From The TV IV
Secondary affiliation was a practice of network affiliated television stations in which they would carry some of the programs of another network. It was used mostly with new networks that did not have the clearances of the already established networks. Indirectly, the term has also applied to independent stations, usually UHF, that in the past carried network programming passed up by that market's regular ABC, CBS and NBC stations.
ABC and DuMont did not have full clearance across the United States in the 1950s, so in many markets, they were the secondaries on stations already affiliated with NBC and CBS. As ABC grew in popularity primary affiliated stations began to pop up in several larger markets, while DuMont was relegated to secondary status (some extra large markets, such as New York and Los Angeles had primary DuMont stations). DuMont never managed to get enough primary affiliates and eventually folded.
The practice was used to a lesser extent with FOX in the late 1980s and early 1990s and The WB and UPN in the late 1990s but with multichannel delivery systems such as cable and satellite out of market stations could be delivered to areas without a local affiliate so there wasn't as much of a need.
With the advent of digital television secondary affiliation has been made obsolete by digital sub-channels. The new smaller networks the CW and MyNetworkTV are often carried on sub-channels of medium-to-smaller market stations. WXTX/channel 54 in Columbus GA currently carries FOX as its primary and MyNetworkTV as a secondary.
Some of the more notable secondary affiliations of the past, along with their primaries:
|WSB||8||Atlanta, GA||NBC||ABC||1951||Moved to ch. 2 in 1951, switched to ABC in 1980|
|KFMB||8||San Diego, CA||CBS||ABC||1956|
|WJHG||7||Panama City, FL||NBC||ABC||CBS||DuMont||1973||Had ABC as primary 1973-77|
|WEWS||5||Cleveland, OH||CBS||ABC||DuMont||1955||Switched to ABC after dropping DuMont|
|KPHO||5||Phoenix, AZ||CBS||NBC||ABC||DuMont||1955||went independent afterwards, became CBS again in 1995|
|WJZ||13||Baltimore, MD||ABC||Dumont||1955||switched to CBS in 1995|
|WHDH||7||Boston, MA||CBS||ABC||Dumont||1957||switched to ABC in 1961; switched to CBS in 1972; switched to NBC in 1995|
|WDSU||6||New Orleans, LA||NBC||CBS||ABC||DuMont||1957|