SMA Connector

• Mastering SMA connector installation is easier than you think.
• A reliable connection protects your signal—and learning the right technique saves money.
• You can do this at home with basic tools and a careful approach.

Are you working with coaxial cables and want your SMA connector connections to be rock solid? If so, you’re in the right place. I recently went hands-on with an LMR240 cable, documenting each step as I installed an SMA connector from start to finish. The process was surprisingly straightforward—if you have a little patience and pay attention to some details.

Why Choose the SMA Connector?

The SMA connector is popular in RF applications due to its reliability and consistency. Whether you’re building a custom antenna cable or repairing old equipment, knowing how to crimp or solder an SMA connector empowers you to extend cable life and ensure strong, low-loss connections. That means a better signal, lower interference, and fewer dropped packets.

Here’s what you’ll need:

• LMR240 coaxial cable (or similar)
• SMA connector set (usually in 3 pieces)
• Cable cutter/stripper
• Crimping tool (with 0.052 and 0.255 dies)
• Heat shrink tubing
• Multimeter (for testing continuity)

Step 1: Preparation—Cut and Strip the Cable

The first thing I did was give the LMR240 cable a clean, square cut. This is important—you want to avoid crushing or distorting the inner insulation. Don’t rush this step. For stripping, I used an RG59 stripper simply because it was handy. You can improvise with a sharp cable cutter if you’re gentle and precise.

I stripped the outer jacket back about 10 millimeters, as this length gives enough room to fold back the braided shield and attach the connector. If you over-strip, it’s not a tragedy, but you’ll want to avoid excess exposed shield.

Pro Tip:
Be careful not to nick the inner foil or the center conductor while stripping. Integrity here means a stronger, longer-lasting connection.

Step 2: Preparing the Shield and Installing the Connector

With the jacket off, I carefully peeled back the braided shield. Sometimes, the strands get messy, but take a few extra seconds to separate them from the foil. Make sure there’s no contact between the braid and inner conductor—this helps prevent shorts that could ruin your signal.

Next comes the metal coupler. Slide it onto the cable before anything else (I’ve forgotten this in the past—it’s frustrating to have to start over). Then, trim the center conductor down to 3 millimeters. It’s a tiny bit of wire, but trimming is crucial for a snug fit in the connector pin.

Step 3: Crimping the Pin and Assembling the SMA Connector

The center pin is the trickiest part. My hands are big, but the pin is really small. I found it easier to pre-load the pin into the 0.052 die of my crimping tool first. After snugging the stripped conductor into the pin, I squeezed gently until the pin felt firmly attached. Soldering is possible for extra security, but not always necessary for a solid mechanical fit.

Once that’s done, slide the main connector body onto the cable. The center pin should poke out nicely, and you can push the braid back up over the ferrule. Didn’t trim enough? That’s okay—just tidy any wild strands. I used the 0.255 die to crimp the shield and main body together.

• Inspect your crimp. It should be secure but not crushed.

Step 4: Sealing and Testing Your SMA Connector

An often overlooked step is heat-shrinking the joint. I added a small section of heat shrink tubing around the connector’s base. When shrunk, it adds strain relief and keeps out moisture—your connection will last longer.

Before calling it a day, I grabbed my multimeter and checked continuity:

• Center to center: Good connection.
• Outer shield to outer shield: Good connection.
• Center to shield: No continuity (this is good).

With everything tested, I felt confident this cable was ready for use.

Final Thoughts: Why DIY Your SMA Connector?

Building your own cable means you can get the exact cable length you need, use high-quality materials, and avoid the expense of custom cables. While commercially pre-made assemblies are widely available—for example, from reputable sources like Times Microwave or RF Industries—installing your own SMA connector can be a cost-effective way to learn and maintain your equipment.

I’ve found that understanding the process makes troubleshooting much easier in the future, too.

Some final pointers:

• Practice on scrap cable before your final assembly.
• Invest in a decent crimping tool: cheap tools can deform connectors.
• If in doubt, consult the Amphenol RF connector guides for diagrams and tips.

Frequently Asked Questions (FAQ)

Q: What does SMA stand for?
SMA stands for SubMiniature version A. It’s a family of coaxial RF connectors prevalent in RF and microwave applications.

Q: Can I solder instead of crimping the SMA connector?
Yes, soldering is an option, especially for center pins. Crimp connections are faster and less likely to damage the dielectric insulation, but solder may provide extra security.

Q: What if my cable doesn’t fit the connector?
Coaxial cables come in various sizes. Make sure your SMA connector is matched for your specific cable. Trying to force a mismatched connector can result in poor performance.

Q: Do I need special tools for SMA connectors?
For consistent results, a proper coaxial cable stripper and crimping tool are highly recommended. You can improvise with a sharp blade, but precision matters for signal quality.

Q: How can I tell if my connection is good?
Test with a multimeter for continuity and absence of shorts. When possible, test with your actual RF device. If you experience high loss or signal degradation, recheck your assembly.