measure a piece of hardware wire to 102 inches. Fold a piece of duct tape lengthwise down the length of the wire.
Cut the end of your coaxial cable so you have the core (should be an individually shielded piece of solid copper wire.) and the braided wire that goes around the center pole's shield. Strip off enough of the coating so you have a few inches of the braid separated from the center wire and a little bit of the center pole wire to strip.
Connect the center pole wire to the end of your makeshift hardware wire/duct tape antenna.
Connect the braid from the coax to the body of your vehicle (make sure it creates a good electrical connection, so no paint in the way.) You could probably connect it to another piece of hardware wire and wrap it the full length around the roof rack (make a big rectangle around the roof) instead of connecting it to the body... but I'm not 100% this would work... theoretically it would I suppose...
This is your base-plane.
Wrap the duct-tape/wire antenna around the roof rack and secure with zip ties. Leave a couple inches of the end free and sticking straight up. It should hold itself up if it's not too long.
Zoom. Free (mostly) 1/4 wave antenna.
Did this on Joe's rig and it worked REALLY well. It's out of the way enough to not get nailed by trees or brush and should give good enough signal for several hundred feet in any direction. Joe was coming in clear as day when he was within a hundred yards or so and I didn't start to loose him in town until we were a thousand feet or more apart.