Analog Communications Questions and Answers – Demodulation of SSB with Large Carrier

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This set of Analog Communications Questions and Answers for Experienced people focuses on “Demodulation of SSB with Large Carrier”.

1. What is the main disadvantage of FM over AM?
a) high modulating power is needed
b) noise is very high for high frequencies
c) high output power is required
d) large bandwidth is required

Explanation: The disadvantage of FM over AM is that in frequency modulation large bandwidth is required. While, in case of advantages, FM is less prone to noise interference and has lower power consumption compared to AM.

2. To prevent over modulation in radio transmitters we use ___________
a) peak clipper
b) oscillator
c) double oscillator
d) filter

Explanation: Clipper is used to prevent the exceeding of output from a predetermined fixed value. It does not distorted the remaining part of the applied waveform.

3. IN EM waves, polarization ___________
a) is always vertical
b) is caused by reflection
c) is due to transverse nature of waves
d) is due to longitudinal nature of waves

Explanation: In electromagnetic waves, polarization is mainly due to the transverse nature of waves only. Transverse nature of electromagnetic waves mean that the electric and magnetic fields are perpendicular to each other as well as perpendicular to the direction of propagation of waves.
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4. In FM receiver, role of amplitude limiter is to amplify low frequency signals.
a) True
b) False

Explanation: Amplitude Limiter circuit is used in FM receiver to remove the noise or any variation in amplitude present in the received signal. Thus, the output of the amplitude limiter has a constant amplitude. So it is only used in frequency modulation and not in amplitude modulation.

5. In a FM receiver, amplitude limiter ________
a) eliminates any change in amplitude of received FM signals
b) eliminates any change in frequency of received FM signals
c) reduce the amplitude of received signals
d) amplifies low frequency signals

Explanation: Amplitude Limiter circuit is used in FM receiver to remove the noise or any variation in amplitude present in the received signal. Thus, the output of the amplitude limiter has a constant amplitude. So it is only used in frequency modulation and not in amplitude modulation.

6. Base modulation is preferred over collector modulation of a class C transistor because of its better efficiency.
a) True
b) False

Explanation: Base modulation is preferred over collector modulation of a class C transistor because low modulating power is required and collector saturation prevents complete modulation of a signal. Generally, Collector modulation has more advantages over Base modulation like high linearity, better collector efficiency and such like.

7. Base modulation is preferred over collector modulation of a class C transistor because it has high power output per transistor.
a) True
b) False

Explanation: Base modulation is preferred over collector modulation of a class C transistor because low modulating power is required and collector saturation prevents complete modulation of a signal. Generally, Collector modulation has more advantages over Base modulation like high linearity, better collector efficiency and such like.

8. What is the standard IF frequency for AM receivers?
a) 100 KHz
b) 455 KHz
c) 1.07 MHz
d) 10.7 MHz

Explanation: In AM receivers, the standard intermediate frequency is approximately 455 KHz.

9. Balanced modulator is used to produce balanced modulation of a carrier wave.
a) True
b) False

Explanation: Balanced modulator is used to produce 100% modulation by suppressing the carrier and passing only the two sidebands.