How to Test Coax Cable? Check Signal Strength, Loss and Connectivity

RF coaxial cables are integral to the functioning of radios and TVs, transferring signals from the transmitter to the antenna. These cables consist of internal metal cords and an external metal braid mesh, forming a resistive coax. However, these cables can get damaged, such as cuts or cracks in their layers, which can disrupt the functioning of the transmitter.

If you notice that your transmitter isn’t performing optimally or if you’re experiencing frequent signal losses without any apparent reason, it’s advisable to test your coax cable. This guide will provide you with reliable methods to test your coax cable for signal loss.

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Testing Coaxial Cable

There are several methods to test a coaxial cable to ensure it’s transmitting reliable signal frequencies. Here are two of the most common methods:

Testing Coax Cable with a Multimeter

To test a coaxial cable with a multimeter and probe, follow these steps:

  • Disconnect both ends of the coax from any devices it’s connected to, such as a cable splitter or TV.
  • Coil the ends of the cable to make measurements with the multimeter easier.
  • Connect the cords of the testing probe to the appropriate ends of the multimeter (red positive into the ‘+’ marked jack and black negative into the ‘COM’ jack).
  • Touch one lead to the outer metal part of the PL-259 plug and the other to the center pin. If you don’t hear any sound, then the coax is not shorted.
  • Set the multimeter to ‘Continuity’ or ‘CONT’ to take measurements.
  • Connect the negative end of the multimeter probe to the center wire/pin at one side of the coax, ensuring it’s not touching the outer layer. Connect the positive end of the multimeter probe to the center wire/pin at the other side of the coax.
  • Analyze the tone emitted from the multimeter’s speaker. If a tone is emitted, then the coaxial cable is working correctly and the signal is not breaking through it.
  • If you’re using a coaxial connector, touch the outer jacket of it with the negative probe. If you’re not using a connector, touch the braided outer wire with the negative probe. If you hear any noise, then the insulation in the coaxial cable is broken and it’s likely the cause of the signal loss. In this case, it’s advisable to replace the wire with a high-quality coaxial cable.

Tracing a Coaxial Cable

If your coaxial cable runs through an attic or wall, you’ll first need to trace it. Here’s how:

  • Gather the necessary tools, such as a continuity tester and explorer for the coax and masking tape to mark the coax cable path.
  • If you have multiple coaxial signal cables connected via a cable splitter, especially when they’re in the wall, you should match the ends of a particular coax cable. Using a coaxial cable tester, you can perform this task easily.
  • If the other end of the coax cable is connected to a satellite dish or antenna on your roof, you can use a multimeter & aluminum coil to trace the right ends of a specific coax cable.
  • A coaxial cable mapper can be used to trace and assess coaxial cables placed at multiple locations.
  • If you’ve lost the coaxial cable in the wall or attic, you can use a coaxial toner probe to trace down the cable. When it finds the coaxial cable inside the wall, it will generate a loud noise, allowing you to easily identify the location of the cable.

For efficient tracing and testing of a coaxial cable, consider using a standard tool like the Klein Tools VDV501-851 Coaxial Cable Explorer & Tester.

This device is highly rated by users worldwide for its ability to test coax cable continuity and map the cable at four locations simultaneously.

It features color-coded remotes for easy identification, LED lights to indicate the status of the coaxial cable, and a compact, lightweight design for easy portability.

Other Checks To Test A Coax Cable

  1. Checking the Impedance:
    • Identify the impedance of your coaxial cable. This information is usually printed on the cable itself.
    • Ensure that the cable’s impedance matches the impedance of the devices it’s connecting. You can find this information in your device’s manual or product specifications.
  2. Using Advanced Testing Techniques:
    • If you have access to specialized testing equipment, set it up according to the manufacturer’s instructions.
    • Connect your coaxial cable to the testing equipment and run the test. The specific steps will depend on the equipment you’re using.
    • Analyze the results provided by the testing equipment. This could include information about signal strength, signal quality, and any potential issues with the cable.
  3. Identifying and Locating Damage:
    • Visually inspect your coaxial cable for any signs of physical damage, such as cuts or cracks.
    • If you have access to a cable tester that can identify the location of damage, connect your cable to the tester and run the test.
    • Analyze the results provided by the tester to identify the location of the damage.
  4. Referring to Coaxial Cable Standards:
    • Research the standards related to your specific type of coaxial cable. This could include standards related to impedance, signal quality, and physical characteristics.
    • Compare the specifications of your cable to the standards to ensure it meets the required specifications.
  5. Considering Cable Length:
    • Measure the length of your coaxial cable.
    • Consider whether the length of your cable could be contributing to any signal issues. Longer cables can result in greater signal loss.
    • If necessary, consider replacing your cable with a shorter one to reduce signal loss.
  6. Inspecting the Connectors:
    • Visually inspect the connectors on your coaxial cable. Look for any signs of damage or wear.
    • If you have a connector tester, connect your cable to the tester and run the test.
    • Analyze the results provided by the tester to identify any potential issues with the connectors.
  7. Considering Environmental Factors:
    • Consider the environmental conditions where your coaxial cable is installed. This could include temperature, humidity, and physical stress.
    • If necessary, make adjustments to the cable’s environment to improve its performance. This could include moving the cable to a cooler location, reducing humidity, or protecting the cable from physical stress.

In conclusion, testing your coaxial cable is a crucial step in ensuring optimal signal transmission. If you know of any other reliable methods to test or trace a coaxial cable, feel free to share your insights in the comments section below.

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