What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz if the highest modulation frequency is 3.5 kHz?

To find the deviation ratio of an FM signal, divide the maximum frequency swing (deviation) by the highest modulation frequency. This mathematical relationship is fundamental in understanding frequency modulation and estimating bandwidth requirements. Here, the maximum frequency swing is 7.5 kHz and the highest modulation frequency is 3.5 kHz. Dividing 7.5 by 3.5 gives approximately 2.1428, which rounds to 2.14. If you accidentally divide the modulation frequency by the deviation (3.5 / 7.5), you will get 0.47, which is an incorrect distractor. Always make sure the frequency swing is the numerator in your calculation.