IMPORTANT PSU QUESTION (microwave,emt,communication)-part-2

Q51 FOR TRANSMISSION LINE LOAD MATCHING OVER A RANGE OF FREQUENCIES ,IT IS BEST TO USE A
 (A)balun
 (b)broadband directional coupler
 (c)double stab
 (d)single stub of adjustable position
 ans-c

Q52 THE MAIN DISADVANTAGE OF THE TWO HOLE DIRECTIONAL COUPLER IS
 (A)low directional coupling
 (b)poor directivity
 (c)high swr
 (d) narrow bw
 ans-d

Q53 TO COUPLE A COAXIAL LINE TO A PARALLEL-WIRE ,IT IS BEST TO USE A
 (a)slotted line
 (b)balun
 (c)directional coupler
 (d)quarter wave transformer
 ans-b

Q54 INDICATE WHICH OF THE FOLLOWING TERM APPLIES TO TROPOSCATTER PROPAGATION
 (a)sids
 (b)fading
 (c)atmospheric storm
 (d)Faraday rotation
 ans-b

Q55 VLF WAVES ARE USED FOR SOME TYPES OF SERVICES BECAUSE
 (a)of the low power required
 (b)the transmitting antennas are of convenient size
 (c)they r very reliable
 (d)they penetrate the ionosphere easily
 ans-c

Q56 HIGH FREQUENCY WAVES ARE
 (a)absorbed by the f2 layer
 (b)reflected by the d layer
 (c)capable of use for long distance communication on the moon
 (d)are affected by solar cycle
 abs-d

Q57 DISTANCE'S NEAR THE SKIP DISTANCE SHOULD BE USED FOR SKY WAVE PROPAGATION
 (A)to avoid titting
 (b)to prevent sky wave and upper ray interference
 (c)to avoid faraday effect
 (d)so as not to exceed the cricticial frequency
 ans-b

Q58 A SHIP TO SHIP COMMUNICATION PLAGNUED BY FADING .THE BEST SOLUTION SEEMS TO BE THE USE OF
 (a)a more directional antenna
 (b)a broad band antenna
 (c)frequency diversity
 (d)space diversity
  ans-c

Q59 A RANGE OF MICROWAVE FREQUENCY MORE EASILY PASSED BY THE ATMOSPHERE THAN THE OTHERS IS CALLED A
 (A)window
 (b)critical frequency
 (c)gyro frequency range
 (d)resonance in atmosphere
 ans-a

Q60 FREQUENCY IN UHF RANGE NORMALLY PROPAGATE BY MEANS OF
 (a)ground wave
 (b)sky wave
 (c)surface wave
 (d)space wave
 ans-d

Q61 TROPOSPHERIC SCATTER IS USED WITH FREQUENCY IN THE FOLLOWING RANGE
 (a)hf
 (b)vhf
 (c)uhf
 (d)vlf
 ans-c

Q62 THE GROUND WAVES EVENTUALLY DISAPPEARS ,AS ONE MOVES AWAY FROM THE TRANSMITTER BECAUSE OF
 (a)interference from the sky wave
 (b)loss of los condition
 (c)maximum single hop distance limitation
 (d)tilting
 ans-d

Q63 IN EM WAVES ,POLARISATION
 (a)is caused by reflection
 (b)is due to inverse nature of the waves
 (c)result from the longitudinal nature of the waves
 (d)is always vertical in an isotropic medium
 ans-b

Q64 AN EM WAVE TRAVELS IN THE FREE SPACE ONLY ONE OF THE FOLLOWING CAN HAPPEN TO THEM
 (a)absorption
 (b)attenuation
 (c)refraction
 (d)reflection
 ans-b

Q65 THE ABSORPTION OF RADIO WAVES BY THE ATMOSPHERE DEPENDS ON
 (a)their frequency
 (b)their distance from the transmitter
 (c)the polarisation of the wave
 (d)the polarisation of the atmosphere
 ans-a

Q66 EM WAVES ARE REFRACTED WHEN THEY
 (a)pass in to medium of different dielectric constants
 (b)r polarised at right angles to the direction of propagation
 (c) encounter a perfectly conducting surface
 (d)pass through a small slot in a conducting plane
 ans-a

Q67 DIFFRACTION OF EM WAVES
 (a)is caused by reflections from the ground
 (b)arises only with spherical wave fronts
 (c)will occur when the waves pas through a large slot
 (d)may occur around the edges of a sharp obstacle
 ans-d

Q68 WHEN MW SIGNALS FOLLOW THE CURVATURE OF THE EARTH ,THIS IS KNOWN AS
 (a)the Faraday effect
 (b)ducting
 (c)tropospheric scatter
 (d)ionospheric reflection
 ans-b

Q69 HELICAL ANTENNA R OFTEN USED FOR SATELLITE TRACKING AT VHF DUE TO
 (a)troposcatter
 (b)superrefraction
 (c)ionospheric refraction
 (d)the faraday effect
 ans-d

Q70 AN UNGROUNDED ANTENNA NEAR THE GROUND
 (a)acts as a single antenna of twice the height
 (b)is unlikely to need an earth mat
 (c)acts as an antenna array
 (d)must be horizontally polarised
 ans-c

Q71 ONE OF THE FOLLOWING CONSISTS OF NON RESONANT ANTENNAS
 (a)the rhombic antenna
 (b)the folded dipole
 (c)the end fire array
 (d)the broad side array
 ans-a

Q72 ONE OF THE FOLLOWING IS VERY USEFUL AS A MULTI BAND HF RECEIVING ANTENNA.THIS IS THE
 (A)conical horn
 (b)folded dipole
 (c)log periodic
 (d)square loop
 ans-c

Q73 WHICH OF THE FOLLOWING ANTENNA IS BEST EXCITED FROM A WAVE GUIDE?
 (a)biconical
 (b)horn
 (c)helical
 (d)discone
 ans-b

Q74 INDICATE THE ANTENNA THAT IS NOT WIDEBAND
 (a)dicone
 (b)folded dipole
 (c)helical
 (d)marconi
 ans-d

Q75 WHICH ONE OF THE FOLLOWING IS NOT APPLY TO THE YAGI UDA ANTENNA
 (a)good bw
 (b)parasitic elements
 (c)folded dipole
 (d)high gain
 ans-d

Q76 AN ANTENNA THAT IS CIRCULARLY POLARISED IS the
 (a)helical
 (b)small circular loop
 (c)parabolic reflector
 (d)yagi uda
 ans-a

Q77 THE STANDARD REFERENCE ANTENNA FOR THE DIRECTIVE GAIN IS THE
 (a)infinitesimal dipole
 (b)isotropic antenna
 (c)elementary doublet
 (d)half wave dipole
 ans-b

Q78 TOP LOADING IS DONE WITH AN ANTENNA IN ORDER TO INCREASE ITS
 (a)effective height
 (b)bw
 (c)beam width
 (d)i/p capacitance
 ans-a

Q79 CASSEGRAIN FEED IS USED WITH A PARABOLIC REFLECTOR TO
 (a)increase the gain of the system
 (b)increase the beamwith of the system
 (c)reduce the size of the main reflector
 (d)allow the feed to be placed at a convenient point
 ans-d

Q80 ZONING IS USED WITH A DIELECTRIC ANTENNA IN ORDER TO
 (a)reduce the bulk of the lens
 (b)increase the bw of the lens
 (c)permit point to point focusing
 (d)correct the curvature of the wavefront from a horn that is too short
 ans-a

Q81 A HELICAL ANTENNA IS USED IN SATELLITE TRACKING BECAUSE OF ITS
 (a)circular polarisation
 (b)maneuverability
 (c)broad bw
 (d)good front to back ratio
 ans-a

Q82 THE DISCONE ANTENNA IS
 (a)a useful direction finding antenna
 (b)used as a radar receiving antenna
 (c)circularly polarised like other circular antennas
 (d)useful as a uhf receiving antenna
 ans-d

Q83 ONE OF THE FOLLOWING IS NOT A OMNIDIRECTIONAL ANTENNA
 (a)half wave dipole
 (b)log-pereodic
 (c)discone
 (d)marconi
 ans-b

Q84 WHEN EM WAVE ARE PROPAGATED IN A WAVEGUIDE
 (a)they travel along the broader walls of the guide
 (b)the reflected from the wall but do not travel along them
 (c)they travel through the dielectric without touching the wall
 (d)they travel along all 4 walls of the waveguide
 ans-b

Q85 WAVEGUIDES R USED MAINLY FOE MICROWAVE SIGNALS BECAUSE
 (a)they depend on straight line propagation which applies to microwaves only
 (b)losses would be too heavy at lower frequencies
 (c)there are no generators powerful enough to excite them at lower frequency
 (d)they would be too bulky at lower frequency
 ans-d

Q86 THE WAVELENGTH OF A WAVE IN A WAVEGUIDE
 (a)is greater than in free space
 (b)depends only on the waveguide dimensions and the free space wavelength
 (c)is inversely proportional to the phase velocity
 (d)is directly proportional to the group velocity
 ans-a

Q87 COMPARED WITH THE EQUIVALENT TRANSMISSION LINES ,3GHZ WAVEGUIDES(INDICATE FALSE STATEMENT)
 (a)r less lossy
 (b)can carry high powers
 (c)r less bulky
 (d)have lower attenuation
 ans-c

Q88 WHEN A PARTICULAR MODE IS EXCITED IN A WAVEGUIDE ,THERE APPEARS AN EXTRA ELECTRIC COMPONENT IN THE DIRECTION OF PROPAGATION.THE RESULTING MODE IS
 (a)transverse electric
 (b)transverse magnetic
 (c)longitudinal
 (d)transverse electromagnetic
 ans-b

Q89 WHEN EM WAVES ARE REFLECTED AT AN ANGLE FROM A WALL,THEIR WAVELENGTH ALONG THE WALL IS
 (a)same as in free space
 (b)the same as the wavelength perpendicular to the wall
 (c)shorter because of the doppler effect
 (d)greater in the actual direction of propagation
 ans-d

Q90 AS A RESULT OF REFLECTIONS FROM A PLANE CONDUCTING WALL ,EM WAVES ACQUIRE AN APPARENT VELOCITY GREATER THAN THE VELOCITY OF LIGHT IN SPACE.THIS IS CALLED THE
 (a)velocity of propagation
 (b)normal velocity
 (c)group velocity
 (d)phase velocity
 ans-d

Q91 INDICATE THE FALSE STATEMENT .WHEN THE FREE SPACE WAVELENGTH OF A SIGNAL EQUALS THE CUTOFF WAVELENGTH OF THE GUIDE
 (a)the group velocity becomes zero
 (b)phase velocity becomes infinite
 (c)the characteristic impedence of the guide becomes infinite
 (d)the wavelength within the waveguide becomes infinite
 ans-c

Q92 THE DOMINANT MODE OF PROPAGATION IS PREFERRED WITH RECTANGULAR WAVE GUIDES BECAUSE(INDICATE THE FALSE STATEMENT)
 (a)it leads to the smallest waveguide dimensions
 (b)it resulting impedance can be matched directly to coaxial lines
 (c)it is easier ti exite than the other modes
 (d)propagation of it without any spurious generation can be ensured
 ans-b

Q93 A CHOCKE FLANGE MAY BE USED TO COUPLE TW WAVEGUIDES
 (a)to help in alignment of the waveguides
 (b)because it is simpler than any other join
 (c)to compensate for discontinuity at the join
 (d)to increase the bw of the system
 ans-c

Q94 IN ORDER TO  COUPLE TWO GENERATORS TO A WAVEGUIDE SYSTEM WITHOUT COUPLING THEM TO EACH OTHER ,ONE COULD NOT USE A
 (a)rat race
 (b)e plane t
 (c)hybrid ring
 (d)magic t
 ans-b

Q95 WHICH OF THE FOLLOWING WAVEGUIDE TUNING IS NOT EASILY ADJUSTABLE
 (a)screw
 (b)stub
 (c)iris
 (d)plunger
 ans-c

Q96 A PISTON ATTENUATOR IS A
 (a)vane attenuator
 (b)waveguide below cutoff
 (c)mode filter
 (d)flap attenuator
 ans-b

Q97 CYLINDRICAL CAVITY RESONATOR R NOT USED WITH KLYSTRON BECAUSE THEY HAVE
 (a)a q taht is too low
 (b)a shape whose resonant frequency is too difficult to calculate
 (c)harmonically related resonant frequency
 (d)too heavy looses
 ans-c

Q98 A DIRECTIONAL COUPLER WITH THREE OR MORE HOLES IS SOMETIMES PREFERRED TO TWO HOLE COUPLER
 (a)because it is more efficient
 (b)to increase coupling of the signal
 (c)to reduce spurious mode generation
 (d)to increase the bw of the system
 ans-d

Q99 A FERRITE IS
 (a)a nonconductor with magnetic properties
 (b)an inter metallic compound with particularly good conductivity
 (c)an insulator with heavily attenuates magnetic fields
 (d)a microwave semiconductor invented by faraday
 ans-a

Q100 A MANGANESE FERRITE MAY BE USED AS A (INDICATE FALSE STATEMENT)
 (a)circulator
 (b)isolator
 (c)garnet
 (d)phase shifter
 ans-c