What does the term "QSO" mean in amateur radio?

The term "QSO" in amateur radio refers to a conversation between two or more amateur radio operators. This term comes from the Q-code, which is a standard set of three-letter brevity codes used in radio communication to convey information succinctly. When operators engage in a QSO, they exchange information, which may include call signs, signal reports, names, and locations, as well as general conversation about various topics related to radio and beyond. This exchange can happen in various modes, including voice, Morse code, or digital communication.

The other options do not align with the established meaning of "QSO." While radio equipment setups and maintenance operations are relevant to amateur radio, they do not correspond to the concept of a communication or dialogue between operators. Similarly, while competitions exist within amateur radio, they are not categorized as a QSO. Thus, understanding "QSO" as a conversation is integral to the operation and social aspects of amateur radio.