Communication Systems – Multiple Choice Questions (MCQs)

1. 49. Companding in PCM is used to:

   • A. Reduce bandwidth
   • B. Improve SNR for low-amplitude signals
   • C. Increase sampling rate
   • D. Reduce quantization error for high-amplitude signals

2. 50. Idle channel noise (granular noise) is a disadvantage of:

   • A. PCM
   • B. DPCM
   • C. Delta Modulation
   • D. All of the above

3. 51. Slope overload distortion occurs in Delta Modulation when:

   • A. Input signal changes too slowly
   • B. Input signal changes too rapidly
   • C. Sampling rate is too high
   • D. Quantization levels are too many

4. 52. Orthogonal Frequency Division Multiplexing (OFDM) is commonly used in:

   • A. 2G mobile communication
   • B. 3G mobile communication
   • C. 4G and 5G mobile communication
   • D. Satellite communication

5. 53. The maximum theoretical efficiency of AM is approximately:

   • A. 33.30%
   • B. 50%
   • C. 80%
   • D. 100%

6. 54. Frequency hopping spread spectrum (FHSS) is known for its ability to combat:

   • A. Multipath fading
   • B. Narrowband interference
   • C. Wideband noise
   • D. Phase distortion

7. 55. Antenna reciprocity means that the transmitting and receiving characteristics of an antenna are:

   • A. Different
   • B. Same
   • C. Opposite
   • D. Unrelated

8. 56. The effective area of an antenna is a measure of its ability to:

   • A. Radiate power
   • B. Capture power
   • C. Filter signals
   • D. Amplify signals

9. 57. The gain of an antenna is proportional to its:

   • A. Size
   • B. Efficiency and directivity
   • C. Bandwidth
   • D. Impedance

10. 58. Sky wave propagation relies on reflection from the:

    • A. Troposphere
    • B. Stratosphere
    • C. Ionosphere
    • D. Mesosphere

11. 59. Ground wave propagation is most effective at ________ frequencies.

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

12. 60. Atmospheric ducts are caused by temperature or humidity inversions

    • A. leading to:
    • B. Long-distance propagation
    • C. Short-distance propagation
    • D. Signal absorption