Originally maritime telegraph shorthand, Q-codes are now used on CW, on digital modes and — often awkwardly — on voice. As a question they end with a query; as a statement they answer it.
| Code | Question | Statement |
|---|---|---|
| QRL | Is this frequency in use? | This frequency is in use |
| QRM | Are you troubled by interference? | I am troubled by interference (man-made) |
| QRN | Are you troubled by static? | I am troubled by static (natural noise) |
| QRO | Shall I increase power? | Increase power |
| QRP | Shall I decrease power? | Decrease power / low power operation |
| QRS | Shall I send more slowly? | Send more slowly |
| QRT | Shall I stop sending? | I am closing down |
| QRU | Have you anything for me? | I have nothing for you |
| QRV | Are you ready? | I am ready |
| QRX | When will you call again? | Stand by |
| QRZ | Who is calling me? | You are being called by … |
| QSB | Is my signal fading? | Your signal is fading |
| QSL | Can you acknowledge receipt? | I acknowledge receipt |
| QSO | Can you communicate with …? | I can communicate with … |
| QSY | Shall I change frequency? | Change frequency to … |
| QTH | What is your location? | My location is … |
| QTR | What is the exact time? | The time is … |
Usage note
On CW they save real time. On voice, plain English is usually clearer — "your signal is fading" is no longer than "QSB" once you have said both. QRZ?, QSL and QTH are the ones that genuinely persist on phone.