An adjustable drive mechanism, which may be used to control the elevation angle of a telescope or antenna, is disclosed. The adjustable drive mechanism can include a base plate configured to couple with a support structure and having a first spherical portion facing away from the support structure. In addition, the adjustable drive mechanism can include a gear box having a pinion gear to interface with a driven gear of a telescope or antenna, and a housing in support of the pinion gear and including a second spherical portion configured to interface with the first spherical portion of the base plate. The first spherical portion and the second spherical portion can be movable relative to one another in three rotational degrees of freedom to facilitate alignment and positioning of the pinion gear relative to the driven gear.