a significant disparity between ibiquity's am hd radio and cam-d is that of time diversity. namely, hd radio's am broadcast scheme broadcasts two copies of the program offset by a few seconds, allowing signal to be briefly lost and maintain uninterrupted program audio (for example, driving under an overpass, multipath in urban areas, lightning, switching transients, etc.). . however, in the field, hd radio, at a distance from the transmitter, is still not immune to the aspects of the am dial such as those below.