# Analog Communications Questions and Answers – Frequency Discrimination Method

This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Frequency Discrimination Method”.

1. FM and PM are two ways of angle modulation.
a) True
b) False

Explanation: In angle modulation, phase or frequency of the carrier wave is varied with respect to the instantaneous amplitude of the message signal. The general expression for FM and PM are as follows:
FM (t) = Ac sin (2πfct + βsin(2πfmt)),
PM (t) = Ac sin (2πfct + βcos(2πfmt)), where symbols have their usual meaning.

2. FM transmitting and receiving equipment is __________ as compared to AM equipment.
a) costly
b) cheaper
c) same price
d) not available

Explanation: Frequency transmitting and receiving equipment is generally costly when compared to amplitude modulated equipment.

3. Which one of the following is analog?
a) PCM
b) PWM
c) Delta modulation
d) Differential PCM

Explanation: Frequency transmitting and receiving equipment are generally costly when compared to amplitude modulated equipment, as the power required in FM transmission is less and bandwidth is high. Also, the noise interference is also less in case of FM.

4. Schmitt trigger is used to generate PDM.
a) True
b) False

Explanation: Pulse density modulation (PDM) is used to represent an analog signal using a digital signal. For generating PDM, a monostable multi-vibrator is used, which is externally triggered and has only one stable state.

5. Which of the following is used to generate PDM?
a) Monostable multi-vibrator
b) Bistable Multivibrator
c) Either monostable of free running multi-vibrator
d) Astable Multivibrator

Explanation: Pulse density modulation (PDM) is used to represent an analog signal using a digital signal. For generating PDM, a monostable multi-vibrator is used, which is externally triggered and has only one stable state.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. In case of FM, if the modulating frequency is lowered and the modulating voltage remains constant then the amplitude of distant sidebands decreases.
a) True
b) False

Explanation: If the modulating frequency in FM lowered and the modulating voltage remains constant then the amplitude of distant sidebands increases, as the modulating frequency has no role to play in determining the amplitude of the sidebands.

7. Skip distance depends on the time of day and angle of incidence.
a) True
b) False

Explanation: A skip distance is a distance between the point, where the radio waves from a transmitter are transmitted and the point where the waves are received, after having been refracted by different layers of the ionosphere. It basically depends on time of day as well as on angle of incidence.

8. Leak type bias is used in plate modulated amplifier to prevent tuned circuit damping.
a) True
b) False

Explanation: Leak bias is a type of bias in which the input signal draws grid current from a circuit made of resistors and capacitors. Thus, Leak bias is mainly used to prevent excessive grid current in plate modulated amplifiers.

9. For telegraphy pulse code modulation (PCM) is widely used.
a) True
b) False

Explanation: FSK (Frequency Shift Keying) is a method used to transmit binary data in form of digital signals. It is mainly used for telegraphy. In telegraphy, a modem is used to convert binary data to FSK and vice-versa, for the communication between computers and over telephone lines.

10. DVD uses a laser beam for recording and video head for playback.
a) True
b) False

Explanation: Digital Versatile Disc (DVD) uses a laser beam for both recording and playback.

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.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!