What is the modulation index of a system with modulating frequency 75kHz and maximum frequency deviation 15kHz?

Aeronautical & Aerospace Engineering : Avionics - Quiz(MCQ)

Correct Answer : 5

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Which of the following is true with respect to the bandwidth of a 2kHz audio signal and a 2kHz binary data?

Bandwidth is higher for binary data than audio signals

Bandwidth is higher for audio signals than binary data

Bandwidth remains the same for both

Bandwidth keeps increasing with time for the binary data

Correct Answer : Option (A) : Bandwidth is higher for binary data than audio signals

Explanation : Since binary data is transmitted in square waves or pulses, they are generally made up of numerous fundamental sine waves. This occupies a huge bandwidth as compared to audio signals which are analog in nature and usually comprise of a lesser number of sine waves.

What is the signal to noise ratio if the maximum allowable frequency deviation is 4kHz and the frequency deviation by noise is 156.42Hz?

0.0364

0.0391

20.45

25.75

Correct Answer : Option (D) : 25.75

Explaination : N/S = Frequency deviation by noise / maximum deviation = 156.42/4000 =0.0391
S/N = (N/S)^-1=25.57.

Calculate the phase difference by noise if the Signal to noise ratio is 7:2.

8.21°

13.65°

15.366°

17.5°

Correct Answer : Option (C) : 15.366°

Explanation : ?=sin^-1(N/S)=sin^-1(2/7)=sin^-1(0.265)=15.366°.