Even if you've tested individual components for shorts (coax, the mount-to-ground connection, etc.), it's still possible that an open short exists somewhere throughout the entire system. A misplaced washer, damaged connection or other issues can often cause an open in your system. If you're not familiar with the concept of resistance or how to measure it, please refer to our guide on Understanding Electrical Resistance before reading further.
Step 1
Using the multimeter, check for continuity (no resistance) between the hot lead of the coax cable that screws into the back of the radio and the tip of the antenna as illustrated in Image 1. Make sure to touch the metallic tunable tip of the antenna. If you're using an antenna with a stainless steel whip, any portion of the whip will suffice as a testing surface.
Image 1 : Test for System-Wide Continuity on the "Hot" Line
Step 2
Using the multimeter, test for continuity (zero resistance) between the ground channel of the coax connection that plugs into the radio and the black ground battery terminal, as illustrated in Image 2.
Image 2 : Test for System-Wide Continuity on the "Ground"
Step 3
Using the multimeter, test for an open circuit between the ground channel of the coax connection that plugs into the radio and the top of the antenna. There should be NO continuity (total resistance), as these two should be seperate circuits. If there is continuity, there is a short in the system in which the ground and hot lines are connected.
Image 3 : Test for System-Wide Resistance Between "Hot" and "Ground"
Troubleshooting Problems
If you find a short along the individual hot or ground lines, or continuity across the hot and ground lines, you have a problem that needs to be fixed. You'll need to use your multimeter to test incrementally along each circuit (from coax end to end, coax end to mount, mount to ground, etc.) to determine exactly where along the circuit the short is taking place in order to isolate the problem.
Once you isolate the problem area, you should be able to identify the problem and arrive at a solution. For example, if the problem area is the coax connection to the mount, you may have a shorted stud mount and need a new one. Similarly, if the mount seems to be the point that continuity breaks, you may have a problem with a solid connection between the mount and the vehicle's chassis.
For additional troubleshooting guidance, we recommend referring to the following article from Firestik that displays which mounting components should exhibit continuity: Firestik Continuity Diagram
