This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Superhetrodyne Receiver”.
1. Which of the following statement is true about frequency modulation?
a) noise gets decrease if we decrease deviation
b) noise gets decrease if we increase deviation
c) noise gets decrease by maintaining deviation constant
d) noise do not depends on deviation
Explanation: In frequency modulated system, if we increase deviation then the noise in system gets decrease.
2. Aspect ratio is the ratio of ________
a) width to height
b) height to width
c) power to width
d) width to power
Explanation: Aspect ratio is the ratio of width to the height of image (screen).
3. Colpitts oscillator is used in frequency modulation.
Explanation: Crystal oscillator is used in frequency modulation.
Explanation: Carrier frequency is given by the formula, where L is inductance and C is Capacitance.
5. The difference between phase and frequency modulation ________
a) lies in the poorer radio response of phase modulation index
b) lies in the different definition of modulation index
c) is too great to make the two systems compatible
d) is purely theoretical
Explanation: It is the difference in definition of modulation index which makes it different between phase and frequency modulated systems.
6. The frequency deviation is proportional to both amplitude and frequency in phase modulated signal.
Explanation: For a phase modulated signal, the frequency deviation is proportional to amplitude only.
7. In a frequency modulated signal, the power _________ as the modulation index increases.
a) remains constant
d) can be increase or decrease
Explanation: In a frequency modulated system, if we increase the modulation index the power remains constant.
8. Frequency fogging is used to reduce noise in a carrier system.
Explanation: Frequency fogging is used to cross talk in a carrier system.
9. Pre-emphasis circuit is used ________
a) before detection
b) after detection
c) before modulation
d) after modulation
Explanation: Pre-emphasis is used in frequency modulated or phase modulated transmitters to equalize the drive power of transmitting signal in terms of deviation ratio. It is done at the transmitter. Its circuit is used before modulation.
10. De-emphasis circuit is used in circuit before detection.
Explanation: De-emphasis means attenuating those frequencies by the amount by which they are boosted. De-emphasis is done at the receiver end i.e. it is used after detection.
Sanfoundry Global Education & Learning Series – Analog Communications.
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