Testing CB Antenna Coax Cable for Shorts and Continuity

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.

NOTE:
If you are testing NGP (no ground plane) coax, you should show resistance since there is a capacitor in the coax.

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[jeffreys.harris]

Question some of us don't know much about multi meters what did you set your meter on???

[IsakAmunkete]

Thanks for this great great video. QUESTION: What are the major problems you might experience with a shorted cable? What effect does it have on the radio?

[Erated]

Thanks for a great video - dumb question: I’m guessing I need to tune my antenna because my antenna checks out good for continuity in all three meter connection tests? It’s a basic mag mount antenna with spring near base, upper is a solid wire

[craiggerlach]

My coax is good, going to look for video on antenna as that appears to be shorted.. both lights go red, , system was out of the truck for 25 years, no clue if people played with antenna itself, but tested coax to antenna mount and was good.. center to shield becomes shorted when antenna is connected..some wideband waterproof whip with fiberglass looking end that works mint last time used...

[stelthcamo]

Why does all wilson 5000 antennas have conntuity between the center pin and the outside sheild

[MayorMcheese]

Are there other ways to tell if your cable is sorted without the multimeter

[scottgrinnell]

My apologies here. What setting on multimeter should i select? Thanks for your knowledge and assist2

[JAWS]

cool thanks for the video!  just what I needed.

[Robasteerjock]

How do you test a ng antenna tip to coupling it shows it has continuity?

[getupgonow]

Define what " continuity" is and how to set up the multimeter taking a close up of meter!

[johnnymc]

What if you're testing the center with the outer shroud for continuity with the radio attached on the other end, and you do get continuity?

[wrestlemaniac]

When I attach my radio to the antenna via coax I hold the antenna in my hand then have it touch the mount on my vehicle it'll arc then short out the fuses in my radio power cable, would that be a bad ground or short in the cable?

[Blenzo]

I tested my cables and everything checks out. I have high SWR. It pegs the garage on my Cobra 29lx and flashes "CB Antenna Warning" when I try to transmit. I'm also only receiving within maybe a quarter mile. It's a 2019 Kenworth T680 with stock dual antennas. I'm not sure what to do.

[cwood]

I have continuity from the center conductor to the threads on the base and the whip. Is the antenna bad? I installed my coax solder fitting, it tested good until I screwed the whip onto the fender mount base, then it read short, that's how I began testing the whip.

[denniswatson]

How often do you have to change the cable

[wearecb]

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[scicero]

You forgot to check the pin and housing on the other cord

[tahotoy]

No wiggle? No acceptable values? This does Not rule out a bad cable even in the 70's when that meter was standard issue.