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How to Test Coaxial Cable [ The Ultimate Guide]

Antennas receive and send signals through RF coaxial cables, which are connected to the radio or television transmitter.

These wires, which are composed of metal cords on the inside and metal braid mesh on the outside, are used to create a resistive coaxial cable.

Sometimes, as a result of the circumstances around it, the coaxial cable is damaged, resulting in a cut or fracture in the layers of the cable.

If this issue occurs, it poses a threat to the proper operation of the transceiver system.

You should test the Coax cable if you suspect that the transmitter’s operation is not up to par, or if you are experiencing frequent signal losses that seem to have no apparent cause.

I’m going to show you several effective techniques for checking coax cables for signal loss in this section. Moving on to the explanations, let’s have a look.

how to test coax cable
How to Test Coaxial Cable

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Overview of the article

Using a multimeter to examine the coax cable signal in a scenario where your transmitter is not functioning optimally will be the subject of this article.

Despite the fact that there are many cable types available on the market, the coax cable is the most common and extensively used cable in contemporary technology.

Because of its durability, adaptability, and simplicity of installation, it has become popular.

The coaxial cable is constructed of metal cables on the inside and metal braid mesh on the outside. When these two materials are combined, they form a resistive coaxial cable.

It is used to transmit radio frequency signals from one location to another through the coaxial cable, which is also known as the coax cable.

It is frequently seen in homes, businesses, and other public places.

This cable may get compromised as a result of certain circumstances or elements in our environment. When there is a fracture or cut in the layers, the signal quality may be compromised.

Getting the coax cable checked using a common instrument such as a multimeter is highly recommended if you are having frequent signal disruptions without a clear cause for the problem.

How to perform a coax cable test is essential if you want to diagnose or determine the precise nature of the problem with your CB radio and antenna system.

The procedures required are straightforward and straightforward to implement.

Throughout the course of this article, you will learn how to diagnose issues related to signal reception, signal transmission, and poor power output that are caused by a broken coax cable.

BASICS

So, what exactly is a coaxial cable, exactly?

An insulating layer of material (usually known as the ‘dielectric’ in coaxial cables) is sandwiched between two conductive layers (often identified as the shield) and all of this is covered by an exterior jacket, which is the fundamental structure of a coaxial cable.

As previously stated, the description of coaxial cables is very generic because they are used for a wide variety of applications ranging from “cable” television to signal transmission on aircraft, and there are countless variations that can be used to meet the specific requirements of each application.

Each cable element (conductor, dielectric, shield, and jacket) has its own set of design and performance criteria, which are specific to that element

Many of these have already been covered in-depth in a previous LECTROMEC ARTICLE.

WHY DO THEY GET USED?

The primary advantage of coaxial cables is that the shield serves as a two-way barrier against electromagnetic interference (EMI).

It is only possible to send high-frequency signals over these cables because of an electric and magnetic field created between the conductor and the cable shield.

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In this case, the external interference is restricted to just interacting with the shield, leaving the internal sent signal completely undisturbed.

Of course, the kind of shielding used makes a significant difference.

Braided shielding provides excellent performance, although it only provides 85 – 95 percent optical coverage on a normal basis (gaps between the braided strand).

Although a spiral-wrapped shield provides more optical coverage, it also decreases the flexibility of the wire.

Testing Coaxial Cable

Internet connection will be weak or non-existent if your Coaxial cable outlet is not working correctly.

The good news is that determining whether or not your Coaxial cable outlet has a signal is a simple and relatively fast process.

There are two ways to check the signal strength of your Coaxial cable outlet:

Manually or using coax testing equipment that makes the job simple and quick.

Manual Test with Cable Modem

You may manually test the signal strength of your coax outlets by moving your cable modem from the cable outlet to the cable outlet and connecting it into each coax outlet to ensure that there is a signal and connection.

In the event that your internet modem connects, as usual, it indicates that a signal has been identified.

If it doesn’t connect, you won’t have any signal at all.

This technique of transporting a modem from one location to another may be very time-consuming.

Coax Testing Tool

Using a coax cable testing instrument that is designed especially for the purpose of evaluating your coax cable outlet signal is the quickest and most convenient method to determine the quality of your coax cable signal.

This Coax Cable Tester from Hitron identifies legitimate signals from your Cable Internet service provider by identifying the particular signal range (range of frequencies) that they utilize.

In other words, you will not get false-positive results as you would with other types of testing.

Additionally, the DSS-01 Coax Cable Tester is capable of operating regardless of whether or not there are concealed splitters on your line, ensuring that you get an exact reading on your signal every time.

How To Test Coax Cable Signal With A Multimeter: 11 Steps (with Pictures)

This section will outline the procedures to be followed when evaluating the signal frequencies of coax cables using a multimeter.

As soon as you discover that the coax cable connections in your house or business have been routed through walls, ceilings, or floors, it becomes a little more difficult to track the cable’s journey.

Before you can perform a coax cable test, you must first trace and identify the specific cable that is being tested. The actions that you must do are listed below.

You’ll need the right instruments.

  • Dummy load with a multimeter

1. Disconnect both ends of the coax cable from the item to which it has been attached, such as a cable splitter, television, or anything else to which the cable has been connected.

2. Now, coil the two ends together to make it more comfortable to take measurements with the multimeter.

3. Connect the testing probe’s cables to the appropriate ends of the multimeter (the red positive into the ‘+’ marked jack and the black negative into the ‘COM’ marked jack).

4. Check the results. Connect one of the leads to the metal portion on the outside of the PL-259 plug and the other lead to the center pin.

If there is no sound, this indicates that the coax has not been properly sorted.

5. To take the measurements, change the dial choice on the multimeter to ‘Continuity’ or ‘CONT’ in the settings.

6. In order to determine whether or not the continuity testing procedure will be successful, contact should be made between both of the probe’s tips. If the gadget produces a tone, this indicates that it is in good functioning order.

test coax cable with a multimeter
Multimeter

7. Connect the negative end of the multimeter probe to the center wire/pin on one side of the coax cable, as shown. Make certain that it does not come into contact with the outer layer.

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8. Connect the positive end of the multimeter probe to the center wire or pin on the other side of the coax cable.  The same care that you took with the positive tip should be followed this time around.

9. After you’ve done that, examine the tone.

If it comes from the speaker of the multimeter, it indicates that the coaxial cable is functioning properly and that the signal is not passing through it.

10. If you are utilizing a coaxial connection, use the negative probe to make contact with the outer jacket of the connector.

If you are not utilizing the connection, then the negative probe should be used to contact the braided outer wire.

Maintain the positive end of the probe in the same position that you established in the previous step.

11. Determine whether or not the tone can be heard via the internal speaker of the multimeter.

Because there is no electrical connection between the center wire/tip and the outer jacket/wire, there should be no sound produced by the device.

Any noise indicates that the insulation in the coaxial cable has been compromised, and this is the source of the signal loss you are experiencing. It is preferable to replace the wire with a high-quality coaxial cable rather than the wire.

How to Trace a Coaxial Cable 

The coaxial cable route becomes harder to track once you have made the coax connections in your different rooms, which may have been through floors, ceilings, walls, and other surfaces.

It is thus necessary to trace the coaxial wire before doing any tests or installing a new television or home theater system.

In order to trace the coax cable, follow the procedures outlined below.

1. Gather the necessary equipment, such as a continuity tester and an explorer for the coax, as well as masking tape to mark the route of the coax cable.

2. If you are using a cable splitter to connect several coaxial signal lines, particularly if they are in the wall, you should make sure that the ends of each coaxial cable are the same length.

This job may be completed quickly and simply with the help of a coaxial cable tester.

Connect one end of the tester to a wall socket and the other end to the place where all of the wires come together to check for continuity.

By touching each cable pin one at a time, you will be able to determine which cable is correct when a sound is heard.

Using a multimeter and an aluminum coil, you can determine which ends of a particular coax cable are linked to the satellite dish or antenna on your roof.

Fill the aluminum foil at the end of the coax wires with a conductive liquid.

3. When you touch the multimeter probe at the end of the right coaxial wire, the meter will read ‘0,’ and you will see a variety of readings for all of the other coaxial cables.

4.  A coaxial cable mapper may be used to track and evaluate coaxial cables that have been installed in various places.

5. If you have misplaced the coaxial cable in a wall or attic, you may use a coaxial toner probe to track the wire back to its source.

When it comes across a coaxial cable within the wall, it will make a loud noise, which will let you quickly determine where the cable is located in the wall.

Bonus Tips for Testing Coaxial Cable

CHECK FOR RESISTANCE

A conventional multimeter is used to test the resistance of the cable and shielding.

Subtracting the resistance of the test leads reveals that the conductor resistance is about 0.0 Ohms (limited accuracy of multimeters) and that the shield resistance is approximately 0.0 Ohms.

The same findings are obtained while testing the “New Cable.”


What is the reason behind this?

Despite the fact that the shield conductor has been broken, there is still more than enough shield to transmit the test voltage from the multimeter.

Unless a significant amount of current is applied to the shield, there will be no discernible change in the measured resistance.

EVALUATION OF CAPACITY

The capacitance test is the next diagnostic procedure to be performed using the two cables.

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Here, the cable is detached at both ends, and the multimeter probes are attached to the shell and the conductor using the connectors on the cable.

The following results were obtained from the measurements made on these two cables:

The capacitance of the damaged cable is 33.6 pF.

The capacitance of the new cable is 34.4 pF.

There was no discernible difference between the two, and the performance variations of the cables were well within the anticipated range.

The fact that we were able to repeat this test indicates that no damage has happened to our Damaged Cable.

CHECK FOR INDUCTANCE

Following that, the inductance test is carried out using the two wires.

There are two connections made at each end of the cable.

At one end, the shield is linked to the central conductor with a short lead, and at its other end, it’s wired up to an inductance measuring device. The following results were obtained from the measurements made on these two cables:

The inductance of the damaged cable: 94nH

The inductance of the new cable is 95nH.

Once again, there is no discernible change.

We can compute the characteristic impedance of both cables based on the information gathered from the capacitance and inductance tests respectively.

The typical impedance of a damaged cable is 53 Ohms.

The typical impedance of the new cable is 53 Ohms.

There is no indication of cable damage based on three different tests of the damaged cable (resistance, capacitance, and inductance), and the cable is not harmed.

It is a good sign that the robustness of aeronautical cables has been shown in this instance.

It is really remarkable that the cable has sustained so much physical damage while yet retaining a significant amount of its electrical characteristics.

Our Final Thoughts

As a result, coaxial cables are very popular in today’s world since they are flexible, can be cut with equipment, and may even be stretched.

As a result, it is highly usual to test the coax cable. Coaxial cables are utilized in a variety of settings, including homes, businesses, and industries.

It becomes very essential and necessary to test the coaxial cable from time to time to ensure if it is correctly functioning or not.

There is a variety of testing performed on these coaxial cables.

Coaxial cables are subjected to a variety of tests, including those for efficiency, power, loss, continuity, and a variety of other parameters.

There are a variety of techniques for testing coaxial cables.

It is extremely simple and effective to test antenna wires using the techniques described here.

Frequently Ask Questions

Is it possible to test coaxial wire in any way?

This job may be completed quickly and simply with the help of a coaxial cable tester.

Connect one end of the tester to a wall socket and the other end to the place where all of the wires come together to check for continuity.

By touching each cable pin one at a time, you will be able to determine which cable is correct when a sound is heard.

How do you determine whether or not a coaxial outlet is operational?

Navigate to the location where the coaxial wires converge at a splitter or distribution panel to complete your task.

If you see a coaxial cable that has been detached from a splitter or distribution hub, reconnect it by screwing it clockwise into the splitter or hub.

If it is not terminated, connect it using the coaxial adaptor connector that comes with it.

Is it possible for coax wires to become faulty?

Because it is fragile, it is possible for a coax cable to get damaged if it is thrown about carelessly.

Coax cables must be kept in a straight posture at all times.

Even the tiniest bend in a coaxial cable may cause its internal components to fail.

To summarize, you should never bend or stomp on a coax wire since it will cause it to malfunction.

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