The first time I heard of Q codes was when reading the novel Seveneves by Neal Stephenson. These are three-letter abbreviations using in Morse code that all begin with Q.
Since Q is always followed by U in native English words, Q can be used to begin a sort of escape sequence .
There are dozens of Q codes used in amateur radio , and more used in other contexts, but there are only 10 Q codes used in Seveneves . All begin with Q, followed by R, S, or T.
Each Q code can be used both as a question and as an answer or statement. For example, QRS can mean “Would you like me to slow down” or “Please slow down.” I’ll just give the interrogative forms below.
Here are the 10 codes that appear in Stephenson’s novel.
- What is your call sign?
- Is my signal intelligible?
- Is static a problem?
- Should I slow down?
- Should I stop sending?
- Is my signal fading?
- Are you still there?
- Could you communicate with …?
- Where are you?
- Will you keep your station open for talking with me?
 Some Q codes have a U as the second letter. I don’t know why—there are plenty of unused TLAs that begin with Q—but it is what it is.
 You can find a list here.
 There is one non-standard code in the novel: QET for “not on planet Earth.”