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BNC Connectors Explained: 50 Ohm vs 75 Ohm

Posted in: BNC Connectors

How do BNC connectors work?

BNC (Bayonet Neill-Concelman) RF connectors make it easy to connect coaxial cables with radio-frequency equipment like radios and TVs, composite video on commercial video devices. The amount of ohms indicated basically measures electrical impedance along the coaxial cable.

They’re easy to install with a simple “snap and lock” mechanism, which ensures a high-quality connection. They arrive tested to 3 GHz. And they come in handy when you need to combine them with, say, an RCA connector on the end of the coaxial cable.

All of our BNC connectors are machined from virgin brass (in accordance with MIL-C39012) and plated with bright nickels, unlike less reliable connectors made from cheaper die cast bodies.

So what’s different?

Physically, the main differences can be found in the center pins and dielectric insulators. 75-ohm BNC connectors feature Teflon as a dielectric and surround the outer spring fingers with air. Its center pin maintains a consistent diameter in both the front and rear areas (this is important - read on to find out why). 50-ohm connectors, on the other hand, use Delrin to surround the spring fingers, and its center pin is larger in the crimp area. You’ll need different crimp tools for each type of center pin.

What’s the difference in functionality?

Both connectors can mate without damage, but you can’t really mix and match and expect to get the same video quality. For example, if you installed a traditional 50-ohm BNC connector on a 75-ohm coaxial video cable, the digital signal would be significantly distorted.

Basically, 50-ohm BNC connectors are used for older analog video applications and some RF applications. But for higher performance A/V applications like HDTVs, 75-ohm BNC devices are necessary. 75-ohm BNC connectors can, however, be used for analog purposes.

(Tip: The center pin MUST have the same diameter in the crimp area as the mating area in order to have true 75-ohm impedance. If a connector claims to be 75-ohm but doesn’t have a consistent pin length, it’s an inferior product that won’t give you what you need.)

Some BNCs have enclosed beryllium copper spring fingers. Is this necessary?

Unless you’re expecting your BNC connector to be subject lots of abuse (like the need for thousands of matings, or foreign objects poking into the connector interface), there’s no need for this design.

How does your cable pull strength stack up?

Our BNC plugs feature a diamond knurling for maximum cable retention. After testing thousands of cable assemblies, our BNCs recorded a pull-test performance of 49.3 inch lbs. on the 735A cable—unparalleled strength and durability. The industry minimum is just 30 lbs.

June 15, 2021