What is the deviation ratio of an FM-phone signal with a maximum frequency swing of ±7.5 kHz and a maximum modulation rate of 3.5 kHz?

To determine the deviation ratio of an FM-phone signal, you can use the formula that relates the maximum frequency deviation to the maximum modulation frequency. The deviation ratio is calculated by dividing the maximum frequency deviation by the maximum modulation frequency.

In this case, the maximum frequency swing is given as ±7.5 kHz, which means the total maximum deviation is 7.5 kHz. To find the deviation ratio, first, note that the maximum modulation rate is 3.5 kHz.

Using the formula:

Deviation Ratio = Maximum Frequency Deviation / Maximum Modulation Frequency

Substituting the values:

Deviation Ratio = 7.5 kHz / 3.5 kHz = 2.142857...

When rounded to two decimal places, this value becomes approximately 2.14.

Therefore, the correct answer for the deviation ratio of this FM-phone signal is indeed 2.14, which aligns with the provided answer choice. This highlights the relationship between the extent to which the carrier frequency is varied and the rate at which it is being modulated, critical in assessing the efficiency and fidelity of FM transmissions.