Call signs in the United States are identifiers assigned to radio and television stations, which are issued by the Federal Communications Commission (FCC) and, in the case of most government stations, the National Telecommunications and Information Administration (NTIA). They consist of from 3 to 9 letters and digits, with their composition determined by a station's service category. By international agreement, all call signs starting with the letters K, N, and W, as well as AAA-ALZ, are reserved exclusively for use in the United States.
AM, FM, TV and shortwave broadcasting stations can request their own call letters, as long as they are unique. The FCC policy covering broadcasting stations limits them to call signs that start with a "K" or a "W", with "K" call signs generally reserved for stations west of the Mississippi River, and "W" limited to stations east of the river. Amateur stations can receive call signs starting with all of the letters "A", "K", "N", and "W". Formerly, prefixes beginning with "A" were exclusively assigned to U.S. Army stations and prefixes beginning with "N" to U.S. Navy stations.
Broadcasting stations
Although most transmitters regulated by the Federal Communications Commission (FCC) are issued call signs for their official identification, the general public is most familiar with the ones used by radio and TV broadcasting stations. However, there is a wide variety in how much emphasis stations give to their call signs; for some it is the primary way they establish public identity, while others largely ignore their call signs, considering a moniker or slogan to be more easily remembered by listeners (and those filling in diaries for the Nielsen Audio ratings measurement). In the United States, the only time broadcasting stations are required to mention their call signs is during station identification announcements, made at a "natural break in programming" as close to the beginning of each hour as possible. (Code of Federal Regulations: Station identification.) Stations are also required to identify their community of license.
Television stations have the option of displaying a small graphic or text ("digital on-screen graphic" or "bug") at the bottom of the screen listing their call sign, community of license, and other identifying information. Sometimes station identification is displayed non-intrusively in small type during short promotions, either for an upcoming show or their next local newscast (even incorporating these identifications at the start of newscasts), that air just before the top of each hour. FM stations with HD Radio digital subchannels must individually identify each program stream, but do not need to do so in any particular form; most licensees use the form "WXXX HD2", but this is not part of their call sign.
A few AM stations have had the same call letters for 100 years or more: KDKA in Pittsburgh, Pennsylvania, has been in continuous use since 1920, while WBZ in Boston, KYW in Philadelphia, and KWG in Stockton, California, all date back to 1921. At the other extreme, reflecting multiple changes in ownership and format, are stations which have changed call letters numerous times, for example KXFN in Saint Louis, Missouri, has switched ten times since 1925.The sequence of call letters has been: KFVE, KWK, KGLD, KASP, WKBQ, KRAM, WKBQ, KKWK, KZJZ, KSLG, and KXFN.
Call signs meanings While the earliest radio call signs were randomly or sequentially assigned and intended merely to distinguish transmitters, they soon became an important part of a station's identity, and since the mid-1920s government regulators have allowed station owners to choose their own. Thousands of radio and TV stations have been established, with a wide variety of reasons for choosing particular call signs. Some common categories include:
Slogans: It is sometimes difficult to determine which came first: a station's call sign, or a slogan attached to it. However, some well-documented examples of call letters being chosen to reflect an existing slogan include: WGN and WGN-TV in Chicago, standing for "World's Greatest Newspaper", used by their original owner, the Chicago Tribune; WIS in Columbia, South Carolina, the "Wonderful Iodine State"; WPTF, Raleigh, North Carolina, which references the motto of previous owner the Durham Life Insurance Company, "We Protect the Family" while Z88.3, in Central Florida prizes itself on its "Positive Hits", with the call-sign WPOZ. Owners: The major owned-and-operated stations of the Big Three television networks—ABC, CBS and NBC—have traditionally had call signs reflecting the network abbreviations. Stations operated by schools and universities commonly incorporate their school's initials, including WWVU-FM (West Virginia University, Morgantown), and KUOM (University of Minnesota, Minneapolis). Locations: Three stations have call signs that fully spell out their community of license: WACO-FM (Waco, Texas), WARE (Ware, Massachusetts) and WISE-FM (Wise, Virginia). Other stations reference their community of license or designated market area (DMA) with an abbreviation or initialism, such as WRAL-TV (Raleigh, North Carolina), WCSC-TV (Charleston, South Carolina), WLOX (Biloxi, Mississippi), WSAV-TV (Savannah, Georgia), WPGH-TV (Pittsburgh, Pennsylvania), or WTSP (Tampa-St. Petersburg, Florida). Numbers: Numerous television stations have chosen call letters that reference their channel number, either spelled out or using Roman numerals: WDIV-TV (channel 4, Detroit, Michigan), WXII-TV (channel 12, Winston–Salem, North Carolina), WXXV-TV (channel 25, Gulfport, Mississippi), KXII (also channel 12, Sherman, Texas), WIIC-TV (now WPXI) (channel 11, Pittsburgh), WPVI-TV (channel 6, Philadelphia), WIVB-TV (channel 4, Buffalo, New York), WTWO (channel 2, Terre Haute, Indiana), KIXE-TV (channel 9, Redding, California - And the last letter selected as it was part of the Educational network, now PBS), and WXXI-TV (channel 21, Rochester). Some, like WGRZ (channel 2, Buffalo) and WDIO-DT (channel 10, Duluth), use letters which have similarities to numerals; in those examples, the "Z" in WGRZ resembles a "2", while the "IO" in WDIO resembles a "10". Examples on the AM band have historically included KIXI in Seattle, which previously broadcast on 910 kHz ("IX-I"); and KIIS (now KEIB) in Los Angeles, which originated on 1150 kHz (as the letters IIS resemble 115, its frequency in myriahertz). Network: Several stations include their network affiliate, such as east coast flagship stations WCBS-TV, WNBC, and WABC-TV, which are affiliated with CBS, NBC, and ABC respectively, all located in New York City, and west coast flagship stations KCBS-TV, KNBC, and KABC-TV in Los Angeles. Outside of flagship stations include WFOX-TV (Jacksonville, Florida) and KFOX-TV (El Paso, Texas), both affiliates of the Fox network, WPBS-TV (Watertown, New York) and KPBS (San Diego, California) both affiliates of PBS, KMEE-TV (Kingman, Arizona), an affiliate of MeTV, and KMYT (Tulsa, Oklahoma) and WMNT-CD (Toledo, Ohio), both affiliates of MyNetworkTV. Several Ion Television stations pertain the "PX" within their names as a call back to the network's original name, PAX, with an extra letter for either their location (WPXN-TV in New York), area where they serve (WQPX-TV in Scranton, Pennsylvania, in which the Q stands for Susquehanna Valley), or to disambiguate from other Pax/Ion stations (WPXJ-TV in Buffalo, New York). Many call signs pertain their previous affiliation, such as WMYT-TV in Charlotte, North Carolina which became an affiliate of The CW network in 2025, or a defunct network, such as KWBQ which stands for The WB Albuquerque, or WUPA, which stands for UPN Atlanta. Words: Very rarely some call signs are named after words. Such as KAKE in Wichita, Kansas named after, and pronounced like the word "cake" (sic). KOLD-TV in Tucson, Arizona, which is pronounced like the word "cold", and derived from then-co-owned KOOL-TV in Phoenix, KARE-TV in Minneapolis which is pronounced and is a homophone to the word "care", WOOD-TV in Grand Rapids, Michigan, pronounced like the word "wood", and came from radio sister station, which was funded originally by furniture manufacturers, WINK-TV in Fort Myers, Florida named after the word "wink", and KEYE-TV in Austin, Texas, named after the word eye, both alluding to the CBS Eyemark logo, WISH-TV in Indianapolis, which is pronounced as "wish" (as in making a wish), WKOW in Madison, Wisconsin, taken from the word "cow", deriving from the Wisconsin dairy industry, WOLF-TV in Hazelton, Pennsylvania, named after the canine, KUBE-TV in Baytown, Texas, named after the word "cube", WALE-LD in Montgomery, Alabama, named after the mammal, and WHAM-TV in Rochester, New York, taken from former sister radio station, and pronounced like "wham" as in the onomatopoeia. While some station spell out words, the call letters are pronounced individually, such as WHO-DT in Des Moines, Iowa.
Geographical separation of K and W call signs
Following a practice inaugurated in 1912 when the federal government first licensed radio stations, beginning in 1921 broadcasting stations have generally been assigned call signs beginning with "K" when their community of license is in the west, and with "W" in the east. (The FCC proposed ending this policy in 1987, in order to allow unrestricted assignments of K and W stations throughout the country. However, after receiving public comments, it was decided to retain the rule, because of its convenience as a geographical identifier)."In the Matter of Amendment of Part 73 Relating to Call Sign Assignments for Broadcast Stations", MM Docket No. 87-11, Adopted: October 20, 1987 (FCC.gov)
The original boundary ran northward from the Texas–New Mexico border. In early 1923 the boundary was moved to its present location, the Mississippi River, in order to balance the populations in the two regions."'K' Calls Are Western", The Wireless Age, April 1923, page 25. The geographical separation of "K" and "W" prefixes applies only to radio and television broadcasting stations, and is not followed for weather radio, highway advisory radio, and time signal stations, nor does it apply to auxiliary licenses held by broadcast stations, such as studio-transmitter links and inter-city relay stations.
For stations in U.S. possessions, too, the Mississippi River is the boundary. Puerto Rico and the U.S. Virgin Islands are east of the river, and all their stations have been given standard "W" call signs. The Pacific Ocean territories—Guam, the Northern Mariana Islands, and American Samoa—are in western, "K" territory, although assignments there have been less consistent. All but one of these stations have "K" calls; the exception is WVUV-FM in Fagaitua, American Samoa, which received its call while it was paired with a now defunct AM station, WVUV.
The 1923 boundary shift meant that a number of existing stations with "W" call letters were in a section of country that was now being issued "K" call letters, but these earlier stations were allowed to keep their now non-standard call signs. These include WBAP (Fort Worth, Texas), and WDAF-FM and WDAF-TV (Kansas City, Missouri), which inherited their calls from the original WDAF (now KFNZ).
Although a long established convention, the K–W division has not always been rigidly followed. One prominent exception is KDKA, in Pittsburgh, Pennsylvania, which was licensed in 1920 during a short period when new land stations were issued call signs from a block of letters that had been reserved for ship stations."New Stations", Radio Service Bulletin, November 1, 1920, page 2. Another is KYW, which was originally launched in Chicago by the Westinghouse corporation in 1921 and later moved to Philadelphia: the call sign was temporarily transferred to Cleveland, where it was used from 1956 to 1965.