BNC Connectors

Specifications

Use

The BNC was originally designed for military use and has gained wide acceptance in video and RF applications to 2 GHz. The BNC uses a slotted outer conductor 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. Both 50 ohm and 75 ohm versions are available. The BNC connector is used for signal connections such as:

• analog and serial digital interface video signals
• amateur radio antennas
• aerospace electronics (avionics)
• test equipment.

It is an alternative to the RCA connector when used for composite video on commercial video devices, although many consumer electronics devices with RCA jacks can be used with BNC-only commercial video equipment via a simple adapter. BNC connectors were commonly used on 10base2 thin Ethernet networks, both on cable interconnections and network cards. The TNC (threaded) connector is used for stable performance at higher frequencies than used with the BNC connector.

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.

Types

BNC connectors exist 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. The 50 and 75 ohm connectors are typically specified for use at frequencies up to 4 and 2 GHz respectively.

Video 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

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