The Q-code is a standardised collection of three-letter codes that each start with the letter "Q". It is an operating signal initially developed for commercial radiotelegraph communication (used e. g. by the Maritime Mobile Service or Amateur Radio Service), later also for TeleTYpe (TTY. e. g. for AFTN, the Aeronautical Fixed Telecommunications Network) and RadioTeleTYpe (RTTY e.g. used by the Maritime Mobile Service or Amateur Radio Service) and in voice communications (e.g. Aeronautical mobile service). Most Q-codes defined in 1947 are still in use today, date back to the International Telecommunication Convention in Atlantic City, 1947 and are standardized in the ITU International Radio Regulations from 1947 (ITU-RR).
Early development The original Q-codes were created, circa 1909, by the British government as a "List of abbreviations ... prepared for the use of British ships and coast stations licensed by the Postmaster General". The Q-codes facilitated communication between maritime radio operators speaking different languages, so they were soon adopted internationally. A total of forty-five Q-codes appeared in the "List of Abbreviations to be used in Radio Communications", which was included in the Service Regulations affixed to the Second International Radiotelegraph Convention in London (The convention was signed on July 5, 1912, and became effective July 1, 1913.)
The following table reviews a sample of the all-services Q-codes adopted by the 1912 convention: + First twelve Q-codes listed in the 1912 International Radiotelegraph Convention Regulations Code Question Answer or notice QRA What ship or coast station is that? This is ____. QRB What is your distance? My distance is ____. QRC What is your true bearing? My true bearing is ____ degrees. QRD Where are you bound for? I am bound for ____. QRF Where are you bound from? I am bound from ____. QRG What line do you belong to? I belong to the ____ Line. QRH What is your wavelength in meters? My wavelength is ____ meters. QRJ How many words have you to send? I have ____ words to send. QRK How do you receive me? I am receiving (1–5).(1) is unreadable and (5) is perfect. QRL Are you busy? I am busy. QRM Are you being interfered with? I am being interfered with. QRN Are the atmospherics strong? Atmospherics (noise) are very strong.
Later use Over the years the original Q-codes were modified to reflect changes in radio practice. For example, QSW / QSX originally stood for, "Shall I increase / decrease my spark frequency?", but in the 1920s spark-gap transmitters were gradually being banned from land stations, making that meaning obsolete. By the 1970s, the Post Office Handbook for Radio Operators listed over a hundred Q-codes, covering a wide range of subjects including radio procedures, meteorology, radio direction finding, and search and rescue.
Some Q-codes are also used in aviation, in particular QNE, QNH and QFE, referring to certain altimeter settings. These codes are used in radiotelephone conversations with air traffic control as unambiguous shorthand, where safety and efficiency are of vital importance. A subset of Q-codes is used by the Miami-Dade County, Florida local government for law enforcement and fire rescue communications, one of the few instances where Q-codes are used in ground voice communication.
The QAA–QNZ code range includes phrases applicable primarily to the aeronautical service, as defined by the International Civil Aviation Organization. The QOA–QQZ code range is reserved for the maritime service. The QRA–QUZ code range includes phrases applicable to all services and is allocated to the International Telecommunication Union. QVA–QZZ are not allocated. Many codes have no immediate applicability outside one individual service, such as maritime operation (many QO or QU series codes) or radioteletype operation (the QJ series).
Many military and other organisations that use Morse code have adopted additional codes, including the Z code used by most European and NATO countries. The Z code adds commands and questions adapted for military radio transmissions, for example, "ZBW 2", which means "change to backup frequency number 2", and "ZNB abc", which means "my checksum is abc, what is yours?"
Used in their formal question / answer sense, the meaning of a Q-code varies depending on whether the individual Q-code is sent as a question or an answer. For example, the message "QRP?" means "Shall I decrease transmitter power?", and a reply of "QRP" means "Yes, decrease your transmitter power", whereas an unprompted statement "QRP" means "Please decrease your transmitter power". This structured use of Q-codes is fairly rare and now mainly limited to amateur radio and military Morse code (CW) traffic networks.
Under U.S. F.C.C. Regulations, CFR 47 97.113(a)(4), amateurs are not permitted to 'transmit codes or ciphers' (historical description), allowing only that 'plain-language communications' may be transmitted. The term 'Q-Signal' has been historically used in that context, not 'Q-Code,' - the use of 'Code' is technically a violation of F.C.C. Regulations. This essentially demonstrates the historic separation between Amateur and Commercial/Military radio services in the U.S.
Use since the International Telecommunication Convention in Atlantic City, 1947 The Q-code was first specified in ITU International Radio Regulations from 1947, Appendix 9, Section 1 which defines:
While some ranges of the Q-codes are for the use of all services, some bands of Q-codes were assigned specifically for the Aeronautical Mobile and the Maritime Mobile Service, which are:
"1. The series of groups QRA to QUZ listed in this Appendix, is for use by all services."
"2. The QAA to QNZ series are reserved for the aeronautical service and the QOA to QQZ series are reserved for the maritime services. These series are not listed in these regulations."
ICAO (International Civil Aviation Organization) specified the Q-codes for aeronautical purposes initially in COM/504/1 - Doc 6100. Amendment "Communication Codes and Abbreviations. Q Code" published 1952.April.01 While not all Q-codes published in 1952 in Doc-6100 are still in use today, the Q-codes used today are documented in ICAO DOC-8400, "ICAO Abbreviations and Codes"
The Q-codes for the Maritime Mobile Service used today are documented in ITU Recommendation ITU-R M.1172, "Miscellaneous Abbreviations and Signals to be used for Radiocommunications in the Maritime Mobile Service", 1995.
"5. Abbreviations are given the form of a question when followed by a question mark. When an abbreviation is used as a question and is followed by additional or complementary information, the question mark should follow this information."
"3. Certain abbreviations may be given an affirmative or negative sense by sending “C” or “N” respectively, immediately following the “Q” code abbreviation." To distinguish the use of a Q-code transmitted in radiotelegraphy communication as a question from the same Q-code transmitted as a statement, operators either prefixed it with the military network question marker "" () or suffixed it with the standard Morse question mark ().
"4. The meanings assigned to “Q” code abbreviations may be amplified or completed by the addition of appropriate other groups, call signs, place names, figures, numbers, etc. It is optional to fill in the blanks shown in parentheses. Any data which is filled in where blanks appear should be sent in the same order as shown in the significations." For the Aeronautic Radio Service QNH 1015 identifies "QNH‡ "Altimeter Sub-Scale Setting to obtain Elevation when on the Ground" 1015 hPa.
"‡ "When radiotelephony is used, the abbreviations and terms are transmitted using the individual letters in non-phonetic form".
"7. All time should be given in Greenwich mean time (G.M.T.) unless otherwise indicated in the question or reply." GMT was replaced in 1972 by UTC (Universal Coordinated Time).
Although Q-codes were created when radio used Morse code exclusively, they continued to be employed after the introduction of voice transmissions. To avoid confusion, transmitter call signs are restricted; countries can be issued unused Q-Codes as their ITU prefix e.g. Qatar is QAT.
"Q" has no official meaning, but it is sometimes assigned a word with mnemonic value, such as "question" or "query", for example in QFE: "query field elevation".
Listing according to service QAA to QNZ – Assigned by the International Civil Aviation Organization (ICAO). QNA to QNZ – The American Radio Relay League (ARRL) has also developed its own QN Signals for message handling located in this range. Even though they overlap with other signals, the ARRL determined that their exclusive use in NTS nets limits confusion. QOA to QQZ – For the Maritime Mobile Service. QRA to QUZ – Assigned by the International Telecommunication Union Radiocommunication Sector (ITU-R).
Aeronautical Code signals (QAA–QNZ; ICAO)
First defined in ICAO publication "Doc 6100-COM/504/1" and in "ICAO Procedures for Air Navigation Services, Abbreviations and Codes (PANS-ABC)" [Doc8400-4] (4th edition 1989), the majority of the Q-codes have fallen out of common use; for example today reports such as QAU ("I am about to jettison fuel") and QAZ ("I am flying in a storm") would be voice or computerised transmissions. But several remain part of the standard ICAO radiotelephony phraseology in aviation. These are also part of ACP131, which lists all ITU-R Q-codes, without grouping them by aeronautical/marine/general use. The currently applicable version of ICAO Doc-8400 has the title "Procedures for Air Navigation Services, ICAO Abbreviations"
and Codes, edition 8, 2010.November.18 Question?Answer or adviceQAB May I have clearance (for ____) from ____ (place) to ____ (place) at flight level/altitude ____ ?You are cleared (or ____ is cleared) by ____ from ____ (place) to ____ (place) at flight level/altitude ____.QAF Will you advise me when you are (were) at (over) ____ (place)? I am (was) at (over) ____ (place) (at ____ hours) at flight level / altitude ____.QAG Arrange your flight in order to arrive over ____ (place) at ____ hours. or I am arranging my flight in order to arrive over ____ (place) at ____ hours. QAH What is your height above ____ (datum)? I am at ____ flight level / altitude ____. or Arrange your flight so as to reach flight level / altitude ____ at ____ (hours or place). QAI What is the essential traffic respecting my aircraft? The essential traffic respecting your aircraft is ____. QAK Is there any risk of collision? There is risk of collision. QAL Are you going to land at ____ (place)? or Has aircraft ____ landed at ____ (place)? I am going to land at ____ (place). or (You may) land at ____ (place). or Aircraft ____ landed at ____ (place). QAM What is the latest available meteorological observation for ____ (place)? Meteorological observation made at ____ (place) at ____ hours was as follows ____. QAN What is the surface wind direction and speed at ____ (place)? The surface wind direction and speed at ____ (place) at ____ hours is ____ (direction) ____ (speed). QAO What is the wind direction in degrees TRUE and speed at ____ (position or zone/s) at each of the ____ (figures) ____ (units) levels above ____ (datum)? The wind direction and speed at (position or zone/s) at flight level/altitude ____ is: ____ (vertical distance) ____ degrees TRUE ____ (speed). QAP Shall I listen for you (or for ____) on ____ kHz (____ MHz)? Listen for me (or for ____) on ____ kHz (____ MHz). QAQ Am I near a prohibited, restricted, or danger area? or Am I near area ____ (identification of area)? You are ____ (number) area ____ (identification of area). 1. near 2. flying withinQAR May I stop listening on the watch frequency for ____ minutes? You may stop listening on the watch frequency for ____ minutes. QAU Where may I jettison fuel? I am about to jettison fuel.