IMPORTANT PSU QUESTION(microwave,emt,communication)-part-4

Q151 THE BIGGEST ADVANTAGE OF GALLIUM ANTIMONIDE OVER GERMANIUM FOR TUNNEL DIODE USE IS THAT FORMER HAS A
 (a)lower noise
 (b)higher ion mobility
 (c)larger voltages swing
 (d)simpler fabrication process
 ans-c

Q152 -VE RESISTANCE IS OBTAINED WITH A GUNN DIODE BECAUSE OF
 (a)electron transfer to less mobile energy level
 (b)avalanche breakdown with the high voltage gradient
 (c)tunneling across the junction
 (d)electron domains forming the junction
 ans-a

Q153 FOR GUNN DIODES,GaAs IS PREFERRED TO SILICON BECAUSE THE FORMER
 (a)has a suitable empty energy band,which silicon does not have
 (b)has a higher ion mobility
 (c)has a lower noise at the highest frequency
 (d)is capable of handling higher power densities
 ans-a

Q154 THE BIGGEST DISADVANTAGE OF THE IMPATT DIODE IS IT'S
 (a)lower efficiency than that of the other microwave diode
 (b)high noise
 (c)inability to provide pulsed operation
 (d)low power handling ability
 ans-b

Q155 THE MAGNETIC FIELD IS USED WITH A RUBY MASER TO
 (a)provide sharp focusing for the electron beam
 (b)increase the population inversion
 (c)allow room temp operation
 (d)provide frequency adjustment
 ans-d

Q156 THE RUBY MASER HAS BEEN PREFERRED TO THE AMMONIA MASER FOR MICROWAVE AMPLIFICATION,BECAUSE THE FORMER HAS
 (a)a much greater bw
 (b)a better frequency stability
 (c)a lower noise figure
 (d)no need for a circulator
 ans-a

Q157 A PARAMETRIC AMPLIFIERS AND MASERS ARE SIMILAR TO EACH OTHER IN THAT(INDICATE FALSE STATEMENT)
 (a)must have pumping
 (b)r extremely low noise amplifiers
 (c)must be cooled down to a few kelvins
 (d)generally require circulators,since they r one port devices
 ans-c

Q158 A MASER RF AMPLIFIER IS NOT REALLY SUITABLE FOR
 (A)radioastronomy
 (b)satellite communications
 (c)radar
 (d)troposcatters receivers
 ans-c

Q159 THE RUBY LASER DIFFERS FROM THE RUBY MASERS IN THAT THE FORMER
 (a)does not require pumping
 (b)needs no resonator
 (c)is an oscillator
 (d)produces much lower power
ans-c

Q160 THE O/P FROM A LASER IS MONOCHROMATIC ,THIS MEANS THAT
 (a)infrared
 (b)polarised
 (c)narrow beam
 (d)single frequency
 ans-d

Q161 FOR A GIVEN AVG POWER ,THE PEAK POWER O/P POWER OF A RUBY LASER MAY BE INCREASED BY
 (a)using cooling
 (b)using q spooling
 (c)increasing the magnetic field
 (d)dispensing with the fabry-perot lasers
 ans-b

Q162 COMMUNICATIONS LASERS R USED WITH OPTICAL FIBERS,RATHER THAT IN OPEN LINKS,TO
 (a)ensure that the beam does not spread
 (b)prevent atmospheric interference
 (c)prevent interference by other lasers
 (d)ensure that people are not blinded by them
 ans-b

Q163 INDICATE THE FALSE STATEMENT .THE DISADVANTAGES OF SEMICONDUCTOR LASERS OVER LED'S INCLUDE
 (a)monochromatic o/p
 (b)highest power o/p
 (c)lower cost
 (d)ability to be pulsed at higher rates
 ans-c

Q165 INDICATE WHICH OF THE FALLOWING IS NOT A BINARY NUMBER
 (a)morse
 (b)baudot
 (c)ccitt-2
 (d)arq
 ans-a

Q166 A SIGNALLING SYSTEM IN WHICH EACH LETTER OF THE ALPHABET IS REPRESENTED BY  A DIFFERENT SYMBOL IS NOT USED BECAUSE
 (a)it would be too difficult for an operator to memorize
 (b)it is redundant
 (c)noise would introduce too many errors
 (d)too many pulses per letter r required
 ans-c

Q167 THE HARTLY LAW STATES THAT
 (a)the maximam rate of information transmission depends on the channel bw
 (b)the maximam rate of information transmission depends on the on the depth of modulation
 (c)reduendancy is essential
 (d)only binary codes may be used
 ans-a

Q168 INDICATE THE FALSE STATEMENT.IN ORDER TO COMBAT NOISE
 (a)the channel bw may be increased
 (b)redundancy may be used
 (c)the transmitted power may be increased
 (d)the signalling rate may be reduced
 ans-a

Q169 THE MOST COMMONLY USED MODULATION TECHNIQUE FOR TELEGRAPHY
 (a)fsk
 (b)two tone modulation
 (c)pcm
 (d)single tone modulation
 ans-a

Q170 PULSE WIDTH MODULATION MAY BE GENERATED
 (a)by differentiating pulse position modulation
 (b)with monostable multi vibrator
 (c)by integrating the signal
 (d)with a free running vibrator
 ans-b

Q171 INDICATE WHICH OF THE FOLLOWING SYSTEM IS DIGITAL
 (a)ppm
 (b)pcm
 (c)pwm
 (d)pulse frequency modulation
 ans-b

Q172 QUANTIZING NOISE OCCURS IN
 (a)tdm
 (b)fdm
 (c)pcm
 (d)pwm
 ans-c

Q173 THE MODULATION SYSTEM INHERENTLY MOST NOISE RESISTANT IS
 (a)ssb,suppressed carrier
 (b)fm
 (c)ppm
 (d)pcm
 ans-d

Q174 IN ORDER TO REDUCE QUANTIZING NOISE ONE MUST
 (a)increase the number of standard amplitudes
 (b)send pulses whose sides r nearly vertical
 (c)use an rf amplifier in the receiver
 (d)increase number of pulses per second
 ans-a

Q175 THE HARTLAY-SHANNON THEOREM SET A LIMIT ON THE
 (a)highest frequency that may be sent over a given channel
 (b)maximum capacity of a channel with a given noise level
 (c)maximum number of coding levels in a channel with a given noise level
 (d)maximum number of quantizing levels in a channel of a given bw
 ans-b

Q176 INDICATE WHICH OF THE FOLLOWING PULSE MODULATION IS ANALOG
 (a)pcm
 (b)differential pcm
 (c)pwm
 (d)delta modulation
 ans-c

Q177 COMPANDING IS USED
 (a)to overcome quantizing noise in pcm
 (b)in pcm transmitters,to allow amplitude limiting in the receivers
 (c)to protect small signals in pcm from quantizing distortion
 (d)in pcm receivers,to overcome impulse noise
 ans-c

Q178 THE BIGGEST DISADVANTAGE OF PCM IS
 (a)inability to handle analog signal
 (b)the high error rate which it's quantizing noise introduces
 (c)incompatibility with tdm
 (d)the large bw required
 ans-d

Q179 DIGITAL SIGNALS
 (a)do not provide a continuous set of value
 (b)represent values as a discrete steps
 (c)can utilize decimal or binary system
 (d)all of the above
 ans-d

Q180 THE BAUD RATE IS
 (a)always equal to the bit  transfer rate
 (b)equal to twice the bw of an ideal channel
 (c)not equal to the signalling rate
 (d)equal to half the bw of an ideal channel
 ans-b

Q181 THE SHANNON-HARTELY LAW
 (a)refers to distortion
 (b)defines bw
 (c)describes signaling rates
 (d)refers to noise
 ans-d

Q182 THE CODE WHICH PROVIDES FOR PARITY CHECKS IS
 (a)baudot
 (b)ascii
 (c)ebcdic
 (d)ccitt-2
 ans-b

Q183 A FORWARD ERROR CORRECTING CODE CORRECTS THE ERRORS  BY
 (a)requiring partial retransmission of the signal
 (b)require retransmission of the entire signal
 (c)requiring no part of the signal to be retransmitted
 (d)using parity to correct the errors in all cases
 ans-c

Q184 FULL DUPLEX OPERATION
 (a)requires two pairs of cables
 (b)can transfer data in both direction at once
 (c)requires modems at both ends of the circuit
 (d)all of the above
 ans-d

Q185 THE RS-232 INTERFACE
 (a)interconnects data dets and transmission circuit
 (b)uses several different connectors
 (c)permits custom wiring of signal lines to the connector pins as desired
 (d)all of the above
 ans-a

Q186 SWITCHING SYSTEMS
 (a)improve the efficiency of data transfer
 (b)r not used in data system
 (c)require additional lines
 (d)r limited to small data networks
 ans-a

Q189 BROADBAND LONG DISTANCE COMMUNICATION WERE ORIGINALLY MADE POSSIBLE BY THE ADVENT OF
 (a)telegraph cables
 (b)repeater amplifiers
 (c)hf radio
 (d)geostationary satellites
 ans-b

Q190 THE NUMBER OF REPEATERS ALONG A COAXIAL CABLE LINK DEPENDS ON
 (a)whether separates tubes r used for the two directions of transmission
 (b)the bw of the system
 (c)the number of coaxial cables in the tube
 (d)the separation of equalizer
 ans-b

Q191 MICROWAVE LINKS REPEATER R TYPICALLY 50 KM APART
 (a)because of atmospheric attenuation
 (b)because of o/p tybe power limitations
 (c)because of the earth's curvature
 (d)to ensure that the applied dc voltage is not excessive
 ans-c

Q192 MICROWAVE LINKS R GENERALLY PREFERRED TO COAXIAL CABLE FOR TELEVISION TRANSMISSION BECAUSE
 (a)they have less overall phase distortion
 (b)they r cheaper
 (c)of their greater bw
 (d)of their relative immunity to impulse noise
 ans-a

Q193 ARMORED SUBMARINE CABLE IS USED
 (a)to protect the cable at great depths
 (b)to prevent inadvertent ploughing-in of the cable
 (c)for shallow shore ends of the cable
 (d)to prevent insulation breakdown from high feed voltages
 ans-c

Q194 A GEOSTATIONARY SATELLITE
 (a)is motionless in spce
 (b)is not really stationary at all,but orbits the earth within a 24 hr period
 (c)appers stationary over the earth's magnetic pole
 (d)is located at a height of 35,800 km to ensure global coverage.
 ans-b

Q195 INDICATE THE CORRECT STATEMENT REGARDING SATELLITE COMMUNICATIONS
 (a)if two earth stations do not face a common satellite,they should communicate via a double satellite hop
 (b)satellites r allocatedso that it is impossible for two earth stations not to face the same the same satellite
 (c)colocated earth stations r used for frequency diversity
 (d)a stellite earth stations must have as many receives chains as they r carriers transmitted to it.
 ans-d

Q196 SATELLITES USED FOR INTERNATIONAL COMMUNICATIONS A KNOWN AS
 (a)cosmat
 (b)dosmat
 (c)marisat
 (d)intelsat
 ans-d

Q197 TELEPHONE TRAFFIC IS MEASURED
 (a)with echo cancelers
 (b)by relative congestion
 (c)in terms of grade of service
 (d)in earlangs
 ans-d

Q198 IN ORDER TO SEPARATE CHANNELS IN A TDM RECEIVER ,IT IS NECESSARY TO USE
 (a)and gates
 (b)band pass filter
 (c)differentiation
 (d)integration
 ans-a

Q199 TO SEPARATE FDM RECEIVER,IT IS NECESSARY TO USE
 (a)and gates
 (b)bpf
 (c)differentiation
 (d)integration
 ans-b

Q200 LOSSES IN OPTICAL FIBERS CAN BE CAUSED BY(INDICATE THE FALSE STATEMENT)
 (a)impurities
 (b)micro bending
 (c)attenuation in the glass
 (d)stepped index operation
 ans-d