This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Comparison Between FM and PM”.
1. Pre-emphasis is used to amplify _________ frequencies.
c) both low and high
d) neither low nor high
Explanation: Pre-emphasis is used in frequency modulated transmitters to equalize the drive power of transmitting signal in terms of deviation ratio. It is done at the transmitter. It is used to amplify high frequencies.
2. De-emphasis circuit is used ________
a) before detection
b) after detection
c) before modulation
d) after modulation
Explanation: De-emphasis means attenuation of those frequencies by the amount by which they are boosted. It is done at the receiver end i.e. it is used after detection.
3. Why frequency fogging is used in a carrier system?
a) to reduce noise
b) to reduce cross talk
c) to converse frequencies
d) to reduce distortion
Explanation: The interchanging of the frequencies of carrier channels to accomplish specific purposes. It is used to prevent feedback and oscillation. It is also used to reduce cross-talk and also to correct for a high frequency response slope in the transmission line.
4. For a phase modulated signal, the frequency deviation is proportional to ________
a) frequency only
b) amplitude only
c) both frequency and amplitude
d) phase only
Explanation: For a phase modulated system, it is amplitude which is directly proportional to the deviation.
5. The frequency deviation is proportional to frequency in phase modulated signal.
Explanation: For a phase modulated signal, the frequency deviation is proportional to amplitude.
6. Which is the true statement about frequency deviation in frequency modulation?
a) frequency deviation is constant
b) frequency deviation is zero
c) frequency deviation is proportional to modulating frequency
d) frequency deviation is proportional to amplitude of modulating signal
Explanation: In frequency modulated system, the frequency deviation is proportional to the amplitude of the modulating signal.
7. Which of the following is not necessarily an advantage of FM over AM?
a) less modulating power is required
b) better noise immunity is provided
c) lower bandwidth is required
d) carrier is of any shape
Explanation: In frequency modulation, frequency of carrier gets varied with respect to the wave being propagated. FM has many advantages over AM but requirement of lower bandwidth is not an efficient condition.
8. What is number of possible outputs if there is 7 line digital input?
Explanation: Total possible outputs will be 27 which is equal to 128.
9. Push pull amplifier is a class B amplifier.
Explanation: Push pull amplifier uses a pair of active devices that alternately supply current to a connected load and also absorb current from a connected load. It is a class B amplifier.
10. What is the frequency of the stereo sub carrier signal in FM broadcasting?
a) 19 KHz
b) 45 KHz
c) 55 KHz
d) 38 KHz
Explanation: Stereo broadcasting is made possible by using a subcarrier on FM radio stations, which takes the left channel and “subtracts” the right channel from it. A subcarrier is basically a sideband of a radio frequency carrier wave, which is modulated to send additional information. The frequency set for stereo sub carrier signal in FM broadcasting is 38 KHz.
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.