➤ Hello In this page provides you Unguided Data Modems MCQs Question/MCQ In this question Based on the Modulation ,Demodulation, pulse code modulation shift keying and ASK,FSK,PSK etc.
Q.1 What does the acronym AM stand for in communications?
Amplitude Mode
Amplitude Modulation
Amplitude Model
None
Explanation
AM stands for Amplitude Modulation, a technique used in electronic communication for transmitting information via a radio carrier wave.
Q.2 How is Amplitude Modulation (AM) defined?
Change in amplitude of the carrier according to modulating signal
Change in frequency of the carrier according to modulating signal
Change in amplitude of the modulating signal according to carrier signal
None
Explanation
In AM, the strength or amplitude of the carrier signal is varied in proportion to the instantaneous amplitude of the message signal.
Q.3 What does the frequency spectrum of an AM signal typically consist of?
Carrier frequency
Upper sideband frequency
Lower sideband frequency
All of these
Explanation
A standard AM signal contains the central carrier frequency plus two sidebands that carry the actual data.
Q.4 The amount of data transmitted over a communication channel in a given amount of time is called?
Bandwidth
Frequency
Noise
None
Explanation
Bandwidth represents the capacity of a transmission medium to carry data, usually measured in bits per second or Hertz.
Q.5 In standard Amplitude Modulation, which of the following remains constant?
Amplitude of the carrier
Frequency of the carrier
Phase of the carrier
Both B & C
Explanation
In pure AM, only the amplitude is varied; the frequency and phase of the carrier wave are kept constant.
Q.6 Which of the following is an indicator or characteristic of analog communication?
AM or FM signal
No numerical coding
Continuous signal with varying amplitude or phase
All of these
Explanation
Analog communication uses continuous waveforms to represent information rather than discrete digital bits.
Q.7 Which of the following are recognized types of continuous-wave analog modulation?
Phase modulation
Frequency modulation
Amplitude modulation
All of these
Explanation
Information can be modulated into a carrier wave by varying its amplitude (AM), frequency (FM), or phase (PM).
Q.8 What is a common advantage of analog communication compared to digital systems?
Data rate is low
Synchronization is not mandatory
Less transmission bandwidth is required
All of these
Explanation
Analog systems are often simpler to implement for basic signals and generally require less bandwidth than their digital equivalents.
Q.9 What is the maximum theoretical transmission efficiency of a standard AM signal?
34.2%
40%
33.33%
32.21%
Explanation
The maximum efficiency for a conventional AM signal (where the modulation index is 1) is 33.33%.
Q.10 In the AM spectrum, the Lower Side Band (LSB) refers to the frequencies that?
Are below the carrier frequency
Include the carrier frequency
Lie within the AM Spectrum
Both A & C
Explanation
The LSB consists of all frequencies produced by modulation that are lower than the carrier frequency.
Q.11 In the AM spectrum, the Upper Side Band (USB) refers to the frequencies that?
Are above the carrier frequency
Include the carrier frequency
Lie within the AM spectrum
Both A & C
Explanation
The USB consists of the frequency range produced by modulation that is higher than the carrier frequency.
Q.12 By which process can a continuous analog signal be converted into a digital signal?
Sampling
Amplitude Modulation
Filtering
Mixing
Explanation
Sampling is the process of taking discrete points from an analog signal at regular intervals to create a digital representation.
Q.13 Which of the following is true regarding 'Low Level' Amplitude Modulation?
Modulation occurs at low carrier power
Output power is initially low
Power amplifiers are needed to boost the final signal
All of these
Explanation
Low-level modulation happens before the final power amplification stage of the transmitter.
Q.14 Which of the following is true regarding 'High Level' Amplitude Modulation?
Modulation is done at high power levels
Collector modulation is a common method used
Amplifiers boost signals before modulation
All of these
Explanation
In high-level modulation, the carrier is amplified to its final power level before the message signal is applied.
Q.15 Which of the following is a classic example of continuous-wave analog modulation?
PCM
AM
DM
All of these
Explanation
Amplitude Modulation (AM) is a continuous-wave technique, while Pulse Code Modulation (PCM) and Delta Modulation (DM) are pulse-based.
Q.16 What is the standard Intermediate Frequency (IF) value used in most AM radio receivers?
430 KHz
455 KHz
480 KHz
None
Explanation
455 KHz is the standard IF used in superheterodyne receivers to provide consistent selectivity and amplification.
Q.17 What is the imaginary line connecting the peaks of a modulated carrier waveform called?
Peak Line
Maximum amplitude ceiling
Modulation index
Envelope
Explanation
The ‘envelope’ of the AM signal mirrors the shape of the original modulating (message) signal.
Q.18 In AM signal analysis, what serves as the reference line for the modulating signal?
Zero Line
Carrier peak line
Modulated peak line
Un-modulated peak line
Explanation
The message signal varies the amplitude relative to the peak voltage level of the unmodulated carrier.
Q.19 What occurs if the amplitude of the message signal exceeds the amplitude of the carrier signal?
Decay
Distortion
Amplification
None
Explanation
This condition is called overmodulation, which causes the signal envelope to become clipped and distorted.
Q.20 What is the primary negative effect of signal distortion in a communication system?
Total loss
Error information
Attenuated information
Amplified information
Explanation
Distortion leads to the corruption of data, resulting in errors in the information received at the destination.
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