I'm assuming you have the Winegard antenna. Maybe this diagram will help. The crank is connected to 7 which is called the elevating shaft and there is a worm gear on the top end of this shaft. It engages 6, a plastic elevating gear. The elevating gear is visible from above. It is likely missing some teeth. This gear is relatively easy to replace and most RV stores carry it. They make it out of plastic in part so that it can function as a mechanical fuse, breaking before something harder to replace breaks. Winegard recommends spraying this assy with silicone lubricant twice a year to flush out any junk and to lubricate the gears. They also recommend removing a small plug to spray silicone lubricant between the rotating base parts. All this is done topside.
Air Safe Hitch, Reese Dual Cam 800#, Centramatics