the north american regional broadcasting agreement of 1941 saw all of westinghouse's original stations move to their current dial positions. with wowo's power increase to 50,000 watts later that year, the westinghouse stations were now also clear-channel stations. a decade later, the fcc forbade common ownership of two or more clear channel stations with overlapping nighttime coverage, though the commission allowed westinghouse to keep wbz, kyw, kdka, and wowo together under a grandfather clause. among them, the four stations' nighttime signals blanketed almost all of the eastern half of north america. despite the assignments which resulted from narba, wbza became a 1,000-watt daytime-only operation as it continued to share a frequency with wbz.