How to bnc connector crimping

What is a BNC Connector?

A BNC (Bayonet Neill–Concelman) connector is a common type of electrical connector used for coaxial cable. It features a bayonet-style coupling mechanism, meaning it locks into place with a quarter-turn twist, making it quick and easy to connect and disconnect. BNC connectors are widely used in radio, television, and other radio-frequency electronic equipment, test instrumentation, and, historically, in video production equipment.

Why Crimp BNC Connectors?

While BNC connectors can also be soldered or clamped, crimping is often the preferred method for professional installations due to its speed, reliability, and durability. A properly crimped connection creates a strong mechanical bond and an excellent electrical connection, minimizing signal loss and interference. This is particularly important in applications like professional video, broadcast, and high-frequency RF transmissions where signal integrity is paramount.

Tools and Materials Needed

To crimp BNC connectors, you will typically need the following:

• Coaxial Cable: The specific type of coaxial cable you are using (e.g., RG59, RG6, RG179). The cable's construction (diameter, dielectric material) will dictate the correct connector and crimp die size.
• BNC Crimp Connectors: Ensure they are compatible with your cable type and are of the 'crimp' variety.
• Coaxial Cable Stripper Tool: A specialized tool designed to strip the coaxial cable to the correct dimensions for BNC connectors. These often have multiple blades to cut the outer jacket, braid, and dielectric simultaneously to precise lengths.
• Crimp Tool: A ratcheting crimp tool with interchangeable dies. The size of the die is critical and must match the connector and cable specifications. Common die sizes for BNC connectors are .213 inches (for the pin) and .068 inches (for the ferrule).
• Cable Cutter: For clean cuts on the coaxial cable.

Step-by-Step Crimping Process

Follow these steps carefully for a successful BNC connector crimp:

1. Prepare the Cable

This is the most critical step. Using a coaxial cable stripper tool is highly recommended to ensure precise measurements. The standard stripping dimensions for most BNC connectors are:

• Outer Jacket: Strip back approximately 1/2 inch to expose the braided shield.
• Braided Shield: Carefully fold the braided shield wires back over the outer jacket. Ensure no stray braid wires are touching the center conductor.
• Dielectric: Strip back the dielectric (the white insulating material) to expose the center conductor. The length of the exposed dielectric should typically be around 3/8 inch.
• Center Conductor: Trim the exposed center conductor to a length of approximately 1/4 inch. It should protrude slightly from the end of the dielectric.

Important Note: Always refer to the manufacturer's specifications for the specific BNC connector and cable you are using, as stripping dimensions can vary slightly.

2. Install the Connector Body and Ferrule

Slide the crimp ferrule (the metal ring that will be crimped) onto the coaxial cable first. Ensure it is positioned over the folded-back braid.

Next, carefully insert the prepared cable end into the BNC connector body. The center conductor should slide through the center hole of the connector's internal pin. The dielectric should butt up against the internal shoulder of the connector body, and the folded-back braid should be visible inside the rear of the connector, ready to be captured by the ferrule.

Push the cable firmly into the connector until the dielectric is fully seated against the connector's internal stop. A properly seated cable will have the center conductor protruding slightly from the front of the connector pin, the dielectric flush with the connector body's rear opening, and the braid extending into the area where the ferrule will sit.

3. Crimp the Center Pin

Before crimping the main connector body, you need to secure the center pin. Some BNC connectors have a separate center pin that needs to be crimped onto the center conductor. If your connector has this, use the appropriate die size on your crimp tool (often .068 inches) to crimp the pin onto the conductor. Ensure a firm crimp without damaging the conductor.

Note: Many modern BNC crimp connectors have the center pin pre-attached or integrated, simplifying this step.

4. Crimp the Connector Ferrule

Slide the crimp ferrule forward, over the folded-back braid and onto the rear section of the BNC connector body. Position the ferrule so it covers the exposed braid entirely.

Using your crimp tool with the correct die size (typically .213 inches for the ferrule on common RG59/RG6), place the ferrule into the die. Squeeze the crimp tool handles firmly until the ratcheting mechanism releases. This ensures a full, consistent crimp.

The crimp should create a secure mechanical connection, effectively binding the braid to the connector body. Inspect the crimp to ensure it is uniform and tight.

5. Test the Connection

After crimping, it's essential to test the connection:

• Visual Inspection: Check for any stray wire strands from the braid that might be shorting the center conductor. Ensure the ferrule is evenly crimped.
• Continuity Test: Use a multimeter or cable tester to check for continuity between the center conductor of one end and the center conductor of the other, and similarly for the outer shield. Also, check for shorts between the center conductor and the shield.
• Signal Test (if applicable): For video or RF applications, connect the cable and test the signal quality.

Common Mistakes and Tips

• Incorrect Stripping Dimensions: Too much or too little exposure of conductor, dielectric, or braid will lead to poor performance or failure.
• Wrong Crimp Die Size: Using the wrong die size will result in a loose connection (too large) or a crushed connector (too small).
• Stray Braid Wires: Ensure no braid strands touch the center conductor, as this causes a short circuit.
• Incomplete Crimp: Always ensure the ratcheting crimp tool completes its cycle for a secure crimp.
• Using the Wrong Connector Type: Ensure the BNC connector is designed for your specific cable type (e.g., RG59 vs. RG6).

By following these steps and paying close attention to detail, you can reliably crimp BNC connectors for a wide range of applications.