This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Switching Circuit”.
1. If we compared to the USB, the power in the LSB is ________
b) twice of USB
d) half of USB
Explanation: The two bands i.e. upper sideband and lower sideband generally contains same information. They also has same power.
2. What will be the effect on power in amplitude modulated system if we increase the modulation index?
a) remains same
b) becomes twice
Explanation: If we increase or decrease modulation index, it not affects our power. So if we increase the modulation index our power remains same.
3. What is the modulation index for getting maximum power in amplitude modulated system?
Explanation: For getting maximum power, it is required to set the maximum and minimum voltage of wave such that we get modulation index equal to unity.
4. How can we derive FM from PM?
a) by integrating the modulating signal before applying to the PM oscillator
b) by integrating signal out of the PM oscillator
c) by differentiating the modulating signal before applying to the PM oscillator
d) by differentiating signal out of the PM oscillator
Explanation: Frequency modulation can be derived from phase modulated system, if we integrate our modulating signal. But this integration must be done before applying our wave to PM oscillator.
5. How an AM radio station increase its signal-to-noise ratio?
a) by increasing its modulation index
b) by decreasing its modulation index
c) by maintaining a constant modulation index
d) by increasing the frequency
Explanation: Signal to noise ratio is the ratio of signal power to the noise power. It is often described in decibels. It is directly proportional with modulation index and thus it increases with modulation index.
6. FM bandwidth can be approximated by ________
a) Carson’s rule
b) Armstrong’s rule
c) Bessel’s rule
d) Pythagoras rule
Explanation: Carson’s rule is made to calculate bandwidth of a frequency modulated system. According to Carson’s rule Bandwidth, B = 2(∆f + fm).
7. Which effect is observed when FM reception deteriorates abruptly due to noise?
a) Threshold effect
b) Capture effect
c) Noise effect
d) Limit effect
Explanation: Threshold effect has low output signal to noise ratio. It contains large noise as compared to input signal to envelope detector. In threshold effect, detection of message signal is difficult.
8. FM stereo _________
a) is implemented using an SCA signal
b) has a higher signal to noise ratio than mono FM
c) is not compatible with mono FM
d) uses DSBSC AM modulation
Explanation: A stereo FM contains three major sections :- monomode, stereo mode and section common to both mono and stereo mode. The stereo section is much complicated than others. It uses DSB AM modulation for its process.
9. Signal to noise ratio of a frequency modulated system is better than amplitude modulated system.
Explanation: Signal to noise ratio is the ratio of signal power to the noise power. It is often described in decibels. It is directly proportional with modulation index and thus it increases with modulation index. It is better for frequency modulated systems.
10. What will be the effect on power if the distance between the sidebands and center frequency increases?
a) power decreases
b) power increases
c) power remains same
d) power becomes twice of its previous value
Explanation: If the distance between the central frequency and sidebands increases, the effective power decreases.
Sanfoundry Global Education & Learning Series – Analog Communications.
To practice all areas of Analog Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.