Section 73.3556 - Sponsorship identification; list retention; related requirements(a) No commercial FM radio station shall operate so as to devote more than 25 percent of the total hours in its average broadcast week to programs that duplicate those of any station in the same service which is commonly owned or with which it has a time brokerage agreement if the principal community contours (predicted 3.16 mV/m) of the stations overlap and the overlap constitutes more than 50 percent of the total principal community contour service area of either station.(b) For purposes of this section, duplication means the broadcasting of identical programs within any 24-hour period.