Q 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".^{[citation needed]} 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:

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 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.^[2]

The QAA–QNZ code range includes phrases applicable primarily to the aeronautical service,^[3] as defined by the International Civil Aviation Organisation.^[4] 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.^[5] QVA–QZZ are not allocated.^[6] 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).^[7]

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?"^[8]

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" (fading); "to QSY" is to change your operating frequency. (See also Informal usage, below.)

Q codes applicable for use in amateur radio

Informal usage

Chart of the Morse code letters and numerals.^[1]

Some of the common usages of amateur radio codes, including in voice and writing, vary somewhat from their formal, official sense. Humorous and unofficial codes may be also be used.

QRL? is the accepted form of the question, "Is this frequency in use (or busy)?", the reply to which is typically the letters^[1] "C" (dah di dah dit), "R" (di dah dit) or "Y" (dah di dah dah) which, in the Amateur radio tradition, are the Morse code shorthand for "Confirm", "Roger" or "Yes."

QSK - "I can hear you during my transmission" - refers to a particular mode of Morse code operating in which the receiver is quickly enabled during the spaces between the dits and dahs, which allows another operator to interrupt transmissions. Many modern transceivers incorporate this function, sometimes referred to as full break-in as against semi-break-in in which there is a short delay before the transceiver goes to receive.

QSO - A conversation or contact via amateur radio is often referred to as a QSO, while QSL cards are collected by both radioamateurs and shortwave listeners as confirmation of having received the signal of a particular station.

QSY - "Change to transmission on another frequency"; colloquially, "move [=change address]". E.g., "When did GKB QSY from Northolt to Portishead....?"^[9]

QTH - "My location is…"; colloquially in voice or writing, "location". E.g., "The OCF [antenna] is an interesting build but at my QTH a disappointing performer."^[10]

QTHR - "at the registered address for my callsign", this is used mainly in the United Kingdom and former colonies. Since business may not be discussed on amateur radio, a ham who has personal equipment to sell might say something like "I have a spare Morse key old chap, please contact me QTHR". Not official but in common use;^[11] probably derived from "QTH" + "R" for "registered".

Aviation

The majority of the Q codes have slipped 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 computerized transmissions. But several remain part of the standard ICAO radiotelephony phraseology in aviation.

Maritime

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

See also

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

References

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