KENNEDY 4 th EDITION MULTIPLE MUL TIPLE CHOICES CHOICE S
INTRO TO COMMUNICATIONS COMMUNICATIONS SYSTEM SYSTE M 1. In a communications system, noise is most likely to affect the signal a. at the transmitter b. in the channel c. in the information source d. at the destination 2. Indicate the wave consist of
false
statement. Fourier analysis shows that a sawtooth
a. funa!ental an "ubha#!$nic "ine %a&e" b. a fundamenta fundamentall sine wave wave and an infinite infinite number number of harmonics harmonics c. fundamental and harmonic sine waves whose amplitude decreases with the harmonic number d. sinusoidal voltages, some of which are small enough to ignore in practice practice
3. Indicate the
false
statement. Modulation is used to
a. #euce the ban%ith u"e b. separate separate differing differing transmiss transmissions ions c. ensure that intelligence may be transmitted over long distances d. allow the use of practicable antennas
. Indicate the false statement. From the transmitter the signal deterioration because of noise is usually a. unwanted energy b. '#eictable in cha#acte# c. present in the transmitter d. due to any cause !. Indicate the
true statement. Most receivers conforms to the
a. amplitude"modulated group b. fre#uency"mo fre#u oup ency"modulated dulated gr gr c. "u'e#hete#$(ne )#$u' d. tuned radio fre#uency receiver group $. Indicate the false statement. %he need for modulation can best be a. Antenna len)th" beoffrom a''#$*i!atel( +4k)* l$n) e&emplified b. c. 'll d. 'n 'and message sound antenna antenna fre#uency by the isisin iconcentrated nfollowing. composed the %ill standard standard unpredictable broadcast broadcast 2( )* 'M to 2( variations band ba nd is 1$,((( 1$, in((( both ft amplitude
+. Indicate the started as early as
true statement. %he process of sending and receiving
a. the middle 13(s b. 1-!( c. the beginning of the twentieth century . the ,-4" -. hich of the steps is not included in the process of reception/ a. decoding b. enc$in) c. storage d. interpretation . %he acoustic channel is used for which of the following/ a. 0)F communications b. single"sideban single"sideband d communication communication c. television communications . 'e#"$n/t$/'e#"$n &$ice c$!!unicati$n" 1(. 'mplitude modulation is the process of a. "u'e#i!'$"in) a l$% f#e0uenc( $n a hi)h f#e0uenc( b. superimposing superimposing a high fre#uency fre#uency on a low fre#uency fre#uency c. carrier interruption d. fre#uency shift and phase shift
NOISE 1. ne of the following types of noise becomes of great importance at high fre#uencies. It is the a. shot noise b. random random noise c. impulse noise . t#an"it/ti!e n$i"e 2. Indicate the
false
statement.
a. )F mi&ers are generally noisier than )F amplifiers. b. I!'ul"e n$i"e &$lta)e i" ine'enent $f ban%ith. c. %hermal noise is independent of the fre#uency at which it is measured. d. Industrial noise is usually of the impulse type. 3. %he value of a resistor creating thermal noise is doubled. %he noise power generator generator is therefore a. halved b. #uadrupled #uadrupled c. doubled . unchan)e . ne of the following is performance performance of receivers receivers
not a useful #uantity for comparing the noise
a. In'ut n$i"e &$lta)e b. #uivalent #uivalent noise noise resistance resistance c. 4oise temperature d. 4oise figure
!. Indicate the noise whose source is in a category different from that of other three. the a. 5olar noise b. 6osmic 6osmic noise c. At!$"'he#ic n$i"e d. 7alactic noise $. Indicate the false statement. %he s#uare of the thermal noise voltage generated by a resistor is proportional to a. its resistance c. 1$lt2!ann3" b. d. the its temperat temperature bandwidth urec$n"tant over which it is measured
+. hich of broad classifications of noise are most difficult to treat/ a. n$i"e )ene#ate in the #ecei&e# b. noise smitter generated generated in the the tran c. e*te#nall( )ene#ate n$i"e d. internally generated noise
-. 5pace noise generally covers a wide fre#uency spectrum, but the strongest interference occurs a. between - M)* and 1.3 7)* b. below below 2( Mh* c. bet%een t$ , MH2 d. above 1.! 7)* . hen dealing with random noise calculations it must be remembered that a. all calculations are based on peak to peak values b. calculation calculationss are based based on peak peak values values c. calculations are based on average values . calculati$n" a#e ba"e $n RMS &alue" 1(. hich of the following is the most reliable measurement for comparing amplifier noise characteristics/ a. signal"to"noi se ratio b. n$i"e fact$# c. shot noise d. thermal noise agitation 11. hich of the following statements is
true /
a. 8andom noise power is inversely proportional to bandwidth b. Flicker Flicker is sometimes sometimes called called demodulation noise c. N$i"e i" !i*e#" i" cau"e b( inae0uate i!a)e f#e0uenc( #e5ecti$n d. ' random voltage across a resistance cannot be calculated
AMPLITUDE MODULA MODULATION TION 1. If the plate supply voltage for a plate"modulated class 6 amplifier is 9, the ma&imum plate"cathode voltage could be almost as high as a. 46 b. 39 c. 29 d. 19
2. In a low"level 'M system, amplifiers following the modulated be stage must a. linea# e&ice" b. harmonic harmonic devices devices c. class 6 amplifiers d. nonlinear devices
3. If the carrier of a 1(( percent modulated 'M wave is suppressed, the percentage percenta ge power saving will will be a. !( b. 1!( c. 1(( . 77.77 . :eak"type bias is used in a plate"modulated class 6 amplifier to a. prevent tuned circuit damping b. '#e&ent e*ce""i&e )#i cu##ent c. prevent overmodulation d. increase the bandwidth !. %he output stage of a television transmitter is most likely to be a a. plate"modulated class 6 amplifier b. )#i/!$ulate cla"" C a!'lifie# c. screen"modulated class 6 amplifier d. grid"modulated class ' amplifier $. %he modulation inde& of an 'M wave is changed from ( to 1. %he transmitted power is a. unchanged b. halved halved . doubled inc#ea"e b( 8 'e#cent c.
+. ne of the advantages of the base modulation over collector modulation of a transistor class 6 amplifier is a. the l$%e# !$ulatin) '$%e# #e0ui#e b. higher power output per transistor c. better efficiency d. better linearity
-. ' carrier is simultaneously modulated by two sine waves with modulation indices of (.3 and (.; the total modulation inde& a. is 1 b. cannot be calculated unless the phase relations are known c. i" .8 d. is (.+ . 'mplitude modulation is used for broadcasting because a. it is more noise immune than other modulation systems. b. 6ompared with other systems it re#uires less transmitting power c. it" u"e a&$i" #ecei&e# c$!'le*it(. d. no other modulation system can provide the necessary bandwidth for high fidelity 1(. hat is the ratio of modulating power to total power at 1(( modulation/ percent a. ,9: b. 12 c. 23 d. 4one of the above
SIN;LE/SIDE1AND TECHNI
b. 9estigial sideband =63F> c. Sin)le/"ieban= "u''#e""e ca##ie# >?:E@ d. ?ouble"sideband, full carrier ='3> 3. Indicate which one of the following advantages of the phase cancellation method of obtaining 55< over the filter method is a. 5witching from one sideband to the other is simpler. b. It is possible to generate 55< at any fre#uency. c. 55< with lower audio fre#uencies present can be generated . The#e a#e !$#e balance !$ulat$#" the#ef$#e the ca##ie# i" "u''#e""e bette#. . %he most commonly used filters in 55< generation are a. !echanical b. 86 c. :6 d. low"pass
!. In an 55< transmitter, one is most likely to find a a. class 6 audio amplifier b. tuned modulator c. cla"" 1 RB a!'lifie# d. class ' 8F output amplifier $. Indicate in which one of the following only one sideband is transmitted. a. H:E b. c. <- d. '3 63F
false
+. ne of the following 55<. %his is the a. filter system b. phase"shift method c. third method . balance !$ulat$#
cannot be used to remove the unwanted sideband in
-. 83 modulation is sometimes used to a. allow the receiver to have a fre#uency synthesi*er b. "i!'lif( the f#e0uenc( "tabilit( '#$ble! in #ece'ti$n c. reduce the power that must be transmitted d. reduce the bandwidth re#uired for transmission . %o provide two or more voice circuits with the same carrier, it is necessary to use a. IS1 b. carrier insertion c. 55< with pilot carrier d. :incompe&
1(. 9estigal sideband modulation =63F> is normally used for a. )F point"to"point communications b. monoaural asting broadc c. T6 b#$aca"tin) d. stereo broadcasting
BRE
-. 5ince noise phase"modulates the FM wave, as the noise sideband fre#uency approaches the carrier fre#uency, the noise amplitude a. remains constant b. i" ec#ea"e c. is increased d. is e#uali*ed . hen the modulating fre#uency is doubled, the modulation inde& is halved, and the modulating voltage remains constant. %he modulation system is a. amplitude modulation b. phase modulation c. f#e0uenc( !$ulati$n d. any of the three 1(. Indicate which one of the following is a.
an advantage not of FM over 'M
11. ne of the following is an indirect way of generating FM. %his is the a. reactance F% modulator b. varactor diode modulator c. A#!"t#$n) !$ulat$# d. reactance bipolar transistor modulator 12. In an FM stereo multiple& transmission, the a. sum signal modulates 1 k)* subcarrier b. difference signal modulates the 1 k)* subcarrier c. iffe#ence "i)nal !$ulate" the :- H2 "ubca##ie# d. difference signal modulates the $+ k)* subcarrier
RADIO RECEI6ERS 1. Indicate which of the following statements about the advantages of the discriminator over the slope detector is phase a. Much easier alignment b.
3. In a radio receiver with simple '76 a. an inc#ea"e in "i)nal "t#en)th '#$uce" !$#e A;C b. the audio stage gain is normally controlled by the '76 c. the faster the '76 time constant the more accurate the output d. the highest '76 voltage is produced
. In a broadcast superheterodyne receiver, the a. local oscillator operates below the signal fre#uency b. !i*e# in'ut !u"t be tune t$ the "i)nal f#e0uenc( c. local oscillator fre#uency is normally double the IF d. 8F amplifier normally works at !! k)* above the carrier fre#uency !. %o prevent overloading of the IF amplifier in a receiver, one should use a. s#uelch b. &a#iable "en"iti&it( c. variable selectivity d. double conversion $. ' superheterodyne receiver with an IF of !( k)* is tuned to a at 12(( k)*. %he image fre#uency is signal . ,k)* H2 b. a. 1$!( c. +!( (( k)* k)*
false
+. In a ratio detector a. the linea#it( i" %$#"e than in 'ha"e i"c#i!inat$# b. stabili*ation against signal strength variations is provided c. the output is twice that obtainable from a similar phase discriminator d. the circuit is the same as in a discriminator, e&cept that the diodes are reversed
-. %he typical s#uelch circuit cuts off a. an aui$ a!'lifie# %hen the ca##ie# i" ab"ent b. 8F interference when the signal is weak c. 'n IF amplifier when the '76 is ma&imum d. 'n IF amplifier when the '76 is minimum
. Indicate the receivers.
false
statement in connection with communications
a. %he noise limiter cuts off the receiverAs output during a noise pulse. b. ' product demodulator could be used for the reception of Morse c. ?ouble conversion is used to improve image reBection code. . 6a#iable "en"iti&it( i" u"e t$ eli!inate "electi&e fain) 1(. %he controlled oscillator synthesi*er is sometimes preferred over the direct one because a. it is a simpler piece of e#uipment b. its fre#uency stability is better c. it does not re#uire crystal oscillator . it i" #elati&el( f#ee $f "'u#i$u" f#e0uenc( 11. %he fre#uency generated by each decade in a direct fre#uency synthesi*er is much higher than the fre#uency shown; this is done to a. #euce the "'u#i$u" f#e0uenc( '#$ble! b. increase the fre#uency stability of the synthesi*er c. reduce the number of decades d. reduce the number of crystals re#uired
12. Indicate which of the following circuits could a.
demodulate not 55<
13. If a F% is used as the first 'F amplifier in a transistor receiver, this will have the effect of a. improving the effectiveness of the '76 b. #eucin) the effect $f ne)ati&e/'ea cli''in) c. reducing the effect of noise at low modulation depths d. improving the selectivity of the receiver 1. Indicate the false statement. %he superheterodyne receiver replaced the %8F receiver because the latter suffered from a. gain variation over the fre#uency coverage range b. in"ufficient )ain an "en"iti&it( c. inade#uate selectivity at high fre#uencies d. instability 1!. %he image fre#uency of a superheterodyne receiver a. is created within the receiver itself b. is due to insufficient adBacent channel reBection c. i" n$t #e5ecte be the IB tune ci#cuit" d. is independent of the fre#uency to which the receiver is tuned 1$. ne of the main functions of the 8F amplifier in a superheterodyne receiver is to a. provide improved tracking b. permit better adBacent"channel reBection c. increase the tuning range of the receiver . i!'#$&e the #e5ecti$n $f the i!a)e f#e0uenc( 1+. ' receiver has poor IF selectivity. It will therefore also have poor a. bl$cin) b. double"spotting c. diversion reception d. sensitivity
1-. %hree"point tracking is achieved with a. variable selectivity b. the 'ae# ca'acit$# c. double spotting d. double conversion c. because otherwise an intermediate fre#uency could not be 1. %he local oscillator of a broadcast receiver is%ith$ut tuned to"%itchin) a fre#uency . t$ all$% ae0uate f#e0uenc( c$&e#a)e higher b. produced a. to than help permit the theincoming easier imagetracking fre#uency fre#uency reBection
2(. If the intermediate fre#uency is very high =indicate
a. image fre#uency reBection is very good b. the local oscillator need not be e&tremely stable c. the or selectivity will be po . t#acin) %ill be i!'#$&e 21. ' low ratio of the ac to the dc load impedance of a diode detector results in a. diagonal clipping b. poor '76 operation c. ne)ati&e/'ea cli''in) d. poor 'F response 22. ne of the following
cannot be used to demodulate 55<
a. Croduct detector b. ?iode
false
statement. 4oting that no carrier is transmitter
a. the receiver cannot use a phase comparator for 'F6 b. a5acent/channel #e5ecti$n i" !$#e ifficult c. production of '76 is a rather complicated process d. the transmission is not compatible with '3 2. hen a receiver has good blocking performance, this means that a. it does not suffer from double"spotting b. its image fre#uency reBection is poor c. it i" unaffecte b( A;C e#i&e f#$! nea#b( t#an"!i""i$n" d. its detector suffers from burnout 2!. 'n 'M receiver uses a diode detector for demodulation. %his satisfactorily to receive enables it a. single"sideband, suppressed"carrier b. single"sideband, reduced"carrier c. I5< . Sin)le/"ieban= full/ca##ie#
statement> false
TRANSMISSION LINES 1. Indicate the false statement. %he 58 on a transmission line is infinity; the line is terminated in a. a short circuit b. a c$!'le* i!'eance c. an open circuit d. a pure reactance 2. ' =+!" j !(>" is connected to a coa&ial transmission line of E at 1( 7)*. %he best method of matching consists in connecting a. a short"circuited stub at the load b. an inductance at the load c. a capacitance at some specific distance . a "h$#t/ci#cuite "tub at "$!e "'ecific i"tance f#$! the l$a 3. %he velocity factor of a transmission line a. e'en" $n the ielect#ic c$n"tant $f the !ate#ial u"e b. increases the velocity along the transmission line c. is govern by the skin effect d. is higher for a solid dielectric than for air
. Impedance inversion may be obtained with a. a short"circuited stub b. an open"circuited stub c. a 0ua#te#/%a&e line d. a half"wave line !. 5hort"circuited stubs are preferred to open"circuited stubs because latter the are a. more difficult to make an connect b. made sion line of awith transmis a different characteristic impedance c. liable t$ #aiate d. incapable of giving a full range of reactances $. For transmission"line load matching over a range of fre#uencies, it best is to use a a. balun b. broadband directional coupler c. $uble "tubof adBustable position d. single stub
+! ,
+. %he main disadvantage of the two"hole directional coupler is a. low directional coupling b. poor directivity c. high 58 . na##$% ban%ith -. %o couple a coa&ial line to a parallel"wire line, it is best to use a a. slotted line b. balun c. directional coupler d. #uarter"wave transformer . Indicate the three types of transmission line energy losses. a. I 2 R, R L , and temperature b. Raiati$n= I 2 R= an ielect#ic heatin) c. ?ielectric separation, insulation breakdown, and radiation d. 6onductor heating, dielectric heating, and radiation resistance. 1(. Indicate the
true statement below. %he directional coupler is
a. a device used to connect a transmitter to a directional antenna b. a c$u'lin) e&ice f$# !atchin) i!'eance c. a device used to measure transmission line power d. an 58 measuring instrument
RADIATION AND PROPA;ATION OB A6ES 1. Indicate which one of the following terms applies to troposcatter propagation a. 5I?s b. Bain) c. 'tmospheric storms d. Faraday rotation 2. 9:F waves are used for some type of services because a. of the low powers re#uired b. the transmitting antennas are of convenient si*e c. the( a#e &e#( #eliable d. the penetrate the ionosphere easily 3. Indicate which of the following fre#uencies beyond"the"hori*on terrestrial communications without repeaters a. 2( k)* b. 1! M)* c. (( M)* . , ;H2 . )igh"fre#uency waves are a. absorbed by the F 2 layer b. reflected by the Dlayer c. capable of use for long"distance communications on the moon . affecte b( the "$la# c(cle !. ?istances near the skip distance should be used for the sky"wave propagation a. to avoid tilting b. t$ '#e&ent "(/%a&e an u''e# #a( inte#fe#ence c. to avoid the Faraday effect d. so as nor to e&ceed the critical fre#uency $. ' ship"to"ship communications system is plagued by fading. %he solution seems to be use of best a. a more directional antenna b. a broadband antenna c. f#e0uenc( i&e#"it( d. space diversity
be cannot used for reliable
+. ' range of microwave fre#uencies more easily passed by the atmosphere than are the others is called a a. %in$% b. critical fre#uency c. gyro fre#uency range d. resonance in the atmosphere
-. Fre#uencies in the 0)F range normally propagate by means of a. ground waves b. sky waves c. surface waves . "'ace %a&e" . %ropospheric scatter is used with fre#uencies in the following range a. )F b. 9)F c. UHB d. 9:F 1(. %he ground wave eventually disappears, as one moves away from the transmitter, because of a. interference from the sky wave b. loss of line"of"sight conditions c. ma&imum single"hop distance limitation . tiltin) 11. In electromagnetic waves, polari*ation a. is caused by reflection b. i" ue t$ the t#an"&e#"e natu#e $f the %a&e" c. results from the longitudinal nature of the waves d. is always vertical in an isotropic medium 12. 's electromagnetic waves travel in free space, only one of the following can happen to them a. absorption b. attenuati$n c. refraction d. reflection 13. b. %he absorption offrom radio by the atmosphere depends on a. the thei# f#e0uenc( c. d. their polari*ation distance of the thewaves waves atmosphere transmitter
1. lectromagnetic waves are refracted when they a. 'a"" int$ a !eiu! $f iffe#ent ielect#ic c$n"tant b. are polari*ed at right angles to the direction of propagation c. encounter a perfectly conducting plane d. pass through a small slot in a conducting plane
1!. ?iffraction of electromagnetic waves a. is caused by reflections from the ground b. arises only with spherical wavefronts c. will occur when the waves pass through a large slot . !a( $ccu# a#$un the e)e $f a "ha#' $b"tacle 1$. hen microwave signals follow the curvature of the earth, this is known as a. the dayFara effect b. uctin) c. tropospheric scatter d. ionospheric reflection 1+. )elical antennas are often used for satellite tracking at 9)F because of a. troposcatter b. superrefraction c. ionospheric ion refract . the Ba#aa( effect
ANTENNAS 1. 'n ungrounded antenna near the ground a. acts as a single antenna of twice the height b. is unlikely to need a ground screen c. act" a" an antenna a##a( d. must be hori*ontally polari*ed 2. ne of the following consists of nonresonant antennas a. The #h$!bic antenna b. %he folded dipole c. %he end"fire array d. %he broadside array
3. ne of the following is very useful as a multiband )F receiving antenna. %his is the a. conical horn b. folded dipole c. l$) 'e#i$ic d. s#uare loop . hich of the following antennas is best e&cited from a waveguide/ a.
not a reason for the use of an antenna coupler
a. %o make the antenna look resistive b. %o provide the output amplifier with the correct load impedance c. %o discriminate against harmonics . T$ '#e&ent #e#aiati$n $f the l$cal $"cillat$# . Ma#c$ni +. Indicate b. a. )elical c. ?iscone Folded the?ipole antenna that is not wideband:
-. Indicate which one of the following reasons for the use of a ground screen with antennas is false: a. Impossibility of a good ground connection b. Crovision of an earth for the antenna c. P#$tecti$n $f 'e#"$nnel %$#in) une#neath d. Improvement of the radiation pattern of the antenna . hich one of the following terms does
apply not to the Gagi"0da array/
a. 7ood bandwidth b. Carasitic elements c. Folded dipole . Hi)h )ain 1(. 'n antenna that is currently polari*ed us the a. helical b. small circular loop c. parabolic reflector d. Gagi"0da
11. %he standard reference antenna for the directive gain is the a. infinitesimal le dipo b. i"$t#$'ic antenna c. elementary doublet d. half"wave dipole 12. %op loading is sometimes used with an antenna in order to increase its a. effecti&e hei)ht b. bandwidth c. beamwidth d. input capacitance 13. 6assegrain feed is used with a parabolic reflector to a. increase the gain of the system b. increase the beamwidth of the system c. reduce the si*e of the main reflector . all$% the fee t$ be 'lace at a c$n&enient '$int 1. Eoning is used with a dielectric antenna in order to a. #euce the the bul $ffocusing the len"e b. c. increase d. correct pin"point thecurvature bandwidth of of the the wavefront lens from a horn that is too short
1!. ' helical antenna is used for satellite tracking because of its a. ci#cula# '$la#i2ati$n b. maneuverability c. broad bandwidth d. good front"to"back ratio
1$. %he discone antenna is a. useful direction"finding antenna b. used as a radar receiving antenna c. circularly polari*ed like other circular antennas . u"eful a" UHB #ecei&in) antenna" 1+. ne of the following is a. )alf"wave dipole b. L$)/'e#i$ic c. ?iscone d. Marconi
not an omnidirectional antenna
A6E;UIDES= RESONATORS AND COMPONENTS 1. hen an electromagnetic waves are propagated in a waveguide a. they travel along a broader walls of the guide b. the( a#e #eflecte f#$! the %all" but $ n$t t#a&el al$n) the! c. they travel through the dielectric without touching the walls d. they travel along all four walls of the waveguide 2. aveguides are used mainly for microwave signals because a. they depend on straight"line propagation which applies to microwaves only b. losses would be too heavy at lower fre#uencies c. there are no generators powerful enough to e&cite them at lower fre#uencies . the( %$ul be t$$ bul( at l$%e# f#e0uencie" 3. %he wavelength of a wave in a waveguide a. i" )#eate# than $f f#ee "'ace b. depends only on the waveguide dimensions and the free"space wavelength c. is inversely proportional to the phase velocity d. is directly propotional to the group velocity
. %he main difference between the operation of transmission lines and waveguides is that a. the latter are not distributed, like transmission lines b. the former can use stubs and #uarter"wave transformers, unlike the latter c. t#an"!i""i$n line" u"e the '#inci'al !$e $f '#$'a)ati$n= an the#ef$#e $ n$t "uffe# f#$! l$%/f#e0uenc( cut/$ff d. terms such as impedance matching and standing-wave ratio cannot be applied to waveguides !. 6ompared with e#uivalent transmission lines, 3"7)* waveguides false =indicate statement> a. are less lossy b. can r powers carry highe c. a#e le"" bul( d. have lower attenuation
$. hen a particular mode is e&cited in a waveguide, three appears an e&tra electric component, in the direction of propagation. %he mode is resulting a. transverse"electric b. t#an"&e#"e/!a)netic c. longitudinal d. transverse"electromagnetic +. hen electromagnetic waves are reflected at an angle from a wall, wavelength along the wall is their a. the same as in free space b. the same as the wavelength perpendicular to the wall c. shortened because of ?oppler effect . )#eate# than in the actual i#ecti$n $f '#$'a)ati$n -. 's a result of reflections from a plane conducting wall, electromagnetic waves ac#uire an apparent velocity greater than the velocity of light in space. %his is called the a. velocity of propagation b. normal velocity c. group velocity . 'ha"e &el$cit( . Indicate the false statement. hen the free space wavelength of a signal e#uals the cut"off wavelength of the guide a. the group velocity of the signal becomes *ero b. the phase velocity of the signal becomes infinite c. the cha#acte#i"tic i!'eance $f the )uie bec$!e" infinite d. the wavelength within the waveguide becomes infinite 1(. ' signal propagation in a waveguide has a full wave of electric intensity change between the two further walls, and no component of the electric field in the direction of propagation. %he mode is a. % 1,1 b. % 1,( c. %M 2,2 . TE = 11. %he dominant mode of propagation is preferred with rectangular waveguides because i!'eance =indicate can be !atche false i#ectl( statement> b. the #e"ultin) t$ c$a*ial line" a. it c. d. propagation leads is easier to the than ofsmallest it the without other waveguide modes any spurious dimensions generation can be ensured
12. ' choke flange may be used to couple two waveguides a. to help in the alignment of the waveguides b. because it is simpler than any other Boin c. t$ c$!'en"ate f$# i"c$ntinuitie" at the 5$in d. to increase the bandwidth of the system 13. In order to couple two generators to a waveguide system without coupling them to each other, on could not use a a. at"race r b. E /'lane T c. hybrid ring d. magic % 1. hich of the following waveguides tuning components is adBustable/ a. 5crew b. 5tub c. I#i" d. Clunger 1!. ' piston attenuator is a a. vane attenuator b. %a&e)uie bel$% cut$ff c. mode filter d. flap attenuator 1$. 6ylindrical cavity resonators are not used with klystrons because they have a. a Qthat is too low b. a shape whose resonant fre#uency is too difficult to calculate c. ha#!$nicall( #elate #e"$nant f#e0uencie" d. too heavy losses 1+. ' directional coupler with three or more holes is sometimes used preference to the two"hole coupler in a. because it is more efficient b. to increase coupling of the signal c. to reduce spurious mode generation . t$ inc#ea"e the ban%ith $f the "("te! a. ferrite n$nc$nucti&e %ith !a)netic '#$'e#tie" 1-. b. ' c. d. an a microwave insulator intemetallic is which semiconductor compound heavily with attenuates invented particularly magnetic by Faraday good fi elds conductivity
easily not
1. Manganese ferrite may be used as a =indicate
a. circulator b. isolato r c. )a#net d. phase shifter 2(. %he ma&imum power that may be handled by a ferrite component is limited by the a. Cu#ie te!'e#atu#e b. 5aturation magneti*ation c. line width d. gyromagnetic resonance
21. ' CI4 diode is a. a metal semiconductor point"contact diode b. a microwave mi&er diode c. often used as a microwave detector . "uitable f$# u"e a" a !ic#$%a&e "%itch 22. ' duple&er is used a. to couple two different antennas to a transmitter without mutual interference b. t$ all$% the $ne antenna t$ be u"e f$# #ece'ti$n $# #et#an"!i""i$n %ith$ut !utual inte#fe#ence c. to prevent interference between two antennas when they are to a receiver connected d. to increase the speed of the pulses in pulses in pulsed radar 23. For some applications, circular waveguides may be preferred to rectangular ones because of a. the section smaller needed crossat any fre#uency b. l$%e# attenuati$n c. freedom from spurious modes d. rotation of polari*ation 2. Indicate which of the following cannot be followed by the word Hwaveguide a. lliptical b. Fle&ible c. d. C$a*ial 8idged
false
answer>
2!. In order to reduce cross"sectional dimensions, the waveguide to use is a. circular b. #i)e c. rectangular d. fle&ible 2$. For low attenuation, the best transmission medium is a. fle&ible waveguide b. ridged waveguide c. #ectan)ula# %a&e)uie d. coa&ial line
MICROA6E TU1ES AND CIRCUITS 1. ' microwave tube amplifier uses an a&ial magnetic field and a radial electric field. %his is the a. refle& klystron b. coa&ial magnetron c. traveling"wave magnetron . CBA 2. ne of the following is unlikely to be used as a pulsed device. It is the a. multicavity klystron b. 1O c. 6F' d. %% 3. ne of the reasons why vacuum tubes eventually fail at microwave fre#uencies is that their a. n$i"e fi)u#e inc#ea"e" b. transit time becomes too short c. shunt capactitive reactances become too large d. series inductive reactances become too small
. Indicate the reduced if
false
statement. %ransit time in microwave tubes will be
a. the electrodes are brought closer together b. a higher anode current is used c. !ulti'le $# c$a*ial lea" a#e u"e d. the anode voltage is made larger !. %he multicavity klystron a. i" n$t a )$$ l$%/le&el a!'lifie# becau"e $f n$i"e b. has a higher repeller voltage to ensure a rapid transit time c. is not suitable for pulsed operation d. needs a long transit time through the buncher cavity to ensure current modulation
$. Indicate the cavities to
false
statement. Jlystron amplifiers may use intermediate
a. '#e&ent the the efficiency $"cillati$n" $ccu# in t%$/ca&it( l("t#$n" b. c. improve d. increase bandwidth power gainof ofthat the theklystron device
+. %he %% is sometimes preferred to the multicavity klystron amplifier, because it a. is more efficient b. ha" a )#eate# ban%ith c. has a higher number of modes d. produces a higher output power -. %he transit time in the repeller space of a refle& klystron must be cycles to ensure that
n K
a. electrons are accelerated by the gap voltage on their return b. #etu#nin) elect#$n" )i&e ene#)( t$ the )a' $"cillati$n" c. it is e#ual to the period of the cavity oscillations d. the repeller is not damaged by striking electrons . %he cavity magnetron uses strapping to a. '#e&ent !$e 5u!'in) b. prevent cathode back"heating c. ensure bunching d. improve the phase"focusing effect
1(. ' magnetic field is used in the cavity magnetron to a. prevent anode current in the absence of oscillation b. ensure that the oscillations are pulsed c. help in focusing the electron beam, thus preventing spre . en"u#e that the elect#$n" %ill $#bit a#$un the cath$e 11. %o avoid difficulties with strapping at high fre#uencies, the type of cavity structure used in the magnetron is th a. hole"and"slot b. slot c. vane . #i"in) "un 12. %he primary purpose of the heli& in a traveling"wave tube is to a. prevent the electron beam from spreading in the long tube b. #euce the a*ial &el$cit( $f the RB fiel c. ensure broadband operation d. reduce the noise figure 13. %he attenuator is used in the traveling"wave tube to b. '#e&ent $"cillati$n" a. help c. d. prevent increase bunching satur gain ation
ading
1. Ceriodic permanent"magnet focusing is used with %%s to a. allow pulsed operation b. improve electron bunching c. a&$i the bul $f an elect#$!a)net d. allow coupled"cavity operation at the highest fre#uencies 1!. %he %% is sometimes preferred to the magnetron as a radar transmitter output tube because it is a. ca'able $f a l$n)e# ut( c(cle b. a more efficient bandwidth c. more broadband d. less noisy
1$. ' magnetron whose oscillating fre#uency is electronically adBustable over a wide range is called a a. coa&ial magnetron b. dither"tuned magnetron c. fre# uency"agile magnetron . 6TM 1+. Indicate which of the following is a. Pe#i$ic/'e#!anent !a)net b. 6oupled cavity c. )eli& d. 8ing"bar
1-. %he glass tube of a %% may be coated with a#uadag to a. help focusing b. '#$&ie attenuati$n c. improve bunching d. increase gain 1. ' backward"wave oscillator is based on the a. rising"sun magnetron b. crossed"field amplifier c. coa&ial magnetron . t#a&elin)/%a&e tube
not a %% slow"wave structure
SEMICONDUCTOR MICROA6E DE6ICES AND CIRCUITS 1. ' parametric amplifier must be cooled a. because parametric amplification generates a lot of heat b. to increase bandwidth c. because it cannot operate at room temperature . t$ i!'#$&e the n$i"e 'e#f$#!ance 2. ' ruby maser amplifier must be cooled a. because maser amplification generates a lot of heat b. to increase bandwidth c. becau"e it cann$t $'e#ate at #$$! te!'e#atu#e d. to improve the noise performance 3. ' disadvantage of microstrip compared with stripline is that microstrip a. does not readily lend itself to printed circuit techni#ues b. i" !$#e liel( t$ #aiate c. is bulkier d. is more e&pensive and comple& to manufacture . %he transmission system using two ground plane is a. microstrip b. elliptical waveguide c. parallel"wire line . "t#i'line !. Indicate the is its
false
statement. 'n advantage of stripline over wveguide
a. smaller bulk b. greater bandwidth c. hi)he# '$%e#/hanlin) ca'abilit( d. greater compatibility with solid"state devices $. Indicate the is its
false
statement. 'n advantage of stripline over microstrip
a. ea"ie# inte)#ati$n %ith "e!ic$nuct$# e&ice" b. lower tendency to radiate c. higher isolation between adBacent circuits d. higher L . 0ua#t2 c#("tal +. 5urface b. a. gallium c. stripline indium acoustics phosphide arsenide waves propagate in
-. 5' devices may be used as a. t#an"!i""i$n !eia lie "t#i'line b. filters c. 0)F amplifiers d. scillators at millimeter fre#uencies
. Indicate the false statement. F%s are preferred to bipolar transistors at the highest fre#uencies because they a. are less noisy b. len the!"el&e" !$#e ea"il( t$ inte)#ati$n c. are capable of higher effeciencies d. can provide higher gains 1(. For best low"level noise performance in the "band, an amplifier should use a. a bipolar transistor b. a 7unn diode c. a "te'/#ec$&e#( i$e d. an IMC'%% diode 11. %he biggest advantage of the %8'C'%% diode over the IMC'%% its diode is a. lower noise b. hi)he# efficienc( c. ability to operator at higher fre#uencies d. lesser sensitivity to harmonics 12. Indicate which of the following diodes will produce the highest pulsed power output a. 9arator b. 7unn c. barrier 5chottky . RIMPATT 13. Indicate which of the following diodes does not use negative resistnace in its operation a. 1ac%a# b. 7unn c. d. IMC'%% %unnel
1. ne of the following is
not used as a microwave mi&er or detector
a. 6rystal diode b. 5chottky"barrier diode c.
1$. %he transferred"electron bulk effect occurs in a. germanium b. )alliu! a#"enie c. silicon d. metal semiconductor Bunctions 1+. %he gain"bandwidth fre#uency of a microwave transistor, fre#uency at which the a. alpha of the transistor falls by 3 d< b. beta of the transistor falls by 3 d< c. power gain of the transistor falls to . beta $f the t#an"i"t$# fall" t$ unit(
is the" !
unity
1-. For a microwave transistor to operate at the highest fre#uencies, the =indicate the false answer> a. collector voltage must be large b. collector current must be high c. base should be thin . e!itte# a#ea !u"t be la#)e 1. ' varactor diode may be useful at microwave fre#uencies false =indicateanswer> the a. for electronic tuning b. for tiplication fre#uency mul c. a" an $"cillat$# d. as a parametric amplifier
2(. If high"order fre#uency multiplication is re#uired from a diode multiplier, a. the resistive cutoff fre#uency must be high b. a small value of the base resistance is re#uired c. a "te'/#ec$&e#( i$e !u"t be u"e d. a large range of capacitance variation is needed 21. ' parametric amplifier has an input and output fre#uency of 2.2! 7)*, and is pumped at .! 7)*. It is a. traveling"wave amplifier b. e)ene#ati&e a!'lifie# c. lower"sideband up"converter d. upper"sideband up"converter 22. ' nondegenerate parametric amplifier has an input fre#uency pump fre#uency f p . %hen idler fre#uency is a. f i b. 2 f i c. f i N f p . f p / f i 23. %raveling"wave parametric amplifiers are used to a. provide a greater gain b. reduce the number of varactor diodes re#uired c. avoid the need for cooling . '#$&ie )#eate# ban%ith 2. ' parametric amplifier sometimes uses a circulator to a. '#e&ent n$i"e feebac b. allow the antenna to be used simultaneously for transmission and reception c. separate the signal and idler fre#uencies d. permit more efficient pumping
2!. %he nondegenerate one"port parametric amplifier should have a high ratio of pump to signal fre#uency because this a. permits fre#uency satisfactory operationhigh" b. (iel" a l$% n$i"e fi)u#e c. reduce the pump power re#uired d. permits satisfactory
and
i
2$. %he tunnel diode a. has a tiny hole through its center to facilitate tunneling b. is a point"contact diode with a very high reverse resi c. u"e" a hi)h $'in) le&el t$ '#$&ie a na##$% 5uncti$n d. works by #uantum tunneling e&hibited by gallium arsenide only 2+. ' tunnel diode is loosely coupled to its cavity in order to a. inc#ea"e the f#e0uenc( "tabilit( b. increase the available negative resistance c. facilitate tuning d. allow operation at the highest fre#uencies
2-. %he negative resistance in a tunnel diode a. is ma&imum at the peak point of the characteristic b. i" a&ailable bet%een the 'ea an &alle( '$int" c. is ma&imum at the valley point d. may be improved by the use of reverse bias 2. %he biggest advantage of gallium antimonide over germanium for diode use it that former has a tunnel" a. lower noise b. higher ion mobility c. la#)e# &$lta)e "%in) d. simpler fabrication process 3(. 4egative resistance is obtained with a 7unn diode because of a. elect#$n t#an"fe# t$ a le"" !$bile ene#)( le&el b. avalanche breakdown with the high voltage gradient c. tunneling across the Bunction d. electron domains forming at the Bunction
31. For 7unn diodes, gallium arsenide is preferred to silicon because former the a. ha" a "uitable e!'t( ene#)( ban= %hich "ilic$n $e" n$t ha&e b. has a higher ion mobility c. has a lower noise at the highest fre#uencies d. is capable of handling higher power densities
32. %he biggest disadvantage of the IMC'%% diode is its b. hi)hpower"handling n$i"e a. lower c. d. inability low efficiency to provide than pulsed ability that ofoperation the other microwave diodes
stance
33. %he 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"temperature operation . '#$&ie f#e0uenc( a5u"t!ent" 3. %he ruby maser has been preferred to the ammonia maser for microwave amplification, because the former has a. a !uch )#eate# ban%ith b. a better fre#uency stability c. a lower noise figure d. no need for a circulator
3!. Carametric amplifiers and masers are similar to each other in that both =indicate false statement> a. must have pumping b. are e&tremely low"noise amplifiers c. !u"t be c$$le $%n t$ a fe% el&in" d. generally re#uired cicultators, since they are one"port devices 3$. ' maser 8F amplifier is not really suitable for a. radioastronomy b. satellite communications c. #aa# d. troposcatter receiver 3+. %he ruby laser differs from the ruby maser in that the former a. does not re#uire pumping b. needs no resonator c. i" an $"cillat$# d. produces much lower powers 3-. %he output from a laser is monochromatic; this means that it is a. infrared b. polari*ed c. narrow"beam . "in)le/f#e0uenc( 3. For a given average power, the be increased by Q"'$ilin) b. u"in)cooling a. increasing c. d. using dispensing the with magnetic the Fabry"Cerot field resonator
pea# output power of a ruby laser may
(. 6ommunications lasers are used with optical fiber, rather than in open links, to a. ensure that the beam does not spr b. '#e&ent at!$"'he#ic inte#fe#ence c. prevent interference by other laser d. ensure that people are not blinded by them 1. Indicate the over :?s include
false
ead
statement. %he advantages of semiconductor lasers
a. monochromatic output b. higher power output c. l$%e# c$"t d. ability to be pulsed at higher rates
DI;ITAL COMMUNICATIONS 1. ?igital signals a. do not provide a continuous set of values b. represent values as discrete steps c. can al orutili*e binary decim systems . all $f the ab$&e 2. %he event which marked the start of the modern computer age was a. design of the 4I'6 computer b. development of the )ollerith code c. e&el$'!ent $f the t#an"i"t$# d. development of disk drives for data storage 3. %he baud rate a. is always e#ual to the bit transfer rate b. i" e0ual t$ t%ice the ban%ith $f an ieal channel c. is not e#ual to the signaling rate d. is e#ual to one"half the bandwidth of an ideal channel . %he 5hannon")artley law a. refers to distortion b. defines bandwidth c. describes signaling rates . #efe#" t$ n$i"e !. %he code which provides for parity checks is a.
-. %he 85"232 interface a. inte#c$nnect" ata "et" an t#an"!i""i$n ci#cuit b. uses several different connectors c. permits custom wiring of signal lines to the connector pins as desired d. all of the above
. 5witching systems a. improve the efficiency of data transfer b. are not used in data systems c. re#uire additional lines . a#e li!ite t$ "!all ata net%$#" 1(. %he data transmission rate of a modem is measured in a. bytes per second b. baud rate c. bit" 'e# "ec$n d. megahert*
1ROAD1AND CUMMUNICATIONS SYSTEMS 1.
3. ' basic group
$
a. $ccu'ie" the f#e0uenc( #an)e f#$! 7 t$ ,- H2 b. consists of erect channels only c. is formed at the group translating e#uipment d. consists of five supergroups
. %ime"division multiple& a. can be used with C6M only b. combines five groups into a supergroup c. stacks 2 channels in adBacent fre#uency slots . inte#lea&e" 'ul"e" bel$n)in) t$ iffe#ent t#an"!i""i$n" !. %he number of repeaters along a coa&ial cable link depends on a. whether separate tubes are used for the two directions of transmission b. the ban%ith $f the "("te! c. the number of coa&ial cables in the tube d. the separation of the e#uali*ers $. ' supergroup pilot is a. applied at each multiple&ing bay b. used to regulate the gain of individual repeaters c. applied at each adBustable e#uali*er . fe in at a ;TE
+. Microwave link repeaters are typically !( km apart a. because of atmospheric attenuation b. because of output tube power limi tations c. becau"e $f the Ea#th3" cu#&atu#e d. to ensure that the applied dc voltage is not e&cessive -. Microwave links are generally preferred to coa&ial cable for television transmission because a. the( ha&e le"" $&e#all 'ha"e i"t$#ti$n b. they are cheaper c. of their greater bandwidths d. of their relative immunity to impulse noise
. 'rmored submarine cable is used a. to protect the cable at great depths b. to prevent inadvertent ploughing"in of the cable c. f$# the "hall$% "h$#e en" $f the cable d. to prevent insulation breakdown from the high feed voltages 1(. ' submarine cable repeater contains, among other e#uipment, a. a dc power supply and regulator b. filte#" f$# the t%$ i#ecti$n" $f t#an"!i""i$n c. multiple&ing and demultiple&ing e#uipment d. pilot inBected pilot e&tract e#uipment 11. ' geostationary satellite a. is motionless in space =e&cept for its spin> b. i" n$t #eall( "tati$na#( at all= but $#bit" the Ea#th %ithin a 4/ h# 'e#i$ c. appears stationary over the arthAs magnetic pole d. is located at a height of 3!,-(( km to ensure global coverage 12. 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. 5atellites are allocated so that it is impossible for two earth stations not to face the same satellite c. 6ollocated earth stations are used for fre#uency diversity . A "atellite ea#th "tati$n !u"t ha&e a" !an( #ecei&e chain" a" the#e a#e ca##ie#" t#an"!itte t$ it
13. 5atellite used for intercontinental communications are known as a. 6omsat b. ?omsat c. Marisat . Intel"at 1. Identical telephone numbers in different parts of a country are distinguished by their a. language digits b. access digits c. a#ea c$e" d. central office codes 1!. %elephone traffic is measured a. with echo cancellers b. by the relative congestion c. in terms of the grade of service . in e#lan)" 1$. In order to separate channels in a use
"D% receiver, it is necessary to
a. AND )ate" b. bandpass filters c. differentiation d. integration
1+. %o separate channels in an F?M receiver, it is necessary to use a. AND )ate" b. bandpass filters c. differentiation d. integration
1-. )igher order %?M levels are obtained by a. i&iin) 'ul"e %ith" b. using the a"law c. using the O"law d. forming supermastergroups
1. :osses in optical fibers can be caused by =indicate the statement> . "te''e ine* $'e#ati$n b. a. attenuation c. impurities microbending in the glass
false
2(. %he 1.!! Om Hwindow is not yet in use with fiber optic systems because a. the attenuation is higher than at (.-! Om b. the attenuation is higher that at 1.3 Om c. suitable laser devices have not . it $e" n$t len it"elf t$ %a&e 21. Indicate which of the following is
yet been developed
not a submarine cable
a. %'%"+ b. INTELSAT 6 c. '%:'4%I5 d. 6'4%'% 2 22. Indicate which of the following is an 'merican domsat system a. INTELSAT b. COMSAT c. %:5%'8 . INMARSAT
RADAR SYSTEMS 1. If the peak transmitted power in a radar system is increased by a factor of 1$, the ma&imum range will be increased by a factor a. b. c. d. 1$
2. If the antenna diameter in a radar system is increased by a factor of , the ma&imum range will be increased by a factor of a. v2 b. 2 c. 4 d. 3. If the ratio of the antenna diameter to the wavelength in a radar system is high this will result in =indicate the
false statement>
a. large ma&imum range b. good target discrimination c. difficult target ac#uisition . inc#ea"e ca'tu#e a#ea . %he radar cross section of a target =indicate the
a. depends on the fre#uency used b. may be reduced by special coating of the target c. depends on the aspect of a target, if this nonspherical . i" e0ual t$ the actual c#$""/"ecti$nal a#ea f$# "!all ta#)et" !. Flat"topped rectangular pulses must be transmitted in radar to =indicate the false statement> a. allow a good minimum range b. !ae the #etu#ne ech$e" ea"ie# t$ i"tin)ui"h f#$! n$i"e c. prevent fre#uency changes in the magnetron d. allow accurate range measurements $. ' high C8F will =indicate the
false
statement>
a. make the returned echoes easier to distinguish from noise b. make target tracking easier with conical scanning c. inc#ea"e the !a*i!u! #an)e d. have no effect on the range resolution
statement> false
+. %he IF bandwidth of a radar receiver is inversely proportional to the a. 'ul"e %ith b. pulse repetition fre#uency c. pulse interval d. s#uare root of the peak transmitted power -. If a return echo arrives after the allocated pulse interval, a. it will interfere with the operation of the transmitter b. the receiver might be overloaded c. it will not be received . the ta#)et %ill a''ea# cl$"e# than it #eall( i" . 'fter a target has been ac#uired, the best scanning system for is tracking a. nodding b. spiral c. c$nical d. helical 1(. If the target cross section is changing, the best system for accurate tracking is a. lobe switching b. se#uential lobing c. conical anning sc . !$n$'ul"e 11. %he biggest disadvantage of 6 ?oppler radar is that a. it does not give the target veloci b. it $e" n$t )i&e the ta#)et #an)e c. a transponder is re#uired at the target d. it does not give the target position
ty
12. %he ' scope displays a. the target position and range b. the ta#)et #an)e= but n$t '$"iti$n c. the target position, but not range d. neither range nor position, but not only velocity 13. %he ?oppler effect is used in =indicate the a. !$&in)/ta#)et b. c. FM d. 6 the M%I radar radar system'l$ttin) $n the PPI
false statement>
1. %he coho in M%I radar operates at the a. inte#!eiate f#e0uenc( b. transmitted fre#uency c. received fre#uency d. pulse repetition fre#uency
1!. %he function of the #uart* delay line in an M%I radar is to a. hel' in "ubt#actin) a c$!'lete "can f#$! the '#e&i$u" "can b. match the phase of the coho and the stalo c. match the phase of the coho and the output oscillator d. delay a sweep so that the ne&t sweep can be subtracted from it
1$. ' solution to the Hblind speed problem is a. to change the ?oppler fre#uency b. t$ &a#( the PRB c. to use monopulse d. to use M%I 1+. Indicate which one of the following applications or advantages of radar beacons is false: a. %arget identification b. 4avigation c. 9ery significant e&tension of the ma&imum range . M$#e accu#ate t#acin) $f ene!( ta#)et" 1-. 6ompared with other types of radar, phased array radar has the following advantages =indicate the false statement> a. very fast scanning b. ability to track and scan simultaneously c. ci#cuit "i!'licit( d. ability to track many targets simultaneously
PULSE COMMUNICATIONS 1. Indicate which of the following is
not a binary code
a. M$#"e b.
2. %o permit the selection of 1 out of 1$ e#ui"probable events, the number of bits re#uired is a. 2 b. log c. . 4
1(
1$
3. ' signaling 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 memori*e b. it is redundant c. n$i"e %$ul int#$uce t$$ !an( e##$#" d. too many pulses per letter are re#uired . %he )artley states that a. the !a*i!u! #ate $f inf$#!ati$n t#an"!i""i$n e'en" $n the ban%ith channel b. the ma&imum rate of information transmission depends on the depth of modulation c. redundancy is essential d. only binary codes may be used
!. Indicate the
false
statement. In order to combat noise,
a. the channel ban%ith !a( be inc#ea"e b. redundancy may be used c. the transmitted power may be increased d. the signaling rate may be reduced
$. %he most common modulation system used for telegraphy is a. f#e0uenc(/"hift e(in) b. two"tone modulation c. pulse"code d. single"tone modulation modulation
+. Culse"width modulation system used for telegraphy is a. by differentiating pulse"position modulation b. %ith a !$n$"table c. by integrating the signal d. with a free"running multivibrator -. Indicate which of the following system is digital. a. Culse"position modulation b. Pul"e/c$e !$ulati$n c. Culse"width modulation d. Culse"fre#uency modulation . Luanti*ing noise occurs in a. time"division multiple& b. fre#uency tiple& division mul c. 'ul"e/c$e !$ulati$n d. pulse"width modulation 1(. %he modulation system inherently most noise"resistant is a. 55<, suppressed"carrier b. Fre#uency modulation c. pulse"position ion modulat . 'ul"e/c$e !$ulati$n 11. In order to reduce #uanti*ing noise, one must a. inc#ea"e the nu!be# $f "tana# a!'litue" b. send pulses whose sides are more nearly vertical c. use an 8F amplifier in the receiver d. increase the number of samples per second
12. %he )artley"5hannon theorem sets a limit on the a. highest fre#uency that may be sent over a given channel b. !a*i!u! ca'acit( $f a channel %ith a )i&en n$i"e le&el c. ma&imum number of coding levels in a channel with a given noise level d. ma&imum number of #uanti*ing levels in a channel of a given bandwidth 13. Indicate which of the following pulse modulation systems is analog a. C6M b. ?ifferential C6M c. PM d. ?elta
1. 6ompanding is used a. to overcome #uanti*ing noise in C6M b. in C6M transmitters, to allow amplitude limited in the rece c. t$ '#$tect "!all "i)nal" in PCM f#$! 0uanti2in) i"t$#ti$n d. in C6M receivers, to overcome impulse noise 1!. %he biggest disadvantage of C6M is a. its inability to handle analog signals b. the high error rate which its #uanti*ing noise introduces c. its incompatibility with %?M . the la#)e ban%ith" that a#e #e0ui#e f$# it
ivers
TELE6ISION BUNDAMENTALS 1. %he number of lines per field in the 0nited 5tates %9 system is a. 7 b. !2! c. 3( d. $(
2. %he number of frames per second in the 0nited 5tates %9 system is a. $( b. 2$2P c. .! d. : 3. %he number of lines per second in the 0nited 5tates %9 system is a. 31,!(( b. ,8=F8 c. 2$2P d. !2! . %he channel width in the 0nited 5tates %9 system, in M)*, is a. 1.2! b. 7 c. .! d. 3.!!. Interlacing is used in television to a. produce the illusion of motion b. ensure that all the lines on the screen are scanned, not merely the alternate ones c. simplify the vertical sync pulse train . a&$i flice# $. %he signals sent by the %9 transmitter to ensure correct scanning in the receiver are called a. "(nc b. chroma c. luminance d. video
+. In the 0nited 5tates color television system, the fre#uency, in M)*, is
intercarrier
a. 3.! b. 3.!+! c. 4.8 d. !.+! -. Indicate which voltages are monochrome receiver video detector.
not
found in the output of a normal
a. 5ync b. 9ideo c. S%ee' d. 5ound . %he carrier transmitted 1.2! M)* above the bottom fre#uency in 0nited 5tates %9 channel is the the a. sound carrier b. chroma carrier c. intercarrier . 'ictu#e ca##ie# 1(. In television, 3 represents the a. interlace ratio b. ma&imum ontal deflection hori* c. a"'ect #ati$ d. ratio of the two diagonals 11. #uali*ing pulses in %9 are sent during a. hori*ontal blanking b. &e#tical blanin) c. the serrations d. the hori*ontal retrace 12. 'n odd number of lines per frame forms part of every one of the worldAs %9 systems. %his is a. $ne t$ a""i"t inte#lace b. purely an accident c. to ensure that line and frame fre#uencies can be obtained from the same original source d. done to minimi*e interference with the chroma subcarrier
13. %he function of the
serrations
in the composite video waveform is to
a. e#uali*e the charge in the integrator before the start of vertical retrace b. help vertical synchroni*ation c. hel' h$#i2$ntal "(nch#$ni2ati$n d. simplify the generation of the vertical sync pulse 1. %he width of the vertical sync pulse in the 0nited 5tates %9 system is a. 21 & b. : H c. & d. (.! & 1!. Indicate which of the following fre#uencies will output of a normal %9 receiver tuner a. 4.8 MH2 b. 1.2! M)* c. !.+! M)* d. 2.1+ M)*
1$. %he video voltage applied to the picture tube of a television receiver is fed in a. between grid and ground b. to the yoke c. to the anode . bet%een )#i an cath$e 1+. %he circuit that separates sync pulses from the composite video waveform is a. the keyed '76 amplifier b. a cli''e# c. an integrator d. a differentiator 1-. %he output of the vertical amplifier, applied to the yoke in a %9 receiver, consists of a. direct current b. amplified vertical sync c. a sawtooth voltage . a "a%t$$th cu##ent
be found not in the
1. %he )9 anode supply for the picture tube of a %9 receiver is generated in the a. mains transformer b. vertical output stage c. h$#i2$ntal $ut'ut "ta)e d. hori*ontal deflection oscillator 2(. 'nother name for the hori*ontal retrace in a %9 receiver is the a. ringing b. burst c. damper . fl(bac 21. Indicate which of the following signals is %9 a' b' c. d' 22. %he
( Q R I shadow mas#
in a color picture tube is used to
a. reduce &"ray emission b. en"u#e that each bea! hit" $nl( it" $%n $t" c. increase screen brightness d. provide degaussing for the screen 23. In a %9 receiver, the
color #iller
a. c ut" $ff the ch#$!a "ta)e" u#in) !$n$ch#$!e #ece'ti$n b. ensures that no color is transmitted to monochrome receivers c. prevents color overloading d. makes sure that the color burst is not mistaken for sync pulses, by cutting off reception during the back porch
transmitted not in color
INTRODUCTION TO BI1ER OPTIC TECHNOLO;Y 1. hat is the fre#uency limit of copper wire/ a. appro&imately (.! M)* b. a''#$*i!atel( ,. MH2 c. appro&imately ( 7)* d. 4one of the above 2. 'ppro&imately what is the fre#uency limit of the optical fiber/ a. 2( 7)* b. 1 M)* c. 1(( M)* d. ( M)* 3. ' single fiber can handle as many voice channel as a. a pair of copper conductors b. a ,8/'ai# cable c. a !(("pair cable d. a 1((("pair cable . 'n incident ray can be defined as a. a light ray reflected from a flat surface b. a li)ht #a( i#ecte t$%a# a "u#face c. a diffused light ray d. a light ray that happens periodically !. %he term
dispersion
describes the process of
a. "e'a#atin) li)ht int$ it" c$!'$nent f#e0uencie" b. reflecting light from a smooth surface c. the process by which light is absorbed by an uneven rough surface d. light scattering
$. hich of the following terms describes the reason that light is refracted at different angles/ a. Choton energy changes with wavelength b. :ight is refracted as a function of surface smoothness c. %he angle is determined partly by a and . The an)le i" ete#!ine b( the ine* $f the !ate#ial"
b
+. %he term critical angle describes a. the point at which light is refracted b. the point at which light becomes invisible c. the '$int at %hich li)ht ha" )$ne f#$! the #ef#acti&e !$e t$ the #eflecti&e !$e d. the point at which light has crossed the boundary layers from one inde& to another -. %he cladding which surrounds the fiber core a. is used to reduce optical interference b. is used to protect the fiber c. act" t$ hel' )uie the li)ht in the c$#e d. ensures that the refractive inde& remains constant . %he reflective inde& number is a. a nu!be# %hich c$!'a#e" the t#an"'a#enc( $f a !ate#ial %ith thatai# $f b. a number assigned by the manufacturer to the fiber in #uestion c. a number which determines the core diameter d. a term for describing core elasticity
1(. %he terms
single mode
and multimode
are best describes as
a. the number of fibers placed into a fiber"optic cable b. the number of voice channels each fiber can suppo c. the nu!be# $f %a&elen)th" each fibe# can "u''$#t d. the inde& number
rt
11. %he higher the inde& number a. the hi)he# the "'ee $f li)ht b. the lower the speed of light c. has no effect on the speed of light d. the shorter the wavelength propagation
12. %he three maBor groups in the optical system are a. the components, the data rate and response time b. the source, the link, and the receiver c. the transmitter, the cable, and the rec . the "$u#ce= the lin= an the etect$#
eiver
13. 's light c. .8 1 reduced b. a. 1.! d. (.((1 (.1 byd< d
1. hen connector losses, splice losses, and coupler losses are what is the final limiting factor/ added, a. 5ource power b. Fiber attenuation c. 6onnector and splice losses . Detect$# "en"iti&it( 1!. %he term described as
responsivit)
as it applies to a light detector is best
a. the time re#uired for the signal to go from 1( to ( percent of ma&imum amplitude b. the #ati$ $f the i$e $ut'ut cu##ent t$ $'tical in'ut '$%e# c. the ratio of output current to output power d. the ratio of output current to input current 1$. :oss comparisons between fusion splices and mechanical splices are a. ,9, b. 1(1 c. 2(1 d. 12( 1+. %he mechanical splice is best suited for a. #uicker installation under ideal conditions b. minimum attenuation losses c. fiel "e#&ice c$niti$n" d. situations in which cost of e#uipment is not a factor 1-. M? is best describe by which statement/ a. F 'e#cent $f the c$#e ia!ete# an FG $f the fibe# NA "h$ul be%ith li)ht fille b. +( percent of the fiber diameter and +(Q of the cone of acceptance should be filled with light c. +( percent of input light should be measured at the output d. +( percent of the unwanted wavelengths should be attenuated by the fiber
1. hich of the following cables will have the highest launch power capability/ a. . !(@12!@(.2 ,+,4+.: b. c. $2.!@12!@(.2 -!@12!@(.2+! +!