Latest Analog Communications MCQs – SSB Modulation ( Analog Communications ) MCQs
Latest Analog Communications MCQs
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Analog Communications MCQs – SSB Modulation ( Analog Communications ) MCQs
The most occurred mcqs of SSB Modulation ( ) in past papers. Past papers of SSB Modulation ( Analog Communications ) Mcqs. Past papers of SSB Modulation ( Analog Communications ) Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related SSB Modulation ( Analog Communications ) Mcqs. The Important series of SSB Modulation ( Analog Communications ) Mcqs are given below:
Filter Method
1. In pulse code modulation bandwidth required is low.
a) True
b) False
Answer: b
Explanation: PCM stands for pulse code modulation. In PCM, the amplitude of the analog signal is discritised and converted into digital form for transmission of binary data. PCM usually requires a large bandwidth.
2. How do we eliminate the ghosts in the picture?
a) by using a long transmission line
b) by using a booster
c) by changing the orientation of antenna
d) by twisting the transmission line
Answer: c
Explanation: Change in antenna orientation helps in improving the reception of signals which further removes ghosts in the picture.
3. For getting maximum undistorted transmitted power in a carrier wave, the value of modulation should be _________
a) 1
b) 0.5
c) 0.2
d) 0.8
Answer: a
Explanation: The possible maximum value of modulation can be one. It signifies 100% modulation and thus at this value we have maximum undistorted transmitted power.
4. To avoid fading in communication, broad band antenna is used.
a) True
b) False
Answer: b
Explanation: It is generally observed that a ship to ship communication suffers from fading. This problem can be avoided by using frequency diversity in which the components of a radio wave are received from different channels thus reducing the error that occurs in the transmission of a single frequency component.
5. What is the commercial channel bandwidth in a frequency modulated system?
a) 150 KHz
b) 250 KHz
c) 500 KHz
d) 900 KHz
Answer: a
Explanation: Bandwidth is the band of frequencies present within a given range of frequency. The standard commercial channel bandwidth for frequency modulated system is about 150 KHz.
6. A buffer amplifier is a ________
a) double tuned amplifier
b) tuned amplifier
c) high gain DC amplifier
d) low gain DC amplifier
Answer: c
Explanation: Gain of an amplifier is its ability to increase the voltage at the input and produce the result at the output. A buffer amplifier is basically a high gain DC amplifier. It is basically used for transferring voltage from a high output impedance level to a low input impedance level circuit.
7. The direction of rotation of a CD is clockwise.
a) True
b) False
Answer: b
Explanation: CD stands for compact disk. The direction of rotation of Compact Disk is anticlockwise.
8. What is the full form of PAM?
a) Pulse Analog Modulation
b) Phase Analog Modulation
c) Pulse Amplitude Modulation
d) Phase Amplitude Modulation
Answer: c
Explanation: In communication, PAM stands for Pulse Amplitude Modulation. In PAM, the amplitude of the individual pulses of the message signal are varied in a specific time interval.
9. In a TV receiver antenna the length of reflector rod is _________
a) same as that of dipole
b) less than that of dipole
c) more than that of dipole
d) is half of that of dipole
Answer: c
Explanation: A dipole antenna is the one having its conductive wire rod equal to half the maximum wavelength of an antenna. The length of receiving antenna in a TV receiver must be more than that of dipole to get a better reception of signals.
Advantages of Filter Method
1. Which of the following does not cause losses in optical fibre cables?
a) Stepped index operation
b) Scattering
c) Microbending
d) Light absorption
Answer: a
Explanation: In Stepped index operation, refractive index within the core is uniform. There is also a sharp decrease in refractive index at the core-cladding interface. It generally does not cause any type os losses in optical fibre cables.
2. In televisions, equalizing pulses are sent during __________
a) horizontal blanking
b) vertical blanking
c) serrations
d) horizontal retrace
Answer: a
Explanation: The duration of an equalizing pulse is approximately 2.5 microseconds. The repetition frequency of equalizing pulses is twice the line frequency. It is necessary to sent equalizing pulses during horizontal blanking in televisions.
3. It is generally observed that a ship to ship communication suffers from fading. This problem can be avoided by using ________
a) space diversity
b) frequency diversity
c) directional antenna
d) filter
Answer: b
Explanation: It is generally observed that a ship to ship communication suffers from fading. This problem can be avoided by using frequency diversity in which the components of a radio wave are received from different channels thus reducing the error that occurs in the transmission of a single frequency component.
4. What is the characteristic impedance of a twin wire feeder used in television?
a) 1000 ohm
b) 100 ohm
c) 10 ohm
d) 300 ohm
Answer: d
Explanation: Twin wire feeder consists of two wires with spacers. For a twin wire feeder the characteristic impedance should be close to 300 ohm.
5. A buffer amplifier is a cathode follower double tuned amplifier.
a) True
b) False
Answer: b
Explanation: Gain of an amplifier is it’s ability to increase the voltage at the input and produce the result at the output. A buffer amplifier is basically a high gain DC amplifier. It is basically used for transferring voltage from a high output impedance level to a low input impedance level circuit.
6. What is the direction of rotation of a CD?
a) anticlockwise
b) clockwise
c) either clockwise or anticlockwise depend on data stored
d) first anticlockwise and then clockwise
Answer: a
Explanation: CD stands for compact disk. The direction of rotation of Compact Disk is anticlockwise.
7. According to Fourier Analysis a square wave can be represented as a fundamental sine wave and even harmonics.
a) True
b) False
Answer: b
Explanation: A square wave is a periodic non-sinusoidal waveform with an uniform frequency, in which the amplitude alternates between a fixed maximum and minimum value. According to Fourier analysis, a square wave can be represented as an infinite sum of sinusoidal waves. A square wave consists of only components of odd integer harmonics.
8. Filter method is the one and only method to produce SSB.
a) True
b) False
Answer: b
Explanation: SSB can be produced by filter method also known as frequency discrimination method. It can also be produced by phase discrimination method.
9. Impulse noise can be reduced in _________
a) FM
b) AM
c) QAM
d) PM
Answer: a
Explanation: Impulse noise includes unwanted, almost instantaneous sharp sounds. It is only in frequency modulated circuits that allow reduction in impulse noise.
Disadvantages of Filter Method
1. Why sampling is used in communication?
a) for getting higher speed of communication
b) for getting higher efficiency
c) cheaper equipment is required
d) for a better transmission
Answer: a
Explanation: Sampling is the conversion of continuous-time signal to discrete-time signal. It samples a continuous time signal depending on a specific range and thus produces the discrete form of the signal. It is highly used in communication for getting higher speed of communication.
2. Which two noises are present in Delta Modulation (DM)?
a) Slope overload and Thermal noise
b) Granular and shot noise
c) Slope overload and granular noise
d) Thermal and shot noise
Answer: c
Explanation: Delta modulation is used for transmission of voice information where quality is not the primarily importance. Its drawback is it has two noises namely slope overload and granular noise. Slope overload noise occurs when the input signal slope is higher than the delta modulator’s capability. Granular noise is produced due to level input signal resulting into the oscillatory output. So for getting rid of these noises we use ADM (Adaptive Delta Modulation).
3. Varacter is used for generation of ________
a) PM signals only
b) FM signals only
c) AM signals only
d) DSB-SC signals
Answer: b
Explanation: Varacter diode or tuning diode that has a variable capacitance. It is operated as reverse-biased and therefore no current flows. It is mainly used for generation of FM signals only.
4. What will happen in amplitude modulation, if the modulation index is more than 1?
a) bandwidth will increase
b) bandwidth will decrease
c) amplitude becomes constant
d) waves will get distorted
Answer: d
Explanation: Modulation index tells us the amount by which the carrier wave is varied with respect to the message signal. If modulation index is greater than 1, then the wave gets distorted and overlap, thus causing overmodulation.
5. The adverse effect of noise in communication system can be seen in ________
a) receiver
b) transmitter
c) source
d) channel
Answer: d
Explanation: Noise is the unwanted signal present in the passband of a signal. It is very much unpleasant thus causing disturbance. Its adverse effect is highly seen on channel.
6. Which among the following is not an advantage of FM over AM?
a) modulating power required is less
b) low bandwidth is required
c) better noise immunity
d) better signal to noise ratio
Answer: b
Explanation: Advantages of FM over AM are less prone to noise, low modulating power required and such like. However, disadvantage of FM is that large bandwidth is required.
7. Which of the following is the advantage of base modulation over collector modulation of a class C amplifier?
a) lower modulation power is required
b) higher power output per transistor
c) better efficiency
d) better linearity of modulation
Answer: a
Explanation: Base modulation is preferred over collector modulation of a class C transistor because low modulating power is required and collector saturation prevents complete modulation of a signal. Generally, Collector modulation has more advantages over Base modulation like high linearity, better collector efficiency and such like.
8. What is the radio frequency range of a frequency modulated signal?
a) 20-80 MHz
b) 100-200 MHz
c) 200-350 MHz
d) 99-108 MHz
Answer: d
Explanation: The standard frequency range of a frequency modulated signal is between 90-105 MHz.
9. Vestigial side band (VSB) is most commonly used in ________
a) Television Transmission
b) Radios
c) Telephony
d) Laser Transmission
Answer: a
Explanation: Vestigial Sideband Modulation (VSB) is a type of amplitude modulation in which the carrier and only one sideband is completely transmitted and the other sideband is partly transmitted. Thus, television production is done using VSB modulation.
Phase Shift Method
1. Which of the following is an indirect way of generating frequency modulated signals?
a) Armstrong modulator
b) Varacter diode modulator
c) Reactance FET modulator
d) Reactance modulator
Answer: a
Explanation: Varacter diode modulator is not an indirect way of generating FM. Instead it’s a direct way of producing FM with the help of voltage controlled oscillator mechanism. It is Armstrong modulator which is an indirect way of generating FM.
2. Which of the following determines carrier deviation in frequency modulation?
a) modulating voltage
b) modulating frequency
c) frequency deviation
d) modulating phase
Answer: a
Explanation: In frequency modulation, frequency of carrier varies with the modulating voltage. In frequency modulation, it is modulating voltage that is responsible for deviation of the carrier.
3. Balance modulator is used to produce __________
a) DSB
b) VSB
c) AM
d) SSB
Answer: a
Explanation: A balance modulator mixes audio signal and radio frequency carrier wave, thereby producing a DSBSC wave, by suppressing the carrier. In DSB_SC, only the two sidebands are present. Thus, it has less power consumption.
4. Full AM signal is preferred over SSB in broadcasting purpose because ________
a) generation of full AM is easier
b) detection of full AM is simpler
c) requires large bandwidth
d) for both detection and generation of full AM
Answer: b
Explanation: SSB is preferred because of its low bandwidth and lesser power consumption. It reduces its bandwidth by suppressing the carrier and removing one of the two sidebands since both sidebands are exactly same. But full amplitude modulation is sometimes preferred over it because in its detection of full AM is simpler due to it’s simpler demodulation circuit.
5. Which among the following is not necessarily the advantage of SSB over AM?
a) required bandwidth for SSB is low
b) less power handled
c) complex circuit
d) simple circuit
Answer: d
Explanation: SSB is preferred because of its low bandwidth and lesser power consumption. It reduces its bandwidth by suppressing the carrier and removing one of the two sidebands since both sidebands are exactly same. But full amplitude modulation is sometimes preferred over it because in it detection of full AM is simpler due to it’s simpler demodulation circuit. SSBSC has a complex circuit anyway.
6. Which filter is used to get back the original signal from sampled signal?
a) low pass filter
b) high pass filter
c) band pass filter
d) band reject filter
Answer: a
Explanation: Sampling is the conversion of continuous-time signal to discrete-time signal by sampling the continuous signal with respect to specific time intervals, thereby discritising it. Now to get back the original signal we have to use low pass filter, which attenuates high frequencies and allows only low frequencies to pass.
7. Carson’s rule is used to ________
a) calculate Bandwidth of FM signal
b) calculate SNR of FM signal
c) determine the carrier frequency
d) calculate Figure of merit of FM signal
Answer: a
Explanation: According to Carson’s rule, the required bandwidth is twice the sum of the maximum frequency deviation and the maximum modulating signal frequency or B = 2(fd + fm)Hz.
8. FM signals can be generated by using ________
a) Varacter diode
b) Laser diode
c) Backward diode
d) Gunn diode
Answer: a
Explanation: Varactor diode is a diode working in the reverse-bias because of which no current flows through it. It has variable capacitance which varies with applied voltage. Varactor diodes are mainly used in generation of FM signals using Voltage Controlled Oscillator.
9. Granular noise occurs in Delta Modulation, when ____________
a) pulse rate decreases
b) pulse amplitude decreases
c) modulating signal increases
d) modulating signal remains constant
Answer: d
Explanation: Delta modulation is used for transmission of voice information where quality is not the primarily importance. Its drawback is it has two noises namely slope overload and granular noise. Granular noise is produced due to constant modulating input signal resulting into oscillatory output. So for getting rid from these noises we use ADM (Adaptive Delta Modulation).
10. DM stands for ________
a) Density Modulation
b) Delta Modulation
c) Double Side Band Modulation
d) Direct Modulation
Answer: b
Explanation: DM stands for Delta Modulation. Delta modulation is used for transmission of voice information where quality is not the primarily importance.
Generation of VSB
1. Which of the following oscillator is not found in FM?
a) Hartley Oscillator
b) Crystal Oscillator
c) Armstrong Oscillator
d) Dynatron Oscillator
Answer: b
Explanation: In frequency modulation, frequency of the carrier wave is varied with the instantaneous amplitude of message signal. Crystal oscillator is used to generate a carrier signal with a precise or fixed frequency. But it has no use in frequency modulation.
2. What is the approximated range of audio frequencies?
a) 20Hz to 20KHz
b) 20Hz to 200KHz
c) 10Hz to 10KHz
d) 20Hz to 20MHz
Answer: a
Explanation: The standard fixed range of audio frequencies is from 20HZ to 20 KHz.
3. What is duty cycle?
a) ratio of time on to time off
b) ratio of time off to time on
c) 1⁄2 × (ratio of time on to time off)
d) 1⁄2 × (ratio of time off to time on)
Answer: a
Explanation: Duty cycle is the fraction of time in which the system is active. It can also be defined as the ratio of time on to time off of a system. At times, duty cycle, expressed as percentage, is the ratio of time on to sum of time on and time off.
4. Which of the following is used for demodulation of PAM signal?
a) a band reject filter
b) a band pass filter
c) a low pass filter
d) a high pass filter
Answer: c
Explanation: Pulse Amplitude Modulation is the transmission of data by varying the amplitude of different pulses. A low pass filter is always used to demodulate a PAM as it attenuates high frequencies and allows only low frequencies to pass.
5. Which of the following is not a part of analogue communication?
a) PPM
b) AM
c) PCM
d) PWM
Answer: c
Explanation: Pulse code modulation (PCM) is a digital form of communication. It has no relation with analog communication. Pulse Code Modulation is a technique in which the amplitude of an analogue signal is converted to a binary value represented as a series of pulses.
6. For demodulation of PCM, it is first converted into ________
a) PAM
b) PWM
c) PPM
d) FM
Answer: a
Explanation: Pulse Code Modulation deals with converting an analog signal to a digital signal. During it’s demodulation, the wave to be treated is to be parallel. The series pulse wave signal is then converted into a parallel digital signal using a serial to parallel converter, after which it is further converted into the original analog signal with the help of a decoder or detector.
7. Inherently most noise resistant modulating system is _________
a) PCM
b) DSB
c) SSB
d) VSB
Answer: a
Explanation: In PCM, the amplitude of the analog signal is discritised and converted into digital form for transmission of binary data. PCM is least prone to noise and can travel long distances.
8. Which of the following modulation is used for radio navigation?
a) Pulse Modulation
b) Amplitude Modulation
c) Phase Modulation
d) Frequency Modulation
Answer: a
Explanation: In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. It is mostly used for radio navigation and for many others.
9. Frequency modulated broadcast band generally lies in ________
a) VHF
b) HF
c) SHF
d) LF
Answer: a
Explanation: VHF (very high frequency) is the ITU designation for the range of radio frequency from 30MHz to 300MHz. Frequency modulated broadcast band generally lies in it only. HF ranges from 3MHz to 30MHz while SHF ranges from 3GHz to 30GHz. And LF ranges from 30KHz to 300KHz.
Applications of VSB
1. Frequency Modulated system needs less bandwidth.
a) True
b) False
Answer: b
Explanation: In frequency modulation, frequency of the carrier wave is varied with the instantaneous amplitude of the message signal. Thus, it requires large bandwidth.
2. When bandwidth is the major consideration a narrow and wide band FM can be approximated to?
a) DSB-SC
b) SSB
c) VSB
d) AM
Answer: d
Explanation: For narrow and wide bands frequency modulation, modulation index is respectively smaller and greater than 1. When bandwidth is considered it can be approximated to AM.
3. Which modulation is used in microwave band?
a) Amplitude Modulation
b) Pulse Modulation
c) Frequency Modulation
d) Phase Modulation
Answer: b
Explanation: In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. It is mostly used for radio navigation, microwave band and for many others.
4. All the output pulses are at full transmitter power for a strong signal in all of the following except ________
a) PAM
b) PFM
c) PCM
d) PWM
Answer: a
Explanation: In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. Pulse amplitude modulation varies amplitude of pulses for transmission of data. Its’ output pulses are not at full transmitter power for a strong signal and thus it is an exception.
5. In pulse transmitter, the ratio of time on to time off is called ________
a) base
b) bandwidth
c) duty cycle
d) efficiency
Answer: c
Explanation: Duty cycle is the fraction of time in which the system is active. It can also be defined as the ratio of time on to time off of a system. At times, duty cycle, expressed as a percentage, is the ratio of time on to sum of time on and time off.
6. In which of the following modulated systems, quantization noise occurs?
a) TDM
b) FM
c) PWD
d) PCM
Answer: d
Explanation: The difference between an input value and its quantized value is called quantization error or we can also see it as that when an analog number is not converted into an exact digital number. It takes place in pulse code modulation (PCM). Pulse Code Modulation is a technique in which the amplitude of an analogue signal is converted to a binary value represented as a series of pulses.
7. Signal to quantization noise ratio in PCM system depends on _________
a) sampling rate
b) signal bandwidth
c) number of quantization levels
d) nature of carrier wave
Answer: c
Explanation: Pulse code modulation (PCM) is a digital form of communication. For demodulation of PCM, it is necessary to convert it into PAM. Quantization noise occurs in PCM only. Signal to quantization noise ratio depends on the number of quantization levels.
8. Pulse Modulation can be used in automatic landing equipments.
a) True
b) False
Answer: a
Explanation: In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. It is mostly used for radio navigation, microwave band and for many others.
9. Which of the following modulation is used in data communication?
a) Pulse Modulation
b) Amplitude Modulation
c) Phase Modulation
d) Frequency Modulation
Answer: a
Explanation: In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. It is mostly used for radio navigation, microwave band and for many others. It is also highly used in data communication.
Comparison of SSB Suppression Techniques
1. What is the expected modulation index in case of wide band FM?
a) less than 1
b) 1
c) 1⁄2
d) more than 1
Answer: d
Explanation: For producing Narrow band frequency modulated wave, modulation index should be less than or equal to1. For wideband frequency modulated wave, modulation index should be greater than 1.
2. What is the expected modulation index in case of narrow band FM?
a) less than or equal to 1
b) infinite
c) 1.5
d) more than 1
Answer: a
Explanation: For producing Narrow band frequency modulated wave, modulation index should be less than or equal to1. For wideband frequency modulated wave, modulation index should be greater than 1.
3. Which of the following statement is true about pulse position modulation system?
a) pulses have constant width but varying amplitude
b) pulses have constant amplitudes and constant widths
c) pulses have constant amplitude but varying widths
d) pulses have varying width and varying amplitude
Answer: b
Explanation: Pulse Position Modulation (PPM) is a type of modulation process in which position of the pulse of the carrier wave is varied with respect to the instantaneous position values of the message signal. In pulse modulation, pulses have constant amplitude and widths.
4. IF stage is a receiver employs ________
a) impedance coupling
b) capacitive coupling
c) single tuned transformer coupling
d) double tuned transformer coupling
Answer: d
Explanation: A frequency to which a carrier wave is shifted as an intermediate step is known as Intermediate Frequency. It employs double tuned transformer coupling.
5. In higher power AM transmission, modulation is done at _________
a) Source stage
b) Transducer Stage
c) Oscillator stage
d) RF power stage
Answer: d
Explanation: RF power amplifier converts a low power radio frequency signal to high power. Modulation is done at RF power stage for high power AM transmission.
6. If modulation index of an AM was in changed from 0 to 1, then transmitted power ________
a) increases by 100%
b) increases by 50%
c) increases by 75%
d) increases by 25%
Answer: b
Explanation: Modulation index indicates amount of modulation in the carrier signal. If modulation index changes to 1 from 0, its transmitted power increases by 50%.
7. In PCM system, output S/N increases ________
a) parabolically with bandwidth
b) exponentially with bandwidth
c) inversely with bandwidth
d) linearly with bandwidth
Answer: b
Explanation: Pulse code modulation (PCM) is a digital form of communication. Pulse Code Modulation is a technique in which the amplitude of an analogue signal is converted to a binary value represented as a series of pulses. if we calculate the ratio of signal to noise ratio for different bandwidth then we observe that it increases exponentially with it.
8. Companding is used in PCM transmitters to overcome quantizing noise in PCM.
a) True
b) False
Answer: b
Explanation: Companding is the process through which the signal to noise ratio of a wave is reduced by compressing and expanding the signal. It decreases the number of bits required to record the strongest signal. Companding also improves signal to noise ratio.