This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Single Tone Modulation”.
1. For Amplitude Modulation, Emitter modulator ________
a) Operates in class C mode
b) Has a low efficiency
c) Output power is high
d) Operates in class B mode
Explanation: Emitter Modulator operates in class A region. It has a very low efficiency. The output power is low so for modulation at high level, it is not suitable.
2. Why AM is used for broadcasting?
a) More immune to noise
b) Less transmitting power is required
c) It has high fidelity
d) Avoids Receivers Complexity
Explanation: AM uses square law and envelope detectors for transmission. Since they both have non complex structures so AM is highly recommended for broadcasting.
3. Singletone amplitude modulation ________
a) consists of only one frequency
b) contains a large number of frequency components
c) contains no frequency components
d) contains infinite number of frequency components
Explanation: Single tone modulation is that in which the baseband signal consists of only one frequency. In other words, modulation is done by a single frequency.
4. AM spectrum consists of ________
a) Carrier frequency
b) Upper sideband
c) Lower sideband
d) Carrier frequency with both upper and lower sideband
Explanation: Spectrum of Am wave consists of a carrier with two sidebands. It is found that if carrier frequency is 5KHz then the two sidebands produced by it is 5KHz away from the carrier.
5. The minimum channel Bandwidth is used by which modulation technique?
Explanation: A signal has two sidebands which are exactly the mirror images of each other. So we can remove one side band which further reduces its bandwidth.
6. Neper is ________ decibel.
a) Larger than
b) Smaller than
c) Same as
d) Exactly twice of
Explanation: Neper is a logarithmic unit used for finding ratios of power quantities. Like decibel it is also a dimensionless unit. 1Np = 20/ln10 = 8.686 db.
7. AM broadcast station transmits modulating frequency upto 6KHz. If transmitting frequency is 810KHz, then maximum and lower sidebands are ________
a) 816KHz and 804KHz
b) 826KHz and 804KHz
c) 916KHz and 904KHz
d) Not possible
Explanation: Maximum frequency = 810 + 6 = 816KHz and Minimum frequency = 810 – 6 = 804KHz. Moreover it has a bandwidth of (816 – 804) = 12KHz.
8. Find lower frequency component in AM wave, given that highest frequency component is 900KHz and bandwidth is 12KHz?
Explanation: Highest frequency component is 900KHz and bandwidth is 12KHz. So lower frequency component is 900 – 12 = 888KHz.
9. Amplitude Modulated wave is ________
a) Sum of carrier and modulating wave
b) Product of carrier and modulating wave
c) Difference of carrier and modulating wave
d) Sum of carrier and its product with modulating wave
Explanation: The modulation of a wave by varying its amplitude is known as amplitude modulation. It is represented as, s(t) = [A + x(t)] (Cos ωc) t.
10. Envelope Detector is a/an ________
a) Coherent detector
b) Asynchronous Detector
c) Synchronous Detector
d) Product Demodulator
Explanation: Envelope detectors are asynchronous in nature. The advantage of asynchronous over synchronous is that it is simple, cheap, setup is faster.
Sanfoundry Global Education & Learning Series – Analog Communications.
To practice all areas of Analog Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.