What does the acronym QRM refer to in radio terminology?

The acronym QRM refers to man-made interference in radio communication. This type of interference is typically caused by unwanted signals from various sources, such as electronic devices, industrial equipment, or other radio transmitters. Understanding QRM is essential for radio operators because it highlights the challenges they may face in maintaining clear communications, especially in congested radio environments.

In contrast, natural interference, represented by other options, might refer to atmospheric phenomena or other natural occurrences that affect signal integrity. Signal distortion and receiver modulation, while related to the characteristics of radio signals and their processing, do not accurately encapsulate the concept of interference caused specifically by human activity. The comprehension of QRM enables operators to implement strategies for noise reduction, frequency selection, and effective communication despite the presence of such interference.