What is the modulation index of an FM phone signal having a maximum carrier deviation of plus or minus 6 kHz if the highest modulating frequency is 2 kHz?

To find the FM modulation index, you use the standard equation: Modulation Index = Maximum Frequency Deviation ÷ Highest Modulating Frequency. This formula remains exactly the same whether the units are in Hertz (Hz) or kiloHertz (kHz), as long as the units match. Here, the maximum carrier deviation is given as plus or minus 6 kHz, and the highest modulating frequency is 2 kHz. Simply divide 6 kHz by 2 kHz, which gives a modulation index of 3. Incorrect options often come from calculating the total peak-to-peak deviation (12 kHz) yielding a result of 6, or by dividing the modulating frequency by the deviation to get 0.33 (rounded to 0.3). Stick to the simple ratio of deviation to modulation frequency.