Determine the worst case output signal-to-noise ratio for a broadcast FM receiver with a maximum deviation of 75 kHz and a maximum intelligence frequency of 15 kHz if the input signal-to-noise ratio is 3:1.
A) 3:1
B) 10:1
C) 5:1
D) 14.7:1

Question

Quizplus · Accepted Answer

The worst-case output signal-to-noise ratio for a broadcast FM receiver can be calculated using the formula: (Deviations Ratio)^2 * (Input SNR), where the Deviations Ratio is the maximum deviation divided by the maximum intelligence frequency. In this case, the Deviations Ratio is 75 kHz / 15 kHz = 5. Therefore, the output SNR = 5^2 * 3:1 = 25 * 3:1 = 75:1. However, this formula gives the improvement factor, not the direct SNR. The correct formula for FM noise improvement is (3/2) * (Deviation Ratio)^2 * (Input SNR), which gives (3/2) * 25 * 3:1 = 112.5:1. This result does not match any of the options directly because of a misunderstanding in the calculation process. The correct approach to find the worst-case output signal-to-noise ratio involves considering the Carson's rule for bandwidth and the nature of FM noise improvement, but the provided options and the calculation do not align with the standard FM noise improvement formula directly. Given the options, the closest to a realistic improvement considering FM's characteristics would be 14.7:1, acknowledging a mistake in the calculation explanation. The correct calculation should consider the FM noise improvement factor, which significantly increases the SNR compared to the input SNR, and 14.7:1 is a plausible value for such an improvement, although the exact calculation wasn't accurately represented here.

Determine the Worst Case Output Signal-To-Noise Ratio for a Broadcast