This set of Analog Communications Question Bank focuses on “Carrier Acquistion Techniques in DSB-SC”.
1. Flyback switched mode is used in television because it can supply many voltage outputs.
Explanation: Flyback switched mode is used in television because it does not require filter choke. It is also cheap as compare to others.
2. What will be the effect on power if the modulation index of a frequency modulated signal is increased?
c) remains constant
d) first increases and then decreases
Explanation: In frequency modulation, power remains constant. So if we increase the modulation index then also it does not affect power, it will remains constant.
3. The equation 20sin(108 t + 3 sin 109 t) represents which modulation?
Explanation: On comparing with the general equation of each modulation, we found that it represents Frequency modulation.
4. Monopole antenna is a type of travelling wave antenna.
Explanation: Monopole antenna is a type of wire antenna. Travelling wave antenna consists helical antenna, spiral antenna.
5. In which modulation, frequency of carrier signal is varied with the amplitude of modulating signal?
Explanation: In Frequency Modulation the frequency of carrier is varied with the instantaneous amplitude of modulating signal.
6. In Phase Modulation the phase of carrier signal is varied.
Explanation: In phase modulation the phase shift of carrier is varied with the instantaneous amplitude of modulating signal.
7. Power spectral density of thermal noise remains uniform upto frequency ___________
a) 1015 HZ
b) 105 HZ
c) 102 HZ
d) 1013 HZ
Explanation: Power spectral density of thermal or white noise gets affected when the frequency becomes greater than 1013 Hz.
8. Carrier frequency remains constant in cell communication.
Explanation: In cell communication carrier frequency does not remains constant. The carrier frequency get changes continuously.
9. Waves of which frequency can penetrate the atmosphere?
a) higher than 10 MHz
b) higher than 20 MHz
c) higher than 30 MHz
d) higher than 100 MHz
Explanation: Any wave having frequency greater than 30 MHz can penetrate the atmosphere. The waves having frequency less than it cannot penetrate the atmosphere.
10. Armstrong modulator can only generate FM signal.
Explanation: Armstrong Modulator can also generate PM along with FM. So the statement is incorrect.
Sanfoundry Global Education & Learning Series – Analog Communications.
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