Which Q signal indicates that you are receiving interference from other stations?

The Q signal that indicates you are receiving interference from other stations is QRM. In amateur radio terminology, QRM is specifically used to denote man-made interference, such as from other operators, electrical devices, or radio frequency interference (RFI), which can disrupt communication on the airwaves.

Understanding the context of the other Q signals may further clarify why QRM is the correct choice. QRN refers to atmospheric noise, which is related to natural phenomena (like thunderstorms) that cause interference but does not pertain to interference from other stations. QTH signifies your location, having no connection to interference issues. QSB represents fading in the received signal strength, which can occur for reasons separate from interference, such as changes in propagation conditions. Thus, QRM is distinctly linked to interference from other stations, making it the correct response to indicate such a condition.