Complex sentence: The television station has been an NBC affiliate from the very first day, though it carried some programming from CBS, DuMont, and ABC until 1953, when WSIX-TV channel 8 (now WKRN-TV channel 2) started as a CBS primary affiliate.
Split into simpler sentences: The television station has been an NBC affiliate from the very first day, though it carried some programming from CBS, DuMont, and ABC. Affiliation with CBS ended in 1953 when WSIX-TV channel 8 (now WKRN-TV channel 2) signed on as a CBS primary affiliate.