What is the "Q" signal used to indicate that you are changing frequency?

The "Q" signal that indicates you are changing frequency is QSY. In amateur radio communication, Q signals are a standardized set of brevity codes used to convey specific information. Each Q signal has a designated meaning recognized universally among operators.

In this case, QSY is specifically used to inform others on the frequency that you are moving to another frequency. This is important in maintaining clear communication and preventing interruptions or confusion among operators who may be utilizing the same frequency.

While there are other Q signals with different meanings—such as QRU for indicating a message has been received and QSL for acknowledging receipt of a message—none of these pertain to changing frequencies. This makes QSY the correct choice for communicating your intention to move to a different frequency.