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Insight - How BNC Connector Works

Written By: 

Abhimanyu Mathur


Named after its inventors Paul Neil and Carl Concelman, Bayonet Neil-Concelman (BNC) Connectors gained popularity in high frequency communication applications soon after they were invented. Categorized in terms of their impedance, these connectors keep signals intact and are resistant to signal attenuation. One of the most common known applications of these connectors is in Cathode Ray Oscilloscope or CROs. A CRO distinctly prefers such connectors in order to be interfaced with any device.

Apart from various test equipments, these connectors are used in aviation electronics, video interfacing and radio connections. They are usually used for frequencies less than 3GHz.  Made up of alloy (preferably steel), these connectors have a tough structure but a quite simple functioning.

Let’s find out what is inside them in this Insight.

Fig. 1: External View of BNC Connector Indicating its Various Parts


External View: Image shows the top view of a conventional BNC Connector. The corrosion resistant body which is fabricated from a metal alloy is light in weight and tough.  There are grips etched in the head of the connector so that it holds firm to a connecting device. The section spring like structure facilitates wires to bent and twist without getting damaged.


Bayonet Region & Pin

Fig. 2: Mechanical Fastening System of Bayonet Mounting System

Female Bayonet Region: The image above shows one half of the bayonet mounting system. In this mechanical fastening system, the male side has pins while the female has a radially cut section. The male pin rotates down to fit at the female section and, once placed, both the parts lock firmly to each other.

Fig. 3:Image of Interfacing Section of Connector Having Pin Layers

Interfacing pin: A closer view on the interfacing section of the connector provides details of the layers near the pin: A plastic section covered by a thick metal alloy layer which is further supported by an alloy outer casing that has grooves for linking the connector.

Wire Terminals & Pattern

Fig. 4: Wire Terminals and Mechanics

Wire Connection Terminals: The terminals where wires are soldered are shown in the image above. The pin extends to give a wired connection at (Region A). The small cut section (Region B) in the connector provides space for other coaxial wire to be connected.

A wire streamliner structure in the center holds the wires together once they are connected to their respective terminals.

Fig. 5: Spiral Pattern and Grip Mechanism of Connector

            Spiral pattern and gripping: The spiral pattern through which the pin region is connected to the spring region of the connector is seen in the image above. To 

enable the user in linking the connector easily, a grip structure is provided near the bayonet connection.

Spring Arrangement & Movement


Fig. 6: Image Showing Bayonet Connector


Spring movement: The bayonet connector has a spring movement to ensure a strong connection that remains intact in case the connector is subject to jerks or shocks.

Fig. 7: Image Showing Spring Mechanism of Connector


            Arrangement of spring: Under the bayonet mount is an arrangement of a semi-circular plate, a spring and a circular plate that provide the spring S  mechanism to the mount.

Pin Structure & Protrusion


Fig. 8: Image Indicating Pin Structure and Plastic--Alloy Moldings Where it is Embedded

Structure of pin: The structure of the pin is seen after it is plucked out from the plastic and alloy moldings around it.

Fig. 9: Image Indicating Circular Pin Protrusions

The pin has two circular protrusions which tighten its placement in the plastic moldings.


Fig. 10: Ground and its Various Components

Ground: The cut section where the reference wire is connected is placed between the plastic molding structures as shown above. Like the connecting pin, its placement to is ensured to be sufficiently tight.


nice article