Choosing the Right BNC Connector for Your CCTV Install
Quick Answer
Use twist-on BNC connectors only for short indoor or temporary runs. Use crimp connectors for standard professional installs. Use compression connectors for outdoor, coastal, or exposed sites, since they form a full seal against moisture that crimp and twist-on cannot match.
Most callbacks on analogue and HD-over-coax CCTV systems trace back to the connector, not the camera or the cable. A BNC connector fitted the wrong way for the job will work fine on the bench and fail six months later on site, usually as signal dropout, image noise, or full video loss. Getting the connector type right at install time is a lot cheaper than a return visit.
BNC (Bayonet Neill-Concelman) connectors use a quarter-turn bayonet lock to join coaxial cable to a camera, DVR, or monitor. For CCTV, they are always specified in 75 ohm to match RG59 and RG6 coaxial cable. A 50 ohm BNC, more common in test equipment and radio applications, will physically fit but will not maintain the correct impedance for a clean video signal.
The Three Connector Types
There are three ways to terminate a BNC connector onto coax, and the right choice depends on the install, not personal preference.
Twist-on connectors screw directly onto the prepared cable end with no tool required. They are the fastest option and fine for short, temporary, or indoor test runs. They are also the least reliable long term, since the connection relies on friction rather than a mechanical crimp or seal, and they are the first thing to fail on outdoor or high-vibration installs.
Crimp connectors are a three-piece assembly, a centre pin, connector body, and a ferrule, fitted with a dedicated crimping tool. The crimp compresses the ferrule firmly onto the cable braid and locks the centre pin in place, giving a secure connection that will not work loose. This is the standard choice for professional CCTV installs.
Compression connectors are a one-piece design fitted with a compression tool that presses the connector down around the cable in a full 360 degree seal. They take a similar amount of time to fit as a crimp connector but form a better seal against moisture, making them the preferred option for outdoor cameras, coastal sites, or anywhere the connection will be exposed to weather.
Matching Connector to Cable
- RG59 coax, the standard for most CCTV runs under 300m, pairs with BNC connectors sized for RG59.
- RG6 coax, used for longer runs or higher bandwidth HD-over-coax signals, needs a BNC connector sized for RG6. RG59 and RG6 connectors are not interchangeable, the centre pin and ferrule dimensions differ.
- Siamese cable, which bundles RG59 video coax with a separate power lead in one jacket, still terminates with a standard BNC connector on the video side and a DC barrel plug on the power side.
Outdoor and Exposed Installs
For any camera mounted outside, under eaves, on a fence line, or anywhere exposed to rain or humidity, compression connectors are worth the small extra time over crimp. Water ingress at the connector is one of the most common causes of gradual signal degradation on outdoor CCTV, often showing up as intermittent noise long before the connection fails outright. For a full breakdown of outdoor cabling considerations, see our Security Camera Cabling Guide.
Where a Siamese cable is also carrying camera power, run distance affects voltage at the camera end the same way it does on any low voltage DC circuit. Our Voltage Drop Calculator covers 12V DC and 24V AC camera power runs alongside the other common voltages used across a site. If the job also involves door contacts, keypads, or other alarm wiring, our Security Cable Core Count & Shielding page covers choosing the right cable for those runs.
Quick Reference
| Connector Type | Tool Required | Best For |
|---|---|---|
| Twist-on | None | Short indoor or temporary runs |
| Crimp | Crimp tool | Standard professional installs, indoor or protected outdoor |
| Compression | Compression tool | Outdoor, coastal, or exposed installs |
Frequently Asked Questions
Can I use a 50 ohm BNC connector for CCTV?
No. CCTV always uses 75 ohm BNC connectors to match the impedance of RG59 and RG6 coax. A 50 ohm connector will physically fit but will not maintain a clean video signal, and is intended for test equipment and radio applications instead.
Are RG59 and RG6 BNC connectors interchangeable?
No. RG59 and RG6 connectors are sized differently to match the centre pin and ferrule dimensions of each cable type. Using the wrong size connector on a cable results in a poor or intermittent connection even if the connector appears to fit.
Do I need a special tool for crimp or compression BNC connectors?
Yes. Crimp connectors require a crimping tool, and compression connectors require a compression tool. Both tools are cable size specific, so check the tool is rated for RG59 or RG6 before buying.
Is a twist-on BNC connector ever good enough for a permanent install?
It can work for short, protected, indoor runs, but it is not recommended for anything outdoor, high vibration, or long term, since the connection relies on friction rather than a mechanical crimp or seal.
What is the difference between crimp and compression connectors?
Crimp connectors use a three piece assembly compressed onto the cable with a crimping tool, giving a secure mechanical connection. Compression connectors are a one piece design that seals fully around the cable, offering better weatherproofing at a similar install time.
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