COMMUNICATION SYSTEMS PREVIOUS YEAR BOARD EXAM QUESTIONS

COMMUNICATION SYSTEMS

PREVIOUS YEAR BOARD EXAM 

QUESTIONS

(2007-2018)

1 MARK QUESTIONS

1. Write the range of frequencies of electromagnetic waves which 

propagate through sky wave mode.

2. Explain the term ‘modulation’ used in communication systems.

3. Which mode of propagation is used by short wave broadcast 

services?

4. Define modulation index. Why is it generally kept less than one?

OR

Why is amplitude of modulating signal kept less than the amplitude 

of carrier wave?

5. Why is sky wave propagation of signals restricted to a frequency 

of 30 MHz?

6. State two reasons why high frequency carrier waves are needed 

in transmitting a message signal.

7. Write the expression for the optimum separation between the 

transmitting and receiving antenna for effective reception of signals 

in this mode of communication.

8. What is the main limitation of space-wave mode of 

propagation?

9. Name the network within an institution, made by connecting all 

or some of their computers.

10. Give the expression for the maximum Line of Sight distance 

between two antennas for space wave propagation.

11. Write two advantages of frequency modulation over amplitude 

modulation.

12. Give the difference between LAN(local area network) and 

WAN(wide area network).

13. Name the essential components of a communication system.

14. What is the function of a band pass filter used in a modulator 

for obtaining AM signal?

15. A signal of 5kHz frequency is amplitude modulated with a 

carrier wave of frequency 2MHz. What are the frequencies of side 

bands produced?

16. Why is the frequency of outgoing and incoming signals different 

in a mobile phone?

17. Distinguish between amplitude modulation and frequency 

modulation.

18. A TV tower has a height of 71 m. What is the maximum distance 

upto which TV transmission can be received? Given that the radius 

of the earth = 6.4 × 106 m.

19. Suggest a possible communication channel for the transmission 

of a message signal which has a bandwidth of 5 MHz.

20. Which basic mode of communication is used for telephonic 

communication?

21. How are side bands produced in amplitude modulation?

22. Which basic mode of communication is used in satellite 

communication? Which type of wave propagation is used in this 

mode?

23. A TV tower is 80 m tall. Calculate the maximum distance upto 

which the signal transmitted from the tower can be received.

24. Justify –“For ground transmission, the size of antenna(L) should 

be comparable to wavelength of signal (L ≈λ/4)”.

25. Why should the broadcast frequencies be sufficiently spaced 

out in Amplitude modulation?

26. Is it necessary for transmitting antenna and receiving antenna 

to be of same height, in Line of Sight propagation? Why?

27. Which two communication methods make use of space wave 

propagation?

28. Why is it not possible for transmission of TV signals to use sky 

wave propagation?

29. In the given diagram C(t) stands for the carrier wave and m(t) 

for the signal to be transmitted. What name do we give to the wave 

labeled as Cm(t) in the diagram?

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