Post on 10-Dec-2015
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1. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal?
a. Amplitudeb. Phasec. Angled. Duty Cycle
2. Both FM and PM are types of what kind of modulation?a. Amplitudeb. Phasec. Angled. Duty Cycle
3. If the amplitude of the modulating signal decreases, the carrier deviationa. Increasesb. Decreasesc. Remains constantd. Both b and c
4. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?
a. Shapeb. Phasec. Frequencyd. Amplitude
5. Maximum frequency deviation of a PM signal occurs ata. Zero crossing pointsb. Peak positive amplitudec. Peak negative amplituded. Peak positive or negative amplitudes
6. A 100-MHz carrier is deviated 50 KHz by a 4 kHz signal. The modulation index isa. 5b. 8c. 12.5d. 40
7. The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. The deviation ratio is
a. 0.2b. 5c. 8d. 40
8. According the Nyquist theorem, the sampling rate that can be used in a PCM system is _____ the highest audio frequency
a. Once
b. Eight timesc. Twiced. Thrice
9. Which of the following pulse modulation systems is analog?a. Deltab. Differential PCMc. PWMd. PCM
10. The phenomenon of a strong FM signal dominating weaker signal on a common frequency is referred to as the
a. Capture effectb. Blot outc. Quieting factord. Dominating syndrome
11. In the stabilized reactance modulator AFC system,a. The discriminator must have a fast time constant to prevent demodulationb. The higher the discriminator frequency, the better the oscillator frequency
stabilityc. The discriminator frequency must not be too low, or the system will faild. Phase modulation is converted into FM by the equalizer circuit
12. In the spectrum of a frequency of a frequency-modulated wavea. The carrier frequency disappears when the modulation index is largeb. The amplitude of any sideband depends on the modulation indexc. The total number of sidebands depends on the modulation indexd. The carrier frequency cannot disappear
13. The difference between phase and frequency modulationa. Is purely theoretical because they are the same in practiceb. Is too great to make the two systems compatiblec. Lies in the poorer audio response of phase modulationd. Lies in the different definitions of the modulation index
14. Indicate the false statement regarding the Armstrong modulation system.a. The system is basically phase, not frequency, modulationb. AFC is not needed, as a crystal oscillator is usedc. Frequency multiplication must be usedd. Equalization is unnecessary
15. An FM signal with a modulation index mf is passed through a frequency tripler. The wave in the output of the tripler will have a modulation index of
a. mf/3b. mf
c. 3 mf
d. 9mf
16. An FM signal with a deviation δ is passed through a mixer, and has its frequency reduced fivefold. The deviation in the output of the mixer is
a. 5 δb. Indeterminatec. δ/5d. δ
17. A pre-emphasis circuit provides extra noise immunity bya. Boosting the bass frequenciesb. Amplifying the higher audio frequenciesc. Pre-amplifying the whole audio bandd. Converting the phase modulation to FM
18. Since noise phase modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude
a. Remains constantb. Decreasedc. Increasedd. Equalized
19. When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulating system is
a. Amplitude modulationb. Phase modulationc. Frequency modulationd. Any of the three
20. Indicate which one of the following is not an advantage of FM over AMa. Better noise immunity is providedb. Lower bandwidth is requiredc. The transmitted power is more usefuld. Less modulating power is required
21. One of the following is an indirect way of generating FM. This is thea. Reactance FET modulatorb. Varactor diode modulatorc. Armstrong modulatord. Reactance bipolar transistor modulator
22. Indicate the false statement regarding the advantages of SSB over double-sideband, full-carrier AM.
a. More channel space is availableb. Transmitter circuits must be more stable, giving better receptionc. The signal is more noise resistance d. Much less power is required for the same signal strength
23. _______ determines the number of sideband components in FM.a. carrier frequencyb. modulation frequencyc. modulation indexd. deviation ratio
24. What produces the sidebands on FM?a. signal amplitudeb. carrier harmonicsc. baseband frequency d. broadband frequency
25. An FM receives signal ______.a. vary in amplitude with modulationb. vary in frequency with modulationc. vary in frequency and amplitude with wideband modulation d. is not immune to noise
26. The frequency of the unmodulated carrier in FM system isa. modulating frequencyb. center frequencyc. carrier frequencyd. deviation frequency
27. The ratio of maximum deviation to the maximum modulating frequency is calleda. carrier swing b. deviation ratioc. modulation factord. modulation index
28. What is the modulation index of an FM signal having a carrier swing of 75 kHz when the modulating signal has frequency of 3 kHz?
a. 25b. 12.5c. 0.04d. 0.08
29. In a FM system, if modulation index is doubled by having the modulating frequency, what will be the effect on the maximum deviation?
a. No effectb. Maximum deviation doublesc. Decreases by ½d. Increases by ¼
30. Which of the following is considered as an indirect method of generating FM?a. Reactance modulatorb. Balanced modulatorc. Varactor diode modulatord. Armstrong system
31. In FM, the Carson’s Rule states that the bandwidth is equal to twice the sum of the modulating frequency and ______.
a. Carrier signalb. Modulating signal
c. Frequency deviationd. Image frequency
32. What is the carrier swing of an FM transmitter when modified by 75%?a. 53.2 kHzb. 48 kHzc. 56.25 kHzd. 112.5 kHz
33. The modulation system inherently more resistant to noisea. Single sideband suppressed carrierb. Frequency modulationc. Pulse-position modulationd. Amplitude shift keying
34. Subcarriers that are arranged so that the channels occupying adjacent frequency bands with some frequency space between them is known as
a. Guard bandsb. AM bandsc. Band gapd. Void bande. Both B and C
35. Frequency modulation and phase modulation are collectively referred to as a. Stereob. Angle modulationc. High fidelity modulationd. FCC modulation
36. In FM, the change in carrier frequency is proportional to what attribute of the modulating signal?
a. Angle b. Frequencyc. Amplituded. Tone
37. A louder sound, when generating the modulating waveform for FM, will cause a greatera. Carrier amplitudeb. Angle amplitudec. Distortion at the receiverd. Frequency deviation
38. If a positive change in modulation signal level of 200 mW will cause a positive frequency deviation of 10 kHz, what will be the frequency deviation for a negative change of 10 mV in the level of the modulating signals?
a. 0b. -5 kHzc. +5 kHzd. +0 kHz
39. A particular 15 kHz modulation tone results in a peak frequency deviation of 75 kHz. What is the modulation index?
a. 5b. 15
c. 75d. 3
40. A 15 kHz sine wave frequency modulates an 88 MHz carrier. A sideband frequency will be found at
a. 87.970 MHzb. 87.985 MHzc. 88.015 MHzd. All of these
41. A device whose capacitance is deliberately made to be a function of the applied voltagea. Varactor diodeb. UJTc. SAWd. Variable capacitor
42. A reactance modulator is one method of obtaining a. Indirect FMb. Direct FMc. Demodulationd. Low frequency filtering
43. A device, now available in IC form, is useful for direct FM and as one element in the phse-locked loop.
a. AFCb. AGCc. VCOd. LPF
44. _____ is a frequency change process, whereby the phase deviation and frequency deviation are multiplied by some fixed constant.
a. Translationb. Multiplicationc. Divisiond. Addition
45. A circuit that has the function of demodulating the frequency-modulated signal.a. AFCb. Envelope detectorc. Decoderd. Foster-Seeley discriminator
46. The ratio detector is superior to the slope detector becausea. It is less sensitive to phase modulationb. It is less sensitive to noise spikesc. It is less sensitive to interference causing AMd. Both B and C
47. One implementation of a pulse averaging discriminator isa. A free-running multivibratorb. A crystal-controlled oscillatorc. A quartz crystal filterd. A triggered multivibrator
48. A 10% increase in the frequency of a constant-width pulse train should cause what change in its average value?
a. -10%b. -1%c. +1%d. +10%
49. Two different signals can be coherent if theya. Have the same amplitudeb. Are both sine waves of different frequenciesc. Originate in the same physical equipment simultaneouslyd. Have the same frequency
50. A quadrature detector requires thata. Four gates bee providedb. The inputs are coherentc. The inputs are incoherentd. The inputs are identical
51. In a phase-locked loop, the VCO is the abbreviation fora. Variable coherent outputb. VHF communication oscillatorc. Voltage-controlled oscillatord. Vien-count oscillator (neutralized)
52. Identify an advantage, or advantages of a properly designed FM system.a. Relative immunity to atmospheric noise (lightning)b. Reduced bandwidth requiredc. No noise of any kindd. The noise figure is inversely proportional to the modulation index
53. What is the modulation index of an FM signal if its modulating frequency is doubled?a. No effectb. Twice the original indexc. Four times the original indexd. One-half the original index
54. _____ is the circuit used to detect frequency modulated signal.a. Discriminatorb. Modulatorc. Modemd. Detector
55. _____ is an information signal that is sent directly without modulating any carrier.a. C-bandb. Q-bandc. Basebandd. Broadband
56. Both frequency and phase modulation utilize ______ modulation.a. Digitalb. Phasec. Amplituded. Angle
57. It is the width of frequencies within the spectrum occupied by a signal and used by the signal for conveying information.
a. Bandb. Bandwidthc. Electronic spectrumd. Frequency band
58. ______ is kind of modulation in which the modulated wave is always present.a. Carrier modulationb. Continuous modulationc. Log-periodic modulationd. Square-wave modulation
59. A type of modulation in which no signal is present between pulses.a. Pulse modulationb. FSKc. QAMd. PAM
60. _______ is a form of amplitude distortion introduced when the positive and negative alternations in the AM modulated signals are not equal.
a. Envelope distortionb. Spurious emissionc. Carrier shiftd. Johnson noise
61. What is the advantage of phase modulation over direct FM frequency modulation?a. Multipliers can be usedb. The deviation is smallerc. Simplicity and practicalityd. The oscillator is crystal-controlled
62. If the spectrum is shifted in frequency with no other changes, this is known as a. Frequency multiplicationb. Sideband movementc. Baseband reorientationd. Frequency translation
63. A device which is capable of causing frequency translationa. High-Q tank circuitb. Balanced modulatorc. Low-Q tank circuitd. IF strip
64. If the frequency of each component in a signal spectrum is increased by the same fixed amount, this known as
a. Modulationb. Frequency translationc. Up conversiond. Both B and C
65. A particular amplifier is designed to be a frequency doubler. If the input signal frequency is 15.4 MHz, a circuit in the output will be tuned to
a. 7.7 MHz
b. 15.4 MHzc. 30.8 MHzd. 61.6 MHz
66. A sine wave of 293 MHz is phase-modulated to achieve a maximum phase deviation of 0.2 radian. After passing through a frequency tripler, the maximum phase deviation will be
a. 0.2 radianb. 0.3 radianc. 0.4 radiand. 0.6 radian
67. Any device to be used as a frequency multiplier must bea. Activeb. Passivec. Lineard. Nonlinear
68. A particular amplifier circuit used for frequency doubling.a. Push-pushb. Push-pullc. Pull-pushd. Pull-pull
69. Frequency division is useful in the implementation of aa. AM demodulatorb. Frequency synthesizerc. AGC circuitd. FM demodulator
70. Frequency division by 12 will require how many flip-flops in the counter?a. 3b. 4c. 6d. 12
71. Identify an electronic device, not specifically designed for the purpose, which can be used as a phase detector.
a. Wien bridgeb. Colpitts oscillatorc. Balanced modulatord. Butterworth filter
72. A particular frequency synthesizer contains only a single crystal. What words describe this synthesizer?
a. Crystal modulatedb. Inexactc. Indirectd. Deficient
73. A recognizable feature of a CW transmitter isa. Keyed transmitterb. Power amplificationc. Frequency generation
d. All of these74. The term “pulling” refers to
a. The change of the crystal oscillator frequency by loadingb. One half-cycle operation of a push-pull amplifierc. Loading on the transmitter caused by the antenna connectiond. Reduction of the power supply terminal voltage as the transmitter is keyed.
75. When frequency modulation is achieved by initial phase modulation, this is calleda. Angular modulationb. Direct FMc. Indirect FMd. Indirect synthesis
76. A disadvantage of direct FM is the need fora. AGCb. AFCc. A frequency synthesizerd. Phase modulation
77. Direct FM can be achieved bya. A reactance tube modulatorb. A varactor diodec. And AGC circuitd. Both A and B
78. The change of the modulated carrier frequency from the original RF to the IF of the superheterodyne receiver is known as
a. Frequency multiplicationb. Frequency allocationc. Frequency substitutiond. Frequency translation
79. The key to achieving receiver sensitivity is the reduction of a. Image responseb. Mixer harmonic productsc. Spurious frequency responsed. Internal noise
80. An FM receiver with an I-F of 10.7 MHz is tuned to 98.7 MHz. What is the numerical value of the image frequency?
a. 77.3 MHzb. 88.0 MHzc. 109.4 MHzd. 120.1 MHz
81. A source of RF interference exists at 109.9 MHz. For which frequency in the FM broadcast band will this be the image frequency?
a. 21.4 MHzb. 88.5 MHzc. 99.2 MHzd. 110.7 MHz
82. The ratio of the superheterodyne receiver response at the desired carrier frequency to that at the image frequency is called
a. The sensitivityb. The selectivityc. The image frequencyd. The image rejection ratio
83. The core of an IF transformer usually containsa. Teflonb. Computer nylonc. Powdered irond. Laminated steel
84. Shape factor is a measure ofa. Bandwidthb. Skirt steepnessc. Coupling coefficientd. Critical coupling
85. _______ is the function which tends to maintain the sound volume level of a voice receiver nearly constant for a large signal strength range.
a. Squelchb. Mutingc. AGCd. AFC
86. The function which tends to silence the receiver in the absence of transmitted carrier.a. Squelchb. Mutingc. AGCd. AFC
87. What device is incorporated in a communications receiver to reduce impulse noise?a. Front-end processorb. Squelch circuitc. AGCd. Noise blanker
88. What type of signal in which a receiver selectivity of 2.4 kHz in the I-F circuitry is optimum?
a. FM voiceb. Double-sideband AM voicec. FSK datad. SBB voice
89. If the input to a detector stage is an amplitude-modulated (A3E) IF signal then the output from the stage is
a. A lower frequency carrier
b. The audio voice informationc. A Morse-code signald. The upper or lower set of sidebands
90. In a capacitive type, reactance-tube modulator connected across an oscillator tuned circuit, a more negative voltage on the grid of the reactance tube will cause
a. An increase of the oscillator frequencyb. An decrease of oscillator frequencyc. An increase of the reactance-tube capacitanced. An increase of the reactance tube ac plate current
91. The limiting condition for sensitivity in a communications receiver is92. When a communications receiver is tuned to a strong signal, the AGC bias is measured
and found to be zero. The fault cannot be caused by a/ana. Defective IF stageb. Defective local oscillatorc. Defective RF staged. Open circuit in the AGC’s filter capacitor
93. The term used to refer to the condition where the signals from a very strong station are superimposed on other signals being received
a. Cross-modulation interferenceb. Intermodulation interferencec. Receiver quietingd. Capture effect
94. The limiter stage of an FM receivera. Behaves as a low-pass filterb. Limits the amplitude of the IF signal to the required levelc. Behaves as a high-pass filterd. Behaves as a bandstop filter
95. Motorboating (low-frequency oscillations) in an amplifier can be stopped bya. Grounding the screen gridb. Connecting a capacitor between the B+ and lead groundc. By passing the screen grid resistor with a 0.1 µF capacitord. Grounding the plate
96. An effect in which, the modulation of an unwanted signal is transferred to the desired carrier.
a. Crossmodulationb. Intermodulationc. Modulation mixingd. Image-channel interference
97. Leads should be kept as short as possible in radio circuit so thata. Skin effect is reducedb. There is less hysteresis effect
c. There is less dielectric lossd. Stray coupling is minimized
98. The number of voice transmissions that can be packed into a given frequency band for amplitude-compandored single-sideband systems over conventional FM-phone systems.
a. 2b. 18c. 16d. 4
99. Neutralization of an RF amplifier stage can be necessary in order toa. Increase the amplifier’s gainb. Prevent the generation of spurious oscillationsc. Reduce the amplifier’s gaind. Reduce the level of the output harmonics
100. The ability of a communications receiver to perform well in the presence of strong signals outside the band of interest is indicated by what parameter?
a. Blocking dynamic rangeb. Noise figurec. Signal-to-noise ratiod. Audio output
101. Stages that are common to both AM and FM receiversa. Tuner, local oscillator, detector, AF amplifierb. RF amplifier, mixer, IF amplifier, AF amplifierc. Local oscillator, RF amplifier, frequency discriminator, detectord. Tuner, IF amplifier, detector, AF amp
102. Occurs during CW reception if too narrow a filter bandwidth is used in the IF stage of a receiver
a. Filter ringingb. Undesired signals will reach the audio stagec. Output-offset overshootd. Cross-modulation distortion
103. What stage mainly determines a communication receiver’s sensitivity?a. IF amplifierb. Mixer stagec. Detector staged. RF amplifier
104. What is the main advantage of FM over AM?a. Better signal-to-noise-ratiob. Narrower bandwidthc. Greater propagation ranged. Total freedom from adjacent-channel interference
105. An amplitude modulation created in an amplifier before the final RF stage.
a. Low-level modulationb. High-level modulationc. Direct modulationd. Indirect modulation
106. Receiver desensitizing can be reduced bya. Increasing the transmitter audio gainb. Decreasing the receiver squelch gainc. Increasing the receiver bandwidthd. Ensuring good RF shielding between the transmitter
107. In a narrow-band FM system, the deviation ratio is commonly one and the highest audio frequency is generally limited to
a. 300 Hzb. 10,000 Hzc. 3,000 Hzd. 7,500 Hz
108. In a phase-modulated signal (indirect FM), the frequency deviation is directly proportional to the
a. Carrier amplitude onlyb. Amplitude of the modulating tone and frequency of the carrierc. Carrier frequency onlyd. Modulating signal amplitude only
109. A system containing a limiter stage, a discriminator, and a de-emphasis circuit?a. Direct FM transmitterb. Indirect FM transmitterc. Single sideband AM receiverd. FM receiver
110. The limiter stage of an FM receivera. Prevents any amplitude modulation of the IF signalb. Limits the amount of frequency deviation in the IF signalc. Limits the overall bandwidth of the IF stagesd. Corrects any deviation in carrier frequency
111. High selectivity occurs when the degree of coupling between a receiver’s RF stages is
a. Tightb. Loosec. Criticald. Adjusted for maximum power transfer
112. A carrier is phase modulated by a test tone. If the amplitude and the frequency of the tone are both doubled, the amount of the deviation is
a. Doubledb. Unchanged
c. Halvedd. Multiplied by four
113. The degree of selectivity desirable in the IF circuitry of a single-sideband receiver.
a. 1 kHzb. 2.4 kHzc. 4.2 kHzd. 4.8 kHz
114. The component most apt to break down in the radio circuit is thea. Crystalb. Resistorc. Transformerd. Diode
115. The base in an RF amplifier is grounded in order toa. Avoid the requirement of neutralizing the stageb. Raise the input impedancec. Lower the output impedanced. Obtain maximum power output
116. The AM detector performs two basic functions in the receiver.a. Rectifies and filtersb. Amplifiers and filtersc. Buffer and amplifierd. Buffer and detector
117. A varactor diode can be used in a/ana. Direct FM modulator circuitb. AFC circuit in a direct FM transmitterc. Phase-modulator circuitd. All of these
118. Receiver interference is not reduced by including a/ana. Crystal filter b. Insulating enclosures around the receiverc. Wave trapd. RF stage
119. Which of the following stages in an FM receiver is responsible for drastically reducing the effect of static noise during the reception of a signal
a. De-emphasis circuitb. Mixer stagec. Squelch circuitd. Limiter stage
120. In most mixers, the oscillator frequency is ______ than the carrier frequency of the input signal.
a. Higherb. Lowerc. The samed. 10 kHz above
121. Features of a transmitter’s buffer stage includea. High stageb. Harmonic generationc. Improvement in frequency stability of the oscillatord. Low input impedance
122. What stage feeds the discriminator of an FM receiver?a. Local oscillatorb. Mixer stagec. Final IF amplifier, which also acts as a limiter staged. Buffer
123. In an FM receiver, the stage that has the IF signal is input and the audio signal output.
a. Limiterb. Audio amplifierc. IF amplifierd. Discriminator
124. What is capture effect?a. All signals on a frequency are demodulated by an FM receiverb. The loudest signal received is the only demodulated signalc. All signals on a frequency are demodulated by an AM receiver d. The weakest signal received is the only demodulated signal
125. A double-sideband phone signal can be generated bya. Feeding a phase-modulated signal into a low-pass filterb. Modulating the plate voltage of a class-C amplifierc. Using a balanced modulator followed by a filterd. Detuning a Hartley oscillator
126. Pre-emphasis is used in FM transmitters to improve the signal-to-noise ratio ofa. High modulating frequenciesb. Low modulating frequenciesc. All modulating frequenciesd. Frequencies carrier
127. The result of cross-modulation is thata. The modulation of an unwanted signal is heard on the desired signalb. A decrease in modulation level of transmitted signalsc. Of receiver quietingd. Of inverting sidebands in the final stage of the amplifier
128. Which of the following contains de-emphasis circuit?
a. FM transmitterb. FM receiverc. VHF transmitterd. VHF receiver
129. Two AM transmitting antennas are close together. As a result the two modulated signals are mixed in the final RF stage of both transmitters. What is the resultant effect on other station?
a. Harmonic interferenceb. Intermodulation interference c. Spurious interferenced. Crossmodulation interference
130. The term used to refer to the reduction of receiver gain caused by the signal of a nearby station transmitter in the same frequency band?
a. Quieting b. Cross-modulation interferencec. Squelch gain rollbackd. Desensitizing
131. What is the bandwidth occupied by the carrier, both sidebands and harmonics?a. Authorized bandwidthb. Bandwidth of emission and occupied bandwidthc. Operating bandwidthd. All of these
132. A class-C RF amplifier is collector amplitude modulated and its average dc level collector current does not change. This means
a. A normal conditionb. Excessive drive to the basec. Insufficient drive to the based. Insufficient audio modulation
133. What determines the percentage modulation of an FM transmitter?a. Amplitude of the carrierb. Modulating frequencyc. Carrier frequencyd. Amplitude of the modulating signal
134. Deviation ratio of an FM transmitter is the ratio of thea. Maximum frequency swing to the highest modulating frequency b. Operating frequency of the assigned frequencyc. Frequency swing to the modulating frequency d. Highest modulating frequency to the minimum frequency
135. The main purpose of the beat frequency oscillator (BFO) is to generatea. A 1 kHz not for Morse receptionb. Aid in the reception of weak voice-modulated signals
c. An output, whose frequency differs from the IF by 1 kHzd. A signal, whose frequency is the same as intermediate frequency
136. Normally, a linear class BRF power amplifier operates with a bias approximately equal to
a. Twice cut-offb. Ten times cut-off valuec. 50% of cut-off valued. Projected cut-off
137. The purpose why an RF amplifier is operated under linear class-B conditions (as opposed to class-C) is to
a. Generate only even harmonicsb. Generate only odd harmonicsc. Increase the efficiencyd. Amplify of an AM signal
138. The term used to refer to the condition where the signal from a very strong station are superimposed on other signal being received.
a. Cross-modulation interferenceb. Intermodulation distoriotionc. Receiver quietingd. Capture effect
139. In an FM-phone signal, ________ is the ratio between the actual frequency deviation to the maximum frequency deviation.
a. FM compressibilityb. Modulating indexc. Percentage of modulationd. Quieting index
140. _______ is used to refer to the reception blockage of one FM-phone signal by another FM-phone signal.
a. Capture effect b. Desensitizationc. Cross-modulation interferenced. Frequency discrimination
141. The receiver circuit that rids FM of noise is thea. Modulatorb. Demodulatorc. Limiterd. Low-pass filter
142. The method of generating FM used by broadcasting station isa. Directb. All of thesec. Indirect
d. Insertion143. Deviation ratio of an FM transmitter is the ratio of the
a. Maximum frequency swing to the highest modulating frequencyb. Operating frequency of the assigned frequencyc. Frequency swing to the modulating frequencyd. Highest modulating frequency to the minimum frequency
144. A phase modulator has Kp= 2 rad/V. What RMS voltage of a sine wave would cause a peak phase deviation of 30 degrees?
a. 0.158 Vb. 0.185 Vc. 0.518 Vd. 0.815 V
145. In a phase-locked loop, VCO stands for a. Variable capacitor oscillatorb. Varactor-capacitor oscillatorc. Voltage-controlled oscillatord. VHF control oscillator
146. Which is a disadvantage of direct FM generation?a. The need for an AFC circuitb. The need for an AGC circuitc. Two balanced modulators are usedd. The use of Class A amplifier which is very inefficient
147. Frequency division is useful in the implementation of a/ana. AM demodulatorb. Frequency synthesizerc. AGC circuitd. FM demodulator
148. A particular synthesizer which contains only a single crystal is a. Directb. Crystal-modulatedc. Indirectd. Exact
149. Type of emission most affected by selective fadinga. FM and DSB AMb. SSB and TVc. CCTV and CWd. CW and SSB
150. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth?
a. 115 kHzb. 230 kHzc. 170 kHzd. 340 kHz
151. A quadrature detector requires that
a. The inputs are coherentb. Four gates are providedc. The inputs are in phased. The inputs are similar
152. Collector current in a class C amplifier isa. Sine waveb. Half-sine wavec. Pulsed. Square wave
153. The final power amplifier in an FM transmitter usually operates classa. Ab. Bc. Cd. D
154. A phase-locked loop has a VCO with a free-running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHz and comes out of lock again at 18 MHz. Calculate the capture range.
a. 4 MHzb. 2 MHzc. 12 MHzd. 8 MHz
155. If the frequency fed to the pre-amplifier of a basic transmitter with multipliers is composed of a pair of triplers and a doubler is 198 MHz, what frequency should the oscillator operate?
a. 11 MHzb. 33 MHzc. 22 MHzd. 66 MHz
156. A phase-locked loop has a VCO with a free running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHZ and comes out of lock again at 18 MHz. Calculate the lock range.
a. 4 MHzb. 2 MHzc. 12 MHzd. 8 MHz
157. A crystal oscillator is accurate within 0.0005%. How far off frequency could its output be at 37 MHz?
a. 135 Hzb. 150 Hzc. 185 Hzd. 224 Hz
158. What is the term used to refer to the reception blockage of one FM-phone signal?a. Desensitizationb. Cross-modulation interference
c. Capture effectd. Frequency discrimination
159. How are FM phone signals detected?a. By a balanced modulatorb. By a frequency discriminatorc. By a product detectord. By a phase splitter
160. What is a frequency discriminator?a. A circuit for detecting FM signalsb. A circuit for filtering two closely adjacent signalsc. An automatic band switching circuitd. An FM generator
161. What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?
a. Intermodulation distortionb. Noise floorc. Noise figured. Dynamic range
162. If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate according to the Nyquist theorem?
a. 200 samples/secb. 500 samples/secc. 1000 samples/secd. 1200 samples/sec
MULTIPLE CHOICE QUESTIONS IN
ANGLE MODULATIONElectronics Systems and Technologies
By
Melvin C. Arceo
ENCODED BY:
SANTOLLO, Dan Alvin
1. He developed the first successful FM radio system
a. B.E.Alpine
b. N.S. Kapany
c. E.H. Armstrong
d. A.C.S. Van Heel
2. Results whenever the phase angle of sinusoidal wave is varied with respect to time
a. angle modulation
b. digital modulation
c. amplitude modulation
d. pulse modulation
3. In the spectrum of a frequency -modulated wave
a. the carrier frequency disappears with a large modulation index
b. the amplitude of any sideband depends on the modulation index
c. the total number of sidebands depends on the modulation index
d. the carrier frequency cannot disappear
4.What is the frequency swing of an FM broadcast transmitter when modulated 60%
a. 60 kHz
b. 45 kHz
c. 30 kHz
d. 25 kHz
5. Varying the frequency of a constant -amplitude carrier directly proportional to the amplitude to the modulating signal at a rate equal to the frequency of the modulating signal
a. amplitude modulation
b. angle modulation
c. phase modulation
d. frequency modulation
6. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the frequency signal?
a. amplitude
b. frequency
c. phase
d. shape
7. It is a modulation where the angle of a wave carrier is varied from its reference value
a. amplitude modulation
b. angle modulation
c. analog modulation
d. digital modulation
8. Both FM and PM are types of what kind of modulation?
a. amplitude
b. phase
c. angle
d. duty cycle
9. Varying the phase of a constant amplitude carrier displacement proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal.
a. amplitude modulation
b. angle modulation
c. phase modulation
d. frequency modulation
10. The difference between phase and frequency modulation
a. is purely theoretical because they are the same in practice
b. is too great to make the two systems compatible
c. lies in the poorer audio responses of phase modulation
d. lies in the different definitions of the modulation index
11. The relative angular displacement of the carrier phase in radians with respect to the reference phase is called __________.
a. phase deviation
b. carrier deviation
c. frequency deviation
d. information deviation
12. If the amplitude of the modulating signal decreases, the carrier deviation
a. increases
b. decreases
c. remains constant
d. goes to zero
13. On an FM signal, maximum deviation occurs at what point on the modulating signal?
a. zero-crossing points
b. peak positive amplitudes
c. peak negative amplitude
d. both peak positive and negative amplitudes
14. The amount of oscillator frequency increase and decrease around the carrier frequency is called _________.
a. frequency deviation
b. phase shift
c. intelligence frequency
d. baseband
15. The relative displacement of the carrier frequency in hertz in respect to its unmodulated value is called _____________.
a. frequency deviation
b. phase deviation
c. information deviation
d. carrier deviation
16. A pre-emphasis circuit provides extra noise immunity by
a. boosting the bass frequencies
b. amplifying the higher audio frequencies
c. preamplfying the whole audio band
d. converting the phase modulation to FM
17. It is the instantaneous change in phase of the carrier at a given instant of time and indicates how much phase of the carrier is changing with respect to its reference phase.
a. instantaneous frequency
b. instantaneous frequency deviation
c. instantaneous phase
d. instantaneous phase deviation
18. Calculate the amount of frequency deviation caused by a limited noise spike that still cause an undesired phase shift of 35 degrees when the input frequency is 5kHz.
a. 2.40kHz
b. 3.05kHz
c. 1.29kHz
d. 4.45kHz
19. Which of the following determines the rate of carrier deviation?
a. intelligence frequency
b. frequency deviation
c. carrier frequency
d. broadband frequency
20. It is the precise phase of the carrier at a given instant of time
a. instantaneous phase deviation
b. instantaneous phase
c. instantaneous frequency deviation
d. instantaneous frequency
21. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?
a. shape
b. phase
c. frequency
d. amplitude
22. In FM, it is a device that in which amplitude variations are derived in response to frequency or phase variations
a. detector
b. discriminator
c. demodulator
d. receiver
23. Maximum frequency deviation of a PM signal occurs at
a. zero-crossing points
b. peak positive amplitudes
c. peak negative amplitude
d. peak positive and negative amplitude
24. Since noise phase-modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude
a. remains constant
b. is decreased
c. is increased
d. is equalized
25. It is the instantaneous change in frequency of the carrier and is defined as the first time derivative of the phase deviation
a. instantaneous frequency
b. instantaneous frequency deviation
c. instantaneous phase
d. instantaneous phase deviation
26. Since noise phase- modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude
a. remains constant
b. is decreased
c. is increased
d. is equalized
27. It is the precise frequency of the carrier at a given instant of time is defined as the first time derivative of the instantaneous phase.
a. instantaneous frequency
b. instantaneous frequency deviation
c. instantaneous phase
d. instantaneous phase deviation
28. It is the output-versus-input transfer functions for modulators which give the relationship between the output parameter changes in respect to specified changes in the input signal.
a. frequency deviation
b. deviation sensitivity
c. transconductance curve
d. phase deviation
29. When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is
a. amplitude modulation
b. phase modulation
c. frequency modulation
d. any of the above
30. In PM, carrier frequency deviation is not proportional to:
a. modulating signal amplitude
b. carrier amplitude and frequency
c. modulating signal frequency
d. modulator phase shift
31. To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and phase modulator?
a. low-pass filter
b. high-pass filter
c. phase shifter
d. bandpass filter
32. Indicate which one of the following is not an advantage of PM over AM:
a. better noise immunity is provided
b. lower bandwidth is required
c. the transmitted power is more useful
d. less modulating power is required
33. With phase modulation, the maximum frequency deviation occurs during what value of the modulating signal?
a. positve peak value
b. rms value
c. negative peak value
d. zero crossings
34. With frequency modulation, maximum frequency deviation occurs _____ of the modulation signal.
a. positive peak value
b. both positive and negative peak value
c. negative peak value
d. zero crossings
36. With phase modulation, peak phase deviation is called _________.
a. modulation index
b. frequency deviation
c. phase deviation
d. instantaneous phase
37. The FM produced by PM is called
a. FM
b. PM
c. indirect FM
d. indirect PM
38. In a broadcast superheterodyne receiver, the
a. local oscillator operates below the signal frequency
b. mixer input must be tuned to the signal frequency
c. local oscillator frequency is normally double the OF
d. RF amplifier normally works at 455kHz above the carrier frequency
39. If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be
a. zero
b. the carrier frequency
c. above the carrier frequency
d. below the carrier frequency
40. To prevent overloading of the last IF amplifier in the receiver, one should use the
a. squelch
b. variable sensitiivity
c. variable selectivity
d. double conversion
41. The peak-to-peak frequency deviation is sometimes called __________.
a. phase deviation
b. peak phase deviation
c. carrier swing
d. instantaneous frequency
42. A 100MHz carrier is deviated 50 kHz by 4kHz signal. The modulation index is
a. 5
b. 8
c. 12.5
d. 20
43. With angle modulation, it is defined as the ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form.
a. modulation index
b. percent modulation
c. frequency deviation
d. phase deviation
44. In a broadcast FM system, the input S/N = 4. Calculate the worst case S/N at the output if the receiver's internal noise effect is negligible.
a. 19.8:1
b. 21.6:1
c. 23:1
d. 15:1
45. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal.
a. frequency modulators
b. amplitude modulators
c. phase modulators
d. mixers
46. In a ratio detector
a. the linearity is worse than in a phase discriminator
b. stabilization against signal strength variations is provided
c. the output is twice that obtainable from the similar phase discriminator
d. the circuit is the same as in a discriminator, except that the diodes are reversed
47. The maximum deviation of an FM carrier is 2kHz by a maximum modulating signal of 400Hz. The deviation ratio is
a. 0.2
b. 5
c. 8
d. 40
48. The unmodulated carrier is a single-frequency sinusoid commonly called _________.
a. unrest frequency
b. rest frequency
c. frequency-modulated frequency
d. carrier frequency
49. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal
a. phase modulator
b. phase deviator
c. amplitude deviator
d. frequency modulator
50. The typical squelch circuit
a. cuts off an audio amplifier when the carrier is absent
b. eliminates the RF interference when the signal is weak
c. cuts off an IF amplifier when the AGC is maximum
d. cuts off an IF amplifier when the AGC is minimum
51. Frequency modulators are also known as _________.
a. phase deviators
b. frequency deviators
c. phase modulators
d. amplitude deviators
52. A 70 kHz carrier has a frequency deviation of 4 kHz with a 1000Hz signal. What is the bandwidth of the FM signal?
a. 4kHz
b. 7kHz
c. 10 kHz
d. 28 kHz
53. The controlled oscillator synthesizer is sometimes preferred to the direct one because
a. it is simpler piece of equipment
b. its frequency stability is better
c. it does not require crystal oscillators
d. it is relatively free of spurious frequencies
54. A system with a differentiator followed by an FM modulator is called
a. PM modulator
b. FM modulator
c. PM demodulator
d. FM demodulator
55. The image frequency of a superheterodyne receiver
a. is created within the receiver itself
b. is due to insufficient adjacent channel rejection
c. is not rejected by the IF tuned circuits
d. is independent of the frequency to which the receiver is tuned
56. A system with FM demodulator followed by an integrator
a. PM modulator
b. PM demodulator
c. FM modulator
d. FM demodulator
57. A system with an integrator followed by a PM modulator
a. PM modulator
b. FM modulator
c. PM demodulator
d. FM demodulator
58. An FM transmitter has a maximum deviation of 12kHz and a maximum modulating frequency of 12 kHz. The bandwidth by Carson's rule is
a. 24kHz
b. 33.6kHz
c. 38.8kHz
d. 48kHz
59. A system with PM demodulator followed by a differentiator
a. PM modulator
b. FM modulator
c. PM demodulator
d. FM demodulator
60. A receiver has poor IF selectivity. It will therefore also have poor
a. blocking
b. double-spotting
c. diversity reception
d. sensitivity
61. Three point tracking is achieved with
a. variable selectivity
b. the padder capacitor
c. double spotting
d. double conversion
62. He mathematically proved that for a given modulating signal frequency a frequency-modulated wave cannot be accommodated in a narrower bandwidth than an amplitude modulated wave.
a. R.C. Alpine
b. E.H. Armstrong
c. J.R. Carson
d. J.J. Thomson
63. The maximum allowed deviation of the FM sound signal in TV is 25 kHz. If the actual deviation is 18kHz, the percent modulation is
a. 43 percent
b. 72 percent
c. 96 percent
d. 139 percent
64. The local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency
a. to help the image frequency rejection
b. to permit easier tracking
c. because otherwise an intermediate frequency could not be produced
d. to allow adequate frequency coverage without switching
65. Which of the following is not a major benefit of FM over AM?
a. greater efficiency
b. noise immunity
c. capture effect
d. lower complexity and cost
66. Low-index FM systems are also known as __________.
a. wideband FM
b. narrowband FM
c. commercial FM
d. medium FM
67. For high-index signal, a method of determining the bandwidth is called ________ approach
a. quasi-stationary
b. quasi-movement
c. quasi-deviation
d. any of these
68. When a receiver has a good blocking performance, this means that
a. it does not suffer from double-spotting
b. its image frequency rejection is poor
c. it is unaffected by AGC derived from a nearby transmission
d. its detector suffers from burnout
69. He established a general rule to estimate the bandwidth for all angle-modulated system regardless of the modulation index.
a. R.C. Alpine
b. E.H. Armstrong
c. J.R. Carson
d. J.J. Thomson
70. An AM receiver uses a diode detector for demodulation. This enables it satisfactority to receive
a. single-sideband, suppressed carrier
b. single-sideband, reduced carrier
c. independent sideband
d. single-sideband, full carrier
71. The primary disadvantage of FM is its
a. higher cost and complexity
b. excessive use of spectrum space
c. noise susceptibility
d. lower efficiency
72. A rule that approximates the bandwidth necessary to transmit an angle-modulated wave as twice the sum of the peak frequency deviation and the highest modulating frequency.
a. Carson's rule
b. Shannon's rule
c. Hartley's law
d. Hartley-Shannon law
73. It is the worst case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating signal frequency
a. peak phase deviation
b. frequency deviation
c. deviation ratio
d. signal to noise ratio
74. The receiver circuit that rids FM noise is the
a. modulator
b. demodulator
c. limiter
d. low-pass filter
75. The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the
a. capture effect
b. blot out
c. quieting factor
d. domination syndrome
76. The highest side frequencies form one channel are allowed to spill over into adjacent channels producing an interference known as _________.
a. co-channel interference
b. adjacent channel interference
c. splatter
d. overmodulation
77. A pre-emphasis is usually a ________.
a. high-pass filter
b. band-stop filter
c. low-pass filter
d. bandpass filter
78. Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier?
a. class A
b. class B
c. class C
d. all of the above
79. Noise interferes mainly with modulating signals that are
a. sinusoidal
b. non-sinusoidal
c. low frequencies
d. high frequencies
80. A de-emphasis is usually a _________.
a. high pass filter
b. band-stop filter
c. low-pass filter
d. bandpass filter
81. A pre-emphasis is a __________.
a. integrator
b. differentiator
c. either integrator or differentiator
d. neither integrator or differentiator
82. A de-emphasis is a _____________.
a. integrator
b. differentiator
c. either integrator or differentiator
d. neither integrator or differentiator
83. Pre-emphasis circuit boost what modulating frequencies before modulation?
a. high frequencies
b. mid-range frequencies
c. low frequencies
d. all of the above
84. The primary disadvantage of direct PM
a. relatively unstable LC oscillators must be used to produce carrier frequency which prohibits using crystal oscillators
b. relatively high frequency deviations and modulation indices are easily obtained due to the fact that the oscillators are inherently unstable.
c. crystal oscillators are inhrently stable and therefore more difficult for them to achieve high phase deviations and modulation indices
d. carrier oscillator is isolated form the actual modulator circuit and therefore can be stable source.
85. It is an angle modulation in which the frequency of the carrier is deviated by the modulating signal
a. direct PM
b. PM
c. indirect FM
d. any of these
86. One of the following is a method of performing frequency up conversion
a. heterodyning
b. amplification
c. modulation
d. none of these
87. A pre-emphasis circuit is a
a. low-pass filter
b. high-pass filter
c. phase shifter
d. bandpass filter
88. Pre emphasis is compensated for the receiver by a
a. phase inverter
b. bandpass filter
c. high-pass filter
d. low-pass filter
89. A circuit that compares the frequency of the noncrystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between the two frequencies
a. AFC
b. squelch circuit
c. AGC
d. heterodyning circuit
90. A frequency selective device whose output voltage is proportional to the difference between the input frequency and its resonant frequency
a. modulator
b. squelch circuit
c. frequency discriminator
d. FM transmitters
91. Allows FM receiver to differentiate between two signals received with the same frequency but different amplitudes
a. flywheel effect
b. amplitude limiting
c. noise immunity
d. capture effect
92. If an FM transmitter employs one doubler, one tripler, and one quadrupler, what is the carrier frequency swing when the oscillator frequency swing is 2kHz?
a. 24 kHz
b. 48 kHz
c. 14 kHz
d. 12 kHz
93. The cut-off frequency of pre-emphasis and de-emphasis circuits is
a. 1 kHz
b. 2.122 kHz
c. 5 kHz
d. 75 kHz
94. Which of the following is not a disadvantage of angle modulation?
a. wide bandwidth
b. complex
c. high cost
d. less noise
95. In FM receivers, which of the following rejects the image frequency?
a. preselector
b. detector
c. IF amplifier
d. mixer
96. In FM receivers, which of the following provides most gain and selectivity of the receiver?
a. detector
b. RF amplifier
c. local oscillator
d. IF amplifier
97. Another name for Voltage Variable Capacitor is
a. PIN diode
b. varactor diode
c. snap diode
d. hot carrier diode
98. The depletion region in a junction diode forms what part of a capacitor?
a. plates
b. leads
c. package
d. dielectric
99. Which of the following removes the information from the modulated wave in FM receivers?
a. amplifiers
b. mixer
c. speakers
d. discriminator
100. The final IF amplifier in FM receivers is sometimes called ___________.
a. tuned amplifier
b. limiter
c. passband filter
d. any of these
101. _________ are frequency-dependent circuits designed to produce an output voltage that is proportional to the instantaneous frequency at its output
a. PM receivers
b. PM demodulators
c. FM demodulators
d. FM receivers
102. Increasing the reverse bias on a varactor diode will it cause its capacitance to
a. decrease
b. increase
c. remains the same
d. drop to zero
103. The capacitance of a varactor diode is in what general range?
a. pF
b. nF
c. uF
d. F
104. Which of the following is the simplest form of tuned-circuit frequency discriminator?
a. Foster-Seeley discriminator
b. Ratio detector
c. slope detector
d. PLL detector
105. It is simply two single-ended slope detectors connected in parallel and fed 180 degrees out phase.
a. Foster-Seeley discriminator
b. quadrature detector
c. balanced slope generator
d. PLL detector
106. The frequency change in crystal oscillator produced by a varactor diode is
a. zero
b. small
c. medium
d. large
107. A phase modulator varies the phase shift of the
a. carrier
b. modulating signal
c. modulating voltage
d. sideband frequency
108. Which of the following tuned-circuit frequency discriminator is relatively immune to amplitude variations in its input signal?
a. ratio detector
b. slope detector
c. balanced slope detector
d. quadrature detector
109. In FM demodulators, it is also called coincidence detector
a. quadrature demodulator
b. PLL demodulator
c. Foster-Seely discriminator
d. ratio detector
110. The widest phase variation is obtained with ________.
a. RC low-pass filter
b. RC high-pass filter
c. LR low-pass filter
d. LC resonant circuit
111. An FM receiver provides 100dB of voltage gain prior to the limiter. Calculate the receiver's sensitivity if the limiter's quieting for an FM receiver is 300mV?
a. 4.5 uV
b. 3.0 uV
c. 2.1 uV
d. 1.3 uV
112. The small frequency change produced by a phase modulator can be increased by using ___________.
a. amplifier
b. mixer
c. frequency multiplier
d. frequency divider
113. In FM receiver, limiters produce a constant-amplitude output of all signals above a prescribed minimum input level called _________.
a. threshold voltage
b. capture level
c. quieting level
d. any of these
114. The inherent ability of FM to diminish the effects of interfering signals is called _______.
a. capture effect
b. noise suppression
c. adjacent channel rejection
115. A crystal oscillator whose frequency can be changed by an input voltage is called _______.
a. VCO
b. VXO
c. VFO
d. VHF
116. Which oscillators are preferred for carrier generators because of their good frequency stability?
a. LC
b. RC
c. LR
d. crystal
117. Which of the following frequency demodulators requires an input limiter?
a. Foster-Seely discriminator
b. Pulse-averaging discriminator
c. quadrature detector
d. PLL
118. Provides a slight automatic control over the local oscillator circuit and compensates for its drift that would otherwise cause a station to become detuned.
a. AGC
b. AFC
c. VVC
d. VCO
119. ________ of an FM receiver is the maximum dB difference signal strength between two received signals necessary for the capture effect to suppress the weaker signal.
a. capture effect
b. capture gain
c. capture ratio
d. capture loss
120. When two limiter stages are used, there is called ___________.
a. double limiting
b. two-time limiting
c. reserve limiting
d. ratio limiting
121. Which discriminator averages pulses in a low-pass filter?
a. ratio detector
b. PLL
c. quadrature detector
d. pulse-averaging discriminator
122. Which of the frequency demodulator is considered the best overall?
a. ratio detector
b. PLL
c. quadrature
d. pulse-averaging discriminator
123. One of the prominent advantage of FM over PM is
a. FM requires frequency multipliers to increase the modulation index and frequency deviation to useful levels
b. the voltage controlled oscillators of FM can be directly modulated and produce outputs with high frequency deviations and high modulation
c. the modulation index of FM is independent of the modulating signal frequency
d. FM offers better signal-to-noise performance than PM
124. What special speaker is used for low frequency?
a. baffle
b. base
c. tweeter
d. woofer
125. Each speaker assembly at the receiver reproduces exactly the same information
a. monophonic
b. multiphonic
c. stereophonic
d. any of these
126. In a pulse averaging discriminator, the pulse are produced by a(n)
a. astable multivibrator
b. zero-crossing detector
c. one-shot
d. low-pass filter
127. A reactance modulator looks like a capacitance of 35pF in parallel with the oscillator-tuned circuit whose inductance is 50 uH and capacitance is 40 pF. What is the center frequency of the oscillator prior to FM?
a. 1.43 MHz
b. 2.6 MHz
c. 3.56 MHz
d. 3.8 MHz
128. The frequency of an SCA channel subcarrier is _______.
a. 38 kHz
b. 15 kHz
c. 67 kHz
d. 53 kHz
129. The L-R stereo channel in FM broadcasting is between
a. 50 Hz to 15 kHz
b. 60 kHz to 74 kHz
c. 23 kHz to 53 kHz
d. 20 Hz to 20 kHz
130. An FM demodulator that uses a differential amplifier and tuned circuits to convert frequency variations into voltage variations is the
a. quadrature detector
b. Foster-Seeley discriminator
c. differential peak detector
d. phase-locked loop
131. The output amplitude of the phase detector in a quadrature detector is proportional to
a. pulse width
b. pulse frequency
c. input amplitude
d. the phase shift value at center
132. The output to a PLL is 2MHz. In order for the PLL to be locked. The VCO output must be
a. 0 MHz
b. 1 MHz
c. 2 MHz
d. 4 MHz
133. With stereo transmission, the maximum frequency deviation is
a. 75 kHz
b. 15 kHz
c. 25 kHz
d. 3 kHz
134. The L + R stereo channel occupies _________.
a. 50 Hz to 15 kHz
b. 60 kHz to 74 kHz
c. 23 kHz to 53 kHz
d. 20 Hz to 20 kHz
135. The band of frequencies over which a PLL will acquire or recognize an input signal is called the
a. circuit bandwidth
b. capture range
c. band of acceptance
d. lock range
136. The three primary frequency bands are allocated by FCC for two-way FM radio communications except:
a. 132 MHz to 174 MHz
b. 450 MHz to 470 MHz
c. 806 MHz to 947 MHz
d. 1026 MHz to 1035 MHz
137. The maximum frequency deviation for two-way transmitters is typically
a. 25 kHz
b. 5 kHz
c. 75 kHz
d. 3 kHz
138. Decreasing the input frequency to be locked PLL will cause the VCO output to
a. decrease
b. increase
c. remains constant
d. jump to the free-running frequency
139. The range of frequencies over which a PLL will track input signal variations is known as the
a. circuit bandwidth
b. capture range
c. band of acceptance
d. lock range
140. The maximum modulating signal frequency for two-way transmitter is typically
a. 3 kHz
b. 5 kHz
c. 15 kHz
d. 75 kHz
141. Over a narrow range of frequencies, the PLL acts like a
a. low-pass filter
b. bandpass filter
c. tunable oscillator
d. frequency modulator
142. The output of a PLL frequency demodulator is taken from the
a. low-pass filter
b. VCO
c. phase detector
d. none of these
143. The primary advantage of FM over AM
a. capture effect
b. noise immunity
c. FM can use class C amplifiers
d. FM is more efficient
144. The usual cutoff frequency of pre-emphasis and de-emphasis in broadcast FM?
a. 50 Hz
b. 75 Hz
c. 2122 Hz
d. 3183 Hz
145. The maximum deviation for narrowband FM?
a. 2500
b. 5
c. 1.67
d. 75
146. Which of the following is best frequency demodulator in use?
a. Foster-Seeley discriminator
b. ratio detector
c. slope detector
d. PLL
147. The range of frequencies over which the PLL will capture an input signal is known as ________.
a. lock range
b. capture range
c. bandwidth
d. sidebands
148. Type of FM demodulator that is widely used in TV audio demodulators
a. ratio detector
b. quadrature detector
c. PLL
d. pulse-averaging discriminator
149. A variation of Foster-Seeley discriminator widely used in oldr TV receiver designs
a. ratio detector
b. PLL
c. quadrature detector
d. crosby modulator
150. The range of frequencies over which a PLL will track an input is called
a. lock range
b. capture range
c. track range
d. driving range
151. What is the maximum deviation for monoaural TV sound
a. 25 kHz
b. 75 kHz
c. 50 kHz
d. 125 kHz
152. What is the maximum deviation for stereo TV sound?
a. 25 kHz
b. 75 kHz
c. 50 kHz
d. 125 kHz
153. In FM stereo broadcasting, the L + R signal
a. double-sideband modulates a subcarrier
b. modulates the FM carrier
c. frequency modulates a subcarrier
d. is not transmitted
154. In FM stereo broadcasting, the L - R signal
a. double-sideband modulates a subcarrier
b. modulates the FM carrier
c. frequency modulates a subcarrier
155. The SCA signal if used in FM broadcasting is transmitted via
a. a 19 kHz subcarrier
b. a 38 kHz subcarrier
c. a 67 kHz subcarrier
d. the main FM carrier
156. Which of the following is considered as an indirect method of generating FM?
a. reactance modulator
b. balanced modulator
c. varactor diode modulation
d. armstrong system
157. In an FM system, if the modulation index is doubled by halving the modulating frequency, what will be the effect on the maximum deviation?
a. remains the same
b. doubles
c. decrease by 1/2
d. increase by 1/4
158. Determine from the following the common use of DSB in broadcast and telecommunication.
a. satellite communications
b. FM/TV stereo
c. two-way communications
d. telephone systems
159. Phase modulation emission type
a. F3F
b. G3E
c. F3E
d. F3C
160. The range of frequencies over which a PLL will cause the input of the VCO signals to remain synchronized is known as the _________ range.
a. capture
b. lock
c. acquisition
d. any of these
161. If the PLL input is zero, the VCO will operate at its ____________ frequency.
a. free-running
b. natural
c. operating
d. any of these
162. Since a PLL will only respond to signals over a narrow frequency range, it acts likes a ________.
a. low-pass filter
b. high-pass filter
c. bandpass filter
d. bandstop filter
163. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the
___________.
a. modulating signal
b. carrier signal
c. carrier amplitude
d. VCO output
164. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ________.
a. FM input
b. VCO input
c. modulating signal
d. error signal
165. After the IF stages have been aligned, the next state to align in FM receiver is
a. local oscillator
b. limiter stage
c. RF amplifier
d. mixer stage
166. The modulation system used for telegraphy is
a. frequency-shift keying
b. two-tone modulation
c. purse-code modulation
d. single-tone modulation
167. What is emission F3F?
a. Facsimile
b. RTTY
c. modulated CW
d. television
168. What is a frequency discriminator?
a. a circuit for filtering two closely adjacent signals
b. a circuit for detecting FM signals
c. an FM generator
d. an automatic bandswitching circuit
169. Type of radio communication transmission utilizing frequency modulation technique
a. television video
b. broadcasting in 535-1606 kHz
c. single sideband HF transmission
d. television audio
170. Why was FM first developed?
a. to compete with AM
b. to overcome noise
c. to increase listeners
d. to supplement AM
171. To what feature of the modulating tone is FM deviation proportional?
a. amplitude
b. frequency
c. phase
d. phase shift
172. Which of the following is not a basic filed of FM?
a. broadcast
b. TV video
c. mobile communications
d. amateur radio
173. Under what condition would a 1 kHz AF signal produce a single pair of FM sidebands?
a. wideband
b. broadcast FM
c. TV audio FM
d. narrowband FM
174. What deviation is considered 100% for FM broadcast stations?
a. 75 kHz
b. 220 kHz
c. 270 kHz
d. 75 kHz or 220 kHz
175. In FM broadcasting, what is the highest required modulating frequency?
a. 75 kHz
b. 50 kHz
c. 25 kHz
d. 15 kHz
176. In FM broadcasting, what is the lowest required modulating frequency?
a. 50 Hz
b. 30 Hz
c. 10 Hz
d. 5 Hz
177. What is the disadvantage of slope detection of FM>
a. no discrimination against noise
b. less AF distortion
c. less AF out
d. no filtering of carrier
178. What is the unction of the dc that comes out of the dc amplifier in a PLL-type FM detector?
a. carrier signal
b. filter signal
c. error signal
d. phase signal
179. What is the function of the dc that comes out of the dc amplifier in a PLL-type FM detector?
a. oscillators
b. AF signal
c. RF signal
d. carrier signal
180. Why should discriminators be tuned for a straight characteristic S-curve?
a. less AF distortion
b. greater AF out
c. less RF out
d. less RF distortion
181. What band for high-Q coils be more desirable for stagger-tuned-type discriminator transformer?
a. wide
b. intermediate
c. interfacing
d. narrow
182. In a Foster-Seeley circuit, the AF output voltage is ________.
a. varying DC
b. varying AC
c. steady DC
d. steady AC183. In a stagger-tuned discriminator, the AF output voltage is _________.
a. varying DC
b. varying AC
c. steady DC
d. steady AC
184. In a ratio detector, the AF output voltage is
a. steady AC
b. varying AC
c. steady DC
d. varying DC
185. In a gated-beam detector, the AF output voltage is _________.
a. steady DC
b. varying AC
c. varying DC
d. steady AC
186. Which of the following discriminator circuits require limiters ahead of them?
a. quadrature detector
b. foster-seeley discriminator
c. slope detector
d. stagger-tuned
187. Which of the following discriminator circuits provide an automatic gain control voltage?
a. ratio detector
b. balanced slope detector
c. quadrature detector
d. stagger-tuned detector
188. Which of the following discriminator circuits has its diodes in series?
a. ratio
b. quadrature detector
c. round-travis detector
d. slope detector
189. To what frequency must the gated-beam quadrature circuit be tuned in a TV receiver?
a. 10.7 MHz
b. 455 kHz
c. 70 MHz
d. 4.5 MHz
190. To what frequency must the gated-beam quadrature circuit be tuned in an FM broadcast receiver?
a. 4.3 MHz
b. 10.7 MHz
c. 11 MHz
d. 4.8 MHz
192. With what FM detectors would AGC be an advantage?
a. foster-seeley detector
b. ratio detector
c. quadrature detector
d. phase-locked loop
193. What is the reason for using pre-emphasis?
a. increase amplitude
b. reduce carrier shift
c. amplify RF signal
d. reduce noise reception
194. What are the two types of stages in an FM receiver that differ from those in an AM receiver?
a. limiting IF and detectors
b. oscillators and IF amplifiers
c. mixers and RF amplifiers
d. local oscillators and mixers
195. What special circuits are used in a squelch system that can follow changing noise levels?
a. noise amplifiers
b. rectifier
c. dc amplifier
d. any of these
196. Why might FM be better than AM for mobile ________.
a. better coverage
b. not affected by solar cycles
c. reduce flutter
d. not absorbed by ionosphere
197. What is the order of circuit alignment in an FM receiver?
a. discriminator, limiters, IF, mixer and RF
b. RF, limiters, IF, mixer and discriminator
c. limiters, mixer, RF, discriminator and IF
d. RF, mixer, RF, IF, limiters and discriminator
198. What is the another name for the reactance-tube modualtor?
a. Crosby
b. Foster-Seeley
c. Round Travis
d. Messier
199. What effect would be produced if a small inductance were used in plasce of the 50 pF capacitance in the reactance-tube modulator?
a. the circuit becomes resistive
b. reactance modulator looks like an inductive circuit
c. reactance modulator looks like Xc
d. any of these
200. The following are significant circuits in the AFC system except:
a. crystal
b. mixer
c. IF
d. filter
201. Besides the reactance-tube modulator, what is another method of producing direct FM?
a. armstrong modulator
b. voltage variable capacitor
c. impeadance modulator
d. slug indicator
202. What is the advantage of PM?
a. can use crystal oscillator
b. uses more multistage
c. less selective fading
d. simplicity
203. What was the first broadcast FM system called?
a. Arc transmitter
b. MOPA
c. Armstrong
d. crystal
204. Why are limtiers used in FM transmitters?
a. any of these
b. clip noise peaks
c. prevent overdrive of discriminators
d. prevent overdeviation
205. Why are limiters used in FM receivers?
a. provide better noise performance
b. clip noise peaks
c. prevent overdrive of discriminators
d. any of these
206. What signals might feed into an FM broadcast station audio control console?
a. microphones
b. turntables
c. remote lines
d. any of these
Moduloation/Demodulation
1. A method that applied the modulated wave to the vertical deflection circuit of the oscilloscope and the modulating signal to the horizontal deflection circuit.
a. Trapezoidal methodb. Circular methodc. Square method
d. Any method2. The heart of all methods of single-sideband modulation and demodulation
a. Modulatorb. Balanced modulatorc. Modulationd. demodulation
3. If the frequency and phase are parameters of carrier angle, which is a function of time, the general term ___________-cover both.
a. Amplitude modulationb. Frequency modulationc. Phase modulationd. Angle modulation
4. In FM radio communication system, narrow-band (NBFM) is used rather than wideband (WBFM), because it,
a. Improves signal to noise rationb. Reduces interchannel interferencec. Provides maximum coverage for a given amount of powerd. All of the above
5. Radio transmitter basically consists of two principal parts, one reproducing a carrier frequency and one for __________.
a. IF Frequencyb. RF Frequencyc. Modulating Frequencyd. Power
6. Is a measure of its ability to maintain as nearly a fixed frequency as possible over as long as time interval as possible.
a. Receiver Noise Factorb. Selectivityc. Sensitivityd. Frequency stability
7. Is the effect of two-transmitter when they are in close proximity. This results into the sum and difference frequencies of two carriers.
a. Intermodulation effectb. Intermodulation interferencec. Intermodulation productd. intermodulation
8. _________ is a continuous frequency capable of being modulated or impressed with a second information carrying signal.
a. Carrier frequencyb. Center frequencyc. IF frequency
d. RF frequency9. The varactor diode used in FM may be represented by the approximate equivalent circuit
of the _____ in series with a ________.a. Diode, capacitorb. Diode, resistorc. Capacitor, resistord. Any of these
10. The name varactor comes from variable _________.a. Resistorb. Capacitorc. Dioded. reactor
11. 75 microseconds pre-emphasis time is used in __________.a. FMb. AMc. TVd. None of these
12. Recovers the modulating voltage from the frequency modulation by utilizing the phase angle shift between primary and secondary voltages of tuned oscillators.
a. Direct methodb. Indirect methodc. Foster-Seeley discriminatord. Slope detector
13. Is used in FM receivers to “lock onto” the received signal and stabilized recetions.a. Automatic Gain Controlb. Automatic Frequency Controlc. Muscle Controld. Automatic Frequency Gain Control
14. Are amplifier circuits that are used to eliminate amplitude modulation and amplitude-modulated noise from received FM Signals before detection.
a. Demodulatorsb. Diode detectorc. Amplitude limitersd. None of these
15. If the total sideband power is 12.5% of the total radiated power, find the modulation index.
a. 50 percentb. 53.4 percentc. 26.2 percentd. 32.3 percent
16. Carriers are spaced at 20 kHz, beginning at 100 kHz. Each carrier is modulated by a signal with a 5 kHz bandwidth. Is there interference from the sideband?
a. Yesb. Noc. Maybed. Secret
17. For an unmodulated carrier of 150 V and a modulated peak value of 230 V. What is the modulation index
a. 0.35b. 0.533c. 0.652d. 0.42
18. New frequencies outside the regular AM spectrum are called ___________.a. Distortionb. Interferencec. Splatterd. Harmonic
19. A DSB-SC has a total power of 350 watts with 100% modulation suppresses 50% of the carrier, and the suppressed carrier power goes to the sidebands. How much power is in the sidebands?
a. 116.67 Wb. 233.33 Wc. 175 Wd. 350 W
20. A DSB-SC system must suppress the carrier by 30 dB from its original value of 30 W. What value must the carrier be reduced?
a. 30000 Wb. 0.03 Wc. 300 Wd. 0.003 W
21. ___________, which further amplifies the signal and has the bandwidth and passband shaping appropriate for the received signal.
a. RF stageb. Mixer and local oscillator stagec. IF staged. AF stage
22. In FM, a bandwidth estimate 98 percent level of Bessel functionsa. Approximate bandwidthb. Narrow-band Bandwidthc. Carson’s ruled. Wideband bandwidth
23. The complete series of stages for reproducing the FM signal with the desired carrier and deviation is the _______.
a. Modulatorb. Exciterc. IF staged. RF stage
24. Is the ability of FM system to provide low-noise, high fidelity music background/broadcast..
a. Monophonicb. Stereophonicc. Stereonicd. SCA
25. It make use of the shape of IF filter frequency response roll-off versus frequency.a. Foster Seeleyb. Slope detectorc. Diode detectord. Quadrature detector
26. In AM, modulation index is a number lying between ____ and 1.a. 2b. 5c. 0d. 3
27. This form of modulation is also known as independent sideband emission.a. A3Eb. R3Ec. H3Ed. B8E
28. An attenuated carrier is reinserted into the SSB signal to facilitate receiver tuning and demodulation.
a. A3Eb. R3Ec. H3Ed. B8E
29. Standard AM used for broadcastinga. A3Eb. R3Ec. H3Ed. B8E
30. Single sideband, suppressed carrier in which the carrier is suppressed by at least 45 dB in the transmitter.
a. A3E
b. R3Ec. H3Ed. B8E
31. The shift in the carrier frequency from the resting point compared to the amplitude of the modulating signal is called _______.
a. Indexb. Deviation ratioc. Carrier frequencyd. Deviation frequency
32. In FM, the amplitude of the modulated frequency wave remains ___________ at all times.
a. Varyingb. Dependentc. Constantd. variable
33. An AM has a maximum span of 30 V, what is the required minimum span to attain 100% modulation?
a. 30 Vb. 20 Vc. 0 Vd. None of these
34. DZMM having a carrier frequency of 630 kHz is modulated by 2.6 kHz audio signal having an amplitude of 37.5 V. What is the amplitude voltage of 630 kHz carrier frequency at 0.35 modulation index?
a. 57.6 Vb. 107.14 Vc. 206.5 Vd. 86.2 V
35. If the sideband power is 50% of the carrier power, what is the modulation index?a. 50%b. 75%c. 90%d. 100%
36. If the increase power is 180 watts at 1 kW unmodulated output power the modulation index is _________.
a. 75%b. 60%c. 50%d. 25%
37. In AM, if the unmodulated power carrier is 10 kW, and the total power is 15 kW, what is the upper sideband power at 100% modulation index?
a. 25 kWb. 2 kWc. 2.5 kWd. 4 kW
38. If the input resistance of the base station of AM broadcast produced 20 kW carrier power, at what modulation index should the antenna rise at 108.63 A?
a. 20%b. 50%c. 60%d. 80%
39. ________ used a phase detector to compare the phase and frequency of the received signal to the VCO output.
a. PILb. PALc. PLLd. PLI
40. A filter with a roll-off of 6 dB/kHz is used as a slope detector. The input signal varies with +3 kHz deviation from center carrier frequency. How many dB down is the output at full deviation?
a. 9 dBb. -18 dBc. 18 dBd. -9 dB
41. A receiver limiter requires a 20 mV signal for quieting operation. The voltage gain between the RF input and the limiter is 57.7 dB, what is the input at the antenna terminal assuming equal resistance?
a. 75.6 mVb. 26.67 uVc. 52.3 uVd. 49.6 uV
42. A 1-MHz carrier is modulated with a resulting 100 Hz deviation. It undergoes x36 multiplication, followed by mixing with a 34.5 MHz signal and remultiplication by 72. What is the final carrier and deviations?
a. 5076 MHz, ± 2592 MHzb. 2592 MHz, ± 259.2 kHzc. 2592MHz, ± 5076 MHzd. 259.2 MHz, ± 108 kHz
43. For standard commercial broadcast FM, the deviation ratio is ________.a. 15b. 75c. 5
d. 1044. A system has 150 kHz of bandwidth available for 10 kHz modulation signal. What is the
approximate deviation to be used?a. 35 kHzb. 65 kHzc. 25 kHzd. 15 kHz
45. An FM has a deviation of 100 kHz and a modulating frequency of 15 kHz, what happen to m if the deviation triples?
a. 6.66b. 2.22c. 4.12d. 0.20
46. A receiver for a signal at 100 MHz uses a 10.7 MHz IF and low tracking. What is the image frequency?
a. 89.3 MHzb. 78.6 MHzc. 52.5 MHzd. 35.2 MHz
47. What is the change in resonant frequency of the actual varactor capacitance value differs by -5% (0.05) of the nominal value?
a. 2.06b. 3.02c. 1.03d. 5.06
48. An oscillator resonate at 1 MHz with a nominal 100 pF capacitor and 0.25 mH inductor, what s the resonant frequency of the actual capacitor value is +20% of the nominal value?
a. 1.006 MHzb. 0.9188 MHzc. 3.625 MHzd. 2.00123 MHz
49. “Front end” is also called _________.a. IF stageb. AF stagec. RF staged. None of these
50. Undesired signal on the other side of the local oscillator output will have the same difference frequency and pass into the IF amplifier.
a. Carrier frequencyb. Sum frequencyc. Difference frequency
d. Image frequency
FREQUENCY MODULATION
1. Using Carson’s rule, what is the bandwidth of an FM signal with 5 kHz maximum frequency deviation and 2.5 kHz maximum modulating frequency?
a. 14 kHz
b. 16 kHz
c. 18 kHz
d. 15kHz
2. Calculate the maximum bandwidth required of a standard FM broadcast station.
a. 156 kHz
b. 180 kHz
c. 154 kHz
d. 160 kHz
3. The operating frequency of an FM transmitter is 168.96 MHz. calculate the frequency of the carrier crystal oscillator if it uses three frequency multipliers – a doubler, a tripler and a quadrupler.
a. 7.04 MHz
b. 7.05 MHz
c. 7.06 MHz
d. 7.07MHz
4. What frequency deviation is caused by noise in an FM receiver which has an input S/N of 2.8 and the modulating frequency of 1.5 kHz?
a. 569.2Hz
b. 587.3Hz
c. 547.8Hz
d. 569.2Hz
5. In GM broadcasting, what is the carrier frequency in MHz of a station with a channel number of 285?
a. 104.9 MHz
b. 104 MHz
c. 8 MHz
d. 104.5 MHz
6. In FM broadcasting, what is the channel number of the station with a given carrier of 99.1 MHz?
a. 254
b. 259
c. 258
d. 256
7. What is the rms output voltage of a PLL FM detector if it uses VCO with proportionality constant of 299 kHz/V and if it receives an FM signal with a deviation of 65 kHz sine-wave modulated?
a. 0.25V
b. 0.23V
c. 0.24V
d. 0.26V
8. A phase-locked loop has a VCO with free-running frequency of 19 MHz. as the frequency of the reference input is gradually raised from zero, the loop locks at 8 MHz and comes out of lock again at 14 MHz. determine the lock range.
a. 5 MHz
b. 6 MHz
c. 8 MHz
d. 9 MHz
9. A phase modulator has kp = 2rad/V. what rms voltage of a sine wave would cause a peak phase deviation of 30 degrees?
a. 0.184V
b. 0.156V
c. 0.187V
d. 0.185V
10. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth?
a. 235 kHz
b. 234 kHz
c. 230 kHz
d. 236kHz
11. A phase-locked loop has a VCO with a free-running frequency of 14 MHz. as the frequency of the reference input is gradually raised from zero. The loop locks at 12 MHz and comes out of lock again at 18 MHz. calculate the capture range.
a. 4 MHz
b. 5 MHz
c. 6 MHz
d. 7MHz
12. What is the frequency swing of an FM broadcast transmitter when modulated 80%?
a. 60 kHz
b. 62 kHz
c. 63 kHz
d. 64kHz
13. Determine the modulation index of a standard FM broadcast having a hypothetical maximum carrier frequency deviation of +- 12 kHz and a maximum modulating frequency of 4 kHz.
a. 5
b. 4
c. 3
d. 2
14. What is the modulation index of an FM transmitter whose frequency deviation is
50 kHz, while its audio frequency is 10 kHz?
a. 8
b. 6
c. 7
d. 5
15. The carrier swing necessary to provide 80% modulation in the FM broadcasting
band is ____?
a. 120 kHz
b. 130 kHz
c. 140 kHz
d. 150 kHz
16. An FM signal has a center frequency of 100 MHz but is swinging between 100.01
MHz and 99.999 MHz at a rate of 100 times per second, what is the modulation
index of the signal?
a. 110
b. 100
c. 90
d. 80
17. If the frequency fed to the pre-amplifier of a basic transmitter with multipliers is
composed of a pair of triples and a doublers multipliers is 198 MHz. what
frequency should the oscillator operate?
a. 10 MHz
b. 11 MHz
c. 12 MHz
d. 13MHz
18. For commercial FM broadcasting the maximum permissible range in modulation
index is 5 – 2500. What is the maximum bandwidth needed for this system?
a. 180 kHz
b. 190 kHz
c. 200 kHz
d. 210kHz
19. A portable radio transmitter has to operate at temperatures from – 5 degrees to 35
degrees C. if its signal is derived from a crystal oscillator with a temperature
coefficient of +1 ppm per degree centigrade, and it transmit at exactly 145 MHz at
20 degrees C, find the transmitting frequency at 35 degrees C.
a. 145.002175 MHz
b. 145.002174 MHz
c. 145.002176 MHz
d. 145.002154MHz
20. What FM channel is 107.5 MHz carrier?
a. 299
b. 298
c. 297
d. 296
21. The instantaneous value of the modulating signal to and FM modulator is -2V,
sensitivity kf = 25 kHz/V and operating at a carrier frequency of 88 MHz.
determine the output frequency of the modulator.
a. 87.59 MHz
b. 95.32 MHz
c. 87.95 MHz
d. 84.65 MHz
22. Calculate the frequency deviation of an Fm modulator that has kf = 20 kHz/V and
operates at a carrier frequency of 99.1 MHz modulated by a 2.5 Vrms sine wave.
a. 70.5 kHz
b. 70.6 kHz
c. 70.7 kHz
d. 70.8kHz
23. Find the deviation ratio of an FM broadcast transmitter if the frequency of the
modulating signal varies from 30 Hz to 20 kHz.
a. 3.75
b. 3.74
c. 3.73
d. 3.72
24. The output signal of a PM demodulator is 0.54 V. what is the sensitivity of the
demodulator if the phase deviation is 30o?
a. 0.99rad/V
b. 0.98rad/V
c. 0.97rad/V
d. 0.96rad/V
25. A PM transmitter produces a maximum phase shift of r/3 rad for a modulating
frequency of 300 Hz. What is the maximum frequency deviation of the system?
a. 315 Hz
b. 314 Hz
c. 316 Hz
d. 317Hz
26. An FM communication system has a sensitivity of kf = 3 kHz/V. how much phase
deviation does it produces with a sine wave input of 3 V peak at a frequency of 2
kHz?
a. 4.2rad
b. 4.5rad
c. 4.3rad
d. 4.8rad
27. An FM broadcast transmitter rated output power is 5 W. what is the peak voltage
developed across a 50 ohms resistive load?
a. 22.34V
b. 22.35V
c. 22.36V
d. 22.37V
28. An FM system has a modulation index of 3 and its corresponding Bessel
coefficient; Jo = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31. Find the RMS carrier voltage
if the total power is 5 W. developed across a 50 ohms resistive load.
a. 4.16V
b. 4.11V
c. 4.23V
d. 4.56V
29. Suppose the total power of an FM signal is 7W. What is the power of the second
sideband if the modulation index is 3? J0 = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31.
a. 3.4W
b. 3.5W
c. 3.6W
d. 3.2W
30. An FM broadcast transmitter has a deviation of 25 kHz and a modulating
frequency of 8 kHz. Calculate the power that is unaccounted, if the total power PT
is 10 W. J0 = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31.
a. 0.289W
b. 0.288W
c. 0.283W
d. 0.254W
31. A certain FM station transmitted a modulating frequency of 25 kHz and a
frequency deviation of 75 kHz. What is the approximate signal-to-noise ratio at
the detector output if the signal-to-noise ratio at the input to the receiver detector
is 20 dB?
a. 34dB
b. 35dB
c. 36dB
d. 37dB
32. An FM broadcast station transmits a 3 kHz test tone, and a frequency deviation of
15 kHz. Determine the modulation index.
a. 2
b. 3
c. 5
d. 4
33. An FM signal with modulation index of 4 and modulating frequency of 8 kHz.
What is the frequency deviation of the signal?
a. 36 kHz
b. 35 kHz
c. 31 kHz
d. 32kHz
34. A certain FM modulator has kf = 25 kHz/V. Suppose the peak amplitude of the
modulating signal is 3 V at a frequency of 3 kHz, determine the modulation index
of the signal.
a. 25
b. 26
c. 27
d. 28
35. The output frequency of the modulator increases by 50 kHz. What is the dc
voltage applied to the FM modulator, if the deviation sensitivity is 25 kHz/V?
a. 5V
b. 4V
c. 3V
d. 2V
36. The maximum instantaneous frequency of the modulated signal is 95.05 MHz. if a
5 kHz signal modulates a 95 MHz carrier, calculate the modulation index of the
signal.
a. 10
b. 1
c. 11
d. 12
37. A PM signal has a RMS signal of 3 V at a frequency of 3 kHz. If the modulation
index of the signal is 15, determine the sensitivity of the modulator.
a. 3.54rad/V
b. 3.53rad/V
c. 3.55rad/V
d. 3.52rad/V
38. The modulation index of the PM signal is 2. If a modulating signal that has
amplitude of 50 mV at a frequency of 3 kHz phase modulates a 90 kHz carrier
signal, what would be the new modulation index of the signal? Assume that the
amplitude of the modulating signal is increased by 50%.
a. 5
b. 4
c. 3
d. 2
39. A sine wave of frequency 15 kHz modulates a carrier at 101.1 MHz. the peak
frequency deviation is 75 kHz. Determine the peak amplitude of the modulating
signal if the sensitivity of the modulator is 50 rad/V.
a. 40mV
b. 300mV
c. 220mV
d. 100mV
40. With a maximum frequency deviation of 75 kHz, what is the maximum phase
deviation that can be present in an FM radio broadcast signal, assuming it
transmits a baseband frequency of 50 Hz to 20 kHz?
a. 1560rad
b. 1500rad
c. 1540rad
d. 1546rad
41. The phase shift of a phase modulated signal is 86 degree. What is the modulation
index of the said signal?
a. 1.2
b. 1.5
c. 1.3
d. 1.6
42. Determine the modulation index of an FM signal, given that the modulating
frequency is 25 kHz and frequency deviation of 75 kHz.
a. 3
b. 5
c. 4
d. 6
43. Suppose a certain FM signal uses a frequency deviation of 100 kHz and a
modulating index of 5. Calculate the band width using Carsons rule.
a. 250kHz
b. 240kHz
c. 260kHz
d. 230kHz
44. An FM station transmits 100 W of power. If the modulation index of the signal is
7, how much power is transmitted at the carrier frequency if Jo = 0.4?
a. 16W
b. 17W
c. 18W
d. 19W
45. A 50 ohms dummy load is used to test a certain FM station. Suppose the
measured power is 12.5 W, what is the voltage level of the second sideband if a
frequency of 5 kHz test tone is used and a 10 kHz frequency deviation?
a. 8.45Vrms
b. 8.56Vrms
c. 8.75Vrms
d. 8.26Vrms
46. An FM receiver can sufficiently receives only the carrier and the first two sets of
side bands. If the total power of the signal is 20 W, deviation of 25 kHz, and a
modulation index of 10, what is the percentage of the total signal power will it
receive?
a. 96.62%
b. 96.65%
c. 96.68%
d. 96.56%
47. An FM receiver sufficiently receives only the carrier and the first two sets of
sidebands. If the total power of the signal is 10 W, deviation is 25 kHz, and the
modulation index is 10, how much power is transmitted at the carrier frequency?
a. 485mW
b. 484mW
c. 456mW
d. 481mW
48. The calculated bandwidth using Carsons rule is 40 kHz if the modulating
frequency of the signal is 5 kHz. Using the same signal, what is the bandwidth if
sidebands with more than 1% of the signal voltage are considered?
a. 61 kHz
b. 62 kHz
c. 60 kHz
d. 63kHz
49. An FM transmitter operates with a carrier power of 10 W. what is the total signal
power if the modulation index of the signal is 5?
a. 308W
b. 309W
c. 310W
d. 311W
50. The maximum phase deviation given to the signal by the noise voltage is
0.01radian. What is the signal to noise ratio at the detectors input?
a. 41dB
b. 42dB
c. 43dB
d. 40dB
51. An FM receiver detects a 100 mV signal. A spurious signal is also detected by the
receiver that resulted to an S/N of 40 dB at the detectors output. Determine the
minimum S/N ratio at the detectors output if the modulating frequency is 2 kHz
and frequency deviation of 50 kHz.
a. 12dB
b. 13dB
c. 14dB
d. 15dB
52. An FM receiver is tuned at 99.1 MHz. what is the IF rejection ratio if the receiver
consists of a single tuned circuit with Q of 45?
a. 23dB
b. 24dB
c. 25dB
d. 26dB
53. An FM detector receives an FM signal with a deviation of 15 kHz. What is the
peak to peak output voltage of the detector if its sensitivity is 75 microV/Hz?
a. 2.25V
b. 2.26V
c. 2.27V
d. 2.28V
54. An FM receiver uses PLL to detect the signal. What is the sensitivity of the VCO
in the PLL if the output of the detector is 1.25 Vp from an FM signal that is
modulated to 10 kHz deviation by a sine wave?
a. 5 kHz/V
b. 6 kHz/V
c. 7 kHz/V
d. 8 kHz/V
55. An FM receiver uses a tuned transformer operating at 10.7 MHz. what is the
bandwidth using the optimum coupling factor if the primary circuit has a Q of 50
and the secondary has Q of 35?
a. 383.6 kHz
b. 383.7 kHz
c. 383.8 kHz
d. 383.9 kHz
56. An FM super heterodyne receiver is tuned to a frequency of 88 MHz. what is the
local oscillator frequency if low side injection is used at the mixer?
a. 77.3 MHz
b. 77.4 MHz
c. 77.5 MHz
d. 77.6MHz