Broadcast call signs

In the United States, the first letter generally is K for stations west of the Mississippi River (including Alaska, America Samoa, Guam, Hawaii, and Northern Mariana Islands) and W for those east of the Mississippi River (including Puerto Rico and the U.S. Virgin Islands). Except for those with their radio channel or physical TV channel number in them, all new callsigns have been four letters (plus any suffix like -FM or -TV) for some decades, though there are historical three-letter callsigns still in use today, such as KSL in Salt Lake City and WGN in Chicago. Co-owned stations were also allowed to adopt their original short AM callsign like WGN-TV and KSL-TV, even after new ones were prohibited.

There are a number of exceptions to the east/west rule, such as KDKA in Pittsburgh and WFAA in Dallas-Fort Worth, but these are historical artifacts grandfathered from a rule change in the 1920s. Most of the exceptions are located in the media markets immediately adjacent to the river, in the state of Louisiana in the metropolitan areas of Baton Rouge and greater New Orleans, and markets north of the river's source such as Fargo-Moorhead and Duluth-Superior.

The westernmost station in the continental United States beginning with W is WOAI in San Antonio. WVUV-FM in Fagaitua, American Samoa, is the westernmost station with a W call sign. KYW in Philadelphia is currently the easternmost station with a K call sign.

Another exception to this is that NIST time-broadcasting stations have a three- or four-letter callsign beginning with WWV. The three current government-operated time stations, WWV (and longwave sister station WWVB), and WWVH, are located in Fort Collins, Colorado and Kekaha, Hawaii, respectively, both of which would normally use call signs beginning with "K". However, the rule dividing W and K only applies to stations governed by the Federal Communications Commission (FCC), whereas U.S. federal government stations are governed by the NTIA. This means that like NIST, the hundreds of NOAA Weather Radio stations across the country have a random mix of W and K callsigns, as do traveler information stations operated by the National Park Service.

The US government-operated international broadcaster the Voice of America no longer uses callsigns assigned to it; however, Radio Canada International's transmitter in Sackville, New Brunswick was assigned CKCX. Privately operated shortwave stations, like WWCR and CFRX, also have call signs.

In Canada, the publicly owned Canadian Broadcasting Corporation uses CB; privately owned commercial broadcast stations use primarily CF and CH through CK prefixes. Four stations licensed to St. John's by the Dominion of Newfoundland government (VOWR, VOAR-FM, VOCM, and VOCM-FM) retain their original VO calls. The CB prefix used by CBC stations actually belongs to Chile rather than Canada, and is in use by the CBC through an international agreement.[1] Low-power broadcast translator stations begin with VF for FM and CH for TV, followed by four numerals assigned sequentially. Unlike the United States, all Digital TV stations use the "-DT" suffix instead of keeping the "-TV" suffix.

In Mexico, AM radio stations use XE call signs (such as XEW-AM), while the majority of FM radio and television stations use XH. Broadcast callsigns are normally four or five letters in length, plus the -FM or -TV suffix where applicable, though several older stations have only three letters. The longest callsign is six letters, plus suffix: XHMORE-FM. All Mexican TV stations using Digital TV signals use the "-TDT" suffix.

Costa Rica uses TI call signs.

El Salvador uses YS call signs.

Guatemala uses TG call signs.

Honduras uses HR call signs.

Nicaragua uses YN call signs.

In Brazil, radio and TV stations are identified by a ZY, a third letter and three numbers. ZYA, ZYB, ZYR, and ZYT are allocated to television stations; ZYI, ZYJ, ZYK and ZYL designate AM stations; ZYG is used for shortwave stations; ZYC, ZYD, ZYM and ZYU are given to FM stations.

Venezuela uses YV call signs.