# Analog Communications Questions and Answers – Demodulation of SSB-SC

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This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Demodulation of SSB-SC”.

1. The disadvantage of FM over AM is that high output power is needed.
a) True
b) False

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. Which theorem states that a noiseless Gaussian channel has zero capacity?
a) Beckman-Quarles theorem
b) Bell’s theorem
c) Cameron-Martin theorem
d) Shannon-Hartley theorem

Explanation: According to Shannon Hartley theorem, a noiseless channel has infinite capacity.

3. Linear devices are used in __________
a) high level AM modulator
b) low level AM modulator
c) high level FM modulator
d) low level FM modulator

Explanation: In low-level modulation, the generation of amplitude modulated signal takes place at low power levels. The generated AM signal is then amplified using a chain of linear amplifiers, which are required to avoid waveform distortion. Thus, linear devices are used in low level amplitude modulated system.
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4. A noiseless Gaussian channel has _____________
a) zero capacity
b) infinite capacity
c) small capacity
d) finite large capacity

Explanation: According to Shannon Hartley theorem, a noiseless channel has infinite capacity.

5. Advantage of high level modulator is that it requires linear amplifiers.
a) True
b) False

Explanation: In high-level modulation, the generation of amplitude modulated signal takes place at high power levels. It has the advantage that linear amplifiers are not required.
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6. Carrier wave in modulation is a wave that is to be transmitted.
a) True
b) False

Explanation: Carrier wave is the wave with frequency higher than the message signal, whose certain characteristics like amplitude, phase or frequency are varied with respect to the instantaneous amplitude of the message signal. Thus forming the modulated wave which is the wave to be transmitted.

7. It is only the wavelength that decides the color of an object.
a) True
b) False

Explanation: Color of any object is decided by the reflected color for opaque object and wavelength transmitted through it for transparent object, while both reflector color and wavelength transmitted are considered for a translucent object.

8. Circular polarization is used in discrimination between reception of adjacent beams.
a) True
b) False

Explanation: In circular polarization at each point the electric field of the electromagnetic wave has a constant magnitude but its direction changes as it rotates with time at a steady rate, in a plane perpendicular to the direction of propagation of wave. It is used to reduce depolarization effect on received waves and not for discrimination between reception of beams.

9. VSB modulation is used in televisions because it results in better reception.
a) True
b) False

Explanation: Vestigial Sideband Modulation (VSB) is a type of amplitude modulation in which the carrier and only one sideband is completely transmitted and the other sideband is partly transmitted. Thus, television production is done using VSB modulation as it reduces bandwidth to half.

10. A cordless telephone that uses separate frequencies for transmission is known as half duplex.
a) True
b) False

Explanation: In duplex communication, two-way interaction is favourable simultaneously. Thus, a cordless telephone is duplex which uses separate frequencies for transmission in base and portable units.

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