This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Disadvantages of Filter Method”.
1. Why sampling is used in communication?
a) for getting higher speed of communication
b) for getting higher efficiency
c) cheaper equipment is required
d) for a better transmission
Explanation: Sampling is the conversion of continuous-time signal to discrete-time signal. It samples a continuous time signal depending on a specific range and thus produces the discrete form of the signal. It is highly used in communication for getting higher speed of communication.
2. Which two noises are present in Delta Modulation (DM)?
a) Slope overload and Thermal noise
b) Granular and shot noise
c) Slope overload and granular noise
d) Thermal and shot noise
Explanation: Delta modulation is used for transmission of voice information where quality is not the primarily importance. Its drawback is it has two noises namely slope overload and granular noise. Slope overload noise occurs when the input signal slope is higher than the delta modulator’s capability. Granular noise is produced due to level input signal resulting into the oscillatory output. So for getting rid of these noises we use ADM (Adaptive Delta Modulation).
3. Varacter is used for generation of ________
a) PM signals only
b) FM signals only
c) AM signals only
d) DSB-SC signals
Explanation: Varacter diode or tuning diode that has a variable capacitance. It is operated as reverse-biased and therefore no current flows. It is mainly used for generation of FM signals only.
4. What will happen in amplitude modulation, if the modulation index is more than 1?
a) bandwidth will increase
b) bandwidth will decrease
c) amplitude becomes constant
d) waves will get distorted
Explanation: Modulation index tells us the amount by which the carrier wave is varied with respect to the message signal. If modulation index is greater than 1, then the wave gets distorted and overlap, thus causing overmodulation.
5. The adverse effect of noise in communication system can be seen in ________
Explanation: Noise is the unwanted signal present in the passband of a signal. It is very much unpleasant thus causing disturbance. Its adverse effect is highly seen on channel.
6. Which among the following is not an advantage of FM over AM?
a) modulating power required is less
b) low bandwidth is required
c) better noise immunity
d) better signal to noise ratio
Explanation: Advantages of FM over AM are less prone to noise, low modulating power required and such like. However, disadvantage of FM is that large bandwidth is required.
7. Which of the following is the advantage of base modulation over collector modulation of a class C amplifier?
a) lower modulation power is required
b) higher power output per transistor
c) better efficiency
d) better linearity of modulation
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 radio frequency range of a frequency modulated signal?
a) 20-80 MHz
b) 100-200 MHz
c) 200-350 MHz
d) 99-108 MHz
Explanation: The standard frequency range of a frequency modulated signal is between 90-105 MHz.
9. Vestigial side band (VSB) is most commonly used in ________
a) Television Transmission
d) Laser Transmission
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.
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