(Certii) Multiple Choice Questions in Communications

8/21/2019 (Certii) Multiple Choice Questions in Communications

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MULTIPLE CHOICE

Questions in

COMMUNICATIONS

CERTII-CONSOLIDATED ENGINEERING REVIEW & TRAINING INSTITUTE, INC.

Encoded by:

VILLAMAYOR !ON RYAN M"

ECE-#$%&&'(&)'()

ECE&&)$C(%


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COMMUNICATIONS

1. In reducing the voltage by ½, there is a decrease of _____.

a. 2 b. 3

c. 4d" '

2. A measure if mismatch in a transmission line.a. Reflection coefficient

b. ro!agation delay

c" St*ndin+ ,*e .*tio

d. All of these

3. "hich ty!e of transmission line has the least velocity factor#

a. Air$insulated !arallel line b. Air insulated coa%ial line

c. olyethylene !arallel line

d" Po/yet0y/ene co*1i*/ /ine

4. It is re&uired to match a '3 ohm antenna to a ()) ohm transmission line, *ith a velocity

factor of ).((, by means of a &uarter$*ave matching transformer. At a fre&uency of 1+)

-, calculate the length of matching section, in feet.

a. 2,2 b. )./

c" ("&

d. 1./

+. A transmitter radiates + 0" *ith unmodulated carrier but *hen the carrier is sinusoidally

modulated, it radiates (.+ 0". o*, another sine*ave corres!onding to 4) modulation

is transmitted simultaneously. etermine the total radiated !o*er.

*" '"2 34 b. (.+ 0"c. (.4 0"

d. '.( 0"

(. A circuit *hich is used to 0ee! the signal levels a!!ro%imately constant in the R stage

and the mi%er of an receiver.

*" A5C

b. A5

c. 6ocal oscillator

d. 6imiter

'. 7he highest fre&uency that can be set bac0 to earth by the ionos!here, if the *ave is sent

vertically u!*ard.*" M*1i6u6 Usu*b/e 7.e8uency 9MU7

b. 5ritical fre&uency

c. ro!agating fre&uency

d. 5ut$off fre&uency/. 7he difference bet*een the farthest !oint the direct *ave e%tend and the nearest !oint the

s0y *ave reflected to ground.a. 80i! distance


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b. Radio horion distance

c" !e*d ;one

d. resnel one9. o*er density is defined as radiated !o*er !er unit area, it follo*s that !o*er density is

reduced to : of its value *hen distance from the source is____.

*" !oub/e b. 7hree$fold

c. our$foldd. ive fold

1). If the clearance above the obstruction is e&ual to the second resnel one, the !ath of the

reflection *ave is !hysically _____ *avelength longer than the direct *ave.

a. ;ne$half

b" One

c. 7*o

d. three

11. Attached around the rim of the !arabolic antenna to eliminate side$lobes causing

interference to nearby micro*ave station.a. Radome b. eed$horn

c. Reflector

d" s0.oud

12. It is !olar diagram re!resenting field strengths or !o*er densities at various angular

!ositions

a. 6obe

b" R*di*tion


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d" t.ou+0

1'. "hat are the basic com!onents of a micro!hone#

a. 5oil and magnet b. 5eramic and crystal

c" !i*

d. Regional 5hannel

2). In television$receiver, the alignment of all these colors guns to a common !oint isreferred to as _____.

a. 5onfetti

b" Cone.+ence

c. emodulationd. blooming

21. It is a form of digital modulation *here the digital information is contained in both the

am!litude and !hase of the transmitted carrier.

*" QAM

b. 8@ c. 5

d. 8@ 22. An error detection scheme that uses !arity to determine if transmission error has occurred

in a message.

a. 5R5 b. >R5

c" HRC

d. All of the above

23. 8ynchroniation modem usually contains aa. 8crambler

b. escrambler

c. Ada!tive e&ualiers

d" A// o? t0e *boe24. or a standard voice band communications channel *ith a 8 of 3) d< and a band*idth

of 2.' 0-, the 8hannon limit for information ca!acity is _______.

a. /.1 0b!s

b. 12.4 0b!s

c. 4.)3 0b!s

d" %'"2 3b


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a. (92

b" '=%

c. 9(d. 4)32

2(. In this mode, a secondary station can not initiate transmission *ithout first receiving

!ermission from the !rimary station.a. NRM 9No.6*/ Res


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c.


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a. 5arrier current

b" Antenn* cu..ent

c. 5urrentd. one of these

42. 5hannels for broadcast station begin at ____ - and continue is successive ste!s of

2)) 0- to and including 1)'.9 -a. /9.1

b" @@"(

c. /9.9

d. one of these

43. 7he carrier *hich is modulated by the chrominance information.a. 5arrier fre&uency

b. I fre&uency

c" C0.o6in*nce subc*..ie.

d. 5olor burst

44. 7he transmission of television signal *hich can be re!roduced is gradations of a single

color only.*" Monoc0.o6e t.*ns6ission

b. egative transmission

c. 5olor transmissiond. >ideo transmission

4+. 7he carrier fre&uency allocated by the authority.

a. re&uency s*ing b. -igh fre&uency

c" Cente. ?.e8uency

d. I fre&uency4(. 8erving as a control signal for use in the rece!tion of stereo!honic broadcast.

a. I fre&uencyb" Pi/ot sub-c*..ie.

c. R fre&uencyd. 5arrier fre&uency

4'. 7he !ea0 difference bet*een the instantaneous fre&uency of the modulated *ave and

carrier fre&uency.

a. odulated inde%

b" 7.e8uency dei*tion

c. odulating fre&uency

d. ercentage modulation

4/. A ideo b. 5arrier

c" Sound

d. o*er

49. Is necessary to bring the main vertical beam tangential to the earth, *hich is curving

a*ay from it.a. Radio horion


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b. 7a0e off angle

c. oney

d" >e*6 ti/t

+). In etro anila and etro 5ebu, the ma%imum effective radiated !o*er of 3+) 0" for

channel 2$( and ____ 0" for channel '$13 are allo*ed.

*" (&&& b. +)))

c. +))d. 2+)

+1. ______ are transmission circuits interconnecting t*o different s*itching centers.

a. 7oll center

b" T.un3 ci.cuits

c. -ybrid circuits

d. Intertoll circuits+2. 7he !hone system begins *ith ______, *hich is the !air of *ires that connects the central

office to the userGs !hone.

a. 6oo! e%tenders b. 6ocal change

c. 8*itching office

d" Loc*/ /oo<

+3. "hen you dial the digit H/, the corres!onding lo* and high grou! tones are generated

by the !hone and sent to the central office are______.

*" @% *nd ())' H;

b. '') and ('9 -

c. 941 and 14'' -d. '') and 12)9 -

+4. A signal travels via cables C!ro!agation velocity ).' cB from e* Dor0 to 6os Angeles, a

distance of 3))) miles. "hat are the tal0er echo and listener echo times#a. 4( ms and '/ ms

b. 3/ ms and (9 ms

c" #' 6s *nd '2 6s

d. 3/ ms and '/ ms

++. 7he *ord tele!hone is derived from the Free0 *ord tele, meaning _____, and !hone,

meaning ________.

a. 7y!e, audio

b" 7*. sound

c. 8co!e, sound

d. ar, handset

+(. "hat are the second harmonics of the tones for the digit H3#a. 1+4), 29+4 -

b" ()2# %2# H;

c. ''), 12)9 -d. 1'14, 1/+2 -

+'. A ?uro!ean unit of the traffic intensity e&ual to 13) of an ?rlang.

a. 5all second

b" E>HC


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c. ?rlang

d. 5all minute

+/. A t*o state s*itching device containing one or more elements that have a lo*

transmission im!edance in one state and a very high one in the others.

*" C.oss


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d" S


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'4. 7he modulated !ea0 value of a signal is 1) > and the unmodulated carrier value is />.

"hat is the modulated inde%#

a. )./)

b" &"%

c. ).+)

d. ).'+'+. "hat is the ma%imum su!!ression for a !hase error of 2o#

a. 41.2 d<

b" )"% d>

c. 23.( d<

d. 12.' d<'(. An information signal that is sent directly *ithout modulating any carrier is called

_________.a. odulating fre&uency

b" >*seb*nd AM

c. 5arrier fre&uency

d.


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d. 1)11 to 1)11 -

/3. lastic fibers have the follo*ing advantage over glass fiberL

a. le%ibility b. Ruggedness

c. ?ase of installation

d" Lo, *ttenu*tion/4. A site that contains the cellular radio e&ui!ment. It can have one or more _____.

*" >*se

b. 5entral


13/36

d" A;R 94. It is referred to as the range and aimuth dis!lay.

a. A$scan

b" >-Sc*n

c. 5$8cand. I

9+. F5A o!erates *ithL

a. ? b. aster and slave stations

c" 5.ound-b*sed .*d*.

d. 6ocal radio stations9(.


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c. 1.1 sec

d" ("& sec


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dB / Transmission Lines

1. If the 1) of the micro*ave !o*er is reflected at the mismatch, find the return loss.

a. ).1 d< b. 1) d

c. 2 d<d. $2 d<

+. 8!ecial semiconductor diode use for electronically adMustable attenuation

a. Ideal diode

b" PIN diode

c. Nener diode

d. 7unel diode(. A +) ohm line is !robed and found to have a 8"R of 2.(, *hat are the t*o !ossible

&uarter *ave transformers sies that may be used to match the load to the line of the

transformer are !ro!erly !ositioned.

a. 22 ohm, /2 ohm

b" )( o06 @&" o06

c. 2(.2 ohm, 12.'1 ohm

d. 12.32 ohm, 2(.' ohm

'. A balanced load of 9)) ohm !ure resistance is fed through a balanced ()) ohm

transmission line *hich is 9) electrical degree long. 7he balanced ()) ohm transmission

line is in turn fed from a +) ohm coa%ial line by means of a half$*ave balancing section.

"hat is the standing *ave ratio on the ()) ohm line#

a. 1.) b. 2.+

c" ("

d. 2.)

/. Fiven cascaded circuitO first stage is a filter circuit *ith insertion loss of 3 d


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b. + d


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1'. ?nergy a!!lied to a transmission line may become dissi!ated before reaching the load.

a. Radiation

b. 5onductor heatingc. ielectric heating

d" A// o? t0e *boe

1/. 7he velocity of light is very nearly 3 % 1)/

ms in a vacuum and ___ in all other media.a. -igher

b" S/o,e.

c. 8amed. All of these

19. At a !oint e%actly a &uarter$*avelength from the load, the current is ______.

a. 1/) degrees in of !hase

b. 1/) degrees out of !hase

c" Pe.6*nent/y ;e.o

d. one of these

2). Is a !iece of transmission line *hich is normally short$circuited at the far end.

a. 7erminator b" Stubc. Juarter *ave transformer d. one of these

21. or high fre&uencies, the best dielectric may be_______.

a. olyethylene b. olyethylene foam

c" Te?/on

d. one of these

22. 5haracteristic im!edance are sometimes called _______.a. ;hmic resistance

b" Su.+e i6


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2(. In a t*o$stage am!lifier, am!lifier 1 has a noise figure of 3 d< and a gain of 2) d6

c. $33 d8"R b. 8"R

c" Re?/ection coe??icient

d. one of these


19/36

34. It is a measure of one *ay loss of !o*er in a transmission line due to reflection from the

load.

a. Return loss

b" T.*ns6ission /oss

c. ro!agation loss

d. one of these3+. If the velocity factor is e&ual to ).((, the s!eed of light *ill be_____.

a. Increase

b" !ec.e*se

c. 8ame

d. one of these3(. In 1939, _________ !ublished a gra!hical device for solving transmission line design.

a. hilli! A. 8mith

b. hilli! R. 8mith

c" P0i//i< H" S6it0

d. hilli! 8. 8mith

3'. In order to ma0e the smith chart universal, the im!edances along the !ure resistance lineare _________.

a. ormal

b" No.6*/i;ed

c. ;!en circuit

d. 8hort circuit

3/. 5alculate the gain off an am!lifier *ith an in!ut !o*er 1) 0" and an out!ut !o*er of

2)) 0".

a. 1+ d<

b" () d>

c. 2) d<

d. 1) d<39. A !erfect termination for a transmission line.

a. Receiving end

b" Lo*d

c. Antenna

d. 7erminal end

4). It can be measured, and includes losses due to reflection and absor!tion inside the

com!onent

a. ading

b. Attenuation

c" Inse.tion /oss

d. Return loss41. A com!onent that sam!les the micro*ave signal traveling in one direction do*n a

transmission line

a. Isolator

b" !i.ection*/ cou


20/36

42. A transmission line having air dielectric is o!erated at a fre&uency of 11) -. "hat is

the !hase shift constant of the line is degrees !er inch#

a. 2.+(

b" )")

c. 4.(

d. 1.2+43. 5onsider the three net*or0s in series, the first is an attenuator *ith a 12 d< loss, the

second net*or0 is an am!lifier *ith 3+ d< gain, and the third has an insertion loss of 1)

d6

4'. etermines ho* the voltage or current decreases *ith distance

a. hase$shift coefficient

b" Attenu*tion coe??icient

c. ro!agation coefficient

d. umerical coefficient4/. etermines the !hase angle of the voltage or current variation *ith distance

*" P0*se-s0i?t coe??icient

b. Attenuation coefficient

c. ro!agation coefficientd. umerical coefficient

49. etermines variation of voltage or current *ith distance along transmission line

a. hase$shift coefficient b. Attenuation coefficient

c" P.o


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a. assive elements

b. Active elements

c" Line


22/36

Antenna Sstem

1. A discone antenna is a radiator *hose im!edance can be directly matched to *hat ty!e of

coa%ial transmission line#

a. ') ohm line

b. 3) ohm linec. 3)) ohm line

d" & o06 /ine

2. In order to increase the gain of Dagi$Eda arrays, *hat element are addad#

*" Usin+ 6*ny di.ecto.

b. Esing many di!ole

c. Esing many reflector

d. All of these3. It is a measure of ho* much the antenna concentrates its transmitted micro*ave !o*er in

a given directiona. e*6,idt0

d. one of these

+. ;rientation of the electric field signal !ro!agated from the antenna.

a. irectivity

b" Po/*.i;*tionc. 8idelobes

d. Fain(. Is not included in the grou!.

a. 8lot

b. -orn

c. -eli%

d" M*.coni

'. Radiation from an antenna at other angles than the desired direction.

a. Antenna direction b. ield strength

c" Side/obed. irectivity

/. If the antenna is not in the e%act dimensionmeasurement, the im!edance of the antenna

turns to beLa. 5a!acitive

b. Resistive

c. Inductive

d" * o. c


23/36

9. Im!edance for free s!ace is _______.

*" (%&9*c3,*.d *nd,idt0

c. Fain


24/36

d. irectivity

1/. Is used to increase the cuurent at the base of the antenna, and also to ma0e the current

distribution more uniform.

a. Am!lifier

b" To< /o*din+

c. ertical antennasd. Rhombic antennas

2(. irectivity higher than that obtained *ith uniform !hase.


25/36

*" Su


26/36

d. one of these

3+. 7he omega match is slightly modified from the ___________.

a. 7 match

b" 5*66* 6*tc0

c. elta match

d. one of these3(. A dish antenna has a diameter of 2m and o!erates at 4( -, find the antenna gain at (+

efficiency.a. 3422.(

b. 3.2( d<

c. 12.3 d<

d" #%''"'=

3'. "hat is the a!!ro%imate effective length of an antenna at 1) -

a. 2.(+ m

b" 2" 6

c. 4.(2 m

d. /.( m3/. 5alculate effective absorbing area o!erating at 1)( - for a standard half$*ave di!ole.

a. ).2(+ mm2

b" &"((= 66%

c. 1.2( mm2

d. 2.3 mm2

39. 7he variation of the slot antenna is _________.

a. Isotro!ic antenna

b" Notc0 *ntenn*

c. 6en antenna

d. -orn antenna

4). A !oint *here the !o*er field strength is ero.a. inimum

b. a%imum

c. 6obe

d" Nu//

41. An area of radiation *hich e%ist bet*een adMacent nulls.

a. inimum b. a%imum

c" Lobe

d. ulls42. 7he !ro!erty of an antenna that causes it to receive signal better from one direction than

from another.a. Fain

b" !i.ectiity

c. i!ole

d. Reflector 43. 7he ').' !oint on the !olar gra!h is 0no*n as the _________ !oint and re!resent the

!oint of ma%imum *idth of the lobe

a. ull !o*er


27/36

b" H*/?-oltage antenna

b" eertical antenna li0e those used in the A broadcast and lo*er fre&uency armature band

rely heavily u!on a good __________ for ma%imum coverage.a. Insulation

b" 5.ound syste6

c. Faind. irectivity

+1. 5lass of citiens band station o!erating at 4(2.++ to 4((.4+ -.

*" C/*ss A

b. 5lass


28/36

c. 5lass 5

d. 5lass

+2. Fround system recommended by the 55 for broadcast stations consists of a minimum

of _______.

*" (%& .*di*/s

b. 1+) radialsc. 13) radials

d. 14) radials+3. 7o achieve ma%imum !ossible energy transfer bet*een transmitting and receiving

stations at !ractical distances, _______ are used.a. -igh gain

b" P*.*bo/ic .e?/ecto.

c. irector d. secret

+4. ________ is the transmission of data metered at a distance from the observer.

a. ata communications

b. Altimeteryc" Te/e6et.y

d. cemetery

++. Im!edance transformation bet*een a balanced and unbalanced im!edances.a. Famma match

b" Es/un t.*ns?o.6e.

c. ecca matchd. atch bo%

+(. 5alculate the !hysical length re&uired of a 14( - 4L1 balun mode of !olyethylene

foam coa%ial cable. Ese velocity factor of )./).

a. 12.( ft

b. 2.+ mc" )%"# inc0es

d. (.2 inches

+'. _______ is an instrument that measures the radiated field from an antenna.

*" 7ie/d st.en+t0 6ete.

b. ield meter

c. 8trength meter

d. Intensity meter +/. 5alculate the number of turns re&uired to ma0e a + u- inductor on a t$+)$( core. Ese

core factor A6 of 4).a. 2+

b" )c. 4+d. +)

+9. 7his resistance is a hy!othetical conce!t that accounts for the fact that r !o*er is

radiated by the antenna.

a. ;hmic resistance

b. Resistance

c" R*di*tion .esist*nce


29/36

d. one of these

(). If 1))) *atts of R !o*er is a!!lied to the feed!oint, and a current of 3.' am!eres *as

measured, *hat is the radiation resistance#

a. +) ohms b. 3)) ohms

c. ()) ohmsd" =) o06s

(1. Antenna theory recognies a !oint of reference called the _________.a. -alf$*ave di!ole

b. ull *ave di!ole

c" Isot.o


30/36

!od"#oation/Demod"#ation

1. A method that a!!lied the modulated *ave to the vertical deflection circuit of the

oscillosco!e and the modulating signal to the horiontal deflection circuit.

*" T.*


31/36

b. 5enter fre&uency

c. I fre&uency

d. R fre&uency9. 7he varactor diode used in may be re!resented by the a!!ro%imate e&uivalent circuit

of the _____ in series *ith a ________.

a. iode, ca!acitor b. iode, resistor

c" C*

d. one of these

12. Recovers the modulating voltage from the fre&uency modulation by utiliing the !hase

angle shift bet*een !rimary and secondary voltages of tuned oscillators.

a. irect method

b. Indirect method

c" 7oste.-See/ey disc.i6in*to.

d. 8lo!e detector

13. Is used in receivers to Hloc0 onto the received signal and stabilied recetions.a. Automatic Fain 5ontrol

b" Auto6*tic 7.e8uency Cont.o/c. uscle 5ontrol

d. Automatic re&uency Fain 5ontrol14. Are am!lifier circuits that are used to eliminate am!litude modulation and am!litude$

modulated noise from received 8ignals before detection.

a. emodulators

b. iode detector

c" A6


32/36

c. aybe

d. 8ecret

1'. or an unmodulated carrier of 1+) > and a modulated !ea0 value of 23) >. "hat is the

modulation inde%a. ).3+

b" &"))c. ).(+2

d. ).421/. e* fre&uencies outside the regular A s!ectrum are called ___________.

a. istortion

b. Interference

c" S


33/36

a. ono!honic

b" Ste.eo


34/36

c" Const*nt

d. variable

33. An A has a ma%imum s!an of 3) >, *hat is the re&uired minimum s!an to attain 1))

modulation#a. 3) >

b. 2) >c" & V

d. one of these34. N having a carrier fre&uency of (3) 0- is modulated by 2.( 0- audio signal

having an am!litude of 3'.+ >. "hat is the am!litude voltage of (3) 0- carrier

fre&uency at ).3+ modulation inde%#

a. +'.( >

b" (&="(# V

c. 2)(.+ >

d. /(.2 >3+. If the sideband !o*er is +) of the carrier !o*er, *hat is the modulation inde%#

a. +) b. '+c. 9)

d" (&&

3(. If the increase !o*er is 1/) *atts at 1 0" unmodulated out!ut !o*er the modulation

inde% is _________.

a. '+

b" '&

c. +)

d. 2+

3'. In A, if the unmodulated !o*er carrier is 1) 0", and the total !o*er is 1+ 0", *hat is

the u!!er sideband !o*er at 1)) modulation inde%#a. 2+ 0" b. 2 0"

c" %" 34

d. 4 0"3/. If the in!ut resistance of the base station of A broadcast !roduced 2) 0" carrier !o*er,

at *hat modulation inde% should the antenna rise at 1)/.(3 A#a. 2)

b. +)

c" '&

d. /)39. ________ used a !hase detector to com!are the !hase and fre&uency of the received

signal to the >5; out!ut.

a. I6

b. A6

c" PLL

d. 6I


35/36

4). A filter *ith a roll$off of ( d

d. 49.( u>42. A 1$- carrier is modulated *ith a resulting 1)) - deviation. It undergoes %3(

multi!lication, follo*ed by mi%ing *ith a 34.+ - signal and remulti!lication by '2.

"hat is the final carrier and deviations#

a. +)'( -, S 2+92 -

b" %2% MH; G %2"% 3H;

c. 2+92-, S +)'( -

d. 2+9.2 -, S 1)/ 0-43. or standard commercial broadcast , the deviation ratio is ________.

a. 1+

b. '+

c"

d. 1)

44. A system has 1+) 0- of band*idth available for 1) 0- modulation signal. "hat is the

a!!ro%imate deviation to be used#

a. 3+ 0-

b" ' 3H;

c. 2+ 0-

d. 1+ 0-

4+. An has a deviation of 1)) 0- and a modulating fre&uency of 1+ 0-, *hat ha!!en

to m if the deviation tri!les#

a. (.(( b. 2.22

c. 4.12

d" &"%&4(. A receiver for a signal at 1)) - uses a 1).' - I and lo* trac0ing. "hat is the

image fre&uency#a. /9.3 -

b" =@"' MH;

c. +2.+ -d. 3+.2 -


36/36

4'. "hat is the change in resonant fre&uency of the actual varactor ca!acitance value differs

by $+ C).)+B of the nominal value#

a. 2.)(

b. 3.)2

c" ("&)

d. +.)(4/. An oscillator resonate at 1 - *ith a nominal 1)) ! ca!acitor and ).2+ m- inductor,

*hat s the resonant fre&uency of the actual ca!acitor value is Q2) of the nominal value#

a. 1.))( -

b" &"2(@@ MH;

c. 3.(2+ -

d. 2.))123 -

49. Hront end is also called _________.a. I stage

b. A stage

c" R7 st*+e

d. one of these+). Endesired signal on the other side of the local oscillator out!ut *ill have the same

difference fre&uency and !ass into the I am!lifier.

a. 5arrier fre&uency

b. 8um fre&uencyc. ifference fre&uency

d" I6*+e ?.e8uency

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(Certii) Multiple Choice Questions in Communications

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