Chapter 1. Introductory Topics
1. Which part of the sinewave expression cannot be varied in accordance with the low-frequency intelligence to create a modulated signal?
a. Phase
b. Frequency c. Time
d. Amplitude
2. Communication systems are most often categorized by what characteristic?
a. Modulation frequency b. Carrier frequency c. Transmission distance d. Information transmitted 3 Voltage gain in decibels is
a. 10 ln
b. 10 log
c. 20 ln
d. 20 log
4 Which expression indicates a measurement using a 1-W reference a. dBm(1) b. dB1 c. dBW d. dB(W)
5 An amplifier operating over a 2-Mhz bandwidth has a 75 input resistance. If it is operating at 22° C and
has a voltage gain of 300, the noise produced at the output of this amplifier would be approximately
a. b. c. d.
6 Which of the following is not an example of external noise a. Fluorescent light
b. Solar emission c. Resistor noise d. Lightning
7 An amplifier's output signal has 25 mV p-p of desired signal mixed in with 45 V rms of undesired noise. The load impedance is 50 . What is the amplifier's output S/N level in dB?
a. 22.9 dB
b. 54.9 dB
c. 45.9 dB
d. 51.9 dB
8 Why does a 5-kHz square wave require a greater bandwidth than a 2-kHz sinewave?
a. The square wave has a larger frequency than the sinewave.
b. The square wave has an infinite number of harmonics, whereas the sinewave has only one. c. The square wave is much easier to cover by noise. d. The square wave must also include an offset (dc) voltage, whereas the sinewave does not.
9 The relationship between information and bandwidth is called
a. Information theory b. Fourier analysis c. FFT
d. Hartley's law
10 Aliasing can be defined as errors occurring when a. The input frequency exceeds the sample rate. b. The bandwidth is less than the input frequency. c. The type of modulation has been incorrectly identified. d. The sampling signal has been incorrectly identified. 11 Which of the following does not hold true for a parallel resonant circuit?
a. At the resonant frequency the impedance of the circuit is a minimum.
b. If Q>10, the resonant frequency is the same as it would be if it were a series.
c. It is commonly referred to as a tank circuit.
d. At the resonant frequency, the circuit draws minimum current from the constant-voltage source.
12 The oscillator design that uses a third capacitor in the tank circuit for swamping out the effect of the
transistor's internal capacitances is the a. Hartley design
b. Clapp design c. Colpitts design d. Crystal design
13 The ability of a crystal to oscillate at its resonant frequency is due to
a. The flywheel effect b. Barkhausen criteria c. The piezoelectric effect d. Frequency synthesis
14 The Barkhausen criteria has to do with a. Receiver noise
b. Fourier analysis c. Oscillation
d. Troubleshooting
15 Which of the following can be called a troubleshooting plan?
a. Symptoms as clues to faulty stages b. Signal tracing and signal injection c. Voltage and resistance measure d. Substitution
e. All the above
Chapter 2. Amplitude Modulation: Transmission
1. In a modulated system, the low-frequency intelligence signal is not called the
a. Modulating signal b. Information signal c. Modulating wave d. Carrier
2. A 7.0-Mhz carrier is modulated by a voice signal that has three frequency components of 100 Hz,
200 Hz, and 300 Hz. What three frequencies comprise the lower sideband?
a. 6.9997 Mhz, 6.9998 Mhz, and 6.9999 Mhz b. 100 Hz, 200 Hz, and 300 Hz
c. 6.9999 Mhz, 7.0000 Mhz, and 7.0001 Mhz d. 7.0001 Mhz, 7.0002 Mhz, and 7.0003 Mhz
3. The total output power of an AM transmitter is measured to be 850 W. What is the total output sideband
power if it has a percent modulation of 100%?
a. 425 W b. 850 W c. 283.3 W d. 141.65 W
4. A 100-kHz carrier is modulated by a 20-Hz – 2kHz signal. The upper sideband is
a. 102 kHz
b. 100.02 kHz to 102 kHz c. 101 kHz
d. 100.002 kHz to 102 kHz
5. One full revolution of a phasor generates which percentage of a full sinewave?
a. 25% b. 50% c. 100% d. 200%
6. An AM waveform at maximum is 100 V p-p and at minimum is 40 V p-p. The modulation percentage is
a. 250% b. 40% c. 25% d. 37.5%
7. A transmitter having a 900-W carrier transmits 1188 W when modulated with a single sinewave. If the carrier is simultaneously modulated with another sinewave at 60% modulation, calculate the total transmitted power. a. 1084 W b. 1170 W c. 1350 W d. 1224 W 8. Low-level modulation is
a. The most economic approach for low-power transmitters.
b. Characterized by the use of "linear" power amplifiers to amplify the AM signal.
c. Characterized by having the carrier and the intelligence signals mix at low power levels
d. All the above.
9. The main advantage of a high-level modulation system compared to a low-level system is that it
a. Allows more efficient amplification.
b. Allows use of low-powered intelligence signal. c. Provides higher modulation percentage. d. Is more economical.
10. What is the purpose of a buffer amplifier stage in a transmitter?
a. It prevents transmitters from producing spurious frequencies in the output signals.
b. It provides power amplification with high efficiency. c. Its high input impedance prevents oscillators from drifting off frequency.
d. It amplifies audio frequencies before modulation occurs. 11. The purpose of an antenna coupler is to
a. Match the output impedance of the transmitter with the antenna's impedance to provide maximum
power transfer.
b. Allow the transmitter to be connected to several antennas at the same time.
c. Filter out the carrier frequency from the transmitter's AM output signal.
d. Cause the transmitter to operate at more than one carrier frequency at the same time.
12. The main reason for using a dummy antenna is to
a. Prevent damage to output circuits. b. Minimize damage to the regular antenna. c. Prevent overmodulation.
d. Prevent undesired transmissions. 13. A spectrum analyzer is
a. An instrument that displays amplitude versus frequency on a CRT.
b. Often used to determine if a transmitter's output signal is free from any spurious signals.
c. Can be thought of as a radio receiver with broad frequency range.
d. All the above.
14.The strategy for repair of electronic equipment includes the following.
a. Verify that a problem exists. b. Isolate the defective stage. c. Isolate the defective component.
d. Replace the defective component and hot check. e. All the above.
15. A technique that helps you understand how a carrier and sideband combine to form the AM waveform
is
a. The tangential method. b. Phasor representation. c. Keying.
d. None of the above.
Chapter 3: Amplitude Modulation: Reception
1. The main problem with the TRF design is
a. Lack of selectivity in receiving all AM stations b. Poor demodulation of an AM station
c. Frustration in tuning to receive more than one station d. Lack of sensitivity in receiving all AM stations 2. The sensitivity of a receiver has to do with its ability to
a. Withstand shock
b. Receive one station versus another c. Receive weak stations
d. All the above
3. When the input to an ideal nonlinear device is an AM waveform consisting of a carrier and its
sidebands, the output of nonlinear mixing produces the original intelligence because
a. The intelligence signal is one of its inputs. b. A dc component is also produced.
c. The difference between the carrier and its sidebands is the original intelligence frequency.
d. The intelligence frequencies are the upper and the lower sideband frequencies.
4. An AM signal having a carrier frequency of 940 kHz is to be mixed with a local oscillator output signal in
order to produce an intermediate frequency of 455 kHz. At what should the L.O. frequency be set?
a. 455 kHz b. 1395 kHz c. 910 kHz d. 1850 kHz
5. Diodes that have been specially fabricated to produce a capacitance that varies inversely proportional to the amount of reverse bias are called
a. Varactor diodes b. Varicap diodes c. VVC diodes d. All the above
6. The image frequency for a standard broadcast receiver using a 455-kHz IF and tuned to a station at 680 kHz would be a. 1135 kHz b. 225 kHz c. 1590 kHz d. 1815 kHz
7. Double conversion is used to overcome the problem of
a. Image frequency b. Tracking c. Diagonal clipping d. Poor sensitivity 8. An auxiliary AGC diode
a. Reduces selectivity b. Increases sensitivity c. Decreases sensitivity d. All the above
9. Which of the following would occur in a receiver not having AGC?
a. The speaker output level would drastically change while tuning from a weak signal to a strong signal.
b. Local stations would easily produce distorted signals in the speaker.
c. There would be a constant need to readjust the volume control as the weather and ionosphere change.
d. All the above
10. The only roadblock to having a complete receiver manufactured on an integrated circuit is
a. Tuned circuits and volume controls b. Cost
c. Phase-locked loops d. Ceramic filters
11. The decibel difference between the largest tolerable receiver input signal and its sensitivity is called
a. The decibel power gain of the receiver b. Automatic gain control (AGC) c. The dynamic range of the receiver d. The IF amplifier gain
12. The simplest AM detector is the
a. Synchronous detector b. Product detector c. Heterodyne detector d. Diode detector
13. Tracking in a superhet receiver is accomplished using a
a. Trimmer capacitor b. Padder capacitor c. Varicap diode d. a and b e. All the above
14. If no stations are picked up on the lower half of the AM band, the likely problem is
a. Low RF gain b. Poor AGC operation c. IF selectivity d. LO tracking
15. If no sound is heard from a receiver, the most likely problem area is the a. Power supply b. RF section c. Audio amplifier d. AGC diode
Chapter 4: Single-Sideband Communications
1. An SSB signal with a maximum level of 200 V p-p into a 50 load results in a PEP rating of
a. 200 W b. 50 W c. 100 W d. 800 W
2. State the chief advantage(s) of a standard SSB system.
a. Maximum signal range with minimum transmitted power b. Easy carrier reinsertion
c. Elimination of carrier interference d. a and c
3. The noise advantage of SSB over AM is
a. 3–5 dB b. 5–7 dB c. 8–10 dB d. 10–12 dB
4. What is the difference between a balanced modulator and a regular modulator?
a. There is no carrier produced in the output of a balanced modulator.
b. In a balanced modulator, there is 180º phase shift between the upper and lower sidebands.
c. In a balanced modulator, only one sideband is produced. d. In a balanced modulator, harmonics of the sidebands are suppressed.
5. In a balanced-ring modulator, the carrier suppression is accomplished by
a. A dual-gate FET having symmetry
b. Center-tapped transformers causing canceling magnetic fields
c. The nonlinearity of the diodes that are used d. Symmetrical differential amplifier stages
6.Which cannot be used successfully to convert DSB-SC to SSB?
a. Crystal filter b. Ceramic filter c. Mechanical filter d. Tank circuit
7. Another term for ripple amplitude for a ceramic filter is
a. The shape factor b. The peak-to-valley ratio c. The insertion loss d. The quality factor
8. Which of the following is not an advantage of the phase method over the filter method in producing SSB?
a. The design of the 90º phase-shift network for the intelligence frequencies is simple.
b. Lower intelligence frequencies can be economically used, because a high-Q filter is not necessary.
c. Intermediate balanced modulators are not necessary, because high-Q filters are not needed.
d. It is easier to switch from one sideband to the other. 9. Once an SSB signal has been generated, it must be amplified by
a. A nonlinear amplifier to conserve bandwidth b. A nonlinear amplifier to conserve energy c. A linear amplifier to conserve bandwidth d. A linear amplifier to avoid distortion
10. The advantages provided by carrier elimination in SSB do not apply to transmission of
a. Code b. Music c. Noise d. All the above
11. Provide the approximate "outside-of-passband" attenuation of a Butterworth filter.
a. 3-dB slope per octave b. 3-dB slope per decade c. 6-dB slope per octave d. 6-dB slope per decade
12. An SSB receiver recreates the original intelligence signal by
a. Mixing the USB with LSB signals and filtering out the resulting different frequencies
b. Filtering out the difference between either sideband and the internally generated carrier signal
c. Filtering out the harmonics of the received sideband signal frequencies
d. Amplifying the dc term produced by mixing action 13. Common types of balanced modulators include
a. Ring modulator b. Phase modulator c. Lattice modulator d. All the above
14. Describe the oscilloscope waveform of an SSB transmitter's balanced modulator if it exhibits carrier leakthrough. a. Trapezoidal wave b. Sinewave c. FM wave d. AM wave
15. The two-tone test is used to
a. Test carrier suppression b. Test filter ripple c. Test amplifier linearity d. None of the above
Chapter 5: Frequency Modulation Transmission 1 Angle modulation includes the following types of
modulation: a. FM b. PM c. AM d. All the above e. a and b
2 The amount of frequency increase and decrease around the center frequency in an FM signal is called the a. Index of modulation
b. Frequency deviation c. Phase deviation
d. Bandwidth of the FM signal
3 The amount of frequency deviation is dependent on the intelligence frequency in
a. An FM signal b. A PM signal
c. Both FM and PM signals d. Neither FM nor PM signals
4 An FM signal has an intelligence frequency of 2 kHz and a maximum deviation of 10 kHz. If its carrier frequency is set at 162.4 Mhz, what is its index of modulation? a. 10
b. 5 c. 2 d. 20
5 The amount an FM carrier frequency deviates for a given modulating input voltage level is called the
a. Frequency deviation b. Index of modulation c. Deviation constant d. Deviation ratio
6 Standard FM broadcast stations use a maximum bandwidth of
a. 150 kHz b. 200 kHz c. 75 kHz d. 15 kHz
7 Carson's rule is used to approximate the necessary a. Frequency deviation
b. Bandwidth c. Capture ratio d. Modulation index
8 An FM transmitter has an output power of 500 W when it is not modulated. When intelligence is added, its modulation index is 2.0. What is its output power with a modulation index of 2.0?
a. 250 W b. 500 W c. 1000 W d. 2000 W
9 Another way to describe the modulation index is using the
a. Deviation ratio b. Deviation constant c. Capture ratio d. Maximum deviation
10 The inherent ability of FM to minimize the effect of undesired signals operating at the same or nearly the same frequency as the desired station is known as the a. Capture effect
b. Signal-to-noise ratio c. Noise figure d. Bessel function
11 In a Crosby FM transmitter, an FM signal having a center frequency of 2.04 Mhz and a deviation of 69 Hz is passed through four cascaded frequency multiplier stages: two triplers, one doubler, and one quadrupler. What type of signal appears at the output of the last multiplier stage?
a. Center frequency of 2.04 Mhz and deviation of 4.96 kHz
b. Center frequency of 146.88 Mhz and deviation of 4.96 kHz
c. Center frequency of 2.04 Mhz and deviation of 69 Hz d. Center frequency of 146.88 Mhz and deviation of 69 Hz
12 The circuitry used to increase the operating frequency of a transmitter up to a specified value is called the a. Multiplier
b. Expander c. Pump chain d. All the above
13 The purpose of the matrix network in a stereo FM broadcast transmitter is to
a. Mix the 38-kHz pilot carrier with the L – R audio b. Convert the L and R channels to L + R and L – R channels
c. Separate the left channel from the right channel d. Modulate the L + R and L – R signals with the carrier signal
14 An FM signal has an intelligence frequency of 5 kHz and a maximum deviation of 25 kHz. Its index of modulation is a. 125 b. 0.2 c. 5 d. 6 15 Frequency multipliers
a. Are used to multiply the frequency of the carrier signal of an FM signal
b. Consist of a class C amplifier followed by a tank circuit that filters out a single harmonic
c. Are used to multiply the frequency deviation of an FM signal
d. All the above
Chapter 6: Frequency Modulation Reception 1 A difference between AM and FM receiver block
diagrams is that the FM version includes a a. Limiter
b. Discriminator
c. Deemphasis network
d. All the above 2 An FM receiver rarely works satisfactorily without
an RF amplifier because
a. FM receivers typically work with smaller input signal levels due to thei noise
characteristics
b. FM receivers have a narrower bandwidth. c. FM receivers do not have very much gain in their IF amplifier stages.
d. FM receivers need RF amplifier stages to be able to decode stereo signals.
3 A certain FM receiver provides a voltage gain of 113 dB prior to its limiter. The limiter's quieting voltage is 400 mV. Its sensitivity is approximately a.
b. c. d.
4 The use of dual-gate MOSFETs in RF amplifier stages
a. Offers increased dynamic range over those of JFETs
b. Produces higher-frequency responses than do JFETs
c. Produces higher values of voltage gain than do JFETs
d. Is not compatible with AGC
5 The Foster-Seely detector design is superior to the ratio detector in that it
a. Does not respond to any undesired amplitude variations
b. Also provides an output AGC signal
c. Offers superior linear response to wideband FM deviations
d. Does not need a limiter stage
6 Local oscillator reradiation refers to radiation through the
a. Receiver's wiring b. IF transformer c. Antenna d. All the above
7 Which is not one of the three stages in which a PLL can be operated? a. Free-running b. Capture c. Locked/tracking d. Searching
8 A PLL is set up so that its VCO free-runs at 8.9 Mhz. The VCO does not change frequency unless its input is within 75 kHz of 8.9 Mhz. After it does lock, the input frequency can be adjusted within 120 kHz of 8.9 Mhz without having the PLL start to free-run again. The capture range of the PLL is
a. 75 kHz b. 120 kHz c. 150 kHz d. 240 kHz
9 Slope detection is seldom used due to a. Nonlinearity
c. Complexity d. All the above
10 In an FM stereo receiver, what is the purpose of the 23–53-kHz filter?
a. To filter out the SCA signal at the output of the discriminator
b. To filter out the L – R signal at the output of the discriminator
c. To filter out the L + R signal at the output of the discriminator
d. To produce separate L and R signals from the L + R and L – signals
11 A dual audio amplifier is rated to provide 65 dB of channel separation. If the right channel has 4 W of output power, how much of this power could be due to the left channel intelligence?
a. 4 W b. 79 nW c. 1.26 W d. 2.25 mW
12 The hold-in range for a PLL concerns the a. Range of frequencies in which it will remain locked
b. Allowable range of dc voltage c. Allowable range of ac input voltage d. Satisfactory range of operating temperatures
13 The input signal into a PLL is at the a. VCO
b. Low-pass filter c. Comparator d. Phase detector
14 The square-law relationship of the FETs input versus output
a. Allows for greater sensitivity in an FM receiver b. Provides improved noise performance c. Reduces shot noise
d. Minimizes cross-modulation
15 When troubleshooting a stereo demodulator, the input signal should be abouto
a. b. c. 1 mV rms d. 100 mV rms
Chapter 7 Communication Technique
1 Why are image frequencies somewhat less of a problem in FM receivers than they are in SSB or AM receivers? a. SSB uses less bandwidth than does FM.
b. FM signals have a capture effect characteristic. c. FM mixer stages are square-law devices.
d. FM receivers do not use the superheterodyne design. 2 The tuned circuits prior to the mixer in a superheterodyne
receiver are called the a. Front end
b. Tuner c. Preselector
d. All the above
3 The strength meter that shows the relative signal-strength level is called the ________ .
a. S meter b. Signal meter c. Strength meter d. All the above
4 An AM broadcast receiver has two identical tuned circuits with a Q of 50 prior to the IF stage. The IF frequency is 460 kHz and the receiver is tuned to a station on 550 kHz. The image-frequency rejection is
a. 41 dB b. 36.2 dB c. 72.4 dB d. 82 dB
5 An AGC that causes a step reduction in receiver gain at some arbitrarily high value of received signal in order to prevent overloading the receiver is known as
a. Arbitrary AGC b. Auxiliary AGC c. Delayed AGC
6 Up-conversion offers the following advantage(s): a. Less expensive filters
b. Good image-frequency rejection c. Minimized tuning range for the LO d. .b and c
7 The range over which the input to a receiver or amplifier provides a usable output is called the
a. Level of acceptability b. Dynamic range c. Degree of usefulness d.Specified input
8 A receiver has a 30-dB noise figure, a 1.5 Mhz bandwidth, a 6-dBm third intercept point, and a 3-dB signal-to-noise ratio. Its sensitivity is
a. –94 dB b. –82.2 dB c. –79.2 dB d. –81 dB
9 Two-modulus dividers are used in the synthesis of frequencies into the VHF band due to
a. Its ability to work at practical power consumptions b. Its ability to work at practical speeds
c. The insufficient speed and power of the basic programmable divider designs
d. All the above
10 The disadvantage of direct digital synthesizers (DDS) over analog frequency synthesizers is
b. Its limited maximum output frequency c. Its higher phase noise
d. All the above
11 The G.E. Phoenix radio is an example of a. An HF amateur transceiver using AM and SSB modulation modes
b. A VHF commercial transceiver using the FM modulation mode and a channel guard function c. A military transceiver using all modes on HF frequencies
d. A cellular telephone transceiver
12 The type of radio transmission that uses pseudorandomly switched frequency or time transmissions is known as a. Synthesizing
b. Facsimile c. Spread spectrum d. Compression
13 The acronym CDMA refers to ________. a. Carrier-division multiple-access systems b. Capture-division multiple-access systems c. Code-division multiple-access systems d. Channel-division multiple-access systems
14 A typical problem encountered when troubleshooting a frequency synthesizer is
a. A small frequency error b. A large frequency error c. No output
d. All the above 15 A transceiver is
a. A transmitter that can be tuned to several bands of frequencies
b. A transmitter that transmits digital data c. A receiver that receives digital data
d. A transmitter and receiver in a single package Chapter 8 Digital Communication : Coding Technique
1 The advantage(s) of digital and/or data communications over analog include
a. Noise performance b. Regeneration
c. Digital signal processing d. All the above
2 In a S/H circuit, the time that it must hold the sampled voltage is
a. Aperture time b. Acquisition time c. Flat-top time d. Dmin
3 Error signals associated with the sampling process are called
a. Foldover distortion b. Aliasing
c. Nyquist rate d. a and b
4 Which of the following is not a common RZ code?
a. RZ-unipolar b. RZ-bipolar c. RZ-M d. RZ-AMI
5 In an asynchronous data system
a. Both sender and receiver are exactly synchronized to the same clock frequency.
b. Each computer word is preceded by a start bit and followed by a stop bit to frame the word.
c. The receiver derives its clock signal from the received data stream.
d. All the above.
6 A CD audio laser-disk system has a frequency bandwidth of 20 Hz to 20 kHz. The minimum sample rate to satisfy the Nyquist criteria is
a. 20 Hz b. 20 kHz c. 40 Hz d. 40 kHz
7 With respect to converter circuits a. DACs include an ADC b. ADCs include a DAC
c. DACs and ADCs are virtually identical d. All the above.
8 The type of modulation that uses sampling on one of the parameters of the transmitted and received signal is known as
a. Phase modulation b. Pulse modulation c. Amplitude modulation d. Frequency modulation
9 An alphanumeric code for representing the decimal values from 0 to 9 that is based on the relationship that only one bit in a binary word changes for each binary step is known as
a. ASCII b. EBCDIC c. Baudot code d. Gray code
10 The quantizing error of PCM systems for weak signals can be made less significant by
a. Companding
b. Using time-division multiplexing c. Using frequency-division multiplexing d. Filtering out the alias frequency
11 When the message and the BCC are transmitted as separate parts within the same transmitted code, it is called a(n)
a. Systematic code b. CRC
c. (n,k) cyclic code d. Interleaved code
12 The value left in the CRC dividing circuit after all data have been shifted in is the
a. Quantile interval b. Codec c. BCC d. Syndrome
13 Which of the following is not an example of code error detection and correction in a data communication channel? a. Parity b. Frequency-shift keying c. Block-check character d. Hamming code
14 Error-correcting techniques that allow for correction at the receiver are called
a. Cyclic redundancy checks (CRC) b. Block-check characters (BCC) c. Forward error correcting (FEC) d. Parity
15 Codes producing random data that closely resemble digital noise are
a. Systematic codes b. PN codes c. Pseudonoise codes d. b and c
Chapter 9 Digital Communications Transmission
1 Using an oscilloscope to display overlayed received data bits that provide information on noise, jitter, and linearity is called a(n) a. Constellation pattern b. Loopback c. Statistical Concentration d. Eye pattern
2 Why isn't Morse code well suited to today's telegraphic equipment?
a. It uses an automatic request for repetition. b. It has excessive redundancy built into the code. c. The parity bit is difficult to detect.
d. Differing between various widths of the pulses is an extremely complicated process.
3 A special digital modulation technique that achieves high data rates in limited-bandwidth channels is called
a. Delta modulation
b. Pulse-coded modulation (PCM) c. Quadrature amplitude modulation (QAM) d. Pulse amplitude modulation (PAM)
4 FSK systems are much superior to two-tone amplitude-modulation systems with respect to
a. Noise performance
b. Bandwidth requirements of the channel c. Ionospheric fading characteristics d. Power consumption
5 Which is not a type of pulse modulation? a. Pulse-amplitude modulation (PAM) b. Pulse-width modulation (PWM) c. Pulse-frequency modulation (PFM) d. Pulse-position modulation (PPM)
6 PPM and PWM are superior to PAM systems in a. Noise characteristics
b. Bandwidth characteristics c. Simplicity in design
d. Frequency response of the intelligence signal 7 Half-duplex operation involves communication
a. In one direction only
b. In both directions, but only one can talk at a time c. Where both parties can talk at the same time d. All the above
8 A procedure that decides which device has permission to transmit at a given time is called
a. Line control b. Protocol c. Flow control d. Sequence control
9 The technique that uses the BPSK vector relationship to generate an output with logical 0s and 1s determined by comparing the phase of two successive data bits is a. CSU/DSU
b. TDM c. CVSD d. DPSK
10 Using radio to transmit gathered data on some particular phenomenon without the presence of human monitors is known as
a. Radio teletype b. Radio multiplexing c. Radio facsimile d. Radio telemetry 11 The bit error rate is
a. The number of bit errors that occur for a given number of bits transmitted
b. The most common method of referring to the quality of a digital communication system
c. Virtually the same as the error probability d. All the above
12 The major difficulty faced by delta modulators is a. Excessive noise producing errors
b. Slope overload
c. Insufficient frequency response of the intelligence signal
d. Complexity of design
13 The capacity of a telephone channel that has an S/N of 2047 if its bandwidth is 3.5 kHz is
a. 30,000 bits per second b. 33,000 bits per second c. 38,500 bits per second d. 35,000 bits per second 14 The AT&T T1 lines
a. Use 16-bit PCM code and include 24 voice channels b. Use delta modulation and include 48 voice channels c. Use 8-bit PCM code and include 24 voice channels d. Use delta modulation and include 24 voice channels 15
A digital transmission has an error probability of and is long. Its expected number of error bits is
a. b. c. d.
Chapter 10 Network Communications
1 An interconnection of users that allows communication with one another is known as a
a. Modem b. UART c. Network d. Protocol
2 A complex LC filter that removes delay distortion from signals that are traveling down long transmission lines is called a(n)
a.. Delay equalizer b. UART
c. Attenuation distortion filter d. Trunk switcher
3 Which of the following is not a way that designers of telephone equipment are adapting to the increasing use of computers and digital coding in telephone
communication links?
a. The use of shorter transmission lines
b. The use of computers in finding unused portions of multiplex systems to maximize use
c. The application of digital switching theory to increase channel capacity
d. Sharing of communication links by voice and data signals
4 The advanced mobile phone services (AMPS) is an example of
a. A cellular telephone system
b. A telephone system that uses frequency reuse c. A cell-splitting telephone system
d. All the above
5 Which is not a major function of a protocol? a. Framing
b. Line control c. Flow control d. Topology e. Sequence control
6 The LAN that was developed by Xerox, Digital Equipment Corporation, and Intel in 1980 is called
a. IEEE-488 b. Ethernet c. OSI d. CSMA/CD
7 A device interconnecting two networks that use different protocols and formats is called a
a. Bridge b. Gateway c. Router d. Node
8 A device interconnecting LANs together that usually have identical protocols at the physical and data link layers is called a
a. Bridge b. Gateway c. Router d. Node
9 In telephony, traffic is defined in a. Hundred-call seconds
b. Average number of calls in a specific period of time c. Erlang
d. All the above
10 The Internet and the WWW are a. The same thing
b. Completely different c. Related
d. Local area networks
a. The ratio of calls lost to calls offered b. The ratio of traffic lost to traffic offered c. The ratio of calls offered to calls lost d. The ratio of traffic offered to traffic lost e. a and b
12 The following term is not a major concept in cellular phone systems. a. Frequency reuse b. Cell reuse c. Cell splitting d. Handoff
13 In local area networks, the following topology or topologies are seldom used.
a. Star b. Ring c. Bus d.a and b
14 The following numeric describing data rates for copper coax and twisted pair is rarely used
a. 10 Base 2 b. 10 Base 5 c. 10 Base T d. 100 Base FX e. a and b
15 The xDSL service with the highest projected data rate is a. VDSL
b. SDSL c. HDSL d. IDSL e. ADSL
Chapter 11 Transmission Lines
1 The chief advantage of coaxial cable over open-wire line is
a. Minimized radiation losses b. Low cost
c. Low noise pick up d. Low resistive losses 2 Unshielded twisted-pair cable is
a. Seldom used due to noise problems b. Increasingly used in computer networking c. More costly than coaxial cable
d. All the above
3 The ratio of actual velocity to free-space velocity is called a. Velocity factor
b. Relative dielectric constant c. Velocity of propagation d. Delay time
4 In a balanced line, the same current flows in each line but is
a. 45º out of phase b. 90º out of phase c. 180º out of phase d. 270º out of phase
5 What is the length of a quarter-wavelength section of RG-8A/U coaxial cable at a frequency of 144.2 Mhz if its velocity factor is 0.69.
a. 52.1 cm b. 35.9 cm c. 143.6 cm d. 2.08 m
6 A nonlossy transmission line that is terminated with a resistive load that is equal to the characteristic impedance of the line
a. Has the same impedance at all points along the line b. Has a VSWR of 1:1
c. Has the same voltage at points along the line d. Has a reflection coefficient at the load equal to zero e. All the above
7 A flat line indicates a. No reflection b. VSWR = 1
c. No physical imperfections d. a and b
8 A nonlossy transmission line terminated with a short circuit has an
a. In-phase reflected voltage that is equal in magnitude to the incident voltage
b. Opposite-phase reflected voltage that is equal in magnitude to the incident voltage
c. In-phase reflected voltage that is smaller in magnitude than the incident voltage
d. Opposite-phase reflected voltage that is smaller in magnitude than the incident voltage
9 A manufacturer's specification dealing with crosstalk and attenuation is
a. ACR b. CAS c. CAA d. AAC
10 A 50- transmission line that has a load impedance of 300 has a VSWR of
a. 6:1 b. 1:6 c. 0.666:1 d. 1.5:1
11 The input impedance of a quarter-wavelength section of a 50- transmission line that is terminated with a short is
a. 50
b. 0 (a short) c. Infinite (open) d. 100
12 A device that is used to match an unbalanced
transmission line to a balanced transmission line is called a
a. Quarter-wavelength matching transformer b. Balun
c. Shorted-stub section d. Slotted line
13 A 50- transmission line with a 300- load impedance has a reflection coefficient of
a. 6 b. 0.166 c. 0.714 d. 1.4
14 A cable has an inductance of 1 nH/ft and capacitance of 1 nF/ft. The delay introduced by a 1-ft section is
a. Not able to be calculated with the given information b.
c. d.
15 A transmission line can be used as a(n) a. Inductor
b. Capacitor c. Filter
d. Matching section e. All the above
Chapter 12 Wave Propagation
1 An antenna can be thought of as a(n) a. Oscillator
b. Capacitor c. Transducer
d. Frequency multiplexer
2 A wave that is characterized by having its direction of propagation perpendicular to its oscillation is known as a. Isotropic
b. Transverse c. Polarized d. Refractive
3 Which is not an effect of our environment on wave propagation?
a. Radiation b. Reflection c. Refraction
d. Diffraction
4 A point in space that radiates electromagnetic energy equally in all directions is called
a. Transverse
b. Isotropic point source c. Omnisphere d. Shadow zone
5 The process of waves, which traveling in straight paths, bending around an obstacle is
a. Radiation b. Reflection c. Refraction d. Diffraction
6 Which is not one of the basic modes of getting a radio wave from the transmitting to receiving antenna? a. Ground wave
b. Shadow wave c. Space wave d. Satellite link e. Sky wave
7 The type of wave that is most affected by the D, E, and F layers of the ionosphere is:
a. Ground wave b. Space wave c. Sky wave d. Satellite
8 The largest frequency that will be returned to earth when transmitted vertically under given ionospheric conditions is called the
a. Critical frequency
b. Maximum usable frequency (MUF) c. Optimum working frequency (OWF) d. Skip zone
9 The characteristic impedance of free space is a. Not known
b. Infinite c. 50 d. 377
10 The area between the point where the ground wave ends and first sky wave returns is called the
a. Quiet zone b. Skip zone c. Null Zone d. All the above e. a and b
11 The refraction and reflection action of a skywave between the ionosphere and ground is known as
b. Skip
c. Tropospheric scattering d. Fading
12 A satellite communication system used by companies such as K-Mart to quickly verify credit cards and check inventory data is called
a. VSAT b. MSAT c. SATCOM d. WESTAR
13 A common type of radio wave interference is a. EMI
b. Fading c. Reflections d. All the above
14 Diversity reception does not include: a. Space diversity
b. Time diversity c. Frequency diversity d. Angle diversity
15 When installing a receiving antenna, you can often overcome diffraction problems by finding a a. Null zone
b. Downlink c. Hot spot d. Skip zone
Chapter 13 Antennas
1 The process of interchangeability of receiving and transmitting operations of antennas is known as a. Polarization
b. Reciprocity c. Efficiency d. Counterpoise
2 A half-wave dipole antenna is also known as a. Marconi antenna
b. Hertz antenna c. Vertical antenna d. Phased array
3 An antenna that is a quarter-wavelength long connected such that the ground acts as a reflecting quarter-wavelength section is called a
a. Hertz antenna b. Dipole antenna c. Marconi antenna d. All the above
4 The angular separation between the half-power points on an antenna's radiation pattern is the
a. Bandwidth b. Front-to-back ratio c. Lobe distribution d. Beamwidth
5 The input impedance at the center of a dipole antenna is approximately
a. 36.6 b. 50 c. 73 d. 300
6 As the height of a half-wavelength antenna is reduced below a quarter-wavelength, the radiation resistance a. Increases
b. Decreases c. Remains the same d. All the above
7 A dipole antenna is being fed with a 300 transmission line. If a quarter-wave matching transformer is to be used as the non-resonant matching section, what must be the characteristic impedance of the cable used in the matching transformer?
a. 186.5 b. 103.9 c. 122.5 d. 147.9
8 An impedance-matching device that spreads the transmission line as it approaches the antenna is called a a. Delta match
b. Quarter-wave matching device c. Director
d. Counterpoise
9 A loading coil is often used with a Marconi antenna in order to
a. Tune out the capacitive reactance portion of the input impedance of the antenna
b. Tune out the inductive reactance portion of the input impedance of the antenna
c. Raise the input impedance of the antenna d. Decrease the losses of the antenna
10 Standard AM broadcast stations usually use what type of transmitting antennas?
a. Driven collinear array b. Marconi array c. Yagi-Uda d. Log-periodic
11 The type of antenna often found in small AM broadcast receivers is a
a. Ferrite loop antenna b. Folded dipole antenna c. Slot antenna
d. Log-periodic antenna 12 The folded dipole antenna has
a. Greater bandwidth than a half-wave dipole b. A 288- input impedance
c. Less bandwidth than a half-wave dipole d.. a and b
e. b and c
13 The Yagi-Uda antenna consists of a. A driven director and parasitic reflector b. A driven reflector and parasitic director c. A parasitic director and reflector d. All the above
14 A grid-dip meter measures the resonant frequency of tuned circuits
a. By connection in series with the inductance b. By connection in parallel with the inductance c. Without power being applied to the tuned circuit d. By connection in series with the capacitance 15 When troubleshooting antennas, the level of VSWR that
indicates a problem is a. Greater than 1 b. Less than 1 c. Greater than 1.5 d. Less than 0.5
Chapter 14 Waveguides & RADAR
1 At a frequency of 1 Ghz and transmitter-receiver distance of 30 mi, which is the most efficient device for energy transfer?
a. Transmission lines b. Waveguides c. Antennas d. None of the above
2 The most efficient means of transmitting a 1-Ghz signal 1500 ft would typically be
a. Transmission lines b. Waveguides c. Antennas d. None of the above
3 The dominant mode for waveguide operation is a. TE10
b. TE01 c. TM10 d. TM01
4 The propagation velocity of the signal in a waveguide, when compared to the speed of light is
a. larger b. smaller c. the same velocity d. either b or c
5 Ridged waveguides are advantageous over rectangular waveguides in their
a. cost b. attenuation
c. ability to work at lower frequency d. ease of construction
6 A circular waveguide is used for a. Efficiency reasons
b. Ease of manufacture c. Rotating section applications d. Greater bandwidth
7 Variable attenuators are used in waveguides to a. Isolate a source from reflections at its load so as to preclude frequency pulling.
b. Adjust the signal levels. c. Measure signal levels. d. All the above.
8 The coupling in dB of a directional coupler that has 85 mW into the main guide and 0.45 mW out the secondary guide is
a. 22.8 b. 18.9 c. 188.9 d. 45.6
9 The resonant frequency of a cavity may be varied by changing the cavity's
a. Volume b. Inductance c. Capacitance d. All the above 10 The guide wavelength is
a. Greater than free-space wavelength b. Equal to free-space wavelength c. Less than free-space wavelength d. All the above
11 The process of employing radio waves to detect and locate physical objects is known as
a. The Doppler effect b. Radar
c. Directional coupling d. Cavity tuning
12 The use of two grounded conductors that sandwich a smaller conductive strip with constant separation by a dielectric material on a printed circuit board for use at frequencies above 500 Mhz is known as
a. Artwork traces b. Dielectric waveguide c. Microstrip/stripline d. MICs or MMICs 13 Second return echoes are
a. Echoes produced when the reflected beam makes a second trip
b. Echoes that arrive after the transmission of the next pulse
c. Echoes caused by the PRT being too long d. All the above
14 The characteristic wave impedance for waveguides is a. 75
b. 377
c. Dependent on frequency d. Dependent on waveguide shape e. c and d
15 A dielectric waveguide is
a. Enclosed by a conducting material b. A waveguide with just a dielectric
c. Dependent on the principle that two dissimilar dielectrics can guide waves
d. b and c
Chapter 15 Microwaves & Lasers
1 Which is not a type of horn antenna design for microwave frequencies?
a. Parabolic horn b. Circular horn c. Pyramidal horn d. Sectoral horn
2 Cassegrain feed to a paraboloid antenna involves a a. Dipole antenna
b. Point-source antenna c. Secondary reflector d. Any of the above
3 Calculate the beamwidth of a microwave dish antenna with a 6-m mouth diameter when used at 5 Ghz. a. 0.49°
b. 4.9° c. 7° d. 0.7° 4 Zoning refers to
a. A method of producing a radome
b. Changing a spherical wavefront into a plane wave c. Creating a polar radiation pattern
d. Fading into nonreality
5 Which microwave oscillator has high gain, low-noise
characteristics, and wide bandwidth? a. Traveling wave tube oscillator b. Gunn Oscillator
c.Klystron oscillator d. Magnetron oscillator
6 Which is not an advantage of the Gunn gallium arsenide oscillator?
a. Ease of removing heat from the chip b. Small size
c. Ruggedness d. Lack of filaments e. Low cost of manufacture 7 The i in P-I-N diode refers to
a. Indium b. Impact c. Integrated d. Intrinsic
8 Which is not a typical application of a ferrite in a microwave system?
a. attenuator b. amplifier c. isolator d. circulator
9 A low noise microwave amplifier that provides
amplification via the variation of a reactance is known as a
a. Maser b. Laser c. Yig
d. Parametric amplifier
10 The major difference between a laser and a maser is the a. Frequency of the signal being amplified
b. Amplitude of the signal being amplified c. Bandwidth of the signal being amplified d. Phase of the signal being amplified 11 Lasers are useful in
a. Industrial welding b. Surgical procedures c. Distance measuring d. Compact disc players e. All the above
12 The following semiconductor is not used as a microwave device:
a. PIN diode b. Baritt diode c. Zener diode d. Tunnel diode
for a TWT amplifier? a. Low gain
b. Spurious modulation c. Poor frequency response d. Low RF output
e. All the above
14 Which of the following is not used as a microwave antenna?
a. Patch antenna b. Marconi antenna c. Lens antenna d. Horn antenna
15 Compared to linear power supplies, switching power supplies are a. Less efficient b. More efficient c. Simpler d. Heavier Chapter 16 Television
1 A television transmitter actually transmits two signals at once. They are
a. An amplitude-modulated video signal and frequency-modulated audio signal
b. Two amplitude-modulated signals: video and audio
c. An amplitude-modulated audio signal and frequency-modulated video signal
d. Two frequency-modulated signals: video and audio
2 The most widely used type of TV camera is the a. Charge couple device
b. Vidicon c. Image orthicon d. Iconoscope
3 Synchronizing pulses that consist of equalizing pulses, followed by serrations, followed by more equalizing pulses at a rate of 60 times per second are called
a. Color synchronizing pulses b. Horizontal retrace pulses c. Vertical retrace pulses d. Eight-cycle back-porch pulses
4 The frame frequency for U.S. television broadcasts is approximately
a. 30 frames per second b. 40 frames per second c. 60 frames per second d. 100 frames per second
5 Channel 12 on U.S. television extends from 204 to 210 Mhz. The channel 12 carrier frequency is Approximately
a. 204.5 Mhz b. 205.25 Mhz c. 211.25 Mhz d. 211.75 Mhz
6 The length of time an image stays on the screen after the signal is removed is termed
a. Retention b. Flicker c. Persistence d. Back porch
7 Which is not part of the tuner section of a TV receiver?
a. The rf amplifier stage b. The mixer stage c. The local oscillator stage d. The video-detector stage
8 The stage in a TV receiver that filters out the vertical and horizontal retrace pulses from the video signal is the
a. Video detector b. Video IF amplifier c. Sync separator d. Sound detector
9 The winding around the CRT yoke that deflects the electron beam with its magnetic field is called the a. Coil
b. Yoke c. Deflector d. Magneto
10 A cumbersome series of adjustments to a color TV receiver in order to make sure that the three electron beams of the picture tube are positioned exactly on their respective color dots on the face of the picture tube is called
a. Alignment b. Convergence c. Interleaving d. Interlacing
11 A faulty TV receiver having symptoms of normal sound and raster but no picture must have a problem in the
a. Horizontal or vertical oscillator or high-voltage power supply
b. Main power supply
c. Video amplifiers following the sound takeoff d. RF, IF, or video amplifiers prior to the sound takeoff
12 Raster refers to
a. CRT illumination by scan lines when no signal is being received
b. CRT resolution c. CRT aspect ratio d. All the above
13 The high voltage for the anode of the CRT is obtained from the low-voltage power supply using a. Its power-line transformer
b. The yoke coil c. The vertical oscillator d. The flyback transformer
14 The introduction of digital television in the United States has been hampered by
a. Delays in chip designs b. Shortages of appropriate chips c. Customer rejection
d. Less than ideal regulatory climate
15 When a digital picture freezes even when there is motion in the video, it is
a. due to bandwidth problems b. Called a pixelate
c. Due to noise d. b and c
Chapter 17 Fiber Optics
1 Which is an advantage of optical communication links over using transmission lines or waveguides?
a. Small size
b. Extremely wide bandwidths
c. Immunity to electromagnetic interference (EMI) d. Lower cost
e. All the above
2 The most common light used in fiber-optic links is a. Infra-red
b. Red c. Violet d. Ultraviolet
3 The optical band designation(s) include a. S
b. C c. L
d. a and b above e. All the above
4 In the telecommunications industry, the most commonly used fiber(s) are
a. 50 micron b. 62.5 micron c. 50 and 62.5 micron d. 125 micron
5 The abrupt change in refractive index from core to cladding of fiber-optic cable is called the
a. Total internal reflection b. Numerical aperture c. Dispersion d. Step index
6 A technique that is used to minimize the pulse dispersion effect is to
a. Use a higher frequency light source b. Use plastic cladding
c. Minimize the core diameter d. All the above
7 The loss (attenuation) of signal in optical fiber is due to
a. Scattering b. Absorption c. Macrobending d. Microbending e. All the above
8 Calculate the optical power 100 km from a 0.5 mW source on a single mode fiber that has 0.10 dB per km loss.
a. 50 nW b. 500 nW c. 5 uW d. 50 uW
9 Which is not an important characteristic of a light detector? a. Responsitivity b. Dark current c. Power consumption d. Response speed e. Spectral respons
10 The dispersion in fiber optics is termed a. Modal
b. Chromatic c. Polarization mode d. All the above e. a and b above
11 Fiber optic connections suffer high loss due to a. Air gaps
b. Rough surfaces c. Axial misalignment d. Angular misalignment e. All the above
12 Fiber optic technology is used in applications of a. Local area networks (LANs)
b. Cable TV (CATV) systems c. Telephone networks
d. All the above
13 The dispersion of light in fiber-optic cable caused by a portion of the light energy traveling in the cladding is called
a. Modal dispersion b. Material dispersion c. Waveguide dispersion d. Cable dispersion
14 Recent laser developments for fiber optic communication include
a. Distributed feedback (DFB) b. Heterojunction
c. Vertical cavity surface emitting (VCSEL) d. a and b above
e. a and c above
15 The following consideration is important when deciding between using a diode laser or an LED a. Response time
b. Power levels
c. Temperature sensitivity d. Failure characteristics e. All the above
ANSWER KEY CHAPTER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 C D C C E D B D D C A C B C A A E 2 B A C D B A C A D A B B B B C A A 3 D C C D B C A D C A A A C A D C E 4 C B B A B A D C C D C B D B B A C 5 D C D B C C B B C D B D C C A B D 6 C D C D B C D D A B E B B C A C C 7 C C A B B D B B B B D C D D D D E 8 B D C A B C C B A A B A A A B C D 9 D A D D A A D D D D A D A D D B C 10 A C A B A B D A D C A E B A A B D 11 A A C C B C B A D E C B A B E C E 12 B D D B C A C D B B B A D C C A D 13 C D D A B D C B C C C D C B E D C 14 C D D D C D D C C E B B C E B D E 15 E B A C D D D D A A E C C D B D A
