Communication Systems – Multiple Choice Questions (MCQs)

1. 25. Frequency Division Multiplexing (FDM) is typically used for ________ signals.

   • A. Digital
   • B. Analog
   • C. Both digital and analog
   • D. Random

2. 26. Wavelength Division Multiplexing (WDM) is used in:

   • A. Radio communication
   • B. Fiber optic communication
   • C. Satellite communication
   • D. Mobile communication

3. 27. Spread Spectrum techniques are used to:

   • A. Increase bandwidth
   • B. Improve security and combat interference
   • C. Reduce power consumption
   • D. Simplify hardware

4. 28. Direct Sequence Spread Spectrum (DSSS) uses a ________ to spread the signal.

   • A. Carrier wave
   • B. Pseudo-noise (PN) code
   • C. Message signal
   • D. Frequency hopper

5. 29. Which theorem states that the maximum data rate for a noisy channel is limited by bandwidth and SNR?

   • A. Shannon-Hartley Theorem
   • B. Nyquist Theorem
   • C. Sampling Theorem
   • D. Parseval's Theorem

6. 30. The unit of channel capacity is:

   • A. Bits
   • B. Symbols
   • C. Hz
   • D. Bits per second

7. 31. The purpose of an antenna in a communication system is to:

   • A. Amplify the signal
   • B. Convert electrical signals to electromagnetic waves and vice-versa
   • C. Filter out noise
   • D. Modulate the signal

8. 32. Propagation of radio waves around the curved surface of the earth is known as:

   • A. Space wave propagation
   • B. Ground wave propagation
   • C. Sky wave propagation
   • D. Line-of-sight propagation

9. 33. Ionospheric propagation is used for ________ frequency communication.

   • A. Very high
   • B. Ultra high
   • C. High
   • D. Low

10. 34. Line-of-sight (LOS) communication is common in ________ frequency ranges.

    • A. VHF and UHF
    • B. MF and HF
    • C. LF and VLF
    • D. All frequency ranges

11. 35. Duct propagation is a type of propagation that occurs due to:

    • A. Temperature inversion
    • B. Rainfall
    • C. Ionospheric reflection
    • D. Obstacles

12. 36. What is the primary role of a mixer in a superheterodyne receiver?

    • A. To amplify the signal
    • B. To change the carrier frequency
    • C. To detect the message signal
    • D. To filter out noise