MODULATION & DEMODULATION Multiple Choice Questions :-
1. Modulation is done in …………..
- Transmitter
- Radio receiver
- Between transmitter and radio receiver
- None of the above
Answer: 1
2. In a transmitter ……………. oscillator is used
- Hartley
- RC phase-shift
- Wien-bridge
- Crystal
Answer: 4
3. In India, ……………. modulation is used for radio transmission
- Frequency
- Amplitude
- Phase
- None of the above
Answer: 2
4. In an AM wave useful power is carrier by ………….
- Carrier
- Sidebands
- Both sidebands and carrier
- None of the above
Answer: 2
5. In amplitude modulation, bandwidth is ……………. the audio signal frequency
- Thrice
- Four times
- Twice
- None of the above
Answer: 3
6. In amplitude modulation, the ………… of carrier is varied according to the strength of the signal.
- Amplitude
- Frequency
- Phase
- None of the above
Answer: 1
7. Overmodulation (amplitude) occurs when signal amplitude is …………. carrier amplitude
- Equal to
- Greater than
- Less than
- None of the above
Answer: 2
8. In an AM wave, the majority of the power is in …………….
- Lower sideband
- Upper sideband
- Carrier
- None of the above
Answer: 3
9. At 100% modulation, the power in each sideband is ………………… of that of carrier
- 50%
- 40%
- 60%
- 25%
Answer: 4
10. Overmodulation results in …………..
- Weakening of the signal
- Excessive carrier power
- Distortion
- None of the above
Answer: 3
11. If modulation is 100% then signal amplitude is ………….. carrier amplitude
- Equal to
- Greater than
- Less than
- None of the above
Answer: 1
12. As the modulation level is increased, the carrier power …………..
- Is increased
- Remains the same
- Is decreased
- None of the above
Answer: 2
13. Demodulation is done in …………
- Receiving antenna
- Transmitter
- Radio receiver
- Transmitting antenna
Answer: 3
14. A high Q tuned circuit will permit an amplifier to have high ……………
- Fidelity
- Frequency range
- Sensitivity
- Selectivity
Answer: 4
15. In radio transmission, the medium of transmission is ……………..
- Space
- An antenna
- Cable
- None of the above
Answer: 1
16. If level of modulation is increased ……………. power is increased
- Carrier
- Sideband
- Carrier as well as sideband
- None of the above
Answer: 2
17. In TV transmission, picture signal is ……………… modulated
- Frequency
- Phase
- Amplitude
- None of the above
Answer: 3
18. In a radio receiver, noise is generally developed at ………….
- IF stage
- Receiving antenna
- Audio stage
- RF stage
Answer: 4
19. Man made noise are …………. variations.
- Amplitude
- Frequency
- Phase
- Both phase and frequency
Answer: 1
20. The signal voltage induced in the aerial of a radio receiver is of the order of …………….
- mV
- µV
- V
- None of the above
Answer: 2
21. Superhertodyne principle refers to
- Using a large number of amplifier stages
- Using a push-pull circuit
- Obtaining lower fixed intermediate frequency
- None of the above
Answer: 3
22. If a radio receiver amplifies all the signal frequencies equally well, it is said to have high …………
- Sensitivity
- Selectivity
- Distortion
- Fidelity
Answer: 4
23. Most of the amplification in a superhetrodyne receiver occurs at ………. stage
- IF
- RF amplifier
- Audio amplifier
- Detector
Answer: 1
24. The letters AVC stand for …………..
- Audio voltage control
- Abrupt voltage control
- Automatic volume control
- Automatic voltage control
Answer: 3
25. The superhetrodyne principle provides selectivity at ………. stage
- RF
- IF
- audio
- Before RF
Answer: 2
26. In superhetrodyne receiver, the input at mixer stage is ……….
- IF and RF
- RF and AF
- IF and AF
- RF and local oscillator signal
Answer: 4
27. The major advantage of FM over AM is …………..
- Reception is less noisy
- Higher carrier frequency
- Smaller bandwidth
- Small frequency deviation
Answer: 1
28. When the modulating signal controls the frequency of the carrier, we get……….
- Phase modulation
- Amplitude modulation
- Frequency modulation
- May be any one of the above
Answer: 3
29. Modulation refers to a low-frequency signal controlling the …………
- Amplitude of the carrier
- Frequency of the carrier
- Phase of the carrier
- May be any of the above
Answer: 4
30. The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator frequency is ………….
- 455 kHz
- 1310 kHz
- 1500 kHz
- 1520 kHz
Answer: 2
31. If Amin = 40 and Amax = 60, what is the percentage of modulation?
- 20 %
- 40 %
- 50 %
- 10 %
Answer: 1
32. The function of ferrite antenna is to …………….
- Reduce stray capacitance
- Stabilise d.c. bias
- Increase the Q of tuned circuit
- Reduce noise
Answer: 3
33. In a radio receiver, we generally use ………….. oscillator as a local oscillator
- Crystal
- Wien-bridge
- Phase-shift
- Hartley
Answer: 4
34. A 100 V carrier is made to vary between 160 V and 40 V by the signal. What is the modulation factor?
- 3
- 6
- 5
- None of the above
Answer: 2
35. A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the carrier power after modulation?
- 50 kW
- 5 kW
- 8 kW
- 25 kW
Answer: 1
36. In the above question, what is the power in sidebands?
- 8 kW
- 6 kW
- 06 kW
- 9 kW
Answer: 3
37. In a superhetrodyne receiver, the difference frequency is chosen as the IF rather than the sum frequency because …………….
- The difference frequency is closer to oscillator frequency
- Lower frequencies are easier to amplify
- Only the difference frequency can be modulated
- None of the above
Answer: 2
38. The diode detector in an AM radio receiver is usually found ………….
- Before the first RF stage
- After the first RF stage
- After several stages of amplification
- None of the above
Answer: 3
39. In a TRF radio receiver, the RF and detection stages are tuned to …………
- Radio frequency
- IF
- Audio frequency
- None of the above
Answer: 1
40. In TV transmission, sound signal is ………………… modulated
- Amplitude
- Frequency
- Phase
- None of the above
Answer: 2