This article applies to ALL standard ground plane dependent antenna system, CB, 10-meter, 2-meter, etc., that are being installed using powder coated or painted mounts. It does not apply to no-ground plane antenna system.
We have had conversations with the manufactures of popular Jeep mounts (taillight, tire carrier] regarding their powder coated antenna mounts. Our suggestion … mask around the mounting holes and the antenna stud mounts 1/2” hole before the coating is applied so bare metal is exposed. Alternately, include in the instructions the need for the mount to be grounded to the vehicle AND that the antenna stud or coax cable MUST have access to chassis ground through the mount or the antennas system WILL NOT WORK.
You MUST have a chassis ground path. I repeat, you must have a chassis ground path. And, to eliminate a false reading through the radios circuitry, you MUST verify the chassis ground path with the coax cable disconnected from the radio.
TAILLIGHT MOUNT: This is the bracket that requires you to remove the taillight assembly, sandwich the mount between the body tub and the taillight assembly. The mount MUST be grounded to the tub. That means scraping paint and/or powder coating off the mount and/or tub. And while you're in there, note how small those taillight assembly screws are … either use the provided extra 1/4” hole to secure the mount to the tub or make one. Heavy or long antennas, especially on rough trails, put a lot of stress on those little taillight assembly mounting screws. So, verify that the mount is chassis grounded. And you're not done yet!
The bottom side of the 1/2” hole for the antenna stud must be cleaned up as well. Either the grounding ring of our FireRing coax, the outer barrel of the SO-239 stud mount or, the grounding lug on a ring terminal terminated coax MUST contact the grounded mount. Their must be a path to ground [with coax disconnected from the radio] from the shield (ground) side of the coax at the antenna end to the vehicles chassis ground.
TIRE CARRIER MOUNT: It will be of benefit to you to first understand the problems described with the above mentioned taillight mounts. And then … any swinging tire carrier adds an additional problem because of the hinge point. Most use nylon bushings (an insulator). Even those aftermarket models with brass bushingS cannot be depended upon for a non-intermittent, low resistance chassis ground. They may test good initially but as soon as you start bouncing down a road or trail, the ground goes from good to non-existence and/or everything in between. So … the carrier must be chassis grounded, the mount in turn must be grounded to the carrier and any thing that keeps the coax ground from accessing chassis ground via the mount/carrier must be removed. In this case, paint and powder coating.
Without the required path to chassis ground ... the antenna just isn't going to work and it will always show up as high SWR readings. The chassis grounding check and SWR procedure should be of interest to everybody … unless your hobby is destroying your radio. In those cases we suggest using a hammer as it will save the installation time and there will be no doubt in your mind as to why your radio isn't working.