Original: E.g., a device that has a bandwidth of 2 MHz with center frequency 10 MHz will have a fractional bandwidth of 2/10, or 20%.
Simplified: It therefore has a bandwidth of 10,000 Hz (545,000 - 535,000). The lowest United States FM radio channel (on the other hand) covers the band from 88,000,000 Hz (88 MHz) to 88,200,000 Hz (88.2 MHz).