Q code

The Q code is a standardized collection of three-letter codes all of which start with the letter "Q". It is a brevity code initially developed for commercial radiotelegraph communication and later adopted by other radio services, especially amateur radio. To distinguish the use of "Q" codes transmitted as questions from those transmitted as statements, operators used the Morse question mark code (di di dah dah di dit) as a prefix to the "Q" code.

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; no country is ever issued an ITU prefix starting with "Q".

Codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QQZ for maritime use and QRA–QUZ for all services.

"Q" has no official meaning, but it is sometimes assigned with a word with mnemonic value, such as "Queen's" (e.g. QFE = Queen's Field Elevation), "Query", "Question", or "reQuest".

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

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 banned in the United States, rendering 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.

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