The Collins WX radar uses digital drive to stepper motors on the antenna, with digital position sensors, and the tilt shown the pilot is actual tilt with respect to the horizon, regardless of any marks on the knob. The flat plate antenna has a 3 degree beam width, and no sidelobes. In case it wasn't mentioned earlier, beam width is defined as the angle of half power point off dead ahead - times two, of course.
Earlier generation radars had parabolic reflectors, typically a 6 degree beam width, and lots of sidelobes. There was usually an altitude arc from spurious ground return.
GB