In general an amateur radio callsign is of one of these forms where: •
P prefix character (letter or numeral, subject to exclusions below). Prefixes can be formed using one-letter, two-letters, a digit and a letter, a letter and a digit, or in rare cases a digit and two letters. There is no ITU allocation of digit-only prefixes. Letter-digit-letter prefixes are possible but there are no known cases of them being issued by national bodies. •
N a single numeral which separates prefix from suffix (any digit from 0 to 9). Often a cross-hatched Ø is used for the numeral zero to distinguish it from the letter O. •
S suffix character (letter or numeral, last character must be a letter). Digits are in practise used sparingly in suffixes and almost always for special events. This avoids confusion with separating numerals and digits in prefixes in regularly issued call signs.
Call signs almost always have one of the following forms: •
PNS, 1×1 call sign • usually for a special event, the prefix is always a single letter character, as is the suffix. Can only be assigned in the B, F, G, I, K, M, N, R, or W prefix range. ''(See discussion on the D9K call sign issued by Korea above 'when 2 characters are needed'.)'' •
PPNS, 2×1 call sign • prefix can be letter-letter, letter-digit, or digit-letter. A call sign composed of a letter, two digits, and one-letter is always a 2×1 call sign, meaning it has a letter-digit prefix and a single-letter suffix. • for all letter-digit-digit-letter callsigns, if the first character is other than B, F, G, I, K, M, N, R, or W then it is a 2×1 call sign •
PNSS, 1×2 call sign • prefix always a letter, suffix almost always two letters to avoid confusion with 2×1 call signs. • As a precaution, the ITU has issued no prefixes in the B, F, G, I, K, M, N, R or W block ranges with letter-number possibilities, meaning that the first digit would have to be the separating numeral anyway. • for all letter-digit-digit-letter callsigns, if the first character is B, F, G, I, K, M, N, R, or W then it is a 1×2 call sign •
PNSSS, 1×3 call sign • these have the same precautions as 1×2 call signs to prevent confusion with 2×2 format •
PPNSS, 2×2 call sign • these have the same precautions as 2×1 call signs to prevent confusion with 1×3 format • confusion might seem to arise with letter-digit-digit-digit-letter call signs, however in that case the second digit would be the numeral separator.
(see 2×1 above) •
PPNSSS, 2×3 call sign • by far the most common format •
PPNSSSS, 2×4 call sign, or more • four-character suffix (or more) assigned by some countries (e.g. Australia to designate operator class), or five or more characters for special events. In New Zealand the first character of the
SSSS suffix is sometimes a digit for special events •
PPPNSS or
PPPNSSS, 3×2, 3×3 or more • assigned when two characters of the prefix are not enough to distinguish jurisdiction (eq. Fiji 3DN–3DZ and Swaziland 3DA–3DM)
Suffix assignment 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 (for example 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 2M indicating Intermediate License holder in Scotland).
Call signs with more than one digit 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 ZL30xxx for up to three months. Technically, the '3' is the separating numeral and the '0' 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. 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. Numerous other cases of multiple numeral prefixes exist. An example occurred in 1987 when the "200" was used in place of district numbers for the many stations that celebrated the bicentennial of the U.S. Constitution.
Exclusions 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). The ITU Article 19 exclusions are those found in ITU-R M.1172. In practice, no prefix begins with the letter 'Q', but 'Q' can be the second letter (e.g. 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 0 (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 0 to 9 are allowed to be used as a separating numeral at the discretion of national allocating bodies.
Secondary prefix or suffix types 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 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 (K7 in the USA) would amend their home-call with a trailing /K7 (e.g. VE7xxx becomes VE7xxx/K7). Radio amateurs from countries that apply the CEPT recommendation T/R 61-01 operating as a visitor in countries that apply the same recommendation are required to use the appropriate host country's prefix before their home call sign (in the case of Peru, after the home call sign) and may use the appropriate operating suffix (see below). For instance a British (English) amateur holding a call of G3xxx operating in France would sign as F/G3xxx, a Swiss amateur operating from a car in Germany as DL/HB9xxx/m. Similar rules apply in cases when bilateral agreements on visitors licenses exist, or a visitor is permitted to operate without being assigned a local call sign. 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), or /A (for operation from an alternative location that is registered with the licensing authorities). Depending on the jurisdiction, the use of these five suffixes may be required for these types of operation. Occasionally self-assigned operating suffixes such as /QRP for operation at low power are heard. Note, the prefixes /M (for mobile operation), /AM (aeronautical mobile), /MM (maritime mobile), are not authorized because they conflict with prefixes assigned to nations (M = England, MM = Scotland, AM = Spain). 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 practice on the grounds that it could be confused with an amateur from the repeater's location working portable in Russia. Some
beacon stations use the self-assigned secondary suffix /B; however, as this is the ITU prefix for China, it is not authorized. ==Callsigns within a country==