The BNC coax connector is one of the most widely used RF connectors today. It is very easy and convenient to use, and offers a very high level of performance. The BNC connector is used on test equipment for everything from oscilloscopes to audio generators, and power meters to function generators. In fact BNC connectors are used in applications where coaxial or screened cable is required, and particularly for RF applications
The BNC connector has many attributes. One its chief mechanical attributes is that it uses a bayonet fixing. This is particularly useful because it prevents accidental disconnection if the cable is pulled slightly or repeatedly moved. The BNC is also what is termed a constant impedance connector. This means that it has the same characteristic impedance across the whole of the connector. Coax cable has what is called a characteristic impedance. Accordingly any RF signals travelling along a coax cable will not see any impedance changes as they pass through the BNC connector. This is particularly important for RF applications as it will result in few reflections and a lower level of loss.
The BNC connector was developed in the late 1940s and it gains its name from a combination of the fact that it has a bayonet fixing and from the names of the designers, the letters BNC standing for Bayonet Neill Concelman. It has also been shown to stand for Bayonet Navy Connector in some references.
The BNC connector is essentially a miniature version of the C connector which was in turn a bayonet version of the N-type connector.
The BNC connector was developed as a result of the need to provide a high quality, robust connector that would be capable of being used in a wide variety of applications. Additionally it needed to be smaller than either the N-type or C-type connectors which were much larger.
The specifications of the BNC connector naturally vary from one manufacturer to another and it is always best to ensure that the particular component being purchased is suitable for the intended application. However there are a number of guidelines that can be used. The connector comes in two basic types:
Of the two versions of the BNC connector, the 50 ohm version is more widely used. Often the BNC connector is specified for operation at frequencies up to 4 GHz and it can be used up to 10 GHz provided the special top quality versions specified to that frequency are used. However it is wise to fully check the specification.