There are many things other than the antenna that can cause high SWR. SWR meter readings take into consideration the antenna, the coaxial cable, the mount, the mounting location, the vehicle and objects in the antennas near-field environment. We broke our list of common high SWR causes into six primary categories. The order of the categories does not imply that one is more common than the other, however, the list within each category is arranged based upon our experience and shows the most common causes higher on the list than the lesser common causes.
- Antenna was not tuned in its final mounting location
- Antenna tip installed AFTER the antenna was tuned
- Testing or tuning with doors, hood or trunk open (altered ground plane)
- Antenna not mounted vertically
- Incompatibility between antenna and vehicle for undetermined reasons
- Insufficient tuning range due to antenna/installation incompatibility
- Antenna tested/tuned inside garage, carport, etc.
- Antenna was tuned then moved to another mounting location or vehicle>
- Ground plane and no-ground plane antennas used with wrong coax cable type
- Antenna grounded to vehicle chassis ground circuit
- Internal antenna issue (verify base to tip continuity)
- Antenna not designed for use with CB radio