Q code

"QRO" redirects here. For the airport in Mexico, see Querétaro International Airport.

For the 2-dimensional barcode standard, see QR Code.

The Q code is a standardized collection of three-letter message encodings, also known as a brevity code, all of which start with the letter "Q", initially developed for commercial radiotelegraph communication, and later adopted by other radio services, especially amateur radio. 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; while an embedded three-letter Q sequence may occur (for instance when requested by an amateur radio station dedicated to low-power operation), no country is ever issued an ITU prefix starting with "Q". The codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QQZ for maritime use and QRA–QUZ for all services.

Early developments

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 Third 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) where 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 are very strong.

Later usage

Over the years, modifications were made to the original Q codes to reflect changes in radio practice. In the original international list, QSW/QSX stood for "Shall I increase/decrease my spark frequency?", however, spark-gap transmitters were banned in the United States in the 1920s, rendering the original meaning of those Q codes obsolete. Over a hundred Q codes were listed in the Post Office Handbook for Radio Operators in the 1970s and cover subjects such as meteorology, radio direction finding, radio procedures, search and rescue, and so on.

Some Q codes are also used in aviation, in particular 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 Organisation. 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 Telecommunications Union. And 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 organizations 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 or not 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". This structured use of Q codes is fairly rare and now mainly limited to amateur radio and military morse code (CW) traffic networks.

Breakdown by service

• QAA to QNZ - Assigned by the International Civil Aviation Organization (ICAO).
• QOA to QQZ - For the Maritime Services.
• QRA to QUZ - Assigned by the International Telecommunications Union (ITU).

Amateur radio

Selected Q codes were soon adopted by amateur radio operators. In December, 1915, the American Radio Relay League began publication of a magazine titled QST, named after the Q code for "General call to all stations". In amateur radio, the Q codes were originally used in Morse code transmissions to shorten lengthy phrases and were followed by a Morse code question mark (··--··) if the phrase was a question.

Q codes are commonly used in voice communications as shorthand nouns, verbs, and adjectives making up phrases. For example, an amateur radio operator will complain about QRM (man-made interference), or tell another operator that there is "QSB on the signal"; "to QSY" is to change your operating frequency.

Aviation

Although the majority of the Q codes have slipped out of common use, several remain part of the standard ICAO radiotelephony phraseology in aviation.

Altimeter Settings

Code	Meaning	Sample use
QFE	Atmospheric pressure at sea level, corrected for temperature and adjusted to a specified datum such as airfield elevation, when set on the altimeter it reads height	Runway in use 22 Left, QFE 990 millibars
QFF	Barometric pressure at a place, reduced to MSL using the actual temperature at the time of observation as the mean temperature
QNE	Atmospheric pressure at sea level in the International Standard Atmosphere (ISA), equal to 1013.25 mbar or hPa and used as reference for measuring the pressure altitude
QNH	Atmospheric pressure at mean sea level (may be either a local, measured pressure or a regional forecast pressure (RPS)). When set the altimeter reads altitude	Request Leeds QNH

Radio Navigation

Code	Meaning	Sample use
QDM	Magnetic heading to a station	(callsign) request QDM (callsign)
QDR	Magnetic bearing from a station	(callsign) request QDR (callsign)
QFU	Magnetic bearing of the runway in use	Runway 22 in use, QFU 220
QTE	True bearing from a station	True bearing, True bearing, (callsign) request QTE (callsign)
QUJ	True bearing to a station

Radio Procedures

Code	Meaning	Sample use
QGH	controller-interpreted DF let-down procedure, on UHF or VHF

Maritime

Q signals are no longer used in the maritime service, as Morse code is now very rarely used.

Royal Air Force: QGH signified "Controlled Descent through Clouds"

See also

• ACP-131
• Ten-code
• Prosigns for Morse code
• International Code of Signals
• International maritime signal flags

External links

• Handbook for Wireless Telegraph Operators, October, 1909.
• Radio Laws and Regulations of the United States: Edition July 27, 1914. (Includes the 1912 London Radiotelegraphic Convention)
• List of Q codes
• A resource for Morse Code operation in the amateur radio hobby