How To Test A Coaxial Cable?

If your signal keeps cutting out or becoming unreliable, the problem might not be with your TV, modem, or other electronic devices—it could be a faulty coaxial cable. These cables play a critical role in signal transmission across many communication systems. Whether used in broadcasting, CCTV, GPS, or automotive networks, a damaged or poorly functioning coaxial cable can lead to frustrating interruptions. At Otto Cable Technology, we manufacture high-quality coaxial cable solutions and encourage customers to test their cables regularly. This step-by-step guide explains how to test a coaxial cable using accessible tools and simple techniques.

Why Test a Coaxial Cable?

Testing a coaxial cable is important for multiple reasons, especially in environments where signal quality is essential.

First, it helps prevent signal attenuation. Over time or under stress, coaxial cables can lose their ability to carry signals efficiently. This results in weaker connections, which can be especially problematic in high-frequency or long-distance systems. Regular testing helps you detect these issues early, before they cause larger problems.

Second, testing allows you to determine if the cable is shorted or internally broken. These types of faults can occur due to physical damage, aging, or improper installation. Without testing, you might mistakenly replace functioning equipment, wasting both time and money.

Lastly, testing helps rule out other sources of system failure. By confirming that your coaxial cable is in good working order, you can shift your attention to other components if performance issues persist. This is a crucial step in structured troubleshooting and is recommended even for non-professional users.

At Otto Cable Technology, our coaxial cables are built for stability and longevity, but we always advise our clients to test their connections before assuming a cable is fault-free.

Tools You Will Need

Before you begin testing, it's important to gather a few essential tools. Fortunately, many of them are simple, inexpensive, and widely available.

The most common tool is a digital multimeter (DMM). This instrument is capable of measuring resistance and checking continuity, which is often enough for most basic testing needs.

For those who need more advanced diagnostics, a Time Domain Reflectometer (TDR) can be helpful. This device sends electrical pulses down the cable and detects where signal reflections occur, indicating breaks or impedance mismatches. Although it's not necessary for most casual users, it’s widely used in professional installations.

Another convenient option is a simple coaxial cable tester with LED indicators. These testers are designed to quickly show whether a cable is open, shorted, or functioning normally, and they are often used in the field for fast checks.

Otto Cable Technology uses all of these tools in our testing and quality assurance process to ensure that every cable meets international performance standards.

Step-by-Step Testing Process

Step 1: Power Off and Prepare the Cable

Start by disconnecting power to all devices connected to the coaxial cable. Remove the cable from both ends so it's isolated for testing. This prevents false readings or the risk of damaging your equipment.

Visually inspect the cable for any obvious signs of wear. Look for frayed ends, crushed sections, or discolored connectors. If you notice any physical damage, testing may confirm what your eyes already suspect: the cable needs to be replaced.

Make sure the connectors at both ends are clean and not rusted. Dirt or corrosion can interfere with accurate readings.

Step 2: Test for Continuity

Next, use your digital multimeter to test for continuity. Set the meter to continuity mode, which typically emits a sound when a circuit is complete.

Place one probe on the center pin of the connector at one end of the cable and the second probe on the center pin at the other end. If the multimeter beeps or shows very low resistance, the center conductor is intact.

Now, repeat the test using the outer shielding contacts on both ends of the cable. Again, a beep or low resistance means that the shielding is continuous.

Finally, check between the center conductor and the outer shield at the same end. There should be no continuity between these two points. If the multimeter emits a beep or shows a reading, that’s a sign of a short circuit inside the cable, and the cable will need to be replaced.

Step 3: Measure Resistance

To further assess the cable’s condition, switch the multimeter to resistance mode (measuring ohms). A healthy coaxial cable will show near-zero resistance—typically less than 2 ohms—between the center pins of each end. This confirms a strong internal connection.

Then, measure resistance between the outer shielding contacts on both ends. Again, the reading should be low.

If the meter shows “OL” (overload) or infinite resistance between the two ends, the cable is likely broken internally. On the other hand, if the resistance between the center conductor and the shield is too low, the cable is shorted and unusable.

At Otto Cable Technology, we ensure all of our coaxial cables maintain strict resistance thresholds, reducing the chances of such faults.

Step 4: Use a TDR for In-Depth Analysis

If you have access to a Time Domain Reflectometer, you can perform a more advanced test. This tool sends a signal pulse through the coaxial cable and measures the time it takes for reflections to return. These reflections help locate exact problem spots.

For example, if you see a sharp reflection shortly after the pulse is sent, the issue may be near the connector, such as a pinched or poorly terminated cable. A gradual slope in the reflection might indicate water damage or signal degradation over time. If no reflection returns at all, the cable could be completely severed.

While a TDR isn’t necessary for basic testing, it can be useful for longer cables or more critical systems such as automotive communication or distributed antenna networks.

How to Interpret the Results

Once you’ve completed testing, interpreting the results properly is key to taking the next step.

If your continuity tests show that both the center conductor and the shield are complete and not shorted, your coaxial cable is probably still functional. Similarly, resistance readings near zero on both the conductor and shield confirm good internal connectivity.

However, if your readings indicate open circuits (infinite resistance), internal breaks are likely. A low resistance between the conductor and the shield is a strong indicator of a short.

Even if these basic tests pass, you may still experience issues like signal drop or lag. This often points to signal attenuation, which isn't always detected through continuity testing. In such cases, using a TDR or simply replacing the cable with a high-performance version from Otto Cable Technology is a smart move.

Common issues like complete signal loss, video distortion, or network instability often trace back to cable faults such as shorts, breaks, or poor shielding. Regular testing helps you catch these issues early.

Conclusion

Testing a coaxial cable may sound technical, but with the right tools and a few minutes of your time, anyone can check whether their cable is still performing reliably. From avoiding signal loss to confirming cable health before replacing expensive devices, knowing how to test a coaxial cable offers significant value. At Otto Cable Technology, we’re proud to offer durable, rigorously tested coaxial cable solutions that meet your needs in RF, GPS, DAS, and more. Contact us today to learn how our products can improve your connectivity and system performance.