How to Test CB Antenna Coax

Knowing how to test coax cable is an important part of diagnosing CB radio and antenna issues. Problems with transmission, problems with receive, high SWR, and low power output are all problems that can be caused by a bad CB coax. Testing your coax cable is a fairly simple process.

There are three tests to perform on your CB Coax Cable. All can be done with a test light or a multimeter. If you are not familiar with using these tools, see our guide to using multimeters and test lights. In our example, we use a multimeter.

Test 1: Center Conductor Continuity

The first thing to check on your coax cable is that you have good continuity in the center conductor from one end of the cable to the other. To test this, touch one probe from your multimeter to the center conductor on one end of the cable, and the other probe to the center conductor at the opposite end of the cable. The meter should read no resistance. If the needle doesn't move, or only moves a little, you will need to replace your cable.

Test 2: Shield 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. If the needle doesn't move, or only moves a little, you will need to replace your cable.

Test 3: Shield to Center

The last thing to check is continuity between the shield and the center conductor. In this case, you do not want continuity between the shield and the center conductor. If you find that you have continuity here, you have a shorted cable, which is bad. Pick one end of your cable and touch one probe to the center conductor and the other probe to the shield. Make sure not to let the probes touch each other, and don't let the probe touching the center conductor contact the shield as well. When you do this, your meter should not react. If it does, you have a short in your coax cable.

How to test coax cable