# Analog Communications Questions and Answers – Amplitude Limiting

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This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Amplitude Limiting”.

1. TRF receivers are used for ________
a) Detection of modulating signal
b) Removal of unwanted signal
c) Mixing modulating signal with unwanted signal
d) Both detection of modulating signal and removal of unwanted signal

Explanation: TRF receivers are used for detection of modulating signal and removal of unwanted signal. The receiver receive the modulated signal and detect the information signal from received modulating signal.

2. Calculate the power in a DSB-SC signal, if the modulation is 60% and power of carrier wave is 600W?
a) 120W
b) 108W
c) 111W
d) 102W

Explanation: The total power for DSB is PC (m22) = 600X(0.622) = 108W.
The total power for DSB-SC = PC (u22). (where Pc = Power of Carrier, u = Modulation Index) = 600 X ((0.6)2/2) = 108W.

3. One of the advantage of using analog communication over digital communication is that in analog communication less transmission bandwidth is required.
a) True
b) False

Explanation: Due to analog to digital conversion, data rate becomes high in digital communication which increases the bandwidth in digital communication. Thus, requirement of bandwidth is more in digital communication than in analog communication.
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4. What is the maximum transmission efficiency of an AM signal?
a) 33.33%
b) 60.25%
c) 38.75%
d) 50.25%

Explanation: The percentage of total power contributed by sidebands of the AM signal is known as transmission efficiency of an amplitude modulated system. The maximum transmission efficiency of an AM signal is 33.33%, thus suppressing the carrier which contains no useful information.

5. Generation of SSB-SC signal is done by ________
a) Phase discrimination method and Frequency discrimination method
b) Phase discrimination method and Square law modulator
c) Square law modulator and Frequency discrimination method
d) Balanced modulator and Square law modulator

Explanation: SSB-SC signals are the signals where only one of the side band is transmitted in an AM wave. SSB-SC signal is generated by two methods, frequency discriminator method or filter method and phase discriminator method or phase shift method.

6. In automatic gain control of the AM receiver ________
c) is an open-loop system
d) gain is received only by stronger signals

Explanation: Automatic Gain Control provides controlled signal amplitude at the output even if there are amplitude variations at the input. This controlled output adjusts the input to output gain to a suitable value.

7. Which of the following is an example of continuous wave analog modulation?
a) PCM
b) DPCM
c) AM

Explanation: Analog communication is a type in which the message to be transmitted is analog in nature. Here the message signal modulates a high frequency carrier signal. In AM, amplitude of the carrier is varied with respect to the instantaneous amplitude of the wave which is to be propagated. It is also an example of continuous wave analog modulation.

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