What is the meaning of term frequency swing in reference to a FM broadcast station?

In the context of FM broadcast stations, term frequency swing refers to the deviation of the carrier frequency from its assigned center frequency.

It occurs when the frequency of a broadcast signal fluctuates around its nominal value, causing the audio quality to deteriorate.

To ensure high-fidelity transmission and reception, the term frequency swing of FM stations must be kept within strict limits set by regulatory bodies, typically around ±75 kHz for mono and ±125 kHz for stereo broadcasts.