Call sign

A callsign is a unique designation for a radio or television station. Callsigns are formal, semi-permanent, and issued by a nation's telecommunication agency.

Informal designations are also used for some services, especially broadcast radio, but strictly speaking these are not callsigns and there is no guarantee that they are unique. Tactical designators or identifiers (often called tactical callsigns) also fall into this category.

Each country has a set of alphabetic or numeric International Telecommunication Union-designated prefixes with which their callsigns must begin. For example:

• The U.S.A. uses the prefixes: W, K, N, and AAA to ALZ
• The United Kingdom uses the prefixes: G, M, and 2
• France uses the prefixes: F, TM
• Chad uses the prefix: TT
• Italy uses the prefix: I

Amateur radio callsigns

Amateur radio callsigns normally consist of a one or two character prefix, a number (which sometimes corresponds to a geographic area within the country) and a 1, 2, or 3 character suffix. The number following the prefix is normally a single number (0 to 9). Some prefixes, such as Djibouti's (J2), consist of a letter followed by a number. Hence, in the hypothetical Djibouti callsign, J29DBA, the prefix is "J2", the number is "9", and the suffix is "DBA". In the Italian callsign, IK1TZO, "IK" is the prefix, the number component is "1" and corresponds to the Piemonte region, and TZO is the suffix. Another example is WB3EBO. "WB" is the prefix, the number "3" most often indicates that the station is located in Delaware, Maryland, Pennsylvania, or the District of Columbia. The suffix is "EBO".

Broadcast callsigns

Broadcast stations in the U.S. and Canada are assigned three or four letter callsigns. Many of these, such as Baltimore television station WJZ, have long historical associations. Others are changed frequently as the station changes format. Many stations prefer not to use callsigns at all, since a slogan is more easily remembered by listeners filling in diaries for the Arbitron Company's radio ratings. However, in the U.S., the Federal Communications Commission does require periodic identification using the formal callsign, as close to the top of each hour as possible.

In the United States, the vast majority of stations east of the Mississippi River have callsigns beginning with "W". Exceptions include: KDKA (Pittsburgh), the first commercial radio station in the world, and KYW (Philadephia). Callsigns of US stations west of the Mississippi River generally begin with "K". Among the grandfathered exceptions to this are WDAF (Kansas City), WTAW (Bryan, Texas), and WACO (Waco, Texas), all issued before the rule took effect.

Many stations also get suffixes to identify which band they are on, and to create separate callsign pools for each type of service. AM, FM, and TV naturally get -AM, -FM, and -TV tacked on. Digital TV stations started with the -HD suffix, but now get -DT instead, and always have the base callsign of the analog station (i.e. WABC-TV's digital station must be WABC-DT). Low-power LPTV and LPFM stations share the -LP suffix. Those LPTV stations protected from interference by so-called "primary" stations use the -CA suffix. Instead of a suffix, translator/repeater stations get a W or K, the channel number (2~69 for TV, 201~300 for FM), and two serial letters, such as W02AA, or K201AA (88.1).

In Canada, stations of the Canadian Broadcasting Corporation or Société Radio-Canada tend to identify themselves as "CBC Radio One/Two" (english AM/FM) or "La Première Chaîne/La Chaîne Culturelle" (french AM/FM) of a city, although they do have official three- and four- letter callsigns. These usually begin with "CB", which actually is assigned to Chile internationally, but is "borrowed" for domestic broadcast use only. Non-CBC stations use a four-letter callsign (two exceptions being CKX and CKY in Manitoba) beginning with "CF" through "CK" -- though older stations in Newfoundland, like VOCM St. John's, usually use "VO" (the ITU prefix assigned before it officially joined the Dominion of Canada).

In Mexico, stations usually have four or five letters in a callsign, but sometimes few as three or as many as six, such as XHMORE in Tijuana. FM stations begin with XH, and AM ones with XE. As in Canada, stations that rebroadcast other stations have the same callsign, but with a different number at the end (such as XEMN and XEMN1).

In Australia, broadcast callsigns begin with a single-digit number indicating the state or territory, followed by two letters for AM stations and three for FM, also, some AM stations retain their old callsigns when moving to FM, or just add an extra letter to the end.

In Europe and much of Asia, callsigns are normally not used for broadcast stations. Japan, South Korea and Taiwan are exceptions to this general rule. Other countries have yet other formats for assigning callsigns to domestic services.

Tactical designators

Police units in the United States tend to use a tactical designator consisting of a letter of the police phonetic alphabet followed by one or two numbers. For example, "Mary One" might identify the head of a city's Homicide Division. Police agency radio systems are assigned official callsigns however. Examples are KQY672 and KYX556. The official headquarters callsigns are usually announced at least hourly.

The United States Army uses tactical designators that change daily.

The United States Air Force uses semi-fixed identifiers consisting of a name followed by a two or three digit number. The name is assigned to a unit on a semi-permanent basis. For example, "JAMBO 51" would be assigned to a particular B-52 aircrew of the 5th Bomb Wing, while "NODAK 1" would be an F-16 fighter with the North Dakota Air National Guard. The most recognizable callsign of this type is "AIR FORCE 1", used when a plane is carrying the U.S. President.

External Resources

• Extensive information on amateur radio callsigns: http://www.ac6v.com/prefixes.htm