This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Need of Transducers”.
1. What is the effect on the transmitted power, if the modulation index changes from 0.8 to 1?
Explanation: The total power in an AM is given by, PT = PC (1+m2⁄2) . When modulation index, m = 0.8 PT = PC (1+0.82⁄2)=1.32Pc and when modulation index, m=1 PT=PC (1+12⁄2)=1.5PC.
So increase in power =
2. Analog signal may be converted into digital signal by ________
Explanation: Conversion of analog signal into digital signal converts a continuous time signal in the form of digits. The conversion is done with the help of sampling technique.
3. Radio waves travel through ________
c) Optical fiber cable
d) Electromagnetic waves
Explanation: Radio communication or wireless communication takes place through electromagnetic waves. The message is transmitted through open space via electromagnetic waves or radio waves.
4. USB (Upper Side Band) is the band of frequencies _________
a) below carrier frequency
b) includes the carrier frequency
c) that lies in AM spectrum
d) that lies in PM spectrum
Explanation: Upper Side Band is the band of frequencies above the carrier frequency that lies in AM spectrum. It is a part of shifted spectrum obtained after amplitude modulation.
5. PDM is generated by ________
a) combination of two series amplifiers
b) Monostable multivibrator
c) Astable multivibrator
d) Schmitt trigger
Explanation: Monostable multivibrators are used to generate a single output pulse of a particular width. Its output can be high or low for an external applying pulse. PDM (Pulse Density Modulation) is used to represent an analog signal with the help of a binary signal.
6. Which of the following is AM demodulation techniques?
a) Square law demodulator and Envelope detector
b) Square law demodulator and PLL detector
c) PLL detector and Envelope detector
d) PLL detector
Explanation: AM signals are detected or demodulated using Square law demodulator and Envelope detector. The demodulator extracts the information from the received AM signal.
7. Vestigial side band signals are detected by ________
a) Balanced modulator
b) Schmitt trigger
c) Square law modulator
d) Synchronous Detection
Explanation: Vestigial side band signals are detected by Synchronous detection or coherent detection technique. The distortion in a VSB signal may be reduced by reducing the modulation index and increasing the width of VSB.
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. What is the function of frequency mixer in super heterodyne receiver?
a) Multiplication of incoming signal and the locally generated carrier
b) Addition of incoming signal and the locally generated carrier
Explanation: The function of a frequency mixer in a super heterodyne receiver is that it mixes or multiplies the incoming modulated signal with the locally generated carrier.
10. The amount of frequency deviation in FM signal depends on ________
a) Modulating frequency
b) Transmitter amplifier
c) Amplitude of the modulating signal
d) Carrier frequency
Explanation: The amount of frequency deviation in FM signal depends on amplitude of the modulating signal. So for any audio signal, as the loudness increases frequency deviation in carrier signal also increases. Frequency deviation helps in determining the bandwidth of FM signal.
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.