77 + Interview Questions in Noise in Analog Communications Page 2 InterviewSolution

51.	Which system is free from noise?(a) FM(b) AM(c) PCM(d) PMThis question was posed to me during an online exam.Query is from Threshold Effect in FM topic in division Noise of Analog Communications
Answer» The correct choice is (a) FM Explanation: Noise is the unwanted SIGNAL or disturbances in a COMMUNICATION SYSTEM. It is a frequency modulated system which REMAINS free from noise.

Discussion

52.	In AM receiver, the oscillator frequency is always ________(a) lower than signal frequency(b) higher than signal frequency(c) equal to signal frequency(d) equal to 1KHzI have been asked this question at a job interview.I'd like to ask this question from Noise in Phase Modulation in division Noise of Analog Communications
Answer» The correct CHOICE is (B) higher than signal frequency To EXPLAIN: The frequency of an OSCILLATOR in AMPLITUDE modulated system is always higher than the frequency of signal.

Discussion

53.	Which of the following receiver does not have an amplitude limiter stage?(a) AM(b) PM(c) FM(d) Both AM and FMThe question was posed to me in an online quiz.This interesting question is from Noise in Phase Modulation in division Noise of Analog Communications
Answer» CORRECT answer is (a) AM The explanation: Amplitude LIMITER circuit is used in FM RECEIVER to remove the noise or any variation in amplitude present in the received signal. Thus, the OUTPUT of the amplitude limiter has a CONSTANT amplitude. So it is only used in frequency modulation and not in amplitude modulation.

Discussion

54.	Most of the amplification of the received signal is obtained in a superheterodyne receiver from ________ stage.(a) IF(b) RF(c) Power Amplifier(d) Local OscillatorThis question was addressed to me in examination.I want to ask this question from Noise in Phase Modulation in portion Noise of Analog Communications
Answer» CORRECT ANSWER is (a) IF Explanation: In superheterodyne receiver, most of the RECEIVED signals gets amplified from an intermediate frequency (IF) due to IF amplifier.

Discussion

55.	Padder capacitor can be used to achieve three point tracking.(a) True(b) FalseThe question was asked in an internship interview.Enquiry is from Noise in Phase Modulation in section Noise of Analog Communications
Answer» Correct option is (a) True To explain: To ACHIEVE three point tracking a capacitor is connected in SERIES with local oscillator coil. This capacitor is CALLED a padder capacitor.

Discussion

56.	If the output power of radio receiver is doubled then the volume is increased by _________(a) 3 dB(b) 2 dB(c) -3 dB(d) -2 dBThe question was asked in exam.My question comes from Noise in Phase Modulation in chapter Noise of Analog Communications
Answer» Right OPTION is (a) 3 DB Explanation: VOLUME of a radio receiver is increased by 3 dB if we DOUBLE the output power of a radio receiver.

Discussion

57.	If selectivity is poor then the receiver has poor _________(a) sensitivity(b) diverse reception(c) blocking(d) fidelityThe question was posed to me in my homework.The origin of the question is Noise in Phase Modulation topic in chapter Noise of Analog Communications
Answer» The correct option is (C) blocking The best EXPLANATION: By SELECTIVITY, RECEIVER responds only to the radio signals, it is TUNED to and reject the other signals. If a receiver has poor selectivity then obviously its blocking of unwanted signals is also poor.

Discussion

58.	In FM the carrier deviation is determined by ________(a) Frequency(b) Modulation(c) Amplitude(d) PhaseThis question was addressed to me during an interview for a job.This key question is from Noise in Phase Modulation in section Noise of Analog Communications
Answer» Right CHOICE is (b) Modulation For explanation I would SAY: In frequency modulated system, it is the modulation who is responsible for the deviation of the carrier WAVE.

Discussion

59.	In systems, pre-emphasis is used to amplify ________(a) high frequency(b) low frequency(c) phase(d) amplitudeI got this question in an online interview.I would like to ask this question from Noise in Phase Modulation in section Noise of Analog Communications
Answer» Correct answer is (a) high frequency Easiest 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. The MODULATING signal is passed through a simple network at the transmitter which amplifies the high frequency COMPONENTS.

Discussion

60.	________ modulator is an indirect way of generating FM.(a) Varactor FET(b) Reactance FET(c) Armstrong(d) Reactance bipolar transistorThe question was asked during an interview.This intriguing question comes from Comparison Between PM and AM in chapter Noise of Analog Communications
Answer» Correct choice is (c) Armstrong The explanation: FM can be GENERATED in TWO ways. One is direct and other is indirect way. In indirect way, there is an Armstrong METHOD which is used to GENERATE FM system, while other methods STATED in the options are direct ways.

Discussion

61.	Which of the following oscillator is not used in frequency modulation?(a) Colpitts Oscillator(b) Crystal Oscillator(c) Hartley Oscillator(d) Both Colpitts and Crystal OscillatorI got this question during a job interview.My question is from Comparison Between PM and AM topic in portion Noise of Analog Communications
Answer» Correct answer is (b) Crystal Oscillator The best I can explain: Crystal Oscillator uses the mechanical resonance of a vibrating crystal which is made up of piezoelectric material to create an signal with a PRECISE frequency. It is used to PRODUCE a SPECIFIC fixed frequency. It has no role in frequency modulated SYSTEMS.

Discussion

62.	In frequency modulation, noise gets decreased if we decrease deviation.(a) True(b) FalseThe question was posed to me by my college professor while I was bunking the class.I'd like to ask this question from Comparison Between PM and AM topic in chapter Noise of Analog Communications
Answer» The correct OPTION is (B) False Best explanation: In frequency modulation, noise is inversely PROPORTIONAL to the frequency deviation. Thus noise also starts decreasing if we INCREASE deviation.

Discussion

63.	Which device is most commonly used for detection in radio receiver?(a) Triode(b) Capacitor(c) Diode(d) TransistorI got this question in an online interview.Question is taken from Comparison Between PM and AM in chapter Noise of Analog Communications
Answer» The correct CHOICE is (c) DIODE To explain I would SAY: In radio RECEIVERS, diode is most preferably used for detection purposes.

Discussion

64.	Three point tracking is achieved by __________(a) Double conversion(b) Variable selectivity(c) Variable Sensitivity(d) Padder capacitorI got this question by my college director while I was bunking the class.The doubt is from Comparison Between PM and AM in division Noise of Analog Communications
Answer» Correct option is (d) Padder capacitor To EXPLAIN I would SAY: To achieve three point tracking a capacitor is connected in series with LOCAL oscillator coil. This capacitor is CALLED padder capacitor.

Discussion

65.	The household radio receiver uses __________ detector.(a) Synchronous(b) Coherent(c) Radio(d) EnvelopeI had been asked this question in an online interview.My question comes from Comparison Between PM and AM in section Noise of Analog Communications
Answer» RIGHT ANSWER is (d) Envelope The BEST I can EXPLAIN: Household receivers generally uses envelope detector.

Discussion

66.	High IF in superheterodyne receiver ____________(a) improves fidelity(b) improves selectivity(c) improves sensitivity(d) increases tracking problemsThe question was asked in class test.I want to ask this question from Comparison Between PM and AM in section Noise of Analog Communications
Answer» CORRECT choice is (d) increases tracking problems Explanation: In superheterodyne RECEIVER, most of the received signals gets AMPLIFIED from intermediate FREQUENCY (IF). HIGH intermediate frequency helps in tracking problems.

Discussion

67.	If the step size of a system is 0.0721, find its quantization power?(a) 3.25 x 10^-3(b) 4.33 x 10^-4(c) 4.33 x 10^-2(d) 3.25 x 10^-1This question was addressed to me in an online quiz.This intriguing question originated from Comparison Between PM and AM in division Noise of Analog Communications
Answer» The correct option is (b) 4.33 X 10^-4 Explanation: Quantization noise is a TYPE of quantization error generated by quantization due to ANALOG-to-digital conversion communication systems. It is an approximate error between the analog input voltage to the ADC and the output discritized value. Therefore, Quantisation power = ∆^2/12, where ∆=0.0721 = (0.0721^2)/12 = 4.33 X 10^-4.

Discussion

68.	Why frequency fogging is used in a carrier system?(a) to reduce noise(b) to reduce cross talk(c) to converge frequencies(d) to reduce distortionThe question was posed to me during an interview.I want to ask this question from Comparison Between FM and PM topic in division Noise of Analog Communications
Answer» CORRECT choice is (b) to REDUCE cross talk Easy explanation: The interchanging of the frequencies of carrier channels to accomplish specific purposes. It is USED to prevent feedback and oscillation. It is also used to reduce cross-talk and also to correct for a HIGH FREQUENCY response slope in the transmission line.

Discussion

69.	De-emphasis circuit is used ________(a) before detection(b) after detection(c) before encoding(d) after encodingI got this question in homework.Question is taken from Comparison Between FM and PM in division Noise of Analog Communications
Answer» The correct ANSWER is (b) after detection Best explanation: De-emphasis means attenuation of those frequencies by the amount by which they are BOOSTED. It is done at the receiver END i.e. it is USED after detection.

Discussion

70.	Find the step size of a signal with peak to peak amplitude of 8V and is quantized into 40 levels?(a) 0.8(b) 1(c) 0.2(d) 0.6I got this question during an interview.My question is based upon Comparison Between PM and AM in division Noise of Analog Communications
Answer» The correct choice is (c) 0.2 The BEST explanation: Step SIZE is the voltage DIFFERENCE between two consecutive digital LEVELS. QUANTIZATION step size is the smallest possible difference in amplitude. Step size,

Discussion

71.	Pre-emphasis is used to amplify _________ frequencies.(a) low(b) high(c) both low and high(d) local oscillatorThis question was posed to me in semester exam.This intriguing question comes from Comparison Between FM and PM in section Noise of Analog Communications
Answer» Right choice is (b) high Explanation: Pre-emphasis is used in FREQUENCY modulated transmitters to EQUALIZE the DRIVE power of transmitting signal in terms of deviation RATIO. It is done at the transmitter. It is used to amplify high FREQUENCIES.

Discussion

72.	Which of the following is not necessarily an advantage of FM over AM?(a) less modulating power is required(b) better noise immunity is provided(c) higher bandwidth is required(d) carrier is of any shapeThe question was asked in an online quiz.My question is from Comparison Between FM and PM in portion Noise of Analog Communications
Answer» Right choice is (c) higher BANDWIDTH is required The explanation: In frequency modulation, frequency of carrier gets varied with respect to the WAVE being propagated. FM has many advantages over AM but REQUIREMENT of higher bandwidth is not an efficient CONDITION.

Discussion

73.	What is number of possible outputs if there is 7 line digital input?(a) 64(b) 32(c) 16(d) 128The question was asked by my college director while I was bunking the class.Asked question is from Comparison Between FM and PM in chapter Noise of Analog Communications
Answer» RIGHT option is (d) 128 Explanation: TOTAL possible OUTPUTS will be 2^7 which is EQUAL to 128.

Discussion

74.	The frequency deviation is proportional to frequency in phase modulated signal.(a) True(b) FalseThe question was asked in a national level competition.I need to ask this question from Comparison Between FM and PM topic in portion Noise of Analog Communications
Answer» The correct choice is (b) False For explanation: In phase modulation, the phase of the carrier signal is VARIED with respect to the amplitude of the message signal. For a phase MODULATED signal, the FREQUENCY deviation is PROPORTIONAL to amplitude.

Discussion

75.	For a phase modulated signal, the frequency deviation is proportional to ________(a) frequency only(b) amplitude only(c) only width(d) phase onlyThis question was addressed to me in final exam.The origin of the question is Comparison Between FM and PM topic in portion Noise of Analog Communications
Answer» The CORRECT OPTION is (b) AMPLITUDE only Explanation: For a phase modulated system, it is amplitude which is directly proportional to the DEVIATION.

Discussion

76.	Which is the true statement about frequency deviation in frequency modulation?(a) frequency deviation is proportional to carrier signal frequency(b) frequency deviation is proportional to amplitude of carrier signal(c) frequency deviation is proportional to modulating frequency(d) frequency deviation is proportional to amplitude of modulating signalThe question was posed to me in examination.Origin of the question is Comparison Between FM and PM in chapter Noise of Analog Communications
Answer» Right CHOICE is (d) frequency deviation is proportional to AMPLITUDE of modulating SIGNAL The best I can explain: In frequency MODULATED system, the frequency deviation is proportional to the amplitude of the modulating signal.

Discussion

77.	What is the frequency of the stereo sub carrier signal in FM broadcasting?(a) 19 KHz(b) 45 KHz(c) 55 KHz(d) 38 KHzThis question was addressed to me in an interview for job.My enquiry is from Comparison Between FM and PM in chapter Noise of Analog Communications
Answer» Correct answer is (d) 38 KHz Explanation: Stereo broadcasting is made possible by using a SUBCARRIER on FM radio stations, which takes the left channel and “subtracts” the right channel from it. A subcarrier is basically a sideband of a radio frequency carrier WAVE, which is MODULATED to send additional INFORMATION. The frequency set for stereo sub carrier SIGNAL in FM broadcasting is 38 KHz.

Discussion

Explore topic-wise InterviewSolutions in .

Which system is free from noise?(a) FM(b) AM(c) PCM(d) PMThis question was posed to me during an online exam.Query is from Threshold Effect in FM topic in division Noise of Analog Communications

Which of the following receiver does not have an amplitude limiter stage?(a) AM(b) PM(c) FM(d) Both AM and FMThe question was posed to me in an online quiz.This interesting question is from Noise in Phase Modulation in division Noise of Analog Communications

Padder capacitor can be used to achieve three point tracking.(a) True(b) FalseThe question was asked in an internship interview.Enquiry is from Noise in Phase Modulation in section Noise of Analog Communications

If the output power of radio receiver is doubled then the volume is increased by _________(a) 3 dB(b) 2 dB(c) -3 dB(d) -2 dBThe question was asked in exam.My question comes from Noise in Phase Modulation in chapter Noise of Analog Communications

If selectivity is poor then the receiver has poor _________(a) sensitivity(b) diverse reception(c) blocking(d) fidelityThe question was posed to me in my homework.The origin of the question is Noise in Phase Modulation topic in chapter Noise of Analog Communications

In FM the carrier deviation is determined by ________(a) Frequency(b) Modulation(c) Amplitude(d) PhaseThis question was addressed to me during an interview for a job.This key question is from Noise in Phase Modulation in section Noise of Analog Communications

In systems, pre-emphasis is used to amplify ________(a) high frequency(b) low frequency(c) phase(d) amplitudeI got this question in an online interview.I would like to ask this question from Noise in Phase Modulation in section Noise of Analog Communications

________ modulator is an indirect way of generating FM.(a) Varactor FET(b) Reactance FET(c) Armstrong(d) Reactance bipolar transistorThe question was asked during an interview.This intriguing question comes from Comparison Between PM and AM in chapter Noise of Analog Communications

In frequency modulation, noise gets decreased if we decrease deviation.(a) True(b) FalseThe question was posed to me by my college professor while I was bunking the class.I'd like to ask this question from Comparison Between PM and AM topic in chapter Noise of Analog Communications

Which device is most commonly used for detection in radio receiver?(a) Triode(b) Capacitor(c) Diode(d) TransistorI got this question in an online interview.Question is taken from Comparison Between PM and AM in chapter Noise of Analog Communications

Three point tracking is achieved by __________(a) Double conversion(b) Variable selectivity(c) Variable Sensitivity(d) Padder capacitorI got this question by my college director while I was bunking the class.The doubt is from Comparison Between PM and AM in division Noise of Analog Communications

The household radio receiver uses __________ detector.(a) Synchronous(b) Coherent(c) Radio(d) EnvelopeI had been asked this question in an online interview.My question comes from Comparison Between PM and AM in section Noise of Analog Communications

High IF in superheterodyne receiver ____________(a) improves fidelity(b) improves selectivity(c) improves sensitivity(d) increases tracking problemsThe question was asked in class test.I want to ask this question from Comparison Between PM and AM in section Noise of Analog Communications

If the step size of a system is 0.0721, find its quantization power?(a) 3.25 x 10^-3(b) 4.33 x 10^-4(c) 4.33 x 10^-2(d) 3.25 x 10^-1This question was addressed to me in an online quiz.This intriguing question originated from Comparison Between PM and AM in division Noise of Analog Communications

De-emphasis circuit is used ________(a) before detection(b) after detection(c) before encoding(d) after encodingI got this question in homework.Question is taken from Comparison Between FM and PM in division Noise of Analog Communications

Find the step size of a signal with peak to peak amplitude of 8V and is quantized into 40 levels?(a) 0.8(b) 1(c) 0.2(d) 0.6I got this question during an interview.My question is based upon Comparison Between PM and AM in division Noise of Analog Communications

Pre-emphasis is used to amplify _________ frequencies.(a) low(b) high(c) both low and high(d) local oscillatorThis question was posed to me in semester exam.This intriguing question comes from Comparison Between FM and PM in section Noise of Analog Communications

What is number of possible outputs if there is 7 line digital input?(a) 64(b) 32(c) 16(d) 128The question was asked by my college director while I was bunking the class.Asked question is from Comparison Between FM and PM in chapter Noise of Analog Communications

The frequency deviation is proportional to frequency in phase modulated signal.(a) True(b) FalseThe question was asked in a national level competition.I need to ask this question from Comparison Between FM and PM topic in portion Noise of Analog Communications

For a phase modulated signal, the frequency deviation is proportional to ________(a) frequency only(b) amplitude only(c) only width(d) phase onlyThis question was addressed to me in final exam.The origin of the question is Comparison Between FM and PM topic in portion Noise of Analog Communications

What is the frequency of the stereo sub carrier signal in FM broadcasting?(a) 19 KHz(b) 45 KHz(c) 55 KHz(d) 38 KHzThis question was addressed to me in an interview for job.My enquiry is from Comparison Between FM and PM in chapter Noise of Analog Communications