The International Telecommunication Union (ITU) allocates call sign prefixes for radio and television stations of all types. Amateur radio operators have since 1927 been allocated unique call letters (call sign) to uniquely identify them, as well as locate then within a geographical region of the world - usually a country.
Prefixes are assigned internationally, and a separating numeral plus suffix are added by a national body to produce this unique identifier. These prefixes are agreed upon internationally, and are a form of country code. Each country must only assign call signs to its nationals or operators under its jurisdiction that begin with the characters allocated for use in that country or its territories.
Call signs meant for amateur radio follow the ITU's Article 19, specifically 19.68 and 19.69.[1]
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An amateur operator's call sign is composed of a prefix, a separating numeral and a suffix.
The prefix can be composed of letters or numbers, the separating numeral is one from Ø to 9, and a suffix is from one to four characters where the last one has to be a letter.
Examples of call signs and their constituent parts are as follows:
| Call Sign | Prefix (within ITU assigned range) | Separating numeral | Suffix | format type |
|---|---|---|---|---|
| K4X | K | 4 | X | 1x1 call sign, usually time limited special event (USA) |
| B2AA | B | 2 | AA | 1x2 call sign (China) |
| A22A | A2 | 2 | A | 2x1 call sign (Botswana) |
| I2ØØØØX | I | 2 | ØØØØX | 1x5 call sign, special event (Italy) |
| 4X4AAA | 4X | 4 | AAA | 2x3 call sign (Israel) |
| 3DAØRS | 3DA | Ø | RS | 3x2 call sign (Swaziland) |
Call signs begin with a one- two- or three-character prefix chosen from a range assigned by the ITU to the amateur's country of operation or other internationally recognized jurisdiction. This is not necessary always the amateur's country of citizenship. An individual operator is assigned a unique call sign beginning with this prefix and then completed with a separating numeral and suffix.[2]
The beginning of the list of call sign ranges is:
(concludes with....)
Beginning at the left of the call sign block, the country chooses one, two or three characters from within the range assigned by the ITU, enough to distinguish its call signs from other jurisdictions.
A "letter range" always first refers to the first letter of a block, meaning that in the letter range "AAA-ALZ", the "A" is the letter range-designator.
Factors for a country to consider when choosing within its assigned range:
The jurisdiction then assigns a single digit (a numeral to separate prefix from suffix) as well as a suffix of from 1 to four characters (the last being a letter) and appends them in that order to their assigned prefix(es). The resulting call sign must uniquely identify a ham radio operator within that jurisdiction.
Sometimes the prefix plus separating numeral is together referred to as the prefix.
This produces internationally recognized, unique call signs to identify licensed operators.
In general an amateur radio callsign is of one of these forms where:
Call signs almost always have one of the following forms:
Since suffixes can also contain digits, some countries issue suffixes (usually temporarily) beginning with enough digits to produce a number, usually associated with the special event (e.g. the number of years, see New Zealand below).
In normal call sign assignment, if a call sign has two digits (e.g. S59DSC or 2S4LGR - PPNSSS), the first digit is almost always a prefix character (e.g. S5 indicating Slovenia, or 2S indicating Scotland).
Call signs with two (or more) digits in them can arise a number of ways. When the digits abut one another, it is important to distinguish which digit belongs to the prefix, which is the separating numeral, and which may belong to the suffix.
In every case (Bahamas being an exception), a jurisdiction assigned a letter-digit prefix by the ITU will have a second digit as their internally assigned prefix/suffix separator. An example is A33A, a Tongan call sign; the first '3' is the second character of the prefix and the second '3' is the numeral separating 'A3' from the single-letter suffix 'A'. There are no single letter prefixes allocated by the ITU with an 'A', so the first 3 must be part of the prefix.
Neither New Zealand's nor the Republic of Ireland's prefixes have numerals as prefix-characters. However, both allow a second numeral as the leading character of the suffix and is not to be confused with the sign's separating numeral. As the first character of the suffix, the two digits can be taken together; for instance, to represent a two-digit number of significance to the operator.
A New Zealand amateur who has been active for 30 years and currently is assigned call sign ZL1xxx can operate as ZL3Øxxx for up to three months.[5] Technically, the '3' is the separating numeral and the 'Ø' is the first character of the suffix.
Similarly a club with call ZL4xxx which has been established for 23 years can operate as ZL23xxx for up to three months.
The New Zealand operator substitutes their identifying separating numeral with another, so long as a second digit is added to the beginning of their normal suffix. This may result in call sign confusion in the rare case of two amateurs in differing numeral-areas also both having the same number of years of operation and suffix.
Ireland also takes advantage of the ITU standard to allow digits as suffix-characters. The Irish Radio Transmitters Society operates as EI75IRTS celebrating 75 Years of incorporation - 1932-2007.[6]
Ofcom in Great Britain also allows numerals in special event call signs. For instance GB75RD was a special event sign for the 75th anniversary of the Reading and District Amateur radio club.[7]
The 26 letters of the English alphabet and ten digits may be used to form call signs, accented letters excluded.
Letter combinations which can be confused with distress calls or which are reserved as abbreviations for radiocommunications services are excluded (e.g. Q codes).[8] The ITU Article 19 exclusions are those found in ITU-R M.1172.[9] In practise, no prefix begins with a the letter 'Q', but 'Q' can be the second letter (eq. Malawi assigned the 7QA-7QZ block).
Double- or single-digit prefixes are excluded. A callsign with a leading digit in the prefix always has a second character which is a letter and in rare cases a third character which is also a letter.
Currently, no allocated prefix has Ø (zero) or 1 (one) as one of its characters as they can be confused with the letters O (Oscar) and I (India).
All ten digits from Ø to 9 are allowed to be used as a separating numeral at the discretion of national allocating bodies.
Ancillary prefixes or suffixes further identify the location and/or operating condition of an amateur operator.
According to the Canada/United States Operating Agreement treaty[10] amateurs from one country operating in the other sign with their home call sign, but attach the call area prefix where they are operating to their call. For instance, an amateur from British Columbia (VE7 in Canada) operating in Washington State (W7 in the USA) would amend their home-call with a trailing /W7 (e.g. VE7xxx becomes VE7xxx/W7).
British amateurs operating as a visitor in CEPT countries are required to append the appropriate host country's prefix before their British call sign.[11] For instance an amateur holding a call of G3xxx operating in France would sign as F/G3xxx.
When a country's separating numeral denotes a geographic area within, an operator from one region operating in another region can affix a secondary suffix indicating so. For instance an amateur from Queensland, Australia, operating in Tasmania can sign as VK4xxx/7 or VK4xxx/VK7.
Other secondary operating suffixes can be attached - such as /P (for portable operation), /QRP (for operation at or below 5 watts), /M (for mobile operation), /AM (aeronautical mobile) or /MM (maritime mobile).
Some repeaters have automatic call sign transmission at regular intervals and use the secondary suffix /R at the call sign's end. Some jurisdictions discourage this practise on the grounds that it could be confused with an amateur from the repeater's location working portable in Russia.
| Ancillary Prefix | Usage | notes: |
|---|---|---|
| /<digit> | VE7xxx/7 | denotes operator in his/her own call area operating away from primary location |
| /P | VE7xxx/P | denotes operator in his/her own call area operating away from primary location, on portable power |
| /<call area> | VE7xxx/6, VE7xxx/VE6 | denotes operator in another call area operating away from primary location, but within national boundary |
| /<call area> | VE7xxx/W7 | denotes operator in another call area operating away from primary location, but outside of national boundary |
| <call area>/ | F/G3xxx | UK operator operating in France |
| /QRP | VE7xxx/QRP | denotes operator running low power, usually less than 5 watts |
| /M | VE7xxx/M | denotes operator in a mobilesetting |
| /MM | VE7xxx/MM | denotes operator in marine mobile setting |
| /AM | VE7xxx/AM | denotes operator in aeronautical mobile setting |
Each national authority has some options in relation to the form of the prefix, as long as enough characters are selected starting from the left of their assigned block to produce a prefix unique to its jurisdiction.
Each country has authority over which numeral separates the prefix and suffix. The prohibition of the use of the digits Ø and 1 in land mobile stations does not apply to amateur stations. The ITU however does not issue prefixes with either a Ø or 1 as one of the characters.
Bahamas issues call signs without a separating numeral. They are assigned the C6A-C6Z block, and the '6' is part of the prefix. Examples are as found on QRZ.COM (C6AFO, C6AGB, etc.).
The suffix can be from one to four characters subject to ITU exclusions (above).[8] On special occasions, for temporary use, administrations may authorize use of call signs with more than four suffix-characters.
Whereas for ITU purposes the prefix does not include the separating numeral, for country purposes often the separating numeral is included when the prefix is referred to. Thus for Canada VE6 or VA6 are the prefixes for Alberta, while VE2 or VA2 are the prefixes denoting Quebec.
A country can consist of many DXCC entities depending on its geographical make-up. Some islands which are separate DXCC entities are uninhabited and can only be worked when a DXpedition travels there. The following are countries and/or entities which appear perennially on various listings of rare countries:[17]
Countries which are rarely heard, roughly in this order:
Islands which are rarely heard DXCC entities:
As political boundaries change through treaty or warfare, sometimes call sign prefixes are reassigned by the ITU to the new controlling government, or are reassigned by national governments for other reasons.[18]
Some call sign block ranges are unassigned by the ITU, e.g. the 1AA-1ZZ block. Any call sign used by an amateur in these unassigned block ranges usually had it assigned to them by a group with an unrecognized national claim.
Amateur radio call sign prefixes almost always locate an operator within one of the 300+ DXCC entities in the world.
Any country or ITU prefix assignment can have many entities within it. For example in the United States Hawaii (with 'H' as the second character of the prefix and '6' as the separating numeral) and Alaska (with 'L' as the second letter of the prefix) are considered different DXCC entities, as are Sable Island and St. Paul Island in Canada.
The DX Century Club (DXCC) is an amateur radio operating award given by the American Radio Relay League to operators making contact with 100 or more geographic entities around the world. As such, the ARRL keeps a list of DXCC entities (not necessarily a country) for this purpose.[24] This list includes deleted entries and prefixes and the dates in which contacts with them will be counted towards the award.
The DXCC List is based upon Clinton B. DeSoto's landmark 1935 QST article defining a "country" as a discrete geographical entity.[25] A geographical portion of one country can be a separate DXCC entity if it is non-contiguous with or significantly distant from the main part of the national entity.
IOTA is a radio amateur abbreviation for Islands on the Air. It refers to a list of Islands worldwide maintained by the Radio Society of Great Britain, which assigns a unique code to an island or group of islands.[26]
Ham radio operators in the United States may pay a small fee and apply to get a specific callsign, including calls from other zones, so long as they have the appropriate license class for the desired callsign format. The callsign also must conform to the prefix standard assigned to that area. For instance, an Amateur Extra might have W0OL (which is a "1 x 2" call), but a General-class licensee could not, because 1 x 2 calls are reserved for the Amateur Extra class. Likewise, a ham on the mainland could not get a callsign beginning with the KH6 prefix, which is assigned to Hawaii.
There are a variety of reasons why someone would request a vanity callsign. Some people want a callsign that has their name or initials embedded in it. Some want a callsign that reflects a specific interest in amateur radio (like W7FM or K7ATV). Others request callsigns that were formerly held by family members or friends, or even callsigns that they themselves formerly held (and gave up for whatever reason). Some people want a callsign that is shorter, or easier to pronounce, or just "fits their personality" better. CW (Morse code) operators might want a callsign that "sounds good" or is short when sent in Morse. (This is referred to as "CW weight".) Since the FCC (in the US) does not restrict most requests (other than those submitted fraudulently), any of these are valid reasons.
The exact rules for available callsigns are defined on the FCC website under Rules and Availability. The FCC web site can be confusing to some people, as it is very rules-based, and does not offer many examples or any utilities to help users. A number of free web sites (e.g., Vanity Headquarters, AE7Q, and RadioQTH) have sprung up, some dating back to 1999. These sites offer a variety of features, such as search tools, sorted lists, prediction capabilities, help files, message boards, and the like, all intended to help someone understand the vanity process and request a new callsign.
Due to the popularity of vanity calls, and the lack of region restriction, it is often impossible to tell which region an amateur radio operator using one calls home.
The term "vanity call" is generally not applied to 1 x 2 and similar "special" call signs attained by amateurs from the FCC under special rules in the 1970s and prior decades.