This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Noise for AM Wave”.
1. The image frequency of a superheterodyne receiver ___________
a) is created within the receiver itself
b) is due to insufficient adjacent channel rejection
c) is not rejected to be the IF tuned circuits
d) is independent of the frequency to which the receiver is tuned
Explanation: To eliminate image frequency of a superheterodyne receiver a sufficient attenuation on the incoming signal by the RF amplifier filter is needed. It is not rejected to be the IF tuned circuits.
2. Which one of the following circuits could not demodulate SSB?
a) Balance Modulator
b) Product Modulator
d) Phase discriminator
Explanation: Phase discriminator cannot be used to demodulate SSB. It is used to discriminate between different phases.
3. Which of the following statement is true about a radio detector?
a) the linearity is worse than in phase discriminator
b) there is stabilization against signal strength variations
c) the final output is twice of that obtainable from a similar phase discriminator
d) the circuit is same as in a discriminator, except that the diodes are reversed.
Explanation: Detector in a radio receiver extracts information that is contained in a modulated radio wave. The linearity of radio detector is worse than in phase discriminator.
4. Envelope of AM wave has the same shape as the message of baseband signal.
Explanation: Modulation Envelope is observed when carrier, upper sideband and lower sideband are combined in a single impedance and observed on time versus amplitude curve. For AM, it has same shape as message of baseband signal.
5. To prevent overloading of the IF amplifier in a receiver, one should use _________
a) variable sensitivity
b) variable selectivity
c) double conversion
Explanation: Squelch is a circuit that is preferably used to prevent overloading of the IF amplifier in a receiver.
6. In a broadcast superheterodyne receiver, the ____________
a) Local oscillator always operates below the frequency of transmitted signal
b) Input of mixer must be tuned to the signal frequency
c) Local oscillator frequency should be double than that of IF
d) RF amplifier normally works at 455 KHz above the carrier frequency
Explanation: For a superheterodyne receiver, the input of mixer must be tuned to the signal frequency. Tuning means that the circuit works for that one signal frequency only.
7. Which of the following statement is false regarding Armstrong modulation system?
a) The system is basically phase, not frequency modulated
b) AFC is not needed as crystal oscillator is used
c) Frequency multiplication must be used
d) Equalization is necessary
Explanation: The Armstrong method generates a double sideband carrier signal, phase shifts this signal and then reinserts the carrier to produce a frequency modulated signal. In Armstrong modulation system equalization is not necessary.
8. If the target cross section is changing, the best system for accurate tracking is __________
a) sequential switching
b) lobe switching
c) conical scanning
Explanation: Monopulse radar compares the received signal from a single radar pulse against itself in order to compare the signal in various aspects. If the target cross section is changing then it is the best system used for accurate tracking.
9. What do you understand by low level AM?
a) Output power is low
b) Modulation is done at high power of carrier and modulating signal
c) Collector Modulation Method is low level AM
d) Output power is high
Explanation: In low level AM, modulation is done at low power of carrier and modulating signal therefore output power is low. Collector Modulation Method is high level AM.
10. After a target has been acquired, the best scanning system for tracking is _________
Explanation: Conical is the best scanning system for tracking. But it is only preferred for tracking after a target has been acquired.
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.