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CHAPTER 1
INTRODUCTION TO
ELECTRONIC
COMMUNICATIONS
1. Communication is the process
ofa. keeping in touchb. broadcastingc. exchanging informationd. entertainment by
electronics
2. Two key barriers to humancommunication are
a. distance
b. costc. ignoranced. language
3. Electronic communicationswas discovered in which century?
a. sixteenthb. eighteenthc. nineteenthd. twentieth
4. Which of the following is not amajor communications medium?
a. free spaceb. waterc. wiresd. fiber optic cable
5. Random interference totransmitted signals is called
a. adjacent channel overlapb. cross talkc. garbage-in-garbage-outd. noise
6. The communications mediumcauses the signal to be
a. amplifiedb. modulated
c. attenuatedd. interfered with
7. Which of the following is not asource of noise?
a. another communications
signal
b. atmospheric effectsc. manufactured electrical
systemsd. thermal agitation in
electronic components
8. One-way communications iscalled
a. half duplex
b. full duplexc. monocommd. simplex
9. Simultaneous two-waycommunications is called
a. half duplexb. full duplexc. bicommd. simplex
10. The original electricalinformation signal to be transmittedis called the
a. modulating signalb. carrierc. baseband signald. source signal
11. The process of modifying a
high-frequency carrier with theinformation to be transmitted iscalled
a. multiplexingb. telemetryc. mixingd. modulation
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12. The process of transmittingtwo or more information signalssimultaneously over the samechannel is called
a. multiplexingb. telemetry
c. mixingd. modulation
13. Continuous voice or videosignals are referred to as being
a. basebandb. analogc. digitald. continuous waves
14. Recovering information from acarrier is known as
a. demultiplexingb. modulationc. detectiond. carrier recovery
15. Transmission of graphicalinformation over the telephonenetwork is accomplished by
a. televisionb. CATVc. videotextd. facsimile
16. Measuring physical conditionsat some remote location andtransmitting this data for analysis isthe process of
a. telemetry
b. instrumentationc. modulationd. multiplexing
17. Receiving electromagneticemissions from stars is called
a. astrologyb. optical astronomyc. radio astronomy
d. space surveillance
18. A personal communicationshobby for individuals is
a. ham radiob. electronic bulletin board
c. CB radiod. cellular radio
19. Radar is based upona. microwavesb. a water mediumc. the directional nature of
radio signalsd. reflected radio signals
20. A frequency of 27 MHz has awavelength of approximately
a. 11 mb. 27 mc. 30 md. 81 m
21. Radio signals are made up ofa. voltages and currentsb. electric and magnetic
fieldsc. electrons and protonsd. noise and data
22. The voice frequency range isa. 30 to 300 Hzb. 300 to 3000 Hzc. 20 Hz to 20 kHzd. 0 Hz to 15 kHz
23. Another name for signals in theHF range isa. microwavesb. RF wavesc. shortwavesd. millimeter waves
24. Television broadcasting occursin which ranges?
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a. HFb. EHFc. VHFd. UHF
25. Electromagnetic waves
produced primarily by heat arecalled
a. infrared raysb. microwavesc. shortwavesd. x-rays
26. A micron isa. one-millionth of a footb. one-millionth of a meter
c. one-thousandth of a meterd. one ten-thousandth of an
inch
27. The frequency range ofinfrared rays is approximately
a. 30 to 300 GHzb. 4000 to 8000 Ac. 1000 to 10,000 A
d. 0.7 to 100 m
28. The approximate wavelengthof red light is
a. 1000 mb. 7000 Ac. 3500 Ad. 4000 A
29. Which of the following is notused for communications?
a. x-raysb. millimeter wavesc. infraredd. microwaves
30. A signal occupies the spectrumspace from 1.115 to 1.122 GHz.The bandwidth is
a. 0.007 MHzb. 7 MHzc. 237 MHzd. 700 MHz
31. In the United States, the
electromagnetic spectrum isregulated and managed by
a. business and industryb. ITUc. FCCd. The United Nations
32. For a given bandwidth signal,more channel space is availablefor signals in the range of
a. VHFb. UHFc. SHFd. EHF
CHAPTER 2
AMPLITUDE MODULATION AND
SINGLE-SIDEBAND
MODULATION
1. Having an information signalchange some characteristic of acarrier signal is called
e. multiplexingf. modulationg. duplexingh. linear mixing
2. Which of the following is not
true about AM?e. The carrier amplitudevaries.
f. The carrier frequencyremains constant.
g. The carrier frequencychanges.
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h. The information signalamplitude changes thecarrier amplitude.
3. The opposite of modulation ise. reverse modulation
f. downward modulationg. unmodulationh. demodulation
4. The circuit used to producemodulation is called a
e. modulatorf. demodulatorg. variable gain amplifierh. multiplexer
5. A modulator circuit performswhat mathematical operation on itstwo inputs?
e. additionf. multiplicationg. divisionh. square root
6. The ratio of the peakmodulating signal voltage to the
peak carrier voltage is referred toas
e. the voltage ratiof. decibelsg. the modulation indexh. the mix factor
7. If m is greater than 1, whathappens?
e. normal operation
f. carrier drops to zerog. carrier frequency shiftsh. information signal is
distorted
8. For ideal AM, which of thefollowing is true?
e. m = 0f. m = 1
g. m < 1h. m > 1
9. The outline of the peaks of acarrier has the shape of themodulating signal and is called the
e. tracef. waveshapeg. envelopeh. carrier variation
10. Overmodulation occurs whene. Vm> Vcf. Vm< Vcg. Vm= Vch. Vm= Vc= 0
11. The values of Vmaxand Vminasread from an AM wave on anoscilloscope are 2.8 and 0.3. Thepercentage of modulation is
e. 10.7 percentf. 41.4 percentg. 80.6 percenth. 93.3 percent
12. The new signals produced bymodulation are called
e. spurious emissionsf. harmonicsg. intermodulation productsh. sidebands
13. A carrier of 880 kHz ismodulated by a 3.5 kHz sine wave.The LSB and USB are,
respectively,e. 873 and 887 kHzf. 876.5 and 883.5 kHzg. 883.5 and 876.5 kHzh. 887 and 873 kHz
14. A display of signal amplitudeversus frequency is called the
e. time domain
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f. frequency spectrumg. amplitude spectrumh. frequency domain
15. Most of the power in an AMsignal is in the
e. carrierf. upper sidebandg. lower sidebandh. modulating signal
16. An AM signal has a carrierpower of 5 W. The percentage ofmodulation is 80 percent. Thetotal sideband power is
e. 0.8 W
f. 1.6 Wg. 2.5 Wh. 4.0 W
17. For 100 percent modulation,what percentage of power is ineach sideband?
e. 25 percentf. 33.3 percent
g. 50 percenth. 100 percent
18. An AM transmitter has apercentage of modulation of 88.The carrier power is 440 W. Thepower in one sideband is
e. 85 Wf. 110 Wg. 170 W
h. 610 W
19. An AM transmitter antennacurrent is measured with nomodulation and found to be 2.6amperes. With modulation, thecurrent rises to 2.9 amperes. Thepercentage of modulation
e. 35 percent
f. 70 percentg. 42 percenth. 89 percent
20. What is the carrier power in theproblem above if the antenna
resistance is 75 ohms?e. 195 Wf. 631 Wg. 507 Wh. 792 W
21. In an AM signal, thetransmitted information iscontained within the
e. carrier
f. modulating signalg. sidebandsh. envelope
22. An AM signal without thecarrier is called a(n)
e. SSBf. Vestigial sidebandg. FM signalh. DSB
23. What is the minimum AMsignal needed to transmitinformation?
e. carrier plus sidebandsf. carrier onlyg. one sidebandh. both sidebands
24. The main advantage of SSB
over standard AM or DSB ise. Less spectrum space isused
f. Simpler equipment is usedg. Less power is consumedh. A higher modulation
percentage
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25. In SSB, which sideband is thebest to use?
e. Upperf. Lowerg. Neitherh. Depends upon the use
26. The typical audio modulatingfrequency range used in radio andtelephone communications is
e. 50 Hz to 5 kHzf. 50 Hz to 15 kHzg. 100 Hz to 10 kHzh. 300 Hz to 3 kHz
27. An AM signal with a maximum
modulating signal frequency of 4.5kHz has a total bandwidth of
e. 4.5 kHzf. 6.75 kHzg. 9 kHzh. 18 kHz
28. Distortion of the modulatingsignal produces harmonics whichcause an increase in the signal
e. carrier powerf. bandwidthg. sideband powerh. envelope voltage
29. The process of translating asignal, with or without modulation,to a higher or lower frequency forprocessing is called
e. frequency multiplication
f. frequency divisiong. frequency shifth. frequency conversion
30. Frequency translation iscarried out by a circuit called a
e. translatorf. converterg. balanced modulator
h. local oscillator
31. An input signal of 1.8 MHz ismixed with a local oscillator of 5MHz. A filter selects the differencesignal. The output is
e. 1.8 MHzf. 3.2 MHzg. 5 MHzh. 6.8 MHz
32. The output of an SSBtransmitter with a 3.85 MHz carrierand a 1.5 kHz sine wavemodulating tone is
e. a 3.8485-MHz sine wave
f. a 3.85-MHz sine waveg. 3.85-, 3.845-, and 3.8515-
MHz sine wavesh. 3848.5- and 3851.5 MHz
sine waves
33. An SSB transmitter produces a400 V peak-to-peak signal across
a 52 antenna load. The PEP
output isa. 192.2 Wb. 384.5 Wc. 769.2 Wd. 3077 W
34. The output power of an SSBtransmitter is usually expressed interms of
a. average power
b. RMS powerc. peak-to-peak powerd. peak envelope power
35. An SSB transmitter has a PEPrating of 1 kW. The averageoutput power is in the range of
a. 150 to 450 Wb. 100 to 300 W
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c. 250 to 333 Wd. 3 to 4 kW
CHAPTER 3
AMPLITUDE MODULATION
CIRCUITS
1. Amplitude modulation is thesame as
i. Linear mixingj. Analog multiplicationk. Signal summationl. Multiplexing
2. In a diode modulator, thenegative half of the AM wave issupplied by a(n)
i. Tuned circuitj. Transformerk. Capacitorl. Inductor
3. Amplitude modulation can beproduced by
i. having the carrier vary aresistance
j. having the modulating
signal vary a capacitancek. varying the carrier
frequencyl. varying the gain of an
amplifier
4. Amplitude modulators that varythe carrier amplitude with themodulating signal by passing itthrough an attenuator work on the
principle ofi. rectificationj. resonancek. variable resistancel. absorption
5. The component used toproduce AM at very highfrequencies is a
i. varactorj. thermistork. cavity resonatorl. PIN diode
6. Amplitude modulation
generated at a very low voltage orpower amplitude is known as
i. high-level modulationj. low-level modulationk. collector modulationl. minimum modulation
7. A collector modulator has asupply voltage of 48 V. The peak-to-peak amplitude of the
modulating signal for 100 percentmodulation is
i. 24 Vj. 48 Vk. 96 Vl. 120 V
8. A collector-modulatedtransmitter has a supply voltage of24 V and a collector current of 0.5
A. The modulator power for 100percent modulation is
i. 6 Wj. 12 Wk. 18 Wl. 24 W
9. The circuit that recovers theoriginal modulating informationfrom an AM signal is known as a
i. modulatorj. demodulatork. mixerl. crystal set
10. The most commonly usedamplitude demodulator is the
i. diode mixerj. balanced modulator
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k. envelope detectorl. crystal filter
11. A circuit that generates theupper and lower sidebands but nocarrier is called a(n)
i. amplitude modulator
j. diode detectork. class C amplifierl. balanced modulator
12. The inputs to a balancedmodulator are 1 MHz and a carrierof 1.5 MHz. The outputs are
i. 500 kHzj. 2.5 MHzk. 1.5 MHz
l. all of the abovem. a and b
13. A widely used balancedmodulator is called the
i. diode bridge circuitj. full-wave bridge rectifierk. lattice modulatorl. balanced bridge modulator
14. In a diode ring modulator, thediodes act like
i. variable resistorsj. switchesk. rectifiersl. variable capacitors
15. The output of a balancedmodulator is
i. AM
j. FMk. SSBl. DSB
16. The principal circuit in thepopular 1496/1596 IC balancedmodulator is a
i. differential amplifierj. rectifier
k. bridgel. constant current source
17. The most commonly used filterin SSB generators uses
i. LC networksj. mechanical resonators
k. crystalsl. RC networks and op amps
18. The equivalent circuit of aquartz crystal is a
i. series resonant circuitj. parallel resonant circuitk. neither a nor bl. both a and b
19. A crystal lattice filter hascrystal frequencies of 27.5 and27.502 MHz. The bandwidth isapproximately
i. 2 kHzj. 3 kHzk. 27.501 MHzl. 55.502 MHz
20. An SSB generator has a
sideband filter centered at 3.0MHz. The modulating signal is 3kHz. To produce both upper andlower sidebands, the followingcarrier frequencies must beproduced:
i. 2.7 and 3.3 MHzj. 3.3 and 3.6 MHzk. 2997 and 3003 kHzl. 3000 and 3003 kHz
21. In the phasing method of SSBgeneration, one sideband iscanceled out due to
i. phase shiftj. sharp selectivityk. carrier suppressionl. phase inversion
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22. A balanced modulator used todemodulate a SSB signal is calleda(n)
i. transponderj. product detectork. converter
l. modulator
23. Frequency translation is donewith a circuit called a
i. summerj. multiplierk. filterl. mixer
24. The inputs to a mixer are fo
and fm. In down conversion, whichof the following mixer outputsignals is selected?
i. foj. fmk. fofml. fo+ fm
25. Mixing for frequencyconversion is the same as
i. rectificationj. AMk. linear summingl. filtering
26. Which of the following can beused as a mixer?
i. balanced modulatorj. FETk. diode modulator
l. all of the above
27. The desired output from amixer is usually selected with a
i. phase-shift circuitj. crystal filterk. resonant circuitl. transformer
28. The two inputs to a mixer arethe signal to be translated and asignal from a(n)
i. modulatorj. filterk. antenna
l. LO
29. An NE602 mixer IC has adifference output of 10.7 MHz.The input is 146.8 MHz. The localoscillator frequency is
i. 101.9 MHzj. 125.4 MHzk. 131.6 MHzl. 157.5 MHz
CHAPTER 4FREQUENCY MODULATION
1. The amount of frequencydeviation from the carrier centerfrequency in an FM transmitter isproportional to what characteristicof the modulating signal?
m. Amplituden. Frequency
o. Phasep. Shape
2. Both FM and PM are types ofwhat kind of modulation?
m. Amplituden. Phaseo. Anglep. Duty cycle
3. If the amplitude of themodulating signal decreases, thecarrier deviation
m. increasesn. decreaseso. remains constantp. goes to zero
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4. On an FM signal, maximumdeviation occurs at what point onthe modulating signal?
m. zero-crossing pointsn. peak positive amplitudeo. peak negative amplitude
p. both b and c
5. In PM, a frequency shift occurswhile what characteristic of themodulating signal is changing?
m. shapen. phaseo. frequencyp. amplitude
6. Maximum frequency deviationof a PM signal occurs at
m. zero crossing pointsn. peak positive amplitudeo. peak negative amplitudep. peak positive or negative
amplitudes
7. In PM, carrier frequencydeviation is not proportional to:
m. modulating signalamplitude
n. carrier amplitude andfrequency
o. modulating signalfrequency
p. modulator phase shift
8. To compensate for increasesin carrier frequency deviation with
an increase in modulating signalfrequency, what circuit is usedbetween the modulating signal andthe phase modulator?
m. low-pass filtern. high-pass filtero. phase shifterp. bandpass filter
9. The FM produced by PM iscalled
m. FMn. PMo. Indirect FMp. Indirect PM
10. If the amplitude of themodulating signal applied to aphase modulator is constant, theoutput signal will be
m. zeron. the carrier frequencyo. above the carrier
frequencyp. below the carrier
frequency
11. A 100 MHz carrier is deviated50 kHz by a 4 kHz signal. Themodulation index is
m. 5n. 8o. 12.5p. 20
12. The maximum deviation of anFM carrier is 2 kHz by a maximummodulating signal of 400 Hz. Thedeviation ratio is
n. 0.2o. 5p. 8q. 40
13. A 70 kHz carrier has a
frequency deviation of 4 kHz with a1000 Hz signal. How manysignificant sideband pairs areproduced?
m. 4n. 5o. 6p. 7
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p. push-pull
25. Frequency modulationtransmitters are more efficientbecause their power is increasedby what type of amplifier?
m. Class An. Class Bo. Class Cp. all of the above
26. Noise interferes mainly withmodulating signals that are
m. sinusoidaln. nonsinusoidalo. low frequencies
p. high frequencies
27. Pre-emphasis circuits boostwhat modulating frequenciesbefore modulation?
m. high frequenciesn. mid-range frequencieso. low frequenciesp. all of the above
28. A pre-emphasis circuit is am. low-pass filtern. high-pass filtero. phase shifterp. bandpass filter
29. Pre-emphasis is compensatedfor at the receiver by a
m. Phase invertern. Bandpass filter
o. High-pass filterp. Low-pass filter
30. The cut-off frequency of pre-emphasis and de-emphasis circuitis
a. 1 kHzb. 2.122 kHzc. 5 kHz
d. 75 kHz
CHAPTER 5
FREQUENCY MODULATION
CIRCUITS
1. Another name for a VVC isq. PIN dioder. Varactor diodes. Snap diodet. Hot-carrier diode
2. The depletion region in ajunction diode forms what part of acapacitor?
q. plates
r. leadss. packaget. dielectric
3. Increasing the reverse bias ona varactor diode will cause itscapacitance to
q. decreaser. increases. remain the same
t. drop to zero
4. The capacitance of a varactordiode is in what general range?
q. pFr. nF
s. Ft. F
5. The frequency change of a
crystal oscillator produced by avaractor diode isq. zeror. smalls. mediumt. large
6. A phase modulator varies thephase shift of the
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q. carrierr. modulating signals. both a and bt. neither a or b
7. The widest phase variation is
obtained with a(n)q. RC low-pass filterr. RC high-pass filters. LR low-pass filtert. LC resonant circuit
8. The small frequency changeproduced by a phase modulatorcan be increased by using a(n)
q. amplifier
r. mixers. frequency multipliert. frequency divider
9. A crystal oscillator whosefrequency can be changed by aninput voltage is called a(n)
q. VCOr. VXOs. VFO
t. VHF
10. Which oscillators are preferredfor carrier generators because oftheir good frequency stability?
q. LCr. RCs. LRt. crystal
11. Which of the followingfrequency demodulators requiresan input limiter?
q. Foster-Seeleydiscriminator
r. Pulse-averagingdiscriminator
s. Quadrature detectort. PLL
12. Which discriminator averagespulses in a low-pass filter?
r. Ratio detectors. PLLt. Quadrature detector
u. Foster-Seeleydiscriminator
13. Which frequency demodulatoris considered the best overall?
q. Ratio detectorr. PLLs. Quadraturet. Pulse-averaging
discriminator
14. In a pulse-averagingdiscriminator, the pulses areproduced by a(n)
q. Astable multivibratorr. Zero-crossing detectors. One shott. Low-pass filter
15. A reactance modulator looks
like a capacitance of 35 pF inparallel with the oscillator-tuned
circuit whose inductance is 50 Hand capacitance is 40 pF. What isthe center frequency of theoscillator prior to FM?
q. 1.43 MHzr. 2.6 MHzs. 3.56 MHzt. 3.8 MHz
16. Which of the following is trueabout the NE566 IC?
q. It is a VCO.r. Its output is sinusoidal.s. It is an FM demodulator.t. It uses LC tuned circuits.
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17. An FM demodulator that usesa differential amplifier and tunedcircuits to convert frequencyvariations into voltage variations isthe
q. Quadrature detector
r. Foster-Seeleydiscriminator
s. Differential peak detector
t. Phase-locked loop
18. The output amplitude of thephase detector in a quadraturedetector is proportional to
q. Pulse width
r. Pulse frequencys. Input amplitudet. The phase shift value at
center frequency
19. The input to a PLL is 2 MHz.In order for the PLL to be locked,the VCO output must be
q. 0 MHzr. 1 MHz
s. 2 MHzt. 4 MHz
20. Decreasing the input frequencyto a locked PLL will cause theVCO output to
q. decreaser. increases. remain constantt. jump to the free-running
frequency
21. The range of frequencies overwhich a PLL will track input signalvariations is known as the
q. circuit bandwidthr. capture ranges. band of acceptancet. lock range
22. The band of frequencies overwhich a PLL will acquire orrecognize an input signal is calledthe
q. circuit bandwidthr. capture range
s. band of acceptancet. lock range
23. Over a narrow range offrequencies, the PLL acts like a
q. Low-pass filterr. Bandpass filters. Tunable oscillatort. Frequency modulator
24. The output of a PLL frequencydemodulator is taken from the
q. Low-pass filterr. VCOs. Phase detectort. none of the above
CHAPTER 6
RADIO TRANSMITTERS
1. Which of the following circuitsis not typically part of every radiotransmitter?
u. carrier oscillatorv. driver amplifierw. mixerx. final power amplifier
2. Class C amplifiers are notused in which type of transmitter?
u. AMv. SSBw. CWx. FM
3. A circuit that isolates thecarrier oscillator from load changesis called a
u. final amplifier
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v. driver amplifierw. linear amplifierx. buffer amplifier
4. A class B amplifier conductsfor how many degrees of an input
sine waveu. 90 to 150
v. 180
w. 180 to 360
x. 360
5. Bias for a class C amplifierproduced by an input RC networkis known as
u. signal bias
v. self biasw. fixed external biasx. threshold bias
6. An FM transmitter has a 9 MHzcrystal carrier oscillator andfrequency multipliers of 2, 3, and 4.The output frequency is
u. 54 MHzv. 108 MHzw. 216 MHzx. 288 MHz
7. The most efficient RF poweramplifier is which class amplifier?
u. Av. ABw. B
x. C
8. Collector current in a class Camplifier is a
u. sine wavev. half sine wavew. pulsex. square wave
9. The maximum power of typicaltransistor RF power amplifiers is inwhat range?
u. milliwattsv. wattsw. hundreds of watts
x. kilowatts
10. Self-oscillation in a transistoramplifier is usually caused by
u. excessive gainv. stray inductancew. internal capacitancex. unmatched impedances
11. Neutralization is the process ofu. canceling the effect of
internal devicecapacitance
v. by passing undesiredalternating current
w. reducing gainx. eliminating harmonics
12. Maximum power transferoccurs when what relationshipexists between the generatorimpedance Zi and the load
impedance Zl?v. Zi= Zlw. Zi> Zlx. Zi< Zl
y. Zi= 0
13. Which of the following is not abenefit of a toroid RF inductor?
u. no shielding requiredv. fewer turns of wire
w. higher Qx. self-supporting
14. A toroid is au. type of inductorv. transformerw. magnetic corex. coil holder
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15. Which of the following is notcommonly used for impedancematching in a transmitter?
u. resistive attenuatorv. transformerw. L network
x. T network
16. To match a 6 amplifier
impedance to a 72 antennaload, a transformer must have aturns ratio Np/Nsof
u. 0.083v. 0.289w. 3.46x. 12
17. Impedance matching in abroadband linear RF amplifier ishandled with a(n)
u. L networkv. parallel tuned circuitw. Pi networkx. Balun
18. A class C amplifier has a
supply voltage of 24 V and acollector current of 2.5 A. Itsefficiency is 80 percent. The RFoutput power is
u. 24 Wv. 48 Ww. 60 Wx. 75 W
19. Which of the following is not a
benefit of speech-processingcircuits?
u. improved frequencystability
v. increased average outputpower
w. limited bandwidthx. prevention of
overmodulation
20. In an AM transmitter, a clippercircuit eliminates
u. harmonicsv. splatterw. overdeviation
x. excessive gain
21. In a speech-processing circuit,a low-pass filter prevents
u. overdeviationv. overmodulationw. high gainx. excessive signal
bandwidth
22. The gain of a transistoramplifier is
u. inversely proportional tocollector current
v. directly proportional tofrequency
w. directly proportional tocollector current
x. inversely proportional tofrequency
23. What values of L and C in an Lnetwork are required to match a 10
transistor amplifier impedance to
a 50 load at 27 MHz?u. L = 47 nH, C = 185 pFv. L = 118 nH, C = 236 pF
w. L = 0.13 H, C = 220 pF
x. L = 0.3 H, C = 330 pF
CHAPTER 7COMMUNICATIONS RECEIVERS
1. The simplest receiver is a(n)y. RF amplifierz. demodulatoraa. AF amplifierbb. tuned circuit
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2. The key conceptual circuit in asuperhet receiver is the
y. mixerz. RF amplifieraa. demodulatorbb. AF amplifier
3. Most of the gain and selectivityin a superhet is obtained in the
y. RF amplifierz. mixeraa. IF amplifierbb. AF amplifier
4. The sensitivity of a receiverdepends upon the receivers
overally. bandwidthz. selectivityaa. noise responsebb. gain
5. The ability of a receiver toseparate one signal from others onclosely adjacent frequencies iscalled the
y. sensitivityz. S/N ratioaa. selectivitybb. gain
6. A mixer has a signal input of50 MHz and an LO frequency of 59MHz. The IF is
y. 9 MHzz. 50 MHz
aa. 59 MHzbb. 109 MHz
7. A signal 2 times the IF awayfrom the desired signal that causesinterference is referred to as a(n)
y. ghostz. imageaa. phantom
bb. inverted signal
8. A receiver has a desired inputsignal of 18 MHz and an LOfrequency of 19.6 MHz. Theimage frequency is
y. 1.6 MHzz. 18 MHzaa. 19.6 MHzbb. 21.2 MHz
9. The main cause of imageinterference is
y. poor front-end selectivityz. low gainaa. a high IF
bb. a low S/N ratio
10. For best image rejection, the IFfor a 30 MHz signal would be
y. 455 kHzz. 3.3 MHzaa. 9 MHzbb. 55 MHz
11. A tuned circuit is resonant at 4
MHz. Its Q is 100. The bandwidthis
y. 400 Hzz. 4 kHzaa. 40 kHzbb. 400 kHz
12. A crystal filter has a 6 dB
bandwidth of 2.6 kHz and a 60 dBbandwidth of 14 kHz. The shapefactor is
z. 0.186aa. 5.38bb. 8.3cc. 36.4
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13. Most internal noise comesfrom
y. shot noisez. transit-time noiseaa. thermal agitationbb. skin effect
14. Which of the following is not asource of external noise?
y. thermal agitationz. auto ignitionsaa. the sunbb. fluorescent lights
15. Noise can be reduced byy. widening the bandwidth
z. narrowing the bandwidthaa. increasing temperaturebb. increasing transistor
current levels
16. Noise at the input to a receivercan be as high as several
y. microvoltsz. millivoltsaa. volts
bb. kilovolts
17. Which circuit contributes mostto the noise in a receiver?
y. IF amplifierz. AF amplifieraa. demodulatorbb. mixer
18. Which noise figure represents
the lowest noise?y. 1.6 dBz. 2.1 dBaa. 2.7 dBbb. 3.4 dB
19. Which filter shape factorrepresents the best skirtselectivity?
y. 1.6z. 2.1aa. 5.3bb. 8
20. Which input signal below
represents the best receiversensitivity?
y. 0.5 V
z. 1 V
aa. 1.8 V
bb. 2 V
21. The transistor with the lowestnoise figure in the microwaveregion is a(n)
y. MOSFETz. Dual-gate MOSFETaa. JFETbb. MESFET
22. The AGC circuits usuallycontrol the gain of the
y. mixerz. detectoraa. IF amplifiers
bb. audio amplifiers
23. Selectivity is obtained in mostreceivers from
y. crystal filtersz. mechanical filtersaa. double-tuned circuitsbb. audio filters
24. Widest bandwidth in a double-
tuned circuit is obtained withu. undercouplingv. critical couplingw. optimum couplingx. overcoupling
25. Automatic gain control permitsa wide range of signal amplitudes
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to be accommodated by controllingthe gain of the
q. RF amplifierr. IF amplifiers. mixert. AF amplifier
26. In an IF amplifier with reverseAGC, a strong signal will cause thecollector current to
q. increaser. decreases. remain the samet. drop to zero
27. Usually AGC voltage is derived
by theq. RF amplifierr. IF amplifiers. demodulatort. AF amplifier
28. An AFC circuit is used tocorrect for
q. audio distortionr. strong input signals
s. instability in the IFamplifier
t. frequency drift in the LO
29. A circuit that keeps the audiocut off until a signal is received isknown as
q. a squelchr. AFCs. AGC
t. a noise blanker
30. A BFO is used in thedemodulation of which types ofsignals?
a. AMb. FMc. SSB or CWd. QPSK
31. Which of the following circuitsare not typically shared in an SSBtransceiver?
a. crystal filterb. mixers
c. power supplyd. LO
32. The basic frequencysynthesizer circuit is a(n)
a. mixerb. frequency multiplierc. frequency dividerd. PLL
33. The output frequencyincrement of a frequencysynthesizer is determined by the
a. frequency division ratiob. reference input to the
phase detectorc. percentage of output
frequencyd. frequency multiplication
factor
34. The output frequency of asynthesizer is changed by varyingthe
a. reference input to thephase detector
b. frequency division ratioc. frequency multiplication
factord. mixer LO frequency
35. The bandwidth of a parallel LC
circuit can be increased bya. increasing XCb. decreasing XLc. decreasing coil resistanced. a resistor connected in
parallel
36. The upper and lower cutofffrequencies of a tuned circuit are
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6. The circuit that performsdemultiplexing in an FDM systemis a(n)
cc. op ampdd. bandpass filter
ee. discriminatorff. subcarrier oscillator
7. Most FDM telemetry systemsuse
cc. AMdd. FMee. SSBff. PSK
8. The best frequencydemodulator is the
cc. PLL discriminatordd. pulse-averaging
discriminatoree. Foster-Seeley
discriminatorff. ratio detector
9. The modulation used in FDM
telephone systems iscc. AMdd. FMee. SSBff. PSK
10. The FDM telephone systemsaccommodate many channels by
cc. increasing the multiplexersize
dd. using many final carriersee. narrowing the bandwidth ofeach
ff. using multiple levels ofmultiplexing
11. In FM stereo broadcasting, theL + R signal
cc. double-sidebandmodulates a subcarrier
dd. modulates the FM carrieree. frequency modulates a
subcarrierff. is not transmitted
12. In FM stereo broadcasting, theLR signal
dd. double-sidebandmodulates a subcarrier
ee. modulates the FM carrierff. frequency modulates a
subcarriergg. is not transmitted
13. The SCA signal if used in FMbroadcasting is transmitted via
cc. a 19 kHz subcarrierdd. a 38 kHz subcarrieree. a 67 kHz subcarrierff. the main FM carrier
14. In TDM, multiple signalscc. share a common
bandwidth
dd. modulate subcarriersee. are sampled at high
speedsff. take turns transmitting
15. In TDM, each signal may usethe full bandwidth of the channel
cc. truedd. false
16. Sampling an analog signalproducescc. PAMdd. AMee. FMff. PCM
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17. The maximum bandwidth thatan analog signal can use with asampling frequency of 108 kHz is
cc. 27 kHzdd. 54 kHzee. 108 kHz
ff. 216 kHz
18. Pulse-amplitude modulationsignals are multiplexed by using
cc. subcarriersdd. bandpass filtersee. A/D convertersff. FET switches
19. In PAM demultiplexing, the
receiver clock is derived fromcc. standard radio station
WWVdd. a highly accurate internal
oscillatoree. the PAM signal itselfff. the 60 Hz power line
20. In a PAM/TDM system,keeping the multiplexer and
DEMUX channels step with oneanother is done by a
cc. clock recovery circuitdd. sync pulseee. samplingff. sequencer
21. Transmitting data as serialbinary words is called
cc. digital communications
dd. quantizingee. PAMff. PCM
22. Converting analog signals todigital is done by sampling and
cc. quantizingdd. compandingee. pre-emphasis
ff. mixing
23. A quantizer is a(n)cc. multiplexerdd. demultiplexeree. A/D converter
ff. D/A converter
24. Emphasizing low-level signalsand compressing higher-levelsignals is called
y. quantizingz. compandingaa. pre-emphasisbb. sampling
25. Which of the following is not abenefit of companding?
u. minimizes noisev. minimizes number of bitsw. minimizes quantizing errorx. minimizes signal
bandwidth
26. A telephone system usingTDM and PCM is called
u. PBXv. RS-232w. T-1x. Bell 212
27. An IC that contains A/D andD/A converters, companders, andparallel-to-serial converters iscalled a
u. codec
v. data converterw. multiplexerx. modem
28. Pulse-code modulation ispreferred to PAM because of its
u. resistance to quantizingerror
v. simplicity
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w. lower costx. superior noise immunity
CHAPTER 9
ANTENNAS AND
TRANSMISSION LINES
1. The most commonly usedtransmission line is a
gg. two-wire balance linehh. single wireii. three-wire line
jj. coax
2. The characteristic impedance
of a transmission line does notdepend upon its
gg. lengthhh. conductor diameterii. conductor spacing
jj. none of the above
3. Which of the following is not acommon transmission lineimpedance?
gg. 50hh. 75
ii. 120
jj. 300
4. For maximum absorption ofpower at the antenna, therelationship between thecharacteristic impedance of theline Zoand the load impedance Zl
should begg. Zo= Zlhh. Zo> Zlii. Zo< Zl
jj. Zo= 0
5. The mismatch betweenantenna and transmission line
impedances cannot be correctedfor by
gg. using an LC matchingnetwork
hh. adjusting antenna lengthii. using a balun
jj. adjusting the length oftransmission line
6. A pattern of voltage andcurrent variations along atransmission line not terminated inits characteristic impedance iscalled
gg. an electric fieldhh. radio waves
ii. standing wavesjj. a magnetic field
7. The desirable SWR on atransmission line is
gg. 0hh. 1ii. 2
jj. infinity
8. A 50 coax is connected to a73 antenna. The SWR is
gg. 0.685hh. 1ii. 1.46
jj. 2.92
9. The most desirable reflectioncoefficient is
gg. 0
hh. 0.5ii. 1
jj. infinity
10. A ratio expressing thepercentage of incident voltagereflected on a transmission line isknown as the
gg. velocity factor
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hh. standing wave ratioii. reflection coefficient
jj. line efficiency
11. The minimum voltage along atransmission line is 260 V, while
the maximum is 390 V. The SWRis
gg. 0.67hh. 1.0ii. 1.2
jj. 1.5
12. Three feet is one wavelengthat a frequency of
hh. 100 MHz
ii. 164 MHzjj. 300 MHzkk. 328 MHz
13. At very high frequencies,transmission lines are used as
gg. tuned circuitshh. antennasii. insulators
jj. resistors
14. A shorted quarter-wave line atthe operating frequency acts likea(n)
gg. series resonant circuithh. parallel resonant circuitii. capacitor
jj. inductor
15. A shorted half-wave line at the
operating frequency acts like a(n)ee. capacitorff. inductorgg. series resonant circuithh. parallel resonant circuit
16. A popular half-wavelengthantenna is the
gg. ground plane
hh. end-fireii. collinear
jj. dipole
17. The length of a doublet at 27MHz is
gg. 8.67 ft.hh. 17.3 ft.ii. 18.2 ft.
jj. 34.67 ft.
18. A popular vertical antenna isthe
gg. collinearhh. dipoleii. ground plane
jj. broadside
19. The magnetic field of anantenna is perpendicular to theearth. The antennas polarization
gg. is verticalhh. is horizontalii. is circular
jj. cannot be determined fromthe information given
20. An antenna that transmits orreceives equally well in alldirections is said to be
gg. omnidirectionalhh. bidirectionalii. unidirectional
jj. quasidirectional
21. The horizontal radiation pattern
of a dipole is agg. circlehh. figure eightii. clover leaf
jj. narrow beam
22. The length of a ground planevertical at 146 MHz is
gg. 1.6 ft.
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hh. 1.68 ft.ii. 2.05 ft.
jj. 3.37 ft.
23. The impedance of a dipole isabout
gg. 50hh. 73
ii. 93
jj. 300
24. A directional antenna with twoor more elements is known as a(n)
cc. Folded dipoledd. ground planeee. loop
ff. array
25. The horizontal radiation patternof a vertical dipole is a
y. figure eightz. circleaa. narrow beambb. clover leaf
26. In an Yagi antenna, maximum
direction of radiation is toward they. directorz. driven elementaa. reflectorbb. sky
27. Conductors in mutlielementantennas that do not receiveenergy directly from thetransmission line are known as
y. parasitic elementsz. drives elementsaa. the boombb. receptors
28. A coax has an attenuation of2.4 dB per 100 ft. The attenuationfor 275 ft is
y. 2.4 dB
z. 3.3 dBaa. 4.8 dBbb. 6.6 dB
29. An antenna has a power gainof 15. The power applied to the
antenna is 32 W. The effectiveradiated power is
u. 15 Wv. 32 Ww. 120 Wx. 480 W
30. Which beam width representsthe best antenna directivity?
a. 7
b. 12c. 19
d. 28
31. The radiation pattern ofcollinear and broadside antennasis
a. omnidirectionalb. bidirectionalc. unidirectional
d. clover-leaf shaped
32. Which antenna has aunidirectional radiation pattern andgain?
a. dipoleb. ground planec. Yagid. collinear
33. A wide-bandwidth multielementdriven array is the
a. end-fireb. log-periodicc. Yagid. collinear
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CHAPTER 10
MICROWAVE TECHNIQUES
1. The main benefit of usingmicrowaves is
kk. lower-cost equipment
ll. simpler equipmentmm. greater transmission
distancesnn. more spectrum space for
signals
2. Radio communications areregulated in the United States bythe
kk. Federal Trade
Commissionll. Congressmm. Federal
CommunicationsCommission
nn. Military
3. Which of the following is not adisadvantage of microwaves?
kk. higher-cost equipment
ll. line-of-sight transmissionmm. conventional
components are notusable
nn. circuits are more difficult toanalyze
4. Which of the following is amicrowave frequency?
kk. 1.7 MHz
ll. 750 MHzmm. 0.98 GHznn. 22 GHz
5. Which of the following is not acommon microwave application?
kk. radarll. mobile radiomm. telephone
nn. spacecraftcommunications
6. Coaxial cable is not widelyused for long microwavetransmission lines because of its
kk. high loss
ll. high costmm. large sizenn. excessive radiation
7. Stripline and microstriptransmission lines are usuallymade with
kk. coaxll. parallel wiresmm. twisted pair
nn. PCBs
8. The most common crosssection of a waveguide is a
kk. squarell. circlemm. trianglenn. rectangle
9. A rectangular waveguide has a
width of 1 in. and a height of 0.6 in.Its cutoff frequency is
kk. 2.54 GHzll. 3.0 GHzmm. 5.9 GHznn. 11.8 GHz
10. A waveguide has a cutofffrequency of 17 GHz. Which of thesignals will not be passed by the
waveguide?kk. 15 GHzll. 18 GHzmm. 22 GHznn. 25 GHz
11. Signal propagation in awaveguide is by
kk. electrons
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ll. electric and magneticfields
mm. holesnn. air pressure
12. When the electric field in a
waveguide is perpendicular to thedirection of wave propagation, themode is said to be
ll. vertical polarizationmm. horizontal propagationnn. transverse electricoo. transverse magnetic
13. The dominant mode in mostwaveguide is
kk. TE0,1ll. TE1,2mm. TM0,1nn. TM1,1
14. A magnetic field is introducedinto a waveguide by a
kk. probell. dipolemm. stripline
nn. capacitor
15. A half-wavelength, closedsection of a waveguide that acts asa parallel resonant circuit is knownas a(n)
ii. half-wave sectionjj. cavity resonatorkk. LCR circuitll. directional coupler
16. Decreasing the volume of acavity causes its resonantfrequency to
kk. increasell. decreasemm. remain the samenn. drop to zero
17. A popular microwave mixerdiode is the
kk. Gunnll. Varactormm. Hot carrier
nn. IMPATT
18. Varactor and step-recoverydiodes re widely used in what typeof circuit?
kk. amplifierll. oscillatormm. frequency multipliernn. mixer
19. Which diode is a popularmicrowave oscillator?
kk. IMPATTll. Gunnmm. Varactornn. Schottky
20. Which type of diodes does notordinarily operate with reversebias?
kk. Varactorll. IMPATTmm. Snap-offnn. Tunnel
21. Low-power Gunn diodes arereplacing
kk. Reflex klystronsll. TWTsmm. Magnetronsnn. Varactor diodes
22. Which of the following is not amicrowave tube?
kk. Traveling-wave tubell. Cathode-ray tubemm. Klystronnn. Magnetron
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23. In a klystron amplifier, velocitymodulation of the electron beam isproduced by the
kk. Collectorll. Catcher cavitymm. Cathode
nn. Buncher cavity
24. A reflex klystron is used asa(n)
gg. amplifierhh. oscillatorii. mixer
jj. frequency multiplier
25. For proper operation, a
magnetron must be accompaniedby a
cc. cavity resonatordd. strong electric fieldee. permanent magnetff. high dc voltage
26. The operating frequency ofklystrons and magnetrons is set bythe
cc. cavity resonatorsdd. DC supply voltageee. input signal frequencyff. number of cavities
27. A magnetron is used only asa(n)
cc. amplifierdd. oscillatoree. mixer
ff. frequency multiplier
28. A common application formagnetrons is in
cc. radardd. satellitesee. two-way radioff. TV sets
29. In a TWT, the electron beam isdensity-modulated by a
y. permanent magnetz. modulation transformeraa. Helixbb. cavity resonator
30. The main advantage of a TWTover a klystron for microwaveamplification is
a. lower costb. smaller sizec. higher powerd. wider bandwidth
31. High-power TWTs are
replacing what in microwaveamplifiers?a. MESFETsb. magnetronsc. klystronsd. IMPATT diodes
32. The most widely usedmicrowave antenna is a
a. half-wave dipoleb. quarter-wave probec. single loopd. horn
33. What happens when a hornantenna is made longer?
a. Gain increasesb. beam width decreasesc. both a and bd. neither a nor b
34. A pyramidal horn used at 5GHz has an aperture that is 7 by 9cm. The gain is about
a. 10.5 dBb. 11.1 dBc. 22.6 dBd. 35.8 dB
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35. Given the frequency anddimensions in Question 34 above,the beam width is about
a. 27
b. 53
c. 60
d. 80
36. The diameter of a parabolicreflector should be at least howmany wavelengths at the operatingfrequency?
a. 1b. 2c. 5d. 10
37. The point where the antenna ismounted with respect to theparabolic reflector is called the
a. Focal pointb. centerc. locusd. tangent
38. Using a small reflector to beam
waves to the larger parabolicreflector is known asa. Focal feedb. Horn feedc. Cassegrain feedd. Coax feed
39. Increasing the diameter of aparabolic reflector causes which ofthe following:
a. decreased beam widthb. increased gainc. increased beam widthd. a and be. b and cf. none of the above
40. A helical antenna is made upof a coil and a
a. directorb. reflectorc. dipoled. horn
41. The output of a helical antennais
a. vertically polarizedb. horizontally polarizedc. circularly polarizedd. both a and b
42. A common omnidirectionalmicrowave antenna is the
a. hornb. parabolic reflectorc. helicald. bicone
CHAPTER 11
INTRODUCTION TO SATELLITE
COMMUNICATIONS
1. As the height of a satellite orbitgets lower, the speed of the
satelliteoo. increasepp. decreasesqq. remains the samerr. none of the above
2. The main function of acommunications satellite is as a(n)
oo. Repeaterpp. Reflector
qq. Beaconrr. Observation platform
3. The key electronic componentin a communications satellite is the
oo. Telemetrypp. On-board computerqq. Command and control
system
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rr. Transponder
4. A circular orbit around theequator with a 24-h period is calleda(n)
oo. Elliptical orbit
pp. Geostationary orbitqq. Polar orbitrr. Transfer orbit
5. A satellite stays in orbitbecause the following two factorsare balanced.
oo. satellite weight and speedpp. gravitational pull and
inertia
qq. centripetal force andspeed
rr. satellite weight and the pullof the moon and sun
6. The height of a satellite in asynchronous equatorial orbit is
oo. 100 mi.pp. 6800 mi.qq. 22,300 mi.rr. 35,860 mi.
7. Most satellites operate inwhich frequency band?
oo. 30 to 300 MHzpp. 300 MHz to 3 GHzqq. 3 GHz to 30 GHzrr. above 300 GHz
8. The main power sources for asatellite are
oo. batteriespp. solar cellsqq. fuel cellsrr. thermoelectric generators
9. The maximum height of anelliptical orbit is called the
oo. perigeepp. apex
qq. zenithrr. apogee
10. Batteries are used to power allsatellite subsystems
oo. at all times
pp. only during emergenciesqq. during eclipse periodsrr. to give the solar arrays a
rest
11. The satellite subsystem thatmonitors and controls the satelliteis the
oo. propulsion subsystempp. power subsystem
qq. communicationssubsystem
rr. telemetry, tracking, andcommand subsystem
12. The basic technique used tostabilize a satellite is
pp. gravity-forward motionbalance
qq. spinrr. thruster control
ss. solar panel orientation
13. The jet thrusters are usuallyfired to
oo. maintain altitudepp. put the satellite into the
transfer orbitqq. inject the satellite into the
geosynchronous orbitrr. bring the satellite back to
earth
14. Most commercial satelliteactivity occurs in which band(s)?
oo. Lpp. C and Kuqq. Xrr. S and P
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15. How can multiple earthstations share a satellite on thesame frequencies?
mm. frequency reusenn. multiplexingoo. mixing
pp. they cant
16. The typical bandwidth of asatellite band is
oo. 36 MHzpp. 40 MHzqq. 70 MHzrr. 500 MHz
17. Which of the following is not
usually a part of a transponder?oo. LNApp. mixerqq. modulatorrr. HPA
18. The satellite communicationschannels in a transponder aredefined by the
oo. LNA
pp. bandpass filterqq. mixerrr. input signals
19. The HPAs in most satellitesare
oo. TSTspp. klystronsqq. vacuum tubesrr. magnetrons
20. The physical location of asatellite is determined by its
oo. distance from the earthpp. latitude and longitudeqq. reference to the starsrr. position relative to the sun
21. The receive GCE system in anearth stations performs whatfunction(s)?
oo. modulation andmultiplexing
pp. up conversion
qq. demodulation anddemultiplexing
rr. down conversion
22. Which of the following types ofHPA is not used in earth stations?
oo. TWTpp. transistorqq. klystronrr. Magnetron
23. A common up-converter anddown-converter IF is
oo. 36 MHzpp. 40 MHzqq. 70 MHzrr. 500 MHz
24. The type of modulation usedon voice and video signals is
kk. AMll. FMmm. SSBnn. QPSK
25. The modulation normally usedwith digital data is
gg. AMhh. FMii. SSB
jj. QPSK
26. Which of the following is not atypical output from a GPSreceiver?
gg. latitudehh. speedii. altitude
jj. longitude
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CHAPTER 12
DATA COMMUNICATIONS
1. Data communications refers tothe transmission of
ss. voicett. videouu. computer datavv. all of the above
2. Data communications usesss. analog methodstt. digital methodsuu. either of the abovevv. neither of the above
3. Which of the following is notprimarily a type of datacommunications?
ss. telephonett. teletypeuu. telegraphvv. CW
4. The main reason that serial
transmission is preferred to paralleltransmission is that
ss. Serial is faster.tt. Serial requires only a
single channel.uu. Serial requires multiple
channels.vv. Parallel is too expensive.
5. Mark and space refer
respectively toss. dot and dashtt. message and intervaluu. binary 1 and binary 0vv. on and off
6. The number of amplitude,frequency, or phase changes that
take place per second is known asthe
ss. data rate in bits persecond
tt. frequency of operationuu. speed limit
vv. baud rate
7. Data transmission of onecharacter at a time with start andstop bits is known as what type oftransmission?
ss. asynchronoustt. serialuu. synchronousvv. parallel
8. The most widely used datacommunications code is
ss. Morsett. ASCIIuu. Baudotvv. EBCDIC
9. The ASCII code hasss. 4 bits
tt. 5 bitsuu. 7 bitsvv. 8 bits
10. Digital signals may betransmitted over the telephonenetwork if
ss. their speed is low enoughtt. they are converted to
analog first
uu. they are ac instead of dcvv. they are digital only11. Start and stop bits,respectively, are
ss. mark, spacett. space, markuu. space, spacevv. mark, mark
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12. Which of the following iscorrect?
tt. The bit rate may begreater than the baudrate.
uu. The baud rate may be
greater than the bit rate.vv. The bit and baud rates are
always the same.ww. The bit and baud rates re
not related.
13. A modem convertsss. analog signals to digitaltt. digital signals to analoguu. both a and b
vv. none of the above
14. Slow-speed modems usess. FSKtt. BPSKuu. QPSKvv. QAM
15. A carrier recovery circuit is notneeded with
qq. BPSKrr. QPSKss. DPSKtt. QAM
16. The basic modulator anddemodulator circuits in PSK are
ss. PLLstt. balanced modulatoruu. shift registers
vv. linear summers
17. The carrier used with a BPSKdemodulator is
ss. generated by an oscillatortt. the BPSK signal itselfuu. twice the frequency of the
transmitted carrier
vv. recovered from the BPSKsignal
18. A 9600-baud-rate signal canpass over the voice-gradetelephone line if which kind of
modulation is used?ss. BPSKtt. QPSKuu. DPSKvv. QAM
19. Quadrature amplitudemodulation is
ss. amplitude modulation onlytt. QPSK only
uu. AM plus QPSKvv. AM plus FSK
20. A QAM modulator does notuse a(n)
ss. XNORtt. bit splitteruu. balanced modulatorvv. 2-to-4 level converter
21. A rule or procedure thatdefines how data is to betransmitted is called a(n)
ss. handshakett. error-detection schemeuu. data specificationvv. protocol
22. A popular PC protocol isss. parity
tt. Xmodemuu. CRCvv. LRC
23. A synchronous transmissionusually begins with whichcharacter?
ss. SYNtt. STX
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uu. SOHvv. ETB
24. The characters making up themessage in a synchronoustransmission are collectively
referred to as a dataoo. setpp. sequenceqq. blockrr. collection
25. Bit errors in data transmissionare usually caused by
kk. equipment failuresll. typing mistakes
mm. noisenn. poor S/N ratio at the
receiver
26. Which of the following is not acommonly used method of errordetection?
kk. parityll. BCCmm. CRC
nn. redundancy
27. Which of the following wordshas the correct parity bit? Assumeodd parity. The last bit is the paritybit.
gg. 1111111 1hh. 1100110 1ii. 0011010 1
jj. 0000001 0
28. Another name for parity isgg. vertical redundancy
checkhh. block check characterii. longitudinal redundancy
checkjj. cyclical redundancy check
29. Ten bit errors occur in twomillion transmitted. The bit errorrate is
cc. 2 x 10-5
dd. 5 x 10
-5
ee. 5 x 10-6
ff. 2 x 10-6
30. The building block of a parityor BCC generator is a(n)
e. shift registerf. XORg. 2-to-4 level converterh. UART
31. A longitudinal redundancy
check produces a(n)e. block check characterf. parity bitg. CRCh. error correction
32. Dividing the data block by aconstant produces a remainderthat is used for error detection. Itis called the
e. vertical redundancy check
f. horizontal redundancycheckg. block check characterh. cyclical redundancy check
33. A CRC generator uses whichcomponents?
e. balanced modulatorf. shift registerg. binary adderh. multiplexer
34. Which of the following is not aLAN?
e. PBX systemf. hospital systemg. office building systemh. cable TV system
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35. The fastest LAN topology isthe
e. ringf. busg. star
h. square
36. Which is not a common LANmedium?
e. twin leadf. twisted pairg. fiber-optic cableh. coax
37. A mainframe computer
connected to multiple terminalsand PCs usually uses whichconfiguration?
e. busf. ringg. starh. tree
38. A small telephone switchingsystem that can be used as a LANis called a
e. ringf. WANg. UARTh. PBX
39. Which medium is the leastsusceptible to noise?
g. twin leadh. twisted pairi. fiber-optic cable
j. coax
40. Which medium is the mostwidely used in LANs?
e. twin leadf. twisted pairg. fiber-optic cableh. coax
41. Transmitting the data signaldirectly over the medium isreferred to as
e. basebandf. broadbandg. ring
h. bus
42. The technique of usingmodulation and FDM to transmitmultiple data channels of acommon medium is known as
e. basebandf. broadbandg. ringh. bus
43. What is the minimumbandwidth required to transmit a56 kbits/s binary signal with nonoise?
a. 14 kHzb. 28 kHzc. 56 kHzd. 112 kHz
44. Sixteen different levels(symbols) are used to encodebinary data. The channelbandwidth is 36 MHz. Themaximum channel capacity is
a. 18 Mbits/sb. 72 Mbits/s
c. 288 Mbits/sd. 2.176 Gbits/s
45. What is the bandwidth requiredto transmit at a rate of 10 Mbits/sin the presence of a 28-dB S/Nradio?
a. 1.075 MHzb. 5 MHzc. 10 MHzd. 10.75 MHz
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46. Which circuit is common toboth frequency-hopping and direct-sequence SS transmitters?
a. correlatorb. PSN code generatorc. frequency synthesizer
d. sweep generator
47. Spread spectrum stationssharing a band are identified byand distinguished from oneanother by
a. PSN codeb. frequency of operationc. clock rated. modulation type
48. The type of modulation mostoften used with direct-sequenceSS is
a. QAMb. SSBc. FSKd. PSK
49. The main circuit in a PSN
generator is a(n)a. X-ORb. multiplexerc. shift registerd. mixer
50. To a conventional narrowbandreceiver, an SS signal appears tobe like
a. noise
b. fadingc. a jamming signald. an intermittent connection
51. Which of the following is not abenefit of SS?
a. jam-proofb. securityc. immunity to fading
d. noise proof
52. Spread spectrum is a form ofmultiplexing.
a. trueb. false
53. The most critical and difficultpart of receiving a direct-sequenceSS signal is
a. frequency synthesisb. synchronismc. PSN code generationd. carrier recovery
CHAPTER 13
FIBER-OPTIC
COMMUNICATIONS
1. Which of the following is not acommon application of fiber-opticcable?
ww. computer networksxx. long-distance telephone
systemsyy. closed circuit TVzz. consumer TV
2. Total internal reflection takesplace if the light ray strikes theinterface at an angle with whatrelationship to the critical angle?
ww. less thanxx. greater than
yy. equal tozz. zero
3. The operation of a fiber-opticcable is based on the principle of
ww. refractionxx. reflectionyy. dispersionzz. absorption
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4. Which of the following is not acommon type of fiber-optic cable?
ww. single-mode step-indexxx. multimode graded-indexyy. single-mode graded-index
zz. multimode step-index
5. Cable attenuation s usuallyexpressed in terms of
ww. loss per footxx. dB/km.yy. intensity per milezz. voltage drop per inch
6. Which cable length has thehighest attenuation?
ww. 1 kmxx. 2 kmyy. 95 ft.zz. 500 ft.
7. The upper pulse rate andinformation-carrying capacity of acable is limited by
ww. pulse shorteningxx. attenuationyy. light leakagezz. modal dispersion
8. The core of a fiber-optic cableis made of
ww. airxx. glassyy. diamond
zz. quartz
9. The core of a fiber-optic cableis surrounded by
ww. wire braid shieldxx. Kevlaryy. claddingzz. plastic insulation
10. The speed of light in plasticcompared to the speed of light inair is
ww. lessxx. moreyy. the same
zz. zero11. Which of the following is not amajor benefit of fiber-optic cable?
ww. immunity from interferencexx. no electrical safety
problemsyy. excellent data securityzz. lower cost
12. The main benefit of light-wave
communications over microwavesor any other communicationsmedia are
xx. lower costyy. better securityzz. wider bandwidthaaa. freedom from
interference
13. Which of the following is not
part of the optical spectrum?ww. infraredxx. ultravioletyy. visible colorzz. x-rays
14. The wavelength of visible lightextends from
ww. 0.8 to 1.6 m.xx. 400 to 750 nm.
yy. 200 to 600 nm.zz. 700 to 1200 nm.
15. The speed of light isuu. 186,000 mi/h.vv. 300,000 mi/h.ww. 300,000 m/sxx. 300,000,000 m/s
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16. Refraction is theww. bending of light wavesxx. reflection of light wavesyy. distortion of light waveszz. diffusion of light waves
17. The ratio of the speed of lightin air to the speed of light inanother substance is called the
ww. speed factorxx. index of reflectionyy. index of refractionzz. speed gain
18. A popular light wavelength in
fiber-optic cable isww. 0.7 m.
xx. 1.3 m.
yy. 1.5 m.
zz. 1.8 m.
19. Which type of fiber-optic cableis the most widely used?
ww. single-mode step-indexxx. multimode step-index
yy. single-mode graded-indexzz. multimode graded-index
20. Which type of fiber-optic cableis best for very high speed data?
ww. single-mode step-indexxx. multimode step-indexyy. single-mode graded-indexzz. multimode graded-index
21. Which type of fiber-optic cablehas the least modal dispersion?
ww. single-mode step-indexxx. multimode step-indexyy. single-mode graded-indexzz. multimode graded-index
22. Which of the following is not afactor in cable light loss?
ww. reflectionxx. absorptionyy. scatteringzz. dispersion
23. A distance of 8 km is the same
asww. 2.5 mi.xx. 5 mi.yy. 8 mi.zz. 12.9 mi.
24. A fiber-optic cable has a lossof 15 dB/km. The attenuation in acable 1000 ft long is
ss. 4.57 dB
tt. 9.3 dBuu. 24 dBvv. 49.2 dB
25. Fiber-optic cables withattenuations of 1.8, 3.4, 5.9, and18 dB are linked together. Thetotal loss is
oo. 7.5 dBpp. 19.8 dB
qq. 29.1 dBrr. 650 dB
26. Which light emitter is preferredfor high-speed data in a fiber-opticsystem?
oo. incandescentpp. LEDqq. neonrr. laser
27. Most fiber-optic light sourcesemit light in which spectrum?
kk. visiblell. infraredmm. ultravioletnn. x-ray
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ccc. 200 lines per inchddd. 400 lines per inch
5. Group 2 fax uses whichmodulation?
aaa. SSB
bbb. FSKccc. Vestigial sideband AMddd. PSK
6. The most widely used faxstandard is
aaa. Group 1bbb. Group 2ccc. Group 3
ddd. Group 4
7. Group 3 fax uses whichmodulation?
aaa. QAMbbb. FSKccc. Vestigial sideband AMddd. FM
8. Most fax printers are of which
type?aaa. impactbbb. thermalccc. electrosensitiveddd. laser xerographic
9. Facsimile standards are set bythe
aaa. FCCbbb. DOD
ccc. CCITTddd. IEEE
10. What type of graphics arecommonly transmitted by radiofax?
aaa. newspaper textbbb. architectural drawingsccc. cable movies
ddd. satellite weatherphotos
11. The transmission speed ofgroup 4 fax is
aaa. 4800 baud
bbb. 9600 baudccc. 56 kbits/sddd. 192 kbits/s
12. The master control center for acellular telephone system is the
bbb. cell siteccc. mobile telephone switching
officeddd. central officeeee. branch office
13. Each cell site contains aaaa. repeaterbbb. control computerccc. direct link to a branch
exchangeddd. touch-tone processor
14. Multiple cells within an areamay use the same channelfrequencies.
aaa. truebbb. false
15. Cellular telephones use whichtype of operation?
yy. simplex
zz. half-duplexaaa. full-duplexbbb. triplex
16. The maximum frequencydeviation of an FM cellulartransmitter is
aaa. 6 kHzbbb. 12 kHz
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ccc. 30 kHzddd. 45 kHz
17. The maximum output power ofa cellular transmitter is
aaa. 4.75 mW
bbb. 1.5 Wccc. 3 Wddd. 5 W
18. Receive channel 22 is 870.66MHz. Receive channel 23 is
aaa. 870.36 MHzbbb. 870.63 MHzccc. 870.96 MHzddd. 870.69 MHz
19. A transmit channel has afrequency of 837.6 MHz. Thereceive channel frequency is
aaa. 729.6 MHzbbb. 837.6 MHzccc. 867.6 MHzddd. 882.6 MHz
20. A receive channel frequency is
872.4 MHz. To develop an 82.2MHz IF, the frequency synthesizermust supply an LO signal of
aaa. 790.2 MHzbbb. 827.4 MHzccc. 954.6 MHzddd. 967.4 MHz
Note: The LO frequency is usually
higher than the receive frequency.
21. The output power of a cellularradio is controlled by theaaa. user or callerbbb. cell siteccc. called partyddd. MTSO
22. When the signal from a mobilecellular unit drops below a certainlevel, what action occurs?
aaa. The unit is handed offto a closer cell.
bbb. The call is terminated.ccc. The MTSO increases
power level.ddd. The cell site switches
antennas.
23. In a cellular radio, the duplexeris a
aaa. ferrite isolatorbbb. waveguide assemblyccc. pair of TR/ATR tubesddd. pair of sharp bandpass
filters
24. The time from the transmissionof a radar pulse to its reception is0.12 ms. The distance to thetarget is how many nautical miles?
ww. 4.85 nmixx. 9.7 nmiyy. 11.2 nmizz. 18.4 nmi
25. The ability of a radar to
determine the bearing to a targetdepends upon the
ss. antenna directivitytt. speed of lightuu. speed of the targetvv. frequency of the signal
26. The pulse duration of a radarsignal is 600 ns. The PRF is 185pulses per second. The duty cycle
is ss. 1.1 percenttt. 5.5 percentuu. 31 percentvv. 47 percent
27. The Doppler effect is used toproduce modulation of which typeof radar signal?
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oo. pulsepp. CW
28. The Doppler effect allowswhich characteristic of a target tobe measured?
oo. distancepp. azimuthqq. altituderr. speed
29. The Doppler effect is a changein what signal characteristicproduced by relative motionbetween the radar set and a
target?kk. amplitudell. phasemm. frequencynn. duty cycle
30. The most widely used radartransmitter component is a
m. klystronn. magnetron
o. TWTp. power transistor
31. Low-power radar transmittersand receiver Los use whichcomponent?
m. GaAs FETn. magnetrono. Gunn diodep. klystron
32. What component in a duplexerprotects the receiver from the high-power transmitter output?
m. waveguiden. bandpass filtero. notch filterp. spark gap
33. Most radar antennas use a
m. dipolen. broadside arrayo. horn and parabolic
reflectorp. collinear array
34. The most common radardisplay is the
m. A scann. color CRTo. liquid-crystal displayp. plan position indicator
35. A radar antenna using multipledipoles or slot antennas in a matrixwith variable phase shifters iscalled a(n)
m. A scann. phased arrayo. broadsidep. circular polarized array
36. Police radars use whichtechnique?
i. pulsej. CW
37. Which of the following is atypical radar operating frequency?
i. 60 MHzj. 450 MHzk. 900 MHzl. 10 GHz
38. The TV signal uses whichtypes of modulation for picture andsound respectively?
i. AM, FM
j. DSB, FMk. FM, AMl. AM, DSB
39. If a TV sound transmitter has acarrier frequency of 197.75 MHz,the picture carrier is
k. 191.75 MHzl. 193.25 MHz
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m. 202.25 MHzn. 203.75 MHz
40. The total bandwidth of anNTSC TV signal is
i. 3.58 MHz
j. 4.5 MHzk. 6 MHzl. 10.7 MHz
41. What is the total number ofinterlaced scan lines in onecomplete frame of a NTSC U.S.TV signal?
i. 262
j. 525k. 480l. 625
42. What keeps the scanningprocess at the receiver in step withthe scanning in the picture tube atthe receiver?
i. nothingj. color burstk. sync pulsesl. deflection oscillators
43. What is the black-and-white ormonochrome brightness signal inTV called?
e. RGBf. color subcarrierg. Q and Ih. luminance Y
44. What is the name of the solid-state imaging device used in TVcameras that converts the light in ascene into an electrical signal?
e. CCDf. photodiode matrixg. vidiconh. MOSFET array
45. The I and Q composite colorsignals are multiplexed onto thepicture carrier by modulating a3.58 MHz subcarrier using
e. FMf. PM
g. DSB AMh. Vestigial sideband AM
46. The assembly around the neckof a picture tube that produces themagnetic fields that deflect andscan the electron beams is calledthe
e. shadow maskf. phosphor
g. electron gunh. yoke
47. The picture and sound carrierfrequencies in a TV receiver IF arerespectively
e. 41.25 and 45.75 MHzf. 45.75 and 41.25 MHzg. 41.75 and 45.25 MHzh. 45.25 and 41.75 MHz
48. The sound IF in a TV receiveris
e. 4.5 MHzf. 10.7 MHzg. 41.25 MHzh. 45.75 MHz
49. What type of circuit is used tomodulate and demodulate the
color signals?e. phase-locked loopf. differential peak detectorg. Quadrature detectorh. balanced demodulator
50. What circuit in the TV receiveris used to develop high voltage
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needed to operate the picturetube?
e. low-voltage power supplyf. horizontal outputg. vertical sweeph. sync separator
51. What ensures proper colorsynchronization at the receiver?
e. sync pulsesf. Quadrature modulationg. 4.5 MHz carrier spacingh. 3.58 MHz color burst
52. Which of the following is not a
benefit of cable TV?c. lower-cost receptiond. greater reliabilitye. less noise, stronger
signalsf. premium cable channels
53. What technique is used topermit hundreds of TV signals toshare a common cable?
e. frequency modulationf. mixingg. frequency division
multiplexingh. time division multiplexing
Data communications refers to thetransmission of
A. voice
B. videoC. computer dataD. all of the above
ANSWER: C
Data communications usesA. analog methodsB. digital methodsC. either of the above
D. neither of the aboveANSWER: C
Which of the following is notprimarily a type of datacommunications?
A. telephoneB. teletypeC. telegraphD. CW
ANSWER: A
The main reason that serialtransmission is preferred to paralleltransmission is that
A. Serial is faster.
B. Serial requires only a singlechannel.C. Serial requires multiplechannels.D. Parallel is too expensive.
ANSWER: B
Mark and space refer respectivelyto
A. dot and dash
B. message and intervalC. binary 1 and binary 0D. on and off
ANSWER: C
The number of amplitude,frequency, or phase changes thattake place per second is known asthe
A. data rate in bits per second
B. frequency of operationC. speed limitD. baud rate
ANSWER: D
Data transmission of one characterat a time with start and stop bits isknown as what type oftransmission?
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A. asynchronousB. serialC. synchronousD. parallel
ANSWER: A
The most widely used datacommunications code is
A. MorseB. ASCIIC. BaudotD. EBCDIC
ANSWER: B
The ASCII code hasA. 4 bits
B. 5 bitsC. 7 bitsD. 8 bits
ANSWER: C
Digital signals may be transmittedover the telephone network if
A. their speed is low enoughB. they are converted to analogfirst
C. they are ac instead of dcD. they are digital onlyANSWER: B
Start and stop bits, respectively,are
A. mark, spaceB. space, markC. space, spaceD. mark, mark
ANSWER: B
Which of the following is correct?A. The bit rate may be greater thanthe baud rate.B. The baud rate may be greaterthan the bit rate.C. The bit and baud rates arealways the same.
D. The bit and baud rates re notrelated.
ANSWER: A
A modem convertsA. analog signals to digital
B. digital signals to analogC. both a and bD. none of the above
ANSWER: C
Slow-speed modems useA. FSKB. BPSKC. QPSKD. QAM
ANSWER: A
A carrier recovery circuit is notneeded with
A. BPSKB. QPSKC. DPSKD. QAM
ANSWER: C
The basic modulator anddemodulator circuits in PSK areA. PLLsB. balanced modulatorC. shift registersD. linears summers
ANSWER: B
The carrier used with a BPSKdemodulator is
A. generated by an oscillatorB. the BPSK signal itselfC. twice the frequency of thetransmitted carrierD. recovered from the BPSK signal
ANSWER: B
A 9600-baud-rate signal can passover the voice-grade telephone
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line if which kind of modulation isused?
A. BPSKB. QPSKC. DPSKD. QAM
ANSWER: D
Quadrature amplitude modulationis
A. amplitude modulation onlyB. QPSK onlyC. AM plus QPSKD. AM plus FSK
ANSWER: C
A QAM modulator does not usea(n)
A. XNORB. bit splitterC. balanced modulatorD. 2-to-4 level converter
ANSWER: A
A rule or procedure that defineshow data is to be transmitted is
called a(n)A. handshakeB. error-detection schemeC. data specificationD. protocol
ANSWER: D
A popular PC protocol isA. parityB. Xmodem
C. CRCD. LRCANSWER: B
A synchronous transmissionusually begins with whichcharacter?
A. SYNB. STX
C. SOHD. ETB
ANSWER: A
The characters making up themessage in a synchronous
transmission are collectivelyreferred to as a data
A. setB. sequenceC. blockD. collection
ANSWER: C
Bit errors in data transmission areusually caused by
A. equipment failuresB. typing mistakesC. noiseD. poor S/N ratio at the receiver
ANSWER: C
Which of the following is not acommonly used method of errordetection?
A. parity
B. BCCC. CRCD. redundancy
ANSWER: D
Which of the following words hasthe correct parity bit? Assume oddparity. The last bit is the parity bit.
A. 1111111 1B. 1100110 1
C. 0011010 1D. 0000001 0ANSWER: B
Another name for parity isA. vertical redundancy checkB. block check characterC. longitudinal redundancy checkD. cyclical redundancy check
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ANSWER: A
Ten bit errors occur in two milliontransmitted. The bit error rate is
A. 2 x 10-5B. 5 x 10-5
C. 5 x 10-6D. 2 x 10-6
ANSWER: C
The building block of a parity orBCC generator is a(n)
A. shift registerB. XORC. 2-to-4 level converterD. UART
ANSWER: B
A longitudinal redundancy checkproduces a(n)
A. block check characterB. parity bitC. CRCD. error correction
ANSWER: A
Dividing the data block by aconstant produces a remainderthat is used for error detection. Itis called the
A. vertical redundancy checkB. horizontal redundancy checkC. block check characterD. cyclical redundancy check
ANSWER: D
A CRC generator uses whichcomponents?A. balanced modulatorB. shift registerC. binary adderD. multiplexer
ANSWER: B
Which of the following is not aLAN?
A. PBX systemB. hospital systemC. office building systemD. cable TV system
ANSWER: D
The fastest LAN topology is theA. ringB. busC. starD. square
ANSWER: B
Which is not a common LAN
medium?A. twin leadB. twisted pairC. fiber-optic cableD. coax
ANSWER: A
A mainframe computer connectedto multiple terminals and PCsusually uses which configuration?
A. busB. ringC. starD. tree
ANSWER: C
A small telephone switchingsystem that can be used as a LANis called a
A. ring
B. WANC. UARTD. PBX
ANSWER: D
Which medium is the leastsusceptible to noise?
A. twin leadB. twisted pair
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C. fiber-optic cableD. coax
ANSWER: C
Which medium is the most widelyused in LANs?
A. twin leadB. twisted pairC. fiber-optic cableD. coax
ANSWER: B
Transmitting the data signaldirectly over the medium isreferred to as
A. baseband
B. broadbandC. ringD. bus
ANSWER: A
The technique of using modulationand FDM to transmit multiple datachannels of a common medium isknown as
A. baseband
B. broadbandC. ringD. bus
ANSWER: B
What is the minimum bandwidthrequired to transmit a 56 kbits/sbinary signal with no noise?
A. 14 kHzB. 28 kHz
C. 56 kHzD. 112 kHzANSWER: B
Sixteen different levels (symbols)are used to encode binary data.The channel bandwidth is 36 MHz.The maximum channel capacity is
A. 18 Mbits/s
B. 72 Mbits/sC. 288 Mbits/sD. 2.176 Gbits/s
ANSWER: C
What is the bandwidth required to
transmit at a rate of 10 Mbits/s inthe presence of a 28-dB S/Nradio?
A. 1.075 MHzB. 5 MHzC. 10 MHzD. 10.75 MHz
ANSWER: A
Which circuit is common to both
frequency-hopping and direct-sequence SS transmitters?
A. correlatorB. PSN code generatorC. frequency synthesizerD. sweep generator
ANSWER: B
Spread spectrum stations sharinga band are identified by and
distinguished from one another byA. PSN codeB. frequency of operationC. clock rateD. modulation type
ANSWER: A
The type of modulation most oftenused with direct-sequence SS is
A. QAM
B. SSBC. FSKD. PSK
ANSWER: D
The main circuit in a PSNgenerator is a(n)
A. X-ORB. multiplexer
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The upper pulse rate andinformation-carrying capacity of acable is limited by
A. pulse shorteningB. attenuationC. light leakage
D. modal dispersionANSWER: B
The core of a fiber-optic cable ismade of
A. airB. glassC. diamondD. quartz
ANSWER: B
The core of a fiber-optic cable issurrounded by
A. wire braid shieldB. KevlarC. claddingD. plastic insulation
ANSWER: C
The speed of light in plastic
compared to the speed of light inair isA. lessB. moreC. the sameD. zero
ANSWER: A
Which of the following is not amajor benefit of fiber-optic cable?
A. immunity from interferenceB. no electrical safety problemsC. excellent data securityD. lower cost
ANSWER: D
The main benefit of light-wavecommunications over microwaves
or any other communicationsmedia are
A. lower costB. better securityC. wider bandwidthD. freedom from interference
ANSWER: C
Which of the following is not part ofthe optical spectrum?
A. infraredB. ultravioletC. visible colorD. x-rays
ANSWER: D
The wavelength of visible lightextends from
A. 0.8 to 1.6 um.B. 400 to 750 nm.C. 200 to 600 nm.D. 700 to 1200 nm.
ANSWER: B
The speed of light isA. 186,000 mi/h.
B. 300,000 mi/h.C. 300,000 m/sD. 300,000,000 m/s
ANSWER: D
Refraction is theA. bending of light wavesB. reflection of light wavesC. distortion of light wavesD. diffusion of light waves
ANSWER: A
The ratio of the speed of light in airto the speed of light in anothersubstance is called the
A. speed factorB. index of reflectionC. index of refractionD. speed gain
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ANSWER: C
A popular light wavelength in fiber-optic cable is
A. 0.7 um.B. 1.3 um.
C. 1.5 um.D. 1.8 um.
ANSWER: B
Which type of fiber-optic cable isthe most widely used?
A. single-mode step-indexB. multimode step-indexC. single-mode graded-indexD. multimode graded-index
ANSWER: B
Which type of fiber-optic cable isbest for very high speed data?
A. single-mode step-indexB. multimode step-indexC. single-mode graded-indexD. multimode graded-index
ANSWER: A
Which type of fiber-optic cable hasthe least modal dispersion?A. single-mode step-indexB. multimode step-indexC. single-mode graded-indexD. multimode graded-index
ANSWER: A
Which of the following is not afactor in cable light loss?
A. reflectionB. absorptionC. scatteringD. dispersion
ANSWER: A
A distance of 8 km is the same asA. 2.5 mi.B. 5 mi.
C. 8 mi.D. 12.9 mi.
ANSWER: B
A fiber-optic cable has a loss of 15dB/km. The attenuation in a cable
1000 ft long isA. 4.57 dBB. 9.3 dBC. 24 dBD. 49.2 dB
ANSWER: A
Fiber-optic cables withattenuations of 1.8, 3.4, 5.9, and18 dB are linked together. The
total loss isA. 7.5 dBB. 19.8 dBC. 29.1 dBD. 650 dB
ANSWER: C
Which light emitter is preferred forhigh-speed data in a fiber-opticsystem?
A. incandescentB. LEDC. neonD. laser
ANSWER: D
Most fiber-optic light sources emitlight in which spectrum?
A. visibleB. infrared
C. ultravioletD. x-rayANSWER: A
Both LEDs and ILDs operatecorrectly with
A. forward biasB. reverse biasC. neither a or b
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D. either a or bANSWER: A
Single-frequency light is calledA. pureB. intense
C. coherentD. monochromatic
ANSWER: D
Laser light is very bright because itis
A. pureB. whiteC. coherentD. monochromatic
ANSWER: C
Which of the following is not acommon light detector?
A. PIN photodiodeB. photovoltaic diodeC. photodiodeD. avalanche photodiode
ANSWER: B
Which of the following is thefastest light sensor?A. PIN photodiodeB. photovoltaic diodeC. phototransistorD. avalanche photodiode
ANSWER: D
Photodiodes operate properly withA. forward bias
B. reverse biasC. neither a or bD. either a or b
ANSWER: B
The product of the bit rate anddistance of a fiber-optic system is2 Gbits-km/s. What is themaximum rate at 5 km?
A. 100 Mbits/sB. 200 Mbits/sC. 400 Mbits/sD. 1000 Gbits/s
ANSWER: C
Which fiber-optic system is better?A. 3 repeatersB. 8 repeatersC. 11 repeatersD. 20 repeaters
ANSWER: A
Printed documents to betransmitted by fax are convertedinto a baseband electrical signal by
the process ofA. reflectionB. scanningC. modulationD. light variation
ANSWER: B
The most commonly used lightsensor in a modern fax machine isa
A. phototubeB. phototransistorC. liquid-crystal displayD. charge coupled device
ANSWER: D
In FM fax, the frequencies forblack and white are
A. 1500 and 2300 HzB. 2300 and 1500 Hz
C. 1300 and 2400 HzD. 1070 and 1270 HzANSWER: A
Which resolution produces thebest quality fax?
A. 96 lines per inchB. 150 lines per inchC. 200 lines per inch
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D. 400 lines per inchANSWER: D
Group 2 fax uses whichmodulation?
A. SSB
B. FSKC. Vestigial sideband AMD. PSK
ANSWER: C
The most widely used fax standardis
A. Group 1B. Group 2C. Group 3
D. Group 4ANSWER: C
Group 3 fax uses whichmodulation?
A. QAMB. FSKC. Vestigial sideband AMD. FM
ANSWER: A
Most fax printers are of whichtype?
A. impactB. thermalC. electrosensitiveD. laser xerographic
ANSWER: B
Facsimile standards are set by the
A. FCCB. DODC. CCITTD. IEEE
ANSWER: C
What type of graphics arecommonly transmitted by radiofax?
A. newspaper textB. architectural drawingsC. cable moviesD. satellite weather photos
ANSWER: D
The transmission speed of group 4fax is
A. 4800 baudB. 9600 baudC. 56 kbits/sD. 192 kbits/s
ANSWER: C
The master control center for acellular telephone system is the
A. cell siteB. mobile telephone switchingofficeC. central officeD. branch office
ANSWER: B
Each cell site contains aA. repeaterB. control computer
C. direct link to a branch exchangeD. touch-tone processorANSWER: A
Multiple cells within an area mayuse the same channel frequencies.
A. trueB. false
ANSWER: A
Cellular telephones use which typeof operation?A. simplexB. half-duplexC. full-duplexD. triplex
ANSWER: C
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The maximum frequency deviationof an FM cellular transmitter is
A. 6 kHzB. 12 kHzC. 30 kHzD. 45 kHz
ANSWER: B
The maximum output power of acellular transmitter is
A. 4.75 mWB. 1.5 WC. 3 WD. 5 W
ANSWER: D
Receive channel 22 is 870.66MHz. Receive channel 23 is
A. 870.36 MHzB. 870.63 MHzC. 870.96 MHzD. 870.69 MHz
ANSWER: D
A transmit channel has afrequency of 837.6 MHz. The
receive channel frequency isA. 729.6 MHzB. 837.6 MHzC. 867.6 MHzD. 882.6 MHz
ANSWER: D
A receive channel frequency is872.4 MHz. To develop an 82.2MHz IF, the frequency synthesizer
must supply an LO signal ofA. 790.2 MHzB. 827.4 MHzC. 954.6 MHzD. 967.4 MHzNote: The LO frequency is usuallyhigher than the receive frequency.
ANSWER: C
The output power of a cellularradio is controlled by the
A. user or callerB. cell siteC. called party
D. MTSOANSWER: D
When the signal from a mobilecellular unit drops below a certainlevel, what action occurs?
A. The unit is handed off to acloser cell.B. The call is terminated.C. The MTSO increases power
level.D. The cell site switches antennas.
ANSWER: A
In a cellular radio, the duplexer is aA. ferrite isolatorB. waveguide assemblyC. pair of TR/ATR tubesD. pair of sharp bandpass filters
ANSWER: D
The time from the transmission ofa radar pulse to its reception is0.12 ms. The distance to thetarget is how many nautical miles?
A. 4.85 nmiB. 9.7 nmiC. 11.2 nmiD. 18.4 nmi
ANSWER: B
The ability of a radar to determinethe bearing to a target dependsupon the
A. antenna directivityB. speed of lightC. speed of the targetD. frequency of the signal
ANSWER: A
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The pulse duration of a radarsignal is 600 ns. The PRF is 185pulses per second. The duty cycleis
A. 1.1 percent
B. 5.5 percentC. 31 percentD. 47 percent
ANSWER: A
The Doppler effect is used toproduce modulation of which typeof radar signal?
A. pulseB. CW
ANSWER: B
The Doppler effect allows whichcharacteristic of a target to bemeasured?
A. distanceB. azimuthC. altitudeD. speed
ANSWER: D
The Doppler effect is a change inwhat signal characteristicproduced by relative motionbetween the radar set and atarget?
A. amplitudeB. phaseC. frequencyD. duty cycle
ANSWER: C
The most widely used radartransmitter component is a
A. klystronB. magnetronC. TWTD. power transistor
ANSWER: B
Low-power radar transmitters andreceiver Los use whichcomponent?
A. GaAs FETB. magnetron
C. Gunn diodeD. klystron
ANSWER: C
What component in a duplexerprotects the receiver from the high-power transmitter output?
A. waveguideB. bandpass filterC. notch filter
D. spark gapANSWER: D
Most radar antennas use aA. dipoleB. broadside arrayC. horn and parabolic reflectorD. collinear array
ANSWER: C
The most common radar display istheA. A scanB. color CRTC. liquid-crystal displayD. plan position indicator
ANSWER: D
A radar antenna using multipledipoles or slot antennas in a matrix
with variable phase shifters iscalled a(n)A. A scanB. phased arrayC. broadsideD. circular polarized array
ANSWER: B
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Police radars use whichtechnique?
A. pulseB. CW
ANSWER: B
Which of the following is a typicalradar operating frequency?
A. 60 MHzB. 450 MHzC. 900 MHzD. 10 GHz
ANSWER: D
The TV signal uses which types ofmodulation for picture and sound
respectively?A. AM, FMB. DSB, FMC. FM, AMD. AM, DSB
ANSWER: A
If a TV sound transmitter has acarrier frequency of 197.75 MHz,the picture carrier is
A. 191.75 MHzB. 193.25 MHzC. 202.25 MHzD. 203.75 MHz
ANSWER: B
The total bandwidth of an NTSCTV signal is
A. 3.58 MHzB. 4.5 MHz
C. 6 MHzD. 10.7 MHzANSWER: C
What is the total number ofinterlaced scan lines in onecomplete frame of a NTSC U.S.TV signal?
A. 262 B. 525C. 480D. 625
ANSWER: B
What keeps the scanning processat the receiver in step with thescanning in the picture tube at thereceiver?
A. nothingB. color burstC. sync pulsesD. deflection oscillators
ANSWER: C
What is the black-and-white ormonochrome brightness signal inTV called?
A. RGBB. color subcarrierC. Q and ID. luminance Y
AN