How to Test a Coax Cable? [Check Signal Loss / Strength] (2023)

Are you bogged down with frequent signal outages? Are the signal drops becoming too difficult to endure? Although coaxial cables are durable, they are vulnerable to damage with prolonged exposure to heat, wear & tear, or moisture. With the damages not being apparent, it gets trickier to narrow down to the root cause. And that’s when you’re required to test the coax cable.

It saves you a lot of time if you know how to test a coax cable. If you are eager about the details involved in testing coax cables for signal loss, this article is just for you. You’ll learn about different methods of troubleshooting coax cable and the list of the ‌equipment required to test coax cable as you go further into the guide.


    • What do you need?
    • Different Tests
    • Things to Remember
  • How to Test Coax Cable Signal with Multimeter?
    • Why do they happen?
  • How to Test Coax Cable without Multimeter?
    • Testing Coaxial Cable with the Coax Signal Tester
    • Using a Modem to Test Cable Outlet
  • Frequently Asked Questions
  • Conclusion

Requirements & Overview

One reason behind the signal loss & performance could be your coaxial cable, the sole reason being exposed to the external environment. If you have to narrow down the issue, you’ll require certain tools before you begin.

What do you need?

You can test if a coax cable is live with two different tools.

  • The coax cable tester – A tool easy to understand even for beginners.
  • Electrical Multimeter – Don’t let those colored wires scare you.

In case you don’t have any of the tools handy, you can still figure out and tell if the coax cable is bad. Curious to know how?

  • Use your cable modem and test every cable outlet manually.

Different Tests

A coaxial cable comprises a copper wire at its core, a dielectric insulator, a metal mesh layer, and an outer plastic sheath. To ensure all the components are intact, you’ll have to conduct three different tests using a multimeter.

The center conductor continuity test: This test checks the continuity of the copper conductor wire, which confirms that the copper wire is in good condition to carry the signals.

The shield continuity test: Shields are essential to reduce interference. Testing the continuity in the shield at different ends ensures the shield layer is intact. It prevents outside interference and signal leaks.

(Video) Using a multimeter to check a coax cable.

The shield to center test: The test is performed to determine continuity between the copper conductor wire and the shield. Continuity, if detected here, signifies a short in the cable, and it’s due to be replaced.

Frequency range test (with coax cable tester): The dedicated coax cable testers can scan specific frequency ranges to determine an active connection. It avoids situations of false-positive signals in your coaxial outlets.

Things to Remember

When checking coaxial cable signal quality, ensure that both ends of the cable are removed from any active connection. The cable shouldn’t be attached to coaxial outlets, i.e., cable splitters, tv outlets, or modems.

In the next section, you will understand how to test cable signals and find out if the cable is the primary reason for the malfunction and poor performance.

How to Test Coax Cable Signal with Multimeter?

Testing coax with a multimeter can be easy and convenient. With three simple tests, you’ll be able to figure out if the coax cable is bad and find solutions to avoid its repeat.

Step 1: Connect the red and black testing prong to the respective slots. Switch on the multimeter and set the black knob towards the Ohm sign.

How to Test a Coax Cable? [Check Signal Loss / Strength] (1)

Step 2: Take one end of the coaxial cable that is required to be checked for live signals and touch the red probe to the center copper wire. Similarly, take the black probe and touch the copper wire at the other end of the coaxial cable.

How to Test a Coax Cable? [Check Signal Loss / Strength] (2)
How to Test a Coax Cable? [Check Signal Loss / Strength] (3)

If you hear a long beep and notice the Ohm indicator reading move, the coaxial cable’s center copper wire has continuity and is intact. If the multimeter reading doesn’t move or moves very little, that shows a loss of signal in copper wire.

Step 3: Repeat the process but instead of the center wire, now connect the shields at either end of the coax cable with the red and black probes.

(Video) Coax Cable Simple Tests (#322)

How to Test a Coax Cable? [Check Signal Loss / Strength] (4)
How to Test a Coax Cable? [Check Signal Loss / Strength] (5)

A long, loud beep shows continuity in the shield, which determines the shield is also intact. Anything otherwise shows a faulty shield and requires attention.

Step 4: Now, take one end of the coax cable. Connect the black probe to the shield and the red probe to the copper center. There should be no continuity here. If you see the multimeter reading move, that implies there is a short in the cable.

How to Test a Coax Cable? [Check Signal Loss / Strength] (6)

If the coaxial cable fails in any of these tests, it is at fault and warrants a replacement.

Why do they happen?

The main reason behind the failure of the copper wire or insulator, or shield is physical wear and tear. Using connectors at ‌junctions would reduce the flexing or twisting of the outer plastic shield, ‌reducing the impact on the layers beneath.

Another way to minimize physical damage is to invest in a high-grade coaxial cable. The multiple layering and shields offer more protection against physical damage and interference.

How to Test Coax Cable without Multimeter?

There are two ways to test a coax cable without a multimeter. There is an easier way that uses a more sophisticated coax signal tester. If you don’t have the signal tester, you have no option but to go for a more tedious way; using your cable modem. In this section, we’ll see the steps involved in both methods.

Testing Coaxial Cable with the Coax Signal Tester

Using the coax signal tester is an easy solution for apartments to test coax outlets and signal output from coaxial cables.

Step 1: Move the knob to the “on” side.

How to Test a Coax Cable? [Check Signal Loss / Strength] (7)
(Video) Coax Cable Repair, Testing to Find the Unused Cable

Step 2: Plug it into the coaxial outlet or any signal output and press the highlighted button.

How to Test a Coax Cable? [Check Signal Loss / Strength] (8)

If the light turns green, there is a valid coaxial signal. The coaxial tester looks for a particular frequency for a valid internet signal. If the light turns red, it denotes an inactive outlet or malfunctioning coaxial cable.

Using a Modem to Test Cable Outlet

You can use a cable modem with an active internet service to test cable outlets or signals from the coax cables. The only hardship is moving the modem around.

Step 1: Ensure you have an active working internet connection at your place. Switch off the modem and use the cable to be tested to connect to the active coaxial outlet to your modem, as shown in the image below.

How to Test a Coax Cable? [Check Signal Loss / Strength] (9)

Step 2: Switch on the modem and wait for the lights to turn on. If the internet light turns green and the modem connects to the internet, the coaxial cable transmits signals. If the internet LEDs don’t light up, you’ll know the coaxial cables are at fault.

In case you need to test other cable outlets, you’ll have to move the modem and ensure you are using a tested coaxial cable to check if the cable outlet is active.

Frequently Asked Questions

How to tell if coax cable is bad? Can it go bad?

Yes, a coax cable can go bad. Any exposure to excessive heat, water, or physical wear tear can affect the cable. You can use an electrical multimeter to check if your coax cable is working or needs a replacement. Conduct resistance, capacitance, and inductance checks will determine the reason behind the defect.

(Video) Coax - How to Check Good Internet LINE Quality From Provider to Home (Xfinity, Cox, Spectrum etc)

Can the length of the cable affect the signal transmission?

Yes, the length of the cable affects signal quality. The longer the cable, the greater the distance the signal has to traverse, making it vulnerable to signal loss. Limiting the cable length to less than 15-20 ft will keep the loss to a minimum. We expect anything more than 50ft to cause over 20% loss to the signal strength.

What can cause the loss of signal strength?

There are two major causes of signal loss. One is the resistance of the conducting material (copper wire). Increased exposure to the conductor’s resistance will increase the chance of loss of signal strength. The type of insulator and its durability in coax cables are determinant factors of signal quality.

How do you measure antenna signal strength?

Standards use a combination of two metrics to measure the antenna’s signal strength, i.e., Noise margin (NM) in dB and Power ratio in dBm. The noise margin gives you the ratio of static signals (noise) in your signal, and the power ratio gives the actual strength of the signal.

How to improve the signal quality?

There are two ways to limit the loss in signal strength and improve the quality. Keep your coaxial cable away from electrical lines and use a quad-shielded cable to minimize interference. Keep the length of your coax wiring to a minimum.

(Video) Testing Flat Coaxial Cable for Signal Loss


Depending on the device you have at your disposal, you’ll be able to test whether the coax outlet is live or if the cable is a reason behind the loss of signal quality and performance. The article focuses on different methods of testing coax cables for signal loss.

It also offers clarity on how to check coax cable. While the methods and tools can be helpful to find out what is at fault, it is essential to recognize that these methods don’t measure the signal strength, which requires a different digital meter.

Suggested Read: Routers with Coax Input


How do you test coax cable signal strength? ›

You can test your coax outlet's signal by taking your cable modem from cable outlet to cable outlet manually, and plugging it in to each coax outlet to verify a signal and connectivity. If your internet modem connects like normal, that means a signal was detected. If it doesn't connect, then you have no signal.

How do I check my cable Internet signal strength? ›

How to Test Cable Signal Presence for Internet
  1. Restarting and reconnecting your Internet modem.
  2. Test each coaxial cable outlet for signal individually using your cable modem.
  3. Use a coax cable tester, like Hitron's DSS-01 Coax Cable Tester, to quickly test for an Internet signal at your coax outlets or wiring.

How do you check coaxial cable continuity? ›

The next thing to check on your coax is that you have good continuity in the shield from one end of the cable to the other. To test this, touch one probe from your multimeter to the shield on one end of the cable, and the other probe to the shield at the opposite end of the cable. The meter should read no resistance.

How can I test my coax cable without a multimeter? ›

To test a coax cable without a multimeter, you either use a coax cable tester to check for signals within the cable or insert it into a modem to test its connectivity. The coax cable tester is the easiest and fastest method of testing for faults within a coax cable.

How do I increase coaxial signal strength? ›

If you get poor picture quality after installing a coax cable splitter for TV and internet, call your cable provider for advice (they may increase your signal strength). You can also install an amplifier to boost the signal coming from your antenna, satellite or cable service.

How many ohms Should a coax cable have? ›

There are two main types of coaxial cables – ones with an impedance of 75 Ohm (Ω) and ones with an impedance of 50 Ohm. Cables with 75 Ohm are mostly used for video signals, while 50 Ohm cables tend to be used for data and wireless communications.

How many ohms should a coaxial cable? ›

That's because 75 Ohm cables are the standard coax cable you find everywhere inside your home and offices. From the back of the tv to cable & satellite tv boxes and internet routers, they're commonly used and are often pre-wired in many homes and businesses.

How many ohms of resistance does a coaxial cable measure? ›

With these details in mind, over time, the industry settled on two characteristic coaxial cable impedances for the vast majority of applications (>90%): 50 Ohm and 75 Ohm.

What is a good cable signal strength? ›

Ideal levels are approximately 40 to 50 dBmV for single channels, 37 to 48 dBmV each for 2 to 4 channels. The Signal to Noise Ratios should also all be within three dB of each other. However, for power level -15 to -6 dBmV the SNR should be 33 dB or higher and for -6 to +15 dBmV the SNR should be 30 dB or higher.

How can I test my network cable without a tester? ›

  1. You can plug the cable in to 2 switches or a switch and a nearby computers network port.
  2. The LINK light at the computer and the link light at the switch will light up.
  3. If one of these does not then you are missing connectivity.

Does coax cable lose signal? ›

Yes, the greater the length of coax cable you use, the more signal loss you will experience.

Does coaxial cable wear out? ›

Coax cables—just like most things in our universe—have a finite lifespan no matter how well you take care of them. They'll eventually deteriorate and go bad. When that happens, replace them to restore service to electronic devices.

Do coax connectors lose signal? ›

Yes. Even the best, and most expensive couplers will add some loss as an impedance bump in the transmission line. However, properly selected, installed, and maintained connectors should be able to attain less than 0.1 dB loss overall.

How does a coax cable tester work? ›

Many coax cable testers use voltage to detect a connection signal on your coax wiring or outlets. While voltage is adequate at detecting connectivity of that wiring or outlet, it does not validate that your Cable Internet is active on that coax wiring or outlet.

How do you fix a weak cable signal? ›

How To Improve Weak TV Signal
  1. Install Your Aerial Outside. ...
  2. Install The Aerial Higher Up. ...
  3. Install A Higher Gain TV Aerial. ...
  4. Align Your TV Aerial For Peak Reception. ...
  5. Install A Masthead Amplifier. ...
  6. Remove Splitters – Install Distribution Amplifiers. ...
  7. Install Good Quality Coaxial Cable. ...
  8. Install Good Quality “Screened” Wall plates.
Mar 11, 2022

What causes poor signal strength? ›

Averse weather, interference from building materials or terrain, distance from your nearest cell tower, or network overload can all contribute to poor signal.

Does a coax splitter reduce signal strength? ›

A splitter weakens the signal level, which can cause intermittent loss of service or, in rare cases, service failure. We recommend connecting your modem or Spectrum receiver directly to a wall outlet rather than using a splitter.

What happens if you use 75 ohm coax instead of 50 ohm? ›

Thorough testing of 75-ohm coax used in place of 50-ohm cables for receiving applications shows practically no detect- able difference, even at frequencies as high as 150 MHz.

Why 75 ohms in coax cable? ›

75 Ohm cables are primarily used for AV signals and can transmit signals up to 50 ft with any installation. This cable can be commonly used for High Def TV signals, Satellite and Cable boxes and police scanners. 75 ohm also offers low attenuation and capacitance acceptance for these digital audio, A/V and data signals.

What does 50 ohm mean for a coaxial cable? ›

At the compromise value of 50 ohms, the power has improved a little. So 50 ohm cables are intended to be used to carry power and voltage, like the output of a transmitter. If you have a small signal, like video, or receive antenna signals, the graph above shows that the lowest loss or attenuation is 75 ohms.

How do you test coax impedance? ›

Just take a piece of the cable (just a short piece is enough) and measure the capacitance between the center core lead and the shield of the cable on one end of it. You need an accurate unit with four wire measurement capability which in my case is an excellent and cheap DER EE DE-5000 handheld LCR Meter.

What is 93 ohm coax used for? ›

Technically 93 Ohm Coaxial Cable has the lowest capacitance of any type. RG62 is a low loss 93 Ohm coaxial cable suitable for use on video, RF signal, antenna and broadcast transmissions.

Should there be voltage on coax cable? ›

Make sure you house grounded, you should NEVER have voltage on your COAX. If it exceeds 50 VAC then it will cause issues.

What is the minimum resistance on a cable? ›

The rule states that insulation resistance should be approximately one megohm for each 1000 volts of operating voltage, with a one megohm minimum. (By following this rule, a motor rated at 2400 volts should have a minimum insulation resistance of 2.4 megohms).

How do you test if a cable is damaged? ›

To test, connect the multimeter to each of the wire's ends. As before if a full circuit is made and there are no problems, when connected the multimeter should show a low reading. If the reading is showing 'I' it means, there is a break.

How do I test my network cable connection? ›

Open Settings > Network & Internet > Status. Check your Ethernet connection status there. It should display You're connected to the Internet underneath the Ethernet network connection. If one Ethernet cable doesn't work and you have another one nearby, try the other Ethernet cable to see if that works.

What tool can we use to test a network cable? ›

A cable tester is an electronic device used to verify the electrical connections in a signal cable or other wired assembly.

How do I know if my signal strength is good? ›

To do this, go to Settings > About phone > Status > Signal strength. This will display the network type, signal strength, and other information about your device's connectivity. The closer the number is to 0, the better the signal strength.

How strong is my signal strength? ›

Tap Settings. Tap About Phone. Tap Status. Your dBm is under Signal strength.

Is higher or lower signal strength better? ›

Strong signal strength results in more reliable connections and higher speeds. Signal strength is represented in -dBm format (0 to -100). This is the power ratio in decibels (dB) of the measured power referenced to one milliwatt. The closer the value is to 0, the stronger the signal.

How do I troubleshoot my cable connection? ›

Complete list of fixes if your internet is not working
  1. Restart your equipment. ...
  2. Connect with an Ethernet cable. ...
  3. Check for an internet outage. ...
  4. Try using a different device. ...
  5. Check your wires and cables. ...
  6. Run your computer's internet troubleshooter. ...
  7. Reposition your router/gateway. ...
  8. Update everything.
Dec 15, 2022

What causes loss in coax? ›

There are two primary causes of signal loss with coax: 1) Resistive loss, and 2) Dielectric loss. Resistive loss arises from the resistance of the center conductor of the cable and results in dissipated heat. Radio frequency currents tend to flow along and near the surface of conductors.

How do I know if my coax cable is damaged? ›

One way that you can check if your coax cables go bad is by using an electrical multimeter. An electrical multimeter can measure the abilities of multiple pieces of electronic equipment using many different calculations. First off, you can use your electronic multimeter to do a resistance check on your coax cable.

How often should coax be replaced? ›

A coaxial cable of modern design and quality construction, say designed and made within the last twenty (20) years, will maintain useful, at or near specified performance, for decades, as long as it is not physically damaged.

How long is coaxial cable good for? ›

Coaxial cable can be cabled over longer distances than twisted-pair cable. For example, Ethernet can run approximately 100 meters (328 feet) using twisted-pair cabling. Using coaxial cable increases this distance to 500m (1640.4 feet).

How long can you run coax cable before it loses connection? ›

When it comes to signal loss over longer cable lengths, the basic rule of thumb is that a 50-foot cable can experience noticeable signal loss, and a 100-foot cable can drop as much as one-third of the original signal.

What is dB loss for coax? ›

For a 900 MHz signal traveling through a 100-foot RG-11 coax cable, signal loss is 5.4 dB. If the signal travels over 50 feet of cable, the loss is 50 percent less. If the cable length is 200 feet, the signal loss doubles.

Which coaxial cable has the least amount of signal loss? ›

Series 11 is the largest, has the least amount of signal loss over length, but is bulky, hard to install, and relatively expensive when compared to Series 6 coaxial cables. Series 6 is the most commonly used size due to the excellent trade off in price, size, handling and signal loss.

Does splitting coax weaken signal? ›

A splitter weakens the signal level, which can cause intermittent loss of service or, in rare cases, service failure. We recommend connecting your modem or Spectrum receiver directly to a wall outlet rather than using a splitter.

How long can a coax cable be before signal loss? ›

Therefore, there is no “maximum length coax cable before signal loss”. Different frequencies of RF signal experience attenuation differently, with higher frequencies experiencing far more cable loss.

How can we reduce signal loss in coaxial cable? ›

The easiest way to lower ohmic loss is to spec higher grade coaxial cable that uses lower resistance metals for both wire and shielding. However, the amount of ohmic loss is proportional to the length of the conductor, so even the highest quality cable will produce unacceptable losses at a certain length.

How many ohms is rg6 coaxial cable? ›

RG-6/U is a common type of coaxial cable used in a wide variety of residential and commercial applications. An RG-6/U coaxial cable has a characteristic impedance of 75 ohms.


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