# Noise Suppression Effects of FM MCQ’s

This set of Avionics Multiple Choice Questions & Answers (MCQs) focuses on “Noise Suppression Effects of FM”.

1. Which circuit in FM receivers cancels or filters out noise?
a) Filter circuits
b) Anti-noise circuits
c) Limiter circuits
d) delimiter circuits

2. Noise introduces a frequency variation into the signal.
a) True
b) False

3. Which of the following is not a source of noise in FM?
a) Weather
b) Electronic circuits
c) Lightning
d) Velocity of motion

4. What is the frequency deviation produced by noise if the signal to noise ratio is 3:1 and modulating frequency is 800Hz?
a) 152.32Hz
b) 482.5Hz
c) 132.8Hz
d) 271.Hz

5. What is the frequency deviation produced by noise if the modulating frequency is 400Hz and the phase difference introduced by noise is 0.43rad?
a) 124Hz
b) 163Hz
c) 172Hz
d) 200Hz

6. What is the ratio of the shift produced by the noise to the maximum allowed deviation if the modulating frequency is 300Hz and the phase shift by noise is 25° and the maximum allowable deviation is 5kHz?
a) 1.3
b) 0.530
c) 0.153
d) 0.0261

7. What is the noise to signal ratio if the phase shift introduced by noise is 0.75°?
a) 0.5
b) 0.966
c) 0.25
d) 1.75

8. Calculate the phase difference by noise if the Signal to noise ratio is 7:2.
a) 15.366°
b) 17.5°
c) 13.65°
d) 8.21°

9. What is the signal to noise ratio if the maximum allowable frequency deviation is 4kHz and the frequency deviation by noise is 156.42Hz?
a) 0.0364
b) 0.0391
c) 25.75
d) 20.45

10. Which of the following pairs of resistors and capacitors can be used in high pass filters for preemphasis circuits?
a) 100Ω and 0.075μF
b) 100Ω and 0.75μF
c) 150Ω and 0.75μF
d) 16Ω and 0.75μF

11. What is the technique in which the high frequency components are amplified more than the low frequency components in FM?
a) Garble
b) Preemphasis
c) Detoriation
d) Selective amplification

12. Find the frequency at which the signal enhancement flattens out in preemphasis circuit if R1=50Ω ,R2=70Ω and C=0.45μF.
a) 12126.09Hz
b) 550Hz
c) 10036..52Hz
d) 9004.56Hz

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