Up To Date SSB Modulation ( Analog Communications ) MCQs – 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:
Single Side Band Transmission
1. What do you understand by the term SSB?
a) Suppressed Side Band
b) Single Side Band
c) Suppressed Single Band
d) Selected Single Band
Answer: b
Explanation: SSB stands for Single Side band. In SSB-SC (Single Side Band Suppressed Carrier), the carrier is suppressed and only either of the two sidebands is transmitted. This reduces power consumption and also lessens the bandwidth.
2. SSB is a standard form for radio communication.
a) True
b) False
Answer: a
Explanation: SSB stands for Single Side band. In SSB-SC (Single Side Band Suppressed Carrier), the carrier is suppressed and only either of the two sidebands is transmitted. Single Side Band can also be seen as a standard form for radio communication. In Single Side Band, carrier wave is suppressed by about 50dB.
3. Ribbon microphone has a bidirectional feature.
a) True
b) False
Answer: a
Explanation: It is correct statement that a ribbon microphone has bidirectional feature. Other microphones such as carbon, condenser etc does not have a bidirectional feature.
4. Antenna can only be used as a transmitter.
a) True
b) False
Answer: b
Explanation: All antennas can be used as transmitter and receiver both. Antenna transmits or receives electromagnetic waves only. Transmitter antenna modulates the message signals and transmits the modulated waves and Receiver antenna receives the modulated wave and demodulates it.
5. TM is a pseudo analog modulation.
a) True
b) False
Answer: a
Explanation: TM stands for Transpositional Modulation. In TM, the message signal is modulated by inserting inflections in the original waveform. The waveform is modified resulting in a modulated. TM is a pseudo analog modulation. In TM carrier also carries a phase variable.
6. What is the full form of PPM?
a) pulse-position modulation
b) position-pulse modulation
c) pulse-pulse modulation
d) position-position modulation
Answer: a
Explanation: PPM is used for both analog and digital signals. In PPM, when a single pulse is transmitted in the allotted time shift, the message bits get encoded. It is mostly used for optical communication such as optic fiber.
7. CVSDM stands for continuously variable slope delta modulation.
a) True
b) False
Answer: a
Explanation: CVSDM stands for continuously variable slope delta modulation. It can also be seen as delta modulation having variable step size. Delta modulation involves analog to digital conversion and vice-versa for the transmission of voice signals.
8. If the target is changing continuously, then the best scanning system for correct tracking is _________
a) monopulse
b) conical
c) lobe switching
d) sequential
Answer: a
Explanation: If the targeting area is changing continuously then it is better to use monopulse scanning system for accurate tracking as it avoids the problems in conical scanning systems, which often arise due to rapid change in signal strength.
9. In NBFM, the modulation index is close to __________
a) 1
b) greater than 1
c) 10
d) infinite
Answer: a
Explanation: In NBFM, the modulation index is less than or close to unity. It is similar to Amplitude modulation except a 180 degree phase shift at the lower sideband.
10. NBFM stands for Narrow Band Frequency Modulation.
a) True
b) False
Answer: a
Explanation: It is a correct statement that NBFM stands for Narrow Band Frequency Modulation. In NBFM, the modulation index is less than or close to unity. It is similar to Amplitude modulation except a 180 degree phase shift at the lower sideband.
Representation of SSB-SC in Time & Frequency Domain
1. Which device is has more chance to be found in SSB transmitter?
a) balanced modulator
b) class A RF amplifier
c) class C audio amplifier
d) class B RF amplifier
Answer: a
Explanation: In SSB-SC transmitter, a balanced modulator is more likely to be found in order to suppress the carrier, after which the result is passed through a band-pass filter in order to transmit the selected sideband.
2. The RF section of radio consists both oscillator and buffer stage.
a) True
b) False
Answer: a
Explanation: RF is an electromagnetic wave frequencies in the range 3 KHz to 300 GHz. RF section of radio consists of oscillator so as to provide the necessary frequency for mixing and it consists of a buffer stage for preventing the damage of signal source.
3. What is the frequency of audio modulation?
a) 10 Hz
b) 20 KHz
c) 30 KHz
d) 40 KHz
Answer: b
Explanation: Audio spectrum ranges from 20Hz to 20KHz and the frequency band for audio modulation ranges from 88MHz to 108 MHZ.
4. In telegraphy we generally use __________
a) Amplitude modulation
b) Frequency modulation
c) Frequency Shift Keying
d) Pulse Code modulation
Answer: c
Explanation: FSK (Frequency Shift Keying) is a method used to transmit binary data in form of digital signals. It is mainly used for telegraphy. In telegraphy, a modem is used to convert binary data to FSK and vice-versa, for the communication between computers and over telephone lines.
5. In FM both the frequency and amplitude of carrier signal is varied in accordance with the instantaneous value of modulating signal.
a) True
b) False
Answer: b
Explanation: In FM, the frequency of the carrier wave is varied with respect to the instantaneous amplitude of the message signal. The general expression for FM is as follows:
FM (t) = Ac sin (2πfct + βsin(2πfmt)), where symbols have their usual meaning.
6. In the equation, 20cos(108 t + 3 sin109 t) the modulation index is ________
a) 1
b) 2
c) 3
d) 4
Answer: c
Explanation: The general expression for FM is as follows:
FM (t) = Ac sin (2πfct + βsin(2πfmt)), where β is the modulation index.
Thus β = 3.
7. Antenna can also be used as a receiver.
a) True
b) False
Answer: a
Explanation: All antennas can be used as transmitter and receiver both. Antenna transmits or receives electromagnetic waves only. Transmitter antenna modulates the message signals and transmits the modulated waves and Receiver antenna receives the modulated wave and demodulates it.
8. What is the advantage of IF modulation?
a) it uses SSB which further reduces its bandwidth
b) modular section and visual exciter can be of any state
c) it cannot be tuned
d) modular section and visual exciter can be solid state devices
Answer: d
Explanation: Advantages of IF modulation is that the modular section and visual exciter can be solid state devices. Its other advantages are it can use VSB filter that can be introduced at low power level. Moreover it is economical.
9. We can use either cone type or horn type loudspeakers in tape recorders.
a) True
b) False
Answer: b
Explanation: In tape recorders, only cone type loudspeakers can be used. It does not work well with horn type loudspeakers.
Method of Generation of SSB-SC
1. A duplex arrangement use separate frequencies for transmission.
a) True
b) False
Answer: a
Explanation: In duplex communication, two-way interaction is favourable simultaneously. Thus, a cordless telephone is duplex which uses separate frequencies for transmission in base and portable units.
2. VSB modulation is used in televisions because it avoids phase distortion at low frequencies.
a) True
b) False
Answer: b
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 as it reduces bandwidth to half.
3. A cordless telephone that uses separate frequencies for transmission in base and portable units is called _________
a) half duplex
b) duplex
c) simplex
d) one-way communication
Answer: b
Explanation: In duplex communication, two-way interaction is favourable simultaneously. Thus, a cordless telephone is duplex which uses separate frequencies for transmission in base and portable units.
4. Which polarization is used to reduce the depolarization effect on received waves?
a) Circular polarization
b) Linear polarization
c) Atomic polarization
d) Dipolar polarization
Answer: a
Explanation: In circular polarization at each point the electric field of electromagnetic wave has a constant magnitude but its direction changes as it rotates with time at a steady rate, in a plane perpendicular to the direction of propagation of wave. It is used to reduce depolarization effect on received waves.
5. Circular polarization involves critical alignment between transmitting and receiving antenna.
a) True
b) False
Answer: b
Explanation: In circular polarization at each point the electric field of the electromagnetic wave has a constant magnitude but its direction changes as it rotates with time at a steady rate, in a plane perpendicular to the direction of propagation of the wave. It is used to reduce depolarization effect on received waves. It does not involve alignment between transmitting and receiving antenna.
6. It is only the reflected color that decided the color of an object.
a) True
b) False
Answer: b
Explanation: Color of any object is decided by the reflected color for opaque object and wavelength transmitted through it for transparent object, while both reflector color and wavelength transmitted are considered for a translucent object.
7. What do you understand by the term “carrier” in modulation?
a) voltage to be transmitted
b) resultant wave
c) voltage for which amplitude, phase or frequency can be varied
d) voltage for which amplitude, phase or frequency remains constant
Answer: c
Explanation: Carrier wave is the wave with frequency higher than the message signal, whose certain characteristics like amplitude, phase or frequency are varied with respect to the instantaneous amplitude of the message signal. Thus forming the modulated wave which is the wave to be transmitted.
8. Carrier wave in modulation is a resultant wave.
a) True
b) False
Answer: b
Explanation: Carrier wave is the wave with frequency higher than the message signal, whose certain characteristics like amplitude, phase or frequency are varied with respect to the instantaneous amplitude of the message signal. Thus forming the modulated wave which is the wave to be transmitted.
9. For a low level AM system, amplifier modulated stage must have _________
a) harmonic devices
b) linear devices
c) non-linear devices
d) class A amplifiers
Answer: b
Explanation: In low-level modulation, the generation of amplitude modulated signal takes place at low power levels. The generated AM signal is then amplified using a chain of linear amplifiers, which are required to avoid waveform distortion. Thus, linear devices are used in low level amplitude modulated system.
Demodulation of SSB-SC
1. The disadvantage of FM over AM is that high output power is needed.
a) True
b) False
Answer: b
Explanation: The disadvantage of FM over AM is that in frequency modulation large bandwidth is required. While, in case of advantages, FM is less prone to noise interference and has lower power consumption compared to AM.
2. Which theorem states that a noiseless Gaussian channel has zero capacity?
a) Beckman-Quarles theorem
b) Bell’s theorem
c) Cameron-Martin theorem
d) Shannon-Hartley theorem
Answer: d
Explanation: According to Shannon Hartley theorem, a noiseless channel has infinite capacity.
3. Linear devices are used in __________
a) high level AM modulator
b) low level AM modulator
c) high level FM modulator
d) low level FM modulator
Answer: b
Explanation: In low-level modulation, the generation of amplitude modulated signal takes place at low power levels. The generated AM signal is then amplified using a chain of linear amplifiers, which are required to avoid waveform distortion. Thus, linear devices are used in low level amplitude modulated system.
4. A noiseless Gaussian channel has _____________
a) zero capacity
b) infinite capacity
c) small capacity
d) finite large capacity
Answer: b
Explanation: According to Shannon Hartley theorem, a noiseless channel has infinite capacity.
5. Advantage of high level modulator is that it requires linear amplifiers.
a) True
b) False
Answer: b
Explanation: In high-level modulation, the generation of amplitude modulated signal takes place at high power levels. It has the advantage that linear amplifiers are not required.
6. Carrier wave in modulation is a wave that is to be transmitted.
a) True
b) False
Answer: b
Explanation: Carrier wave is the wave with frequency higher than the message signal, whose certain characteristics like amplitude, phase or frequency are varied with respect to the instantaneous amplitude of the message signal. Thus forming the modulated wave which is the wave to be transmitted.
7. It is only the wavelength that decides the color of an object.
a) True
b) False
Answer: b
Explanation: Color of any object is decided by the reflected color for opaque object and wavelength transmitted through it for transparent object, while both reflector color and wavelength transmitted are considered for a translucent object.
8. Circular polarization is used in discrimination between reception of adjacent beams.
a) True
b) False
Answer: b
Explanation: In circular polarization at each point the electric field of the electromagnetic wave has a constant magnitude but its direction changes as it rotates with time at a steady rate, in a plane perpendicular to the direction of propagation of wave. It is used to reduce depolarization effect on received waves and not for discrimination between reception of beams.
9. VSB modulation is used in televisions because it results in better reception.
a) True
b) False
Answer: b
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 as it reduces bandwidth to half.
10. A cordless telephone that uses separate frequencies for transmission is known as half duplex.
a) True
b) False
Answer: b
Explanation: In duplex communication, two-way interaction is favourable simultaneously. Thus, a cordless telephone is duplex which uses separate frequencies for transmission in base and portable units.
Demodulation of SSB with Large Carrier
1. What is the main disadvantage of FM over AM?
a) high modulating power is needed
b) noise is very high for high frequencies
c) high output power is required
d) large bandwidth is required
Answer: d
Explanation: The disadvantage of FM over AM is that in frequency modulation large bandwidth is required. While, in case of advantages, FM is less prone to noise interference and has lower power consumption compared to AM.
2. To prevent over modulation in radio transmitters we use ___________
a) peak clipper
b) oscillator
c) double oscillator
d) filter
Answer: a
Explanation: Clipper is used to prevent the exceeding of output from a predetermined fixed value. It does not distorted the remaining part of the applied waveform.
3. IN EM waves, polarization ___________
a) is always vertical
b) is caused by reflection
c) is due to transverse nature of waves
d) is due to longitudinal nature of waves
Answer: c
Explanation: In electromagnetic waves, polarization is mainly due to the transverse nature of waves only. Transverse nature of electromagnetic waves mean that the electric and magnetic fields are perpendicular to each other as well as perpendicular to the direction of propagation of waves.
4. In FM receiver, role of amplitude limiter is to amplify low frequency signals.
a) True
b) False
Answer: b
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.
5. In a FM receiver, amplitude limiter ________
a) eliminates any change in amplitude of received FM signals
b) eliminates any change in frequency of received FM signals
c) reduce the amplitude of received signals
d) amplifies low frequency signals
Answer: a
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.
6. Base modulation is preferred over collector modulation of a class C transistor because of its better efficiency.
a) True
b) False
Answer: b
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.
7. Base modulation is preferred over collector modulation of a class C transistor because it has high power output per transistor.
a) True
b) False
Answer: b
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 standard IF frequency for AM receivers?
a) 100 KHz
b) 455 KHz
c) 1.07 MHz
d) 10.7 MHz
Answer: b
Explanation: In AM receivers, the standard intermediate frequency is approximately 455 KHz.
9. Balanced modulator is used to produce balanced modulation of a carrier wave.
a) True
b) False
Answer: b
Explanation: Balanced modulator is used to produce 100% modulation by suppressing the carrier and passing only the two sidebands.
Applications of SSB
1. What is the purpose of peak clipper circuits in radios?
a) prevent overmodulation
b) reduce bandwidth
c) increase bandwidth
d) regulate oscillator input voltage
Answer: a
Explanation: Clipper is used to prevent the output of a circuit from exceeding a predetermined voltage. It does not distorted the remaining part of the applied waveform.
2. In FM receiver, role of amplitude limiter is to reduce the amplitude of signals.
a) True
b) False
Answer: b
Explanation: Role of amplitude limiter in frequency modulation is to eliminate any change in amplitude of received FM signals.
3. Balanced modulator is used to suppress carrier signal to create an SSB or DSB.
a) True
b) False
Answer: b
Explanation: Balanced modulator is used to produce 100% modulation.
4. What is the main function of a balanced modulator?
a) to limit the noise picked by a receiver
b) to produce balanced modulation of a carrier wave
c) to suppress carrier signal
d) to produce 100% modulation
Answer: d
Explanation: For achieving 100% modulation, balanced modulator is mainly used in circuits.
5. For classifying a modem as low speed its data rate is ________
a) upto 100bps
b) upto 200bps
c) upto 400bps
d) upto 600bps
Answer: d
Explanation: According to standard data for modem, if the data rate is upto 600bps then modem is classified as having a low speed.
6. Varacter diode modulator is an indirect way of generating FM.
a) True
b) False
Answer: b
Explanation: Varacter diode modulator is not an indirect way of generating FM. It is a Armstrong modulator which is an indirect way of generating FM.
7. Which of the following is an indirect way of generating FM?
a) By reactance modulator
b) By bipolar transistor
c) By varacter diode
d) By armstrong modulator
Answer: d
Explanation: Armstrong modulator which is the only way for indirect generating of frequency modulation.
8. Convex lens has negative focal power and concave lens have positive focal power.
a) True
b) False
Answer: b
Explanation: Convex lens has positive focal power and concave lens have negative focal power.
9. All lens have positive focal power.
a) True
b) False
Answer: b
Explanation: Convex lens has negative focal power and concave lens have positive focal power.
Frequency Discrimination Method
1. FM and PM are two ways of angle modulation.
a) True
b) False
Answer: a
Explanation: In angle modulation, phase or frequency of the carrier wave is varied with respect to the instantaneous amplitude of the message signal. The general expression for FM and PM are as follows:
FM (t) = Ac sin (2πfct + βsin(2πfmt)),
PM (t) = Ac sin (2πfct + βcos(2πfmt)), where symbols have their usual meaning.
2. FM transmitting and receiving equipment is __________ as compared to AM equipment.
a) costly
b) cheaper
c) same price
d) not available
Answer: a
Explanation: Frequency transmitting and receiving equipment is generally costly when compared to amplitude modulated equipment.
Elements Of Communication System MCQs
3. Which one of the following is analog?
a) PCM
b) PWM
c) Delta modulation
d) Differential PCM
Answer: b
Explanation: Frequency transmitting and receiving equipment are generally costly when compared to amplitude modulated equipment, as the power required in FM transmission is less and bandwidth is high. Also, the noise interference is also less in case of FM.
4. Schmitt trigger is used to generate PDM.
a) True
b) False
Answer: b
Explanation: Pulse density modulation (PDM) is used to represent an analog signal using a digital signal. For generating PDM, a monostable multi-vibrator is used, which is externally triggered and has only one stable state.
5. Which of the following is used to generate PDM?
a) Monostable multi-vibrator
b) Bistable Multivibrator
c) Either monostable of free running multi-vibrator
d) Astable Multivibrator
Answer: a
Explanation: Pulse density modulation (PDM) is used to represent an analog signal using a digital signal. For generating PDM, a monostable multi-vibrator is used, which is externally triggered and has only one stable state.
6. In case of FM, if the modulating frequency is lowered and the modulating voltage remains constant then the amplitude of distant sidebands decreases.
a) True
b) False
Answer: b
Explanation: If the modulating frequency in FM lowered and the modulating voltage remains constant then the amplitude of distant sidebands increases, as the modulating frequency has no role to play in determining the amplitude of the sidebands.
7. Skip distance depends on the time of day and angle of incidence.
a) True
b) False
Answer: a
Explanation: A skip distance is a distance between the point, where the radio waves from a transmitter are transmitted and the point where the waves are received, after having been refracted by different layers of the ionosphere. It basically depends on time of day as well as on angle of incidence.
8. Leak type bias is used in plate modulated amplifier to prevent tuned circuit damping.
a) True
b) False
Answer: b
Explanation: Leak bias is a type of bias in which the input signal draws grid current from a circuit made of resistors and capacitors. Thus, Leak bias is mainly used to prevent excessive grid current in plate modulated amplifiers.
9. For telegraphy pulse code modulation (PCM) is widely used.
a) True
b) False
Answer: b
Explanation: FSK (Frequency Shift Keying) is a method used to transmit binary data in form of digital signals. It is mainly used for telegraphy. In telegraphy, a modem is used to convert binary data to FSK and vice-versa, for the communication between computers and over telephone lines.
10. DVD uses a laser beam for recording and video head for playback.
a) True
b) False
Answer: b
Explanation: Digital Versatile Disc (DVD) uses a laser beam for both recording and playback.
Singletone SSB Modulation
1. PDM can be generated by either free running multi-vibrator or monostable multi-vibrator.
a) True
b) False
Answer: b
Explanation: Pulse density modulation (PDM) is used to represent an analog signal using a digital signal. For generating PDM, monostable multi-vibrator is used, which is externally triggered and has only one stable state.
2. In case of FM, if the modulating frequency is lowered and the modulating voltage remains constant then the amplitude of distant sidebands first increases and then decreases.
a) True
b) False
Answer: b
Explanation: If the modulating frequency in FM lowered and the modulating voltage remains constant then the amplitude of distant sidebands increases, as the modulating frequency has no role to play in determining the amplitude of the sidebands.
3. Skip distance depends on the time of day.
a) True
b) False
Answer: b
Explanation: A skip distance is a distance between the point, where the radio waves from a transmitter are transmitted and the point where the waves are received, after having been refracted by different layers of the ionosphere. It basically depends on time of day as well as on angle of incidence.
4. Leak type bias is used in plate modulated amplifier to ________
a) increase bandwidth
b) decrease bandwidth
c) prevent tuning
d) prevent excessive grid current
Answer: d
Explanation: Leak bias is a type of bias in which the input signal draws grid current from a circuit made of resistors and capacitors. Thus, Leak bias is mainly used to prevent excessive grid current in plate modulated amplifiers.
5. Full duplex operation allows transmission in only one direction at the same time.
a) True
b) False
Answer: b
Explanation: Full duplex operations allow simultaneous communication between two points whereas Half Duplex operation allows transmission between two points one at a time.
6. A woofer is connected from the input through a ________
a) high pass filter
b) low pass filter
c) band pass filter
d) band stop filter
Answer: b
Explanation: A woofer is connected from the input through a low pass filter to restrict the high frequencies and only allows the low frequencies to pass through it.
7. Which of the following is used for attenuating high frequencies?
a) shunt resistance
b) shunt inductance
c) series capacitance
d) shunt capacitance
Answer: d
Explanation: Shunt capacitance is used to improve the power factor in the network. It also improves voltage stability. It serves as a low pass filter and thus is used in the communication system for attenuating high frequencies.
8. If the length of antenna is equal to whole wavelength the radiation is zero in all direction.
a) True
b) False
Answer: b
Explanation: If the length of antenna is equal to whole wavelength only the radiations which is at right angles is zero.
9. For getting zero radiation at right angles, length of antenna should be __________
a) ʎ
b) ʎ⁄8
c) ʎ⁄4
d) ʎ⁄5
Answer: a
Explanation: For getting zero radiation at right angles, length of antenna should be equal to the whole wavelength.
10. What is the commercial frequency deviation of frequency modulation?
a) 70 KHz
b) 75 KHz
c) 80 KHz
d) 85 KHz
Answer: b
Explanation: Frequency deviation is the difference between the maximum instantaneous modulated frequency and carrier frequency. Frequencies lying nearly about 75KHz is considered as commercial frequency deviation for frequency modulation.