In broadcasting and radio communications, a call sign (also known as a
call name or call letters—and historically as a call signal—or
abbreviated as a call) is a unique designation for a transmitter
station. In the United States of America, they are used for all
FCC-licensed transmitters. A call sign can be formally assigned by
a government agency, informally adopted by individuals or
organizations, or even cryptographically encoded to disguise a
The use of call signs as unique identifiers dates to the landline
railroad telegraph system. Because there was only one telegraph line
linking all railroad stations, there needed to be a way to address
each one when sending a telegram. In order to save time, two-letter
identifiers were adopted for this purpose. This pattern continued in
radiotelegraph operation; radio companies initially assigned
two-letter identifiers to coastal stations and stations aboard ships
at sea. These were not globally unique, so a one-letter company
identifier (for instance, 'M' and two letters as a Marconi station)
was later added. By 1912, the need to quickly identify stations
operated by multiple companies in multiple nations required an
international standard; an
ITU prefix would be used to identify a
country, and the rest of the call sign an individual station in that
3 Amateur radio
4 Military call signs
5 Transmitters requiring no call signs
7 See also
9 Further reading
10 External links
Russian nuclear icebreaker Arktika with call sign UKTY
Main article: Maritime call signs
Merchant and naval vessels are assigned call signs by their national
licensing authorities. In the case of states such as
Panama, which are flags of convenience for ship registration, call
signs for larger vessels consist of the national prefix plus three
letters (for example, 3LXY, and sometimes followed by a number, i.e.
3LXY2). United States merchant vessels are given call signs beginning
with the letters "W" or "K" while US naval ships are assigned
callsigns beginning with "N". Originally, both ships and broadcast
stations were given call signs in this series consisting of three or
four letters, but as demand for both marine radio and broadcast call
signs grew, gradually American-flagged vessels were given longer call
signs with mixed letters and numbers.
Leisure craft with VHF radios may not be assigned call signs, in which
case the name of the vessel is used instead. Ships in the US still
wishing to have a radio license are under FCC class SA: "Ship
recreational or voluntarily equipped." Those calls follow the land
mobile format of the initial letter K or W followed by 1 or 2 letters
followed by 3 or 4 numbers (such as KX0983 or WXX0029). U.S. Coast
Guard small boats have a number that is shown on both bows (i.e. port
and starboard) in which the first two digits indicate the nominal
length of the boat in feet. For example, Coast Guard 47021 refers to
the 21st in the series of 47-foot motor lifeboats. The call sign might
be abbreviated to the final two or three numbers during operations,
for example: Coast Guard zero two one.
Aviation call signs
Call signs in aviation are derived from several different policies,
depending upon the type of flight operation and whether or not the
caller is in an aircraft or at a ground facility. In most countries,
unscheduled general aviation flights identify themselves using the
call sign corresponding to the aircraft's registration number (also
called N-number in the U.S., or tail number). In this case, the call
sign is spoken using the International Civil
(ICAO) phonetic alphabet.
Aircraft registration numbers
internationally follow the pattern of a country prefix, followed by a
unique identifier made up of letters and numbers. For example, an
aircraft registered as N978CP conducting a general aviation flight
would use the call sign November-niner-seven-eight-Charlie-Papa.
However, in the United States a pilot of an aircraft would normally
omit saying November, and instead use the name of the aircraft
manufacturer or the specific model. At times, general aviation pilots
might omit additional preceding numbers and use only the last three
numbers and letters. This is especially true at uncontrolled fields
(those without control towers) when reporting traffic pattern
positions, or at towered airports after establishing two-way
communication with the tower controller. For example, Skyhawk
eight-Charlie-Papa, left base.
In most countries, the aircraft call sign or "tail number"/"tail
letters" (also known as registration marks) are linked to the
international radio call sign allocation table and follow a convention
that aircraft radio stations (and, by extension, the aircraft itself)
receive call signs consisting of five letters. For example, all
British civil aircraft have a five-letter call sign beginning with the
letter G. Canadian aircraft have a call sign beginning with C–F or
C–G, such as C–FABC. Wing In Ground-effect vehicles (hovercraft)
in Canada are eligible to receive C–Hxxx call signs, and ultralight
aircraft receive C-Ixxx call signs. In days gone by, even American
aircraft used five letter call signs, such as KH–ABC, but they were
replaced prior to World War II by the current American system of
civilian aircraft call signs (see below).
Main article: Spacecraft call signs
Radio call signs used for communication in manned spaceflight is not
formalized or regulated to the same degree as for aircraft. The three
nations currently launching manned space missions use different
methods to identify the ground and space radio stations; the United
States uses either the names given to the space vehicles, or else the
project name and mission number. Russia traditionally assigns code
names as call signs to individual cosmonauts, more in the manner of
aviator call signs, rather than to the spacecraft.
The only continuity in call signs for spacecraft have been the
issuance of "ISS"-suffixed call signs by various countries in the
Amateur Radio service as a citizen of their country has been assigned
there. The first Amateur Radio call sign assigned to the International
Space Station was NA1ISS by the United States. OR4ISS (Denmark),
DP0ISS (Germany), and RS0ISS (Russia) are examples of others, but are
not all-inclusive of others also issued.
QSL card for WWV, indicating its early location in the U.S.
state of Maryland.
Main article: Broadcast call signs
Broadcasters are allocated call signs in many countries. While
broadcast radio stations will often brand themselves with plain-text
names, identities such as "cool FM", "rock 105" or "the ABC network"
are not globally unique. Another station in another city or country
may (and often will) have a similar brand, and the name of a broadcast
station for legal purposes is normally its internationally recognised
ITU call sign. Some common conventions are followed in each country.
Broadcast stations in North America generally use call signs in the
international series. In the United States, the first letter generally
is K for western stations and W for eastern stations. Historic
exceptions in the east include KYW in Philadelphia and KDKA in
Pittsburgh. Stations in the central United States use call signs
beginning with either "K" or "W". All new call signs have been
4-character for some decades, though there are historical 3-character
call letters still in use today, such as KSL in Salt Lake City, KOA in
Denver, WHO in Des Moines, WJW in Cleveland, WSM in Nashville, and WGN
in Chicago. American radio stations announce their call signs at the
top of each hour, as well as sign-on and sign-off for stations that do
not broadcast 24 hours.
In Canada, the publicly owned Canadian
Broadcasting Corporation uses
the prefix CB; privately owned commercial broadcast stations use
primarily CF and CH through CK prefixes; and four stations licensed to
St. John's by the
Dominion of Newfoundland
Dominion of Newfoundland government retain their
original VO calls. 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 call signs
Broadcast call signs are normally four or five alpha
characters in length, plus the -FM, -TV, or -TDT suffix where
In South America call signs have been a traditional way of identifying
radio and TV stations. Some stations still broadcast their call signs
a few times a day, but this practice is becoming very rare.
Argentinian broadcast call signs consist of two or three letters
followed by multiple numbers, the second and third letters indicating
region. In Brazil, radio and TV stations are identified by a ZY, a
third letter and three numbers. ZYA and ZYB are allocated to
television stations, ZYI, ZYJ, ZYL and ZYK designate AM stations, ZYG
is used for shortwave stations, ZYC, ZYD, ZYM and ZYU are given to FM
In Australia, broadcast call signs are optional, but are allocated by
Australian Communications and Media Authority
Australian Communications and Media Authority and are unique for
each broadcast station. Most European and Asian countries do not use
call signs to identify broadcast stations, but Japan, South Korea,
Indonesia, the Philippines and Taiwan do have call sign systems.
Britain has no call signs in the American sense, but allow broadcast
stations to choose their own trade mark call sign up to six words in
Amateur radio call signs
All U.S. states issue call sign license plates for motor vehicles
owned by amateur radio operators. This road vehicle is from
Amateur radio call signs
Amateur radio call signs are in the international series and normally
consist of a one or two character prefix, a digit (which may be used
to denote a geographical area, class of license, or identify a
licensee as a visitor or temporary resident), and a 1, 2, or 3 letter
suffix. In Australia, call signs are structured with a two letter
prefix, a digit (which identifies geographical area), and a 2, 3 or 4
letter suffix. This suffix may be followed by a further suffix, or
personal identifier, such as /P (portable), /M (mobile), /AM
(aeronautical mobile) or /MM (maritime mobile). 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 call sign, J29DBA, the prefix is J2, the
number is 9, and the suffix is DBA. Others may start with a number
followed by a letter, for example, Jamaican call signs begin with 6Y.
When operating with reciprocal agreements under the jurisdiction of a
foreign government, an identifying station pre-pends the call sign
with the country prefix and number of the country/territory from which
the operation is occurring. For example, W4/G3ABC would denote a
licensed amateur from the United Kingdom who is operating in the
fourth district of the United States. There are exceptions; in the
case of U.S./Canadian reciprocal operations, the country/territory
identifier is, instead, appended to the call sign; e.g., W1AW/VE4, or
Special call signs are issued in the amateur radio service either for
special purposes, VIPs, or for temporary use to commemorate special
events. Examples include VO1S (VO1 as a
Dominion of Newfoundland
Dominion of Newfoundland call
sign prefix, S to commemorate Marconi's first trans-Atlantic message,
Morse code S sent from Cornwall, England to Signal
Hill, St. John's in 1901) and GB90MGY (GB as a Great Britain call sign
prefix, 90 and MGY to commemorate the 90th anniversary of historic
1912 radio distress calls from MGY, the
Marconi station aboard the
famed White Star luxury liner RMS Titanic).
The late King
Hussein of Jordan
Hussein of Jordan was issued a special amateur license
number, JY1, which would have been the shortest possible call sign
issued by the Hashemite Kingdom of Jordan.
When identifying a station by voice, the call sign may be given by
simply stating the letters and numbers, or using a phonetic alphabet.
Some countries mandate the use of the phonetic alphabet for
Military call signs
Main article: Military call signs
In wartime, monitoring an adversary's communications can be a valuable
form of intelligence. Consistent call signs can aid in this
monitoring, so in wartime, military units often employ tactical call
signs and sometimes change them at regular intervals. In peacetime,
some military stations will use fixed call signs in the international
United States Army
United States Army uses fixed station call signs which begin with
W, such as WAR, used by U.S. Army Headquarters. Fixed call signs for
United States Air Force
United States Air Force stations begin with A, such as AIR, used
by USAF Headquarters. The United States Navy, United States Marine
United States Coast Guard
United States Coast Guard use a mixture of tactical call
signs and international call signs beginning with the letter N.
In the British military, tactical voice communications use a system of
call signs of the form letter-digit-digit. Within a standard infantry
battalion these characters represent companies, platoons and sections
respectively, so that 3 Section, 1 Platoon of F Company might be F13.
In addition, a suffix following the initial call sign can denote a
specific individual or grouping within the designated call sign, so
F13C would be the Charlie fire team. Unused suffixes can be used for
other call signs that do not fall into the standard call sign matrix,
for example the unused 33A call sign is used to refer to the Company
Transmitters requiring no call signs
No call signs are issued to transmitters of long-range navigation
systems (Decca, Alpha, Omega), or transmitters on frequencies below
10 kHz, because frequencies below 10 kHz are not subject to
international regulations. In addition, in some countries lawful
unlicensed low-power personal and broadcast radio signals (Citizen's
Part 15 or ISM bands) are permitted; an international call sign
is not issued to such stations due to their unlicensed nature. Also,
wireless network routers or mobile devices and computers using Wi-Fi
are unlicensed and do not have call signs. On some personal radio
services, such as Citizen's Band, it is considered a matter of
etiquette to create one's own call sign, which is called a handle (or
trail name). Some wireless networking protocols also allow an
MAC address to be set as an identifier, but with no guarantee that
this label will remain unique.
International regulations no longer require a call sign for broadcast
stations; however, they are still required for broadcasters in many
countries, including the United States. Mobile phone services do not
use call signs on-air because the phones and their users are not
licensed, instead the cell operator is the one holding the license.
However, the U.S. still assigns a call sign to each mobile-phone
In the United States, voluntary ships operating domestically are not
required to have a call sign or license to operate VHF radios, radar
or an EPIRB. Voluntary ships (mostly pleasure and recreational) are
not required to have a radio. However, ships which are required to
have radio equipment (most large commercial vessels) are issued a call
FCC callbook, 1919
A directory of radio station call signs is called a callbook.
Callbooks were originally bound books that resembled a telephone
directory and contains the name and addressees of licensed radio
stations in a given jurisdiction (country). Modern Electrics published
the first callbook in the United States in 1909.
Today, the primary purpose of a callbook is to allow amateur radio
operators to send a confirmation post card, called a
QSL card to an
operator who they have communicated via radio. Callbooks have evolved
to include on-line databases that are accessible via the
instantly obtain the address of another amateur radio operator and
their QSL Managers. The most well known and used on-line QSL databases
include QRZ.COM, IK3QAR, HamCall, F6CYV, DXInfo,
OZ7C and QSLInfo.
NATO phonetic alphabet
^ "CALL SIGNS/LETTERS - The Museum of Broadcast Communications".
Museum.tv. Retrieved 2016-03-05.
^ "Radio Call Letters". U.S. Department of Commerece, Bureau of
Navigation. 1913-05-09. Retrieved 2012-12-22.
^ GB90MGY Archived 2008-09-08 at the Wayback Machine., Titanic
Wireless Commemorative Group, Godalming, Surrey
^ "FCC: Wireless Services: Ship Radio Stations: Licensing".
^ Gernsback, H (May 1909). First Annual Official Wireless Blue Book of
the Wireless Association of America (PDF). New York: Modern Electrics
Publication. Retrieved 2010-11-24.
^ "QRZ.COM". Retrieved 2010-11-24.
^ "Qsl Manager - Qsl Info on-line". Retrieved 2010-11-24.
^ "World Wide HamCall Callsign Server". Retrieved 2010-11-24.
^ "QSL INFORMATION by F6CYV". Retrieved 2010-11-24.
^ "DXInfo, your DX web resource". Archived from the original on
2010-11-11. Retrieved 2010-11-24.
^ "QSL Search machine by OZ7C". Retrieved 2010-11-24.
^ "QSLInfo". Retrieved 2010-11-24.
United States Federal
Aviation Administration, Aeronautical
Information Manual, Official Guide to Basic Flight Information and ATC
Procedures, 2004. Chapter 4, Section 2
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