for analog composite video and digital video interconnections. We will not typically outfit consumer electronic devices with BNC connectors. We usually reserve this privilege for commercial A/V devices. However, we can still mate devices if we use an adapter. Digital recording studios also use BNC connectors to synchronize multiple audio recordings to a transmitted world clock timing signal. Finally, the 10BASE2 thin ethernet cables use BNC connectors to connect to the coaxial cable.
BNC connectors will typically be connected into a panel of connections, called a BNC field, since these setups can regularly house ten or more BNC connections. Cable connections are made to be fitted using the crimping method rather than soldering. However, crimping requires a special tool or power tools to complete. So, you won’t be able to install BNC connectors with your bare hands unless you have the female connector pre-fitted.
Types of BNC Connectors and Compatibility
- BNC Female to Coaxial F Female adapter
- All metal construction for improved durability
- For use with CCTV cameras
- Size: 6 x 4 x 1 inches
There are several types of BNC connectors on the market. We can typically sort them into two primary categories of 50 and 75-ohm configurations. 50 and 75-ohm BNC connectors are not the same and should not be mated. However, with some force, you can actually mate a 50 and 75-ohm BNC connector despite the differences in dimension. 50-ohm cables are used for video signals topping out 4GHz, stably, while 75-ohm cables should only be used with signals topping out at 2GHz in transmission signals. 75-ohm connectors see the most usage in video and DS3 Telco signals, while the 50-ohm connectors are more commonly used for radio frequencies and data transfer. Additionally, VHF receivers commonly use a 75-ohm antenna input. So, we use 75-ohm BNC connectors for these devices.
- Length: 20cm
- Female RP-BNC-J to Male MCX-JW cable
- Used for Audio transmission
- Brand: Aexit
(As of July 14, 2023, this product is currently unavailable on Amazon. Please check back later.)
There are also reverse-polarity BNC connectors (RP-BNC) that reverse the direction of the signal’s polarity when it passes through the connector. However, RP-BNC cables cannot mate with standard BNC cables. Swapping the configuration of the male and female connectors in the reverse polarity setup ensures this.
- Male Mini BNC to Female BNC cable
- Length: 30cm
- Impedance: 75 ohm
- Used for: Video monitor, cameras, camcorders
Additionally, smaller market variations of the BNC connector include the Mini BNC and the High-Density BNC (HD-BNC). Amphenol alone produces these alternate sizes of BNC connectors. They have a smaller electronic footprint than the standard BNC connector while maintaining their power by increasing their density on the circuit board. They also have a true 75-ohm impedance, which is ideal for transmitting HD video.
- Female BNC to Female HD Micro BNC cable
- Length: 1ft
- Impedance: 75 ohm
- Includes braided dual copper shielding against interference in addition to increased strength and flexibility.
Different types of BNC connectors are actually constructed to mate with various other types of BNC connectors. However, this can cause some issues when the signal matches only one side of the connection. In fact, for signals under 10MHz, whether you’re using a 50 or 75-ohm connector is entirely negligible. So it won’t matter if you mate two different cables. Thus, all BNC connectors are designed to run at 50 ohms and can adapt to the cable’s impedance.
Do I Need a BNC Inserter/Remover Tool?
You do not need a BNC inserter/remover tool for a single BNC connection. BNC inserter/remover tools are designed for use in a large studio with BNC fields. BNC fields are typically tight, and it is hard to install the connections with your bare hands because your fingers are just too fat to fit between the cable connectors. Thus, BNC inserter/remover tools were born and designed to mass insert and remove BNC connections from BNC fields. Therefore, as long as you have full use of your hands, you should be able to install a single BNC connection without any assistance or tools.
Similar Connectors to the BNC Connector
There are a lot of connectors out there for cables, especially coaxial cables. The US military standard goes over the requirements and testing conditions for the various cables that might be used, including BNC connections.
The SR connection is the USSR’s equivalent of the BNC connector. The two connections are mostly analogous. However, due to slight changes that were made when converting the Imperial measurements used to design the connector, the dimensions of the two connectors are very slightly different. Despite this issue, you can still typically mate the two cables by sheer brute force.
Threaded Neill-Concelman (TNC)
The TNC is simply a BNC cable featuring threading for additional stability and durability. It’s almost entirely analogous to the BNC connection. However, the Threaded cable consistently outperforms the standard BNC cable when transmitting microwave frequencies.
Twin BNC (Twinax)
- Male Twin BNC (Twinax) to Female jack addapters
- Compatible with RG59, RG108A, and RG108
- Brand: Youkitty
The Twinax connector has an identical bayonet latching shell to the BNC connector but maintains two contact points, allowing for a 78 or 95-ohm connection shielded as a differential pair. We can operate them up to 100MHz and 100 volts and we cannot make them mate with a traditional BNC connector. The official abbreviation for the Twinax connector is BNO.
- Male TRX BNC (triax) adapter
- Brand: Keithley Instruments
- For use in audio / video applications
- Weight: 1.5lb
A Triax connector is a connector based on the BNC connector that carries a signal, guard, and ground conductor. Triaxes are typically used in high-sensitivity electronic measurement systems. We could force early Triax cables to mate with BNC cables, but recent cables have a third lug to prevent this.
We can sometimes use MHV and SHV connectors with BNC connectors, especially MHV connectors. We can force MHV connectors to mate with BNC connectors. However, the SHV connector was made specifically to combat the forced misuse of the MHV connector with incompatible connectors. We typically use these connections for electronics that run above 500 volts.
While BNC connectors maintain a position of relative importance in the electronics industry, some manufacturers are slowly beginning to replace them with LEMO 00 miniature connections that allow for greater densities than standard BNC connections, making them ideal for some connections. However, DIN 1.0/2.3 and HD BNC connectors are still the industry standard for transmitting HD video signals in the current video industry.
If you want to or have already started work in the video industry, it’s going to be essential that you get comfortable with BNC connections; they’ll be everywhere! Identifying and servicing BNC connectors can save you a lot of money and time when servicing your electronics.
We hope you enjoyed a little walk down the historical path of the BNC connector. If you liked what we brought to the table here, leave us a comment here or on social media!
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