Though rare, a defective or broken antenna can be the cause of high SWR problems and poor performance. Luckily, testing an antenna is a fairly easy process. 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 proceeding further.
Using your multimeter, touch one of the probes to the metallic end of the antenna. For fiberglass antennas, this will usually be the tunable tip on the antenna's end. For magnetic and center-loaded antennas, this will usually be a stainless steel whip.
Image 1: The Antenna's Metallic End
Touch the other probe to the metallic threads at the end of the antenna. For magnetic antennas, you'll need to touch the center pin of the coax cable connected to the antenna instead.
Image 2: The Antenna's Threads (Fiberglass Antennas)
As you maintain contact with both probes, measure the circuit's resistance. There should be little to no resistance, as the circuit should be continuous all the way through the antenna. If total resistance is found, indicating no continuity, the antenna or one of the antenna components is damaged and will need to be replaced.
If no resistance is found, the antenna is fine, and the source of the problem is something else.