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Q-code
Standardised short message codes

The Q-code is an international standardised system of 3-letter mnemonics, each starting with the letter 'Q', developed around 1909 by the British Government as a List of abbreviations for use aboard British ships and by coast stations licenced by the Postmaster General. It improved and facilitated communication between maritime radio operators speaking different languages [1].

Although initially developed for commercial radio telegraphy, the codes were soon adopted internationally by other radio services, including the armed forces. The use of the Q-codes serves two purposes: (1) is allows people with different languages or backgrounds to communicate, and (2) it generally reduces the length of a message.

In commercial radio telegraphy, messages were usually charged per letter or word. As a Q-code replaces a complete sentence, it made the mes­sage much cheaper. The image on the right [A] shows the Combined Operating Signals of 1944.
  

This book contains additional Q-codes and was introduced during WWII for joint use by American and British armed forces. The same codes were used by the Germans. In clandestine telegraphy, short messages reduce the risk of detection by means of Radio Direction Finding (RDF). Although the Q-codes were primarily deve­loped for messages in morse code, they were later also used with teleprinter traffic and voice communication. Amateur radio operators still use Q-codes today [1].

 Read the Combined Operating Signals

  1. IMI is the combination of the morse code letters I (··) M (--) and I (··) without a pause between the letters.
  2. INT is the combination of the morse code letters I (··) N (·-) and T (-) without a pause between the letters.

Vombined Operating Signals (Q-codes) 1944
First page of the Combined Operating Signals
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Vombined Operating Signals (Q-codes) 1944
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First page of the Combined Operating Signals

Ranges
  • QAA-QNZ
    Aeronautical use
  • QOA-QQZ
    Maritime use
  • ARA-QUZ
    All services
Examples
Below are a few examples of Q-codes that are still commonly used in radio communication, in particular by amateur radio operators (HAMs). For a more complete list, check out [A] or visit Wikipedia. The (popular) meaning of some Q-codes has changed over time.

Code Question Answer or statement Popular/amateur
QRL Are you busy? I am busy Work address
QRM Are you being interfered with? I am being interfered with  
QRN Static interference? Static interference  
QRP Shall I decrease transmitter power Decrease transmitter power Low power
QRT Shall I stop sending? Stop sending  
QRV Are you ready? I am ready  
QRX When will you call me again? I will call you at ... Back in a second
QRZ Who is calling me? Tou are being called by ...  
QSL Can you acknowlege receipt? I can acknowledge receipt QSL card
QSO Can you communicate with ...? I can communicated with ... Chat
QSY Change frequency? Change frequency to ...  
QTH What is your location? My location is ... Home address
Documentation
  1. Combined Operating Signals (Second Edition)
    Short title CCBP 2-2. Combined Communications Board.
    Washington DC (USA), 1944.
References
  1. Wikipedia, Q code
    Visited 28 January 2024.
Further information
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Crypto Museum. Created: Sunday 28 January 2024. Last changed: Tuesday, 30 January 2024 - 11:45 CET.
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