IIT JEE/IIT JEE Principles Of Communication set-1 Sample Test,Sample questions

Question:
7.Ring modulator is used to produce




1.FM

2.SSB

3.DSB-SC

4.None of these


Question:
A 400 W carrier AM modulated to a depth of 75%. The total power of the system is




1.512 W

2.200 W

3.450 W

4.None of these


Question:
A 500 W carrier is amplitude modulated with modulation index of 60%. What will be total power of modulated wave




1.640.5 W

2.590 W

3.780 W

4.450 W


Question:
A glass coating surrounding the glass core in an optical fibre is called




1.Coating

2.Mixing

3.Modulating

4.Cladding


Question:
A radiowave signal propagating from one point to other following the surface of Earth is called




1.sky wave

2.ultrasonic wave

3.sound wave

4.ground wave


Question:
Absorption of radiowaves by atmosphere depends upon




1.distance from transmitter

2.polarization of wave

3.polarization of atmosphere

4.frequency


Question:
Audio signal can t be directly transmitted into the space because




1.Audio signals can t propagate through air

2.Audio signals are high frequency signal

3.Audio signal need some external help for propagation

4.A very high antenna is needed for their propagation


Question:
Balance modulator is used to produce




1.DSB-SC

2.SSB

3.VSB

4.None of these


Question:
Base band pulses travels




1.Along wires

2.In space

3.In wave guides

4.None of these


Question:
Bit rate is given by




1.sampling rate + number of bits per cycle

2.sampling rate/number of bits per cycle

3.sampling rate * number of bits per cycle

4.None of these


Question:
Broadcast band in which FM lies is





1.UHF

2.VHF

3.SHF

4.None of these


Question:
Crystal oscillator is used to generate carrier waves because of

 

1.good stability

2.high power output no buffer stage is

3.required

4.None of these


Question:
Data communicated by optical fibres system is generally




1.digital

2.analog

3.modulated

4.unmodulated


Question:
Demodulation




1.is done at the transmitting stations

2.is done at the receiving station

3.removes side bands

4.rectifies modulated signal


Question:
Dibits in PM are





1.Two-phase signals

2.Four-frequency signals

3.Four-phase signals

4.Two-frequency signals


Question:
he digital transmission is done mostly via




None of these

1.Telephone links

2.Satellite links

3.Computer to computer links

4.None of these


Question:
If 100% modulation is produced in AM then


 

1.carrier frequency is equal to signal frequency

2.carrier frequency exceeds signal frequency amplitude exceeds signal

3.amplitude

4.amplitude equals signal amplitude


Question:
If AM having 100% modulation of the total transmitted power each side band carries




1.one third

2.one half

3.one fourth

4.one sixth


Question:
If carrier frequency is 100 kH and modulating frequency is 5kH  then band width of AM transmission is




1.10

2.20

3.50

4.80


Question:
If the frequency of EM radiations is halved then the energy of EM radiation will become




1.double

2.remains unchanged

3.becomes half

4.becomes one fourth


Question:
If the ratio of wavelength emitted from two different sources is 1 : 2 then ratio of their velocities will be




None of these

1.1:01

2.1:02

3.2:01

4.None of these


Question:
In a true WBFM all the energy is associated with




None of these

1.Side bands

2.Carrier terms

3.Both (a) and (b)

4.None of these


Question:
In AM if modulation index is more than 100% then




1.The wave gets distorted

2.Efficiency increases

3.Power increases

4.None of these


Question:
In AM transmission which modulator is being used ?




1.Class-C modulator

2.Class-A modulator

3.Class-B modulator

4.None of these


Question:
In AM wave the modulation index is 100% If the carrier is suppressed the percentage saving in power will be




1.66.60%

2.50%

3.75%

4.None of these


Question:
In amplitude modulated wave power content of the carrier is maximum when A17m is


1.0

2.5

3.0.3

4.0.4


Question:
In an AM system full information can be conveyed by transmitting only



1.the lower side band

2.the upper side band

3.any one side band

4.the carrier


Question:
In an AM transmission band width is equal to





1.maximum frequency of audio signal

2.minimum frequency of audio signal

3.twice the maximum frequency of audio signal

4.half the maximum frequency of audio signal


Question:
In FM if frequency deviation is doubled




1.modulation is doubled

2.modulation remains unchanged

3.modulation is halved

4.None of these


Question:
In optical fibre propagation angle of light must be less than or equal to




1.incident angle

2.refraction angle

3.reflection angle

4.critical angle


Question:
Intelsat satellite is used in





1.Intercontinental communication

2.Radio communication

3.Radar communication

4.None of these


Question:
Intelsat satellite works as a




1.absorber

2.repeater

3.transmitter

4.None of these


Question:
Lasers are used as an endoscope in which field ?




1.Medical

2.Scientific

3.Communication

4.Entertainment


Question:
Lasers are used in alignment of pipes because




1.they are coherent

2.they are highly directional

3.Both (a) and (b)

4.None of these


Question:
Modulation index in FM depends upon




1.Amplitude of modulating signal

2.Frequency of modulating signal

3.Both (a) and (b)

4.None of these


Question:
Optical fibra communication have an advantage over general communication because




1.It is more efficient

2.Of security of signal

3.Of both (a) and (b)

4.None of these


Question:
Optical fibres made of glass or plastic are




1.brittle

2.leaky

3.fragile

4.insulators


Question:
Out of following which wave disappears because of tilting ?




1.Space waves

2.Microwaves

3.Sky waves

4.Surface waves


Question:
Out of the following subsystems which is used for satellite or+A68bit position and altitude



1.Antenna subsystem

2.Thrust subsystem

3.Stabilization subsystem

4. Power subsystem


Question:
Out of the following which is not a correct statement for FM ?




1.Total power remain constant w. r. t. modulation index

2.Carrier never becomes zero

3.-coefficients are occasionally negative

4.None of these


Question:
Out of the following which is not a correct statement for FM ?



1.Modulate the digital signals

2.Covert analog signals to digital ones

3.Both (a) and (b)

4.None of these


Question:
Out of the following which type of sampling is preferred ?




1.Non-uniform

2.Uniform

3.Linear

4.Both (b) and C


Question:
Purpose of modulator is




1.to increase the energy of carrier

2.to impress the information on carrier

3.to separate the carrier and information

4.None of these


Question:
Satellite used for only reflecting back the signal to earth stations is called




1.Passive satellite

2.Neutral satellite

3.Active satellite

4.Natural satellite


Question:
Select the incorrect statement




1.FM receptions is quite immune the noise

2.Efficiency of FM transmission if high

3.High fidelity reception is obtained in FM

4.FM signals can be easily coded


Question:
Select the wrong statement in case of EM waves.





1.EM waves are transverse in nature

2.Travel in free space at a speed of light

3.Are produced by accelerating charges

4.Travel in all media with same speed.


Question:
Space waves normally propagated in




1.UHF

2.SHF

3.HF

4.VHF


Question:
The antenna current of an AM transmission is 8A when only carrier is sent but is increases to 893 A when the carrier is modulate The modulation of the wave is




1.43%

2.60%

3.57%

4.Power subsystem


Question:
The carrier suppression is done son as to




1.minimize the cost

2.simple the design

3.never done practically

4.All of the above


Question:
The circuits that produces PDM requires




1.Save tooth wave generator

2.Clipping and squaring circuits

3.Both (a) and (b)

4.None of these


Question:
The disadvantage of FM over AM is




1.Noise is very high for high frequency signals

2.High modulation power is required

3.Larger band width is required

4.None of these


Question:
The DSB-SC signal are detected by




1.Reinecting the carrier

2.Removing the carrierr

3.Removing one side band

4.None of these


Question:
The fading process applies to





1.Atmospheric storm

2.Ionospheric propagation

3.Faraday rotation

4.Troposcatter propagation


Question:
The frequency used in TV and radar system lies in




1.VHF

2.UHF

3.UHF

4.VLF


Question:
The layer that absorbs largest proportion of UV rays is




1.Ozone layer

2.Isoposphere

3.Ionosphere

4.Mesosphere


Question:
The loop gain in case of two wire repeater is must be




1.greater than 1

2.equal to 1

3.less than 1

4.None of these


Question:
The modulation index in case of FM is defined for





1.Multi-tone modulation

2.Tone-modulation only

3.All types of modulating signals

4.None of these


Question:
The modulation index of an ores-modulated wave is




1.Less than 1

2.Equal to 1

3.Greater than 1

4.Infinite


Question:
The number of AM broadcast stations that can be accommodated in a 300 kHz band w+A65idth for the highest modulating frequency 15 kHz will be

1.10

2..In optical fibre propagation angle of light must be less than or equal to

3.7

4.12


Question:
The process in which the wave follows the Earth s curvature is called as




1.The faraday s affect

2.Windowing

3.Dusting

4.Ionospheric reflection


Question:
The product demodulator is also known as




1.Balance demodulator

2.SSB demodulator

3.Amplitude discriminator

4.None of these


Question:
The product modulator basically is a




1.Mixer

2.Ampliffer

3.Balanced modulator

4.Frequency separator


Question:
The region that contains free electrons and negative ions and positive ions and positive ions is




1.Isoposphere

2.Mesophere

3.Ionosphere

4.Stratosphere


Question:
The sampling rate lies between




1.W to 2W

2.0 to W

3.0 to 2W

4.2W to 4W


Question:
The satellite that seems stationary w r t Earth is




1.Intelsat

2.Geostationary satellite

3.Telstar

4.Marisat


Question:
The threshold in FM depends upon




1.Frequency deviation

2.Power levels of frequency radiated

3.Both (a) and (b)

4.None of these


Question:
The total channel band width allotted to FM is




1.100 KHz

2.75 KHz

3.300 KHz

4.200 KHz


Question:
The total power contact of an AM wave is 1200 W. What will be modulation index if each side band contains 150 W of power




1.81.60%

2.60%

3.75%

4.None of these


Question:
The transmission band width in WBFM is




1.Independent of message band width

2.Dependent of message band width

3.Both (a) and (b)

4.None of these


Question:
The waves that are related to telecommunication are




1.Ultra-violet

2.Microwaves

3.Infra-red

4.Visible light


Question:
Tropospheric scatter happens in





1.VHF

2.UHF

3.HF

4.SHF


Question:
Voice communication is done by using




1.SSB

2.DSB-SC

3.Both (a) and (b)

4.None of these


Question:
Wavelength of the waves having frequency 3000 MHz is




1.10 cm

2.50 cm

3.100 cm

4.150 cm


Question:
Waves used for long distance broadcast are





1.short waves

2.long waves

3.light waves

4.any waves


Question:
Which of the following waves gets affected by solar cycle ?




1.Very low frequency

2.High frequency

3.Low frequency

4.Very high frequency


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