7.Ring modulator is used to produce
1.FM
2.SSB
3.DSB-SC
4.None of these
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
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
A glass coating surrounding the glass core in an optical fibre is called
1.Coating
2.Mixing
3.Modulating
4.Cladding
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
Absorption of radiowaves by atmosphere depends upon
1.distance from transmitter
2.polarization of wave
3.polarization of atmosphere
4.frequency
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
Balance modulator is used to produce
1.DSB-SC
2.SSB
3.VSB
4.None of these
Base band pulses travels
1.Along wires
2.In space
3.In wave guides
4.None of these
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
Broadcast band in which FM lies is
1.UHF
2.VHF
3.SHF
4.None of these
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
Data communicated by optical fibres system is generally
1.digital
2.analog
3.modulated
4.unmodulated
Demodulation
1.is done at the transmitting stations
2.is done at the receiving station
3.removes side bands
4.rectifies modulated signal
Dibits in PM are
1.Two-phase signals
2.Four-frequency signals
3.Four-phase signals
4.Two-frequency signals
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
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
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
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
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
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
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
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
In AM transmission which modulator is being used ?
1.Class-C modulator
2.Class-A modulator
3.Class-B modulator
4.None of these
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
In amplitude modulated wave power content of the carrier is maximum when A17m is
1.0
2.5
3.0.3
4.0.4
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
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
In FM if frequency deviation is doubled
1.modulation is doubled
2.modulation remains unchanged
3.modulation is halved
4.None of these
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
Intelsat satellite is used in
1.Intercontinental communication
2.Radio communication
3.Radar communication
4.None of these
Intelsat satellite works as a
1.absorber
2.repeater
3.transmitter
4.None of these
Lasers are used as an endoscope in which field ?
1.Medical
2.Scientific
3.Communication
4.Entertainment
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
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
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
Optical fibres made of glass or plastic are
1.brittle
2.leaky
3.fragile
4.insulators
Out of following which wave disappears because of tilting ?
1.Space waves
2.Microwaves
3.Sky waves
4.Surface waves
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
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
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
Out of the following which type of sampling is preferred ?
1.Non-uniform
2.Uniform
3.Linear
4.Both (b) and C
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
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
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
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.
Space waves normally propagated in
1.UHF
2.SHF
3.HF
4.VHF
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
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
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
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
The DSB-SC signal are detected by
1.Reinecting the carrier
2.Removing the carrierr
3.Removing one side band
4.None of these
The fading process applies to
1.Atmospheric storm
2.Ionospheric propagation
3.Faraday rotation
4.Troposcatter propagation
The frequency used in TV and radar system lies in
1.VHF
2.UHF
3.UHF
4.VLF
The layer that absorbs largest proportion of UV rays is
1.Ozone layer
2.Isoposphere
3.Ionosphere
4.Mesosphere
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
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
The modulation index of an ores-modulated wave is
1.Less than 1
2.Equal to 1
3.Greater than 1
4.Infinite
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
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
The product demodulator is also known as
1.Balance demodulator
2.SSB demodulator
3.Amplitude discriminator
4.None of these
The product modulator basically is a
1.Mixer
2.Ampliffer
3.Balanced modulator
4.Frequency separator
The region that contains free electrons and negative ions and positive ions and positive ions is
1.Isoposphere
2.Mesophere
3.Ionosphere
4.Stratosphere
The sampling rate lies between
1.W to 2W
2.0 to W
3.0 to 2W
4.2W to 4W
The satellite that seems stationary w r t Earth is
1.Intelsat
2.Geostationary satellite
3.Telstar
4.Marisat
The threshold in FM depends upon
1.Frequency deviation
2.Power levels of frequency radiated
3.Both (a) and (b)
4.None of these
The total channel band width allotted to FM is
1.100 KHz
2.75 KHz
3.300 KHz
4.200 KHz
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
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
The waves that are related to telecommunication are
1.Ultra-violet
2.Microwaves
3.Infra-red
4.Visible light
Tropospheric scatter happens in
1.VHF
2.UHF
3.HF
4.SHF
Voice communication is done by using
1.SSB
2.DSB-SC
3.Both (a) and (b)
4.None of these
Wavelength of the waves having frequency 3000 MHz is
1.10 cm
2.50 cm
3.100 cm
4.150 cm
Waves used for long distance broadcast are
1.short waves
2.long waves
3.light waves
4.any waves
Which of the following waves gets affected by solar cycle ?
1.Very low frequency
2.High frequency
3.Low frequency
4.Very high frequency