47 C.F.R. § 73.6017
Class A TV station protection of Class A TV stations
An application to change the facilities of a Class A TV station will not be accepted if it fails to protect authorized Class A stations in accordance with the requirements of § 74.793 (b) through (d), (g), and (j) of this chapter. This protection must be afforded to applications for changes in other authorized Class A stations filed prior to the date the Class A application is filed.