That is the ARB antenna bracket, right? My bumper mounted antenna (I only have one now, used to have two) follow pretty much what Gary says. I ran a ground strap from the frame of my truck to the bumper and then each of the mounts got a short ground strap to the bumper. I would also suggest you knock off some of the powdercoat around the hole for the antenna and the hole the grounded bolt goes through. This helped a lot for me, it seems the powdercoat is a pretty decent insulator and equally tough for the mount to bite in to. It finally took a Dremel and a mini wire wheel to get the powdercoat to come off, sandpaper didn't do it on mine. I put dielectric grease under the mount when I installed it to keep the bare steel from rusting.