R4RIN – MCQs, Mock Tests | IIT JEE IIT JEE Principles Of Communication set-1

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

✅ Correct Answer: 4

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

✅ Correct Answer: 1

Out of the following which type of sampling is preferred ?

1. Non-uniform
2. Uniform
3. Linear
4. Both (b) and C

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 2

Base band pulses travels

1. Along wires
2. In space
3. In wave guides
4. None of these

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

✅ Correct Answer: 2

In FM if frequency deviation is doubled

1. modulation is doubled
2. modulation remains unchanged
3. modulation is halved
4. None of these

✅ Correct Answer: 1

The threshold in FM depends upon

1. Frequency deviation
2. Power levels of frequency radiated
3. Both (a) and (b)
4. None of these

✅ Correct Answer: 3

Waves used for long distance broadcast are

1. short waves
2. long waves
3. light waves
4. any waves

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

1. 0
2. 5
3. 0.3
4. 0.4

✅ Correct Answer: 7

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

✅ Correct Answer: 2

Demodulation

1. is done at the transmitting stations
2. is done at the receiving station
3. removes side bands
4. rectifies modulated signal

✅ Correct Answer: 2

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

✅ Correct Answer: 4

Dibits in PM are

1. Two-phase signals
2. Four-frequency signals
3. Four-phase signals
4. Two-frequency signals

✅ Correct Answer: 1

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

✅ Correct Answer: 3

The sampling rate lies between

1. W to 2W
2. 0 to W
3. 0 to 2W
4. 2W to 4W

✅ Correct Answer: 4

Optical fibres made of glass or plastic are

1. brittle
2. leaky
3. fragile
4. insulators

✅ Correct Answer: 4

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

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

✅ Correct Answer: 4

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

1. Coating
2. Mixing
3. Modulating
4. Cladding

✅ Correct Answer: 4

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

1. Isoposphere
2. Mesophere
3. Ionosphere
4. Stratosphere

✅ Correct Answer: 3

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

✅ Correct Answer: 1

Voice communication is done by using

1. SSB
2. DSB-SC
3. Both (a) and (b)
4. None of these

✅ Correct Answer: 1

Wavelength of the waves having frequency 3000 MHz is

1. 10 cm
2. 50 cm
3. 100 cm
4. 150 cm

✅ Correct Answer: 1

Broadcast band in which FM lies is

1. UHF
2. VHF
3. SHF
4. None of these

✅ Correct Answer: 2

The DSB-SC signal are detected by

1. Reinecting the carrier
2. Removing the carrierr
3. Removing one side band
4. None of these

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

The frequency used in TV and radar system lies in

1. VHF
2. UHF
3. UHF
4. VLF

✅ Correct Answer: 2

Which of the following waves gets affected by solar cycle ?

1. Very low frequency
2. High frequency
3. Low frequency
4. Very high frequency

✅ Correct Answer: 2

The total channel band width allotted to FM is

1. 100 KHz
2. 75 KHz
3. 300 KHz
4. 200 KHz

✅ Correct Answer: 4

Intelsat satellite is used in

1. Intercontinental communication
2. Radio communication
3. Radar communication
4. None of these

✅ Correct Answer: 1

Out of following which wave disappears because of tilting ?

1. Space waves
2. Microwaves
3. Sky waves
4. Surface waves

✅ Correct Answer: 4

In AM transmission which modulator is being used ?

1. Class-C modulator
2. Class-A modulator
3. Class-B modulator
4. None of these

✅ Correct Answer: 1

Tropospheric scatter happens in

1. VHF
2. UHF
3. HF
4. SHF

✅ Correct Answer: 2

The product demodulator is also known as

1. Balance demodulator
2. SSB demodulator
3. Amplitude discriminator
4. None of these

✅ Correct Answer: 2

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.

✅ Correct Answer: 4

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

✅ Correct Answer: 1

Space waves normally propagated in

1. UHF
2. SHF
3. HF
4. VHF

✅ Correct Answer: 1

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

✅ Correct Answer: 2

Balance modulator is used to produce

1. DSB-SC
2. SSB
3. VSB
4. None of these

✅ Correct Answer: 1

The product modulator basically is a

1. Mixer
2. Ampliffer
3. Balanced modulator
4. Frequency separator

✅ Correct Answer: 1

The satellite that seems stationary w r t Earth is

1. Intelsat
2. Geostationary satellite
3. Telstar
4. Marisat

✅ Correct Answer: 2

The fading process applies to

1. Atmospheric storm
2. Ionospheric propagation
3. Faraday rotation
4. Troposcatter propagation

✅ Correct Answer: 4

The modulation index of an ores-modulated wave is

1. Less than 1
2. Equal to 1
3. Greater than 1
4. Infinite

✅ Correct Answer: 3

7.Ring modulator is used to produce

1. FM
2. SSB
3. DSB-SC
4. None of these

✅ Correct Answer: 3

The waves that are related to telecommunication are

1. Ultra-violet
2. Microwaves
3. Infra-red
4. Visible light

✅ Correct Answer: 2

Intelsat satellite works as a

1. absorber
2. repeater
3. transmitter
4. None of these

✅ Correct Answer: 2

Data communicated by optical fibres system is generally

1. digital
2. analog
3. modulated
4. unmodulated

✅ Correct Answer: 1

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

✅ Correct Answer: 1

Absorption of radiowaves by atmosphere depends upon

1. distance from transmitter
2. polarization of wave
3. polarization of atmosphere
4. frequency

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 4

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

✅ Correct Answer: 2

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 2

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

✅ Correct Answer: 2

The layer that absorbs largest proportion of UV rays is

1. Ozone layer
2. Isoposphere
3. Ionosphere
4. Mesosphere

✅ Correct Answer: 1

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

✅ Correct Answer: 2

Lasers are used as an endoscope in which field ?

1. Medical
2. Scientific
3. Communication
4. Entertainment

✅ Correct Answer: 1

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

✅ Correct Answer: 1

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

✅ Correct Answer: 3

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

✅ Correct Answer: 3

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

✅ Correct Answer: 1