The Q Code is a standardized collection of three-letter message encodings, all starting 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 have often been limited to restrict ones starting with "Q" or having an embedded three-letter Q sequence. The codes in the range QAA-QNZ are reserved for aeronautical use; QOA-QOZ for maritime use, and QRA-QUZ for all services.

"Q" Signal	Question ?	Answer, Advise, or Order
QLF		Unofficial for "Your CW sounds like you're sending with your left foot."
QRG	Will you tell me my exact frequency (or that of ...)?	Your exact frequency (or that of ... ) is ... khz (or Mhz).
QRH	Does my frequency vary?	Your frequency varies.
QRI	How is the tone of my transmission?	The tone of your transmission is (1. Good; 2. Variable; 3. Bad).
QRK	What is the readability of my signals (or those of ...)?	The readability of your signals (or those of ...) is ... (1 to 5).
QRL	Are you busy?	I am busy. (or I am busy with ... ) Please do not interfere.
QRM	Are you being interfered with?	I am being interfered with.
QRN	Are you troubled by static?	I am troubled by static.
QRO	Shall I increase power?	Increase power
QRP	Shall I decrease power?	Decrease power
QRQ	Shall I send faster?	Send faster (... wpm)
QRS	Shall I send more slowly?	Send more slowly (... wpm)
QRT	Shall I stop sending?	Stop sending
QRU	Have you anything for me?	I have nothing for you
QRV	Are you ready?	I am ready.
QRW	Shall I inform ... that you are calling him on ... khz (or Mhz)?	Please inform ... that I am calling him on ... khz
QRX	When will you call me again?	I will call you again at (time) , or "please stand-by"
QRZ	Who is calling me?	You are being called by ... on ... khz (or Mhz)
QSA	What is the strength of my signals (or those of ... )?	The strength of your signals (or those of ...) is ... (1 to 5).
QSB	Are my signals fading?	Your signals are fading.
QSD	Is my keying defective?	Your keying is defective.
QSG	Shall I send ... telegrams (messages) at a time?	Send ... telegrams (messages) at a time
QSK	Can you hear me between your signals?	I can hear you between my signals.
QSL	Can you acknowledge receipt?	I am acknowledging receipt.
QSN	Did you hear me (or ... (call sign)) on .. khz (or Mhz)?	I did hear you (or ... (call sign)) on ... khz (or Mhz).
QSO	Can you communicate with ... direct or by relay?	I can communicate with ... direct
QST		Attention all Amateur Radio Operators for this message...
QSU	Shall I send or reply on this frequency	Send or reply on this frequency
QSV	Shall I send a series of V's on this frequency (or ... khz (or Mhz))?	Send a series of V's on this frequency (or ... khz (or Mhz))
QSX	Will you listen to ... (call sign(s) on ... khz (or Mhz))?	I am listening to ... (call sign(s) on ... khz (or Mhz))
QSY	Shall I change to transmission on another frequency?	Change to transmission on another frequency (or on ... khz (or Mhz)).
QSZ	Shall I send each word or group more than once?	Send each word or group twice (or ... times).
QTA	Shall I cancel telegram (message) No. ... as if it had not been sent?	Cancel telegram (message) No. ... as if it had not been sent.
QTB	Do you agree with my counting of words?	I do not agree with your counting of words; I will repeat the first letter or digit of each word or group.
QTC	How many telegrams (messages) have you to send?	I have ... telegrams (messages) for you (or for ...).
QTH	What is your position in latitude and longitude (or according to any other indication)?	My position is ... latitude...longitude
QTR	What is the correct time?	The correct time is ... hours