In an FM-phone signal, what is the term for the maximum deviation divided by the maximum audio modulating frequency?

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Multiple Choice

In an FM-phone signal, what is the term for the maximum deviation divided by the maximum audio modulating frequency?

The concept here is that the amount of FM modulation can be described by a ratio of how far the carrier deviates at most to the highest frequency present in the modulating signal. This ratio uses the maximum frequency deviation (the largest frequency swing the carrier experiences) divided by the maximum audio modulating frequency (the highest frequency in the audio that modulates the carrier). That single number is called the deviation ratio, and it helps indicate how wide the signal’s spectrum will be, since greater deviation relative to the highest modulating frequency means more bandwidth is needed. For example, if the peak deviation is 75 kHz and the highest modulating frequency is 15 kHz, the deviation ratio is 75 kHz divided by 15 kHz, which equals 5. The other terms aren’t the standard name for this specific ratio: deviation index isn’t a common term in this context, modulation index is typically defined as Δf/ fm for a particular modulation frequency (and not necessarily the maximum), and modulation ratio isn’t used here. So the best term for this definition is deviation ratio.

The concept here is that the amount of FM modulation can be described by a ratio of how far the carrier deviates at most to the highest frequency present in the modulating signal. This ratio uses the maximum frequency deviation (the largest frequency swing the carrier experiences) divided by the maximum audio modulating frequency (the highest frequency in the audio that modulates the carrier). That single number is called the deviation ratio, and it helps indicate how wide the signal’s spectrum will be, since greater deviation relative to the highest modulating frequency means more bandwidth is needed. For example, if the peak deviation is 75 kHz and the highest modulating frequency is 15 kHz, the deviation ratio is 75 kHz divided by 15 kHz, which equals 5. The other terms aren’t the standard name for this specific ratio: deviation index isn’t a common term in this context, modulation index is typically defined as Δf/ fm for a particular modulation frequency (and not necessarily the maximum), and modulation ratio isn’t used here. So the best term for this definition is deviation ratio.

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