Online Questions and Answers Topic Outline
- MCQs in Amplitude Modulation
- MCQs in Phase Modulation
- MCQs in Sound Pressure Level
- MCQs in Frequency Modulation
- MCQs in Pulse Modulation
MCQs in Modulation Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part II of the Series
51. What will be the result of the gain level being too high for signals entering the modulator?
- A. Receiver noise
- B. Excessive volume of receiver output
- C. Oscillator disturbances
- D. Distortion and splatter
52. Amplitude modulation causes the amount of transmitter power to
- A. Increase
- B. Decrease
- C. Remain the same
- D. Double
53. When a carrier is modulated 100%, the total power increases by what percentage over that of the carrier alone?
- A. 25 %
- B. 50 %
- C. 75 %
- D. 100 %
54. When the amplitude of the modulating voltage is increased for AM, the antenna current will
- A. Increase
- B. Decrease
- C. Remain constant
- D. Decrease exponentially
55. An increase in transmitter power from 25W to 30W will cause the antenna current to increase from 700mA to
- A. 800 mA
- B. 750 mA
- C. 767 mA
- D. 840 mA
56. A second modulating tone having the same amplitude but a different frequency is added to the first at the input to the modulator. The modulation index will be increased by a factor of
- A. sq. root of 3
- B. sq. root of 2
- C. 2
- D. 3
57. A 1000 kHz carrier is modulated by a 2500Hz tone. One frequency component of the modulated signal is
- A. 1200 Hz
- B. 5000 Hz
- C. 1002.5 kHz
- D. 2500 Hz
58. A 1200 kHz carrier is amplitude-modulated by two tones of 500 Hz and 700 Hz. Which one is a frequency component of the modulated wave?
- A. 1195 kHz
- B. 1199.3 kHz
- C. 1199.7 kHz
- D. 1205 kHz
59. Identify a modulation method, or methods in use for a common-emitter configuration
- A. Base modulation
- B. Emitter modulation
- C. Collector modulation
- D. Both A and C
60. The RF signal injected into a balanced modulator is 10MHz and the modulating frequency is 1 kHz. Which frequency, or frequencies, will not appear in the output?
- A. 9.999 MHz
- B. 10 MHz
- C. 10.0001 MHz
- D. Both A and B
61. Unwanted sidebands in SSB equipment can be suppressed by one or more of the following methods.
- A. Phasing method
- B. Filter method
- C. Decoder method
- D. Both A and B
62. Envelope detection is concerned with the process of
- A. Mixing
- B. Heterodyning
- C. Modulation
- D. Rectification
63. Diagonal clipping in envelope detection will result in
- A. Distortion
- B. Phase reversal
- C. Reduced sensitivity
- D. Amplitude damage
64. Product detection requires the process of
- A. Rectification
- B. Heterodyning
- C. Decoding
- D. Phase shifting
65. A sine wave which is coherent with carrier has identical
- A. Amplitude
- B. Frequency
- C. Phase angle
- D. Both B and C
66. Frequency modulation and phase modulation are collectively referred to as
- A. Stereo
- B. Angle modulation
- C. High fidelity modulation
- D. FCC modulation
67. In FM, the change in carrier frequency is proportional to what attribute of the modulating signal?
- A. Angle
- B. Frequency
- C. Amplitude
- D. Tone
68. A louder sound, when generating the modulating waveform for FM, will cause a greater
- A. Carrier amplitude
- B. Angle amplitude
- C. Distortion at the receiver
- D. Frequency deviation
69. 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. 0
- B. -5 kHz
- C. +5 kHz
- D. +0 kHz
70. A particular 15 kHz modulation tone results in a peak frequency deviation of 75 kHz. What is the modulation index?
- A. 5
- B. 15
- C. 75
- D. 3
71. A 15 kHz sine wave frequency modulates an 88 MHz carrier. A sideband frequency will be found at
- A. 87.970 MHz
- B. 87.985 MHz
- C. 88.015 MHz
- D. All of these
72. A device whose capacitance is deliberately made to be a function of the applied voltage
- A. Varactor diode
- B. UJT
- C. SAW
- D. Variable capacitor
73. A reactance modulator is one method of obtaining
- A. Indirect FM
- B. Direct FM
- C. Demodulation
- D. Low frequency filtering
74. A device, now available in IC form, is useful for direct FM and as one element in the phse-locked loop.
- A. AFC
- B. AGC
- C. VCO
- D. LPF
75. _____ is a frequency change process, whereby the phase deviation and frequency deviation are multiplied by some fixed constant.
- A. Translation
- B. Multiplication
- C. Division
- D. Addition
76. A circuit that has the function of demodulating the frequency-modulated signal.
- A. AFC
- B. Envelope detector
- C. Decoder
- D. Foster-Seeley discriminator
77. The ratio detector is superior to the slope detector because
- A. It is less sensitive to phase modulation
- B. It is less sensitive to noise spikes
- C. It is less sensitive to interference causing AM
- D. Both B and C
78. One implementation of a pulse averaging discriminator is
- A. A free-running multivibrator
- B. A crystal-controlled oscillator
- C. A quartz crystal filter
- D. A triggered multivibrator
79. 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 %
80. Two different signals can be coherent if they
- A. Have the same amplitude
- B. Are both sine waves of different frequencies
- C. Originate in the same physical equipment simultaneously
- D. Have the same frequency
81. A quadrature detector requires that
- A. Four gates bee provided
- B. The inputs are coherent
- C. The inputs are incoherent
- D. The inputs are identical
82. In a phase-locked loop, the VCO is the abbreviation for
- A. Variable coherent output
- B. VHF communication oscillator
- C. Voltage-controlled oscillator
- D. Vien-count oscillator (neutralized)
83. Identify an advantage, or advantages of a properly designed FM system.
- A. Relative immunity to atmospheric noise (lightning)
- B. Reduced bandwidth required
- C. No noise of any kind
- D. The noise figure is inversely proportional to the modulation index
84. The output of a balanced modulator
- A. LSB and USB
- B. LSB
- C. USB
- D. Carrier
85. If the modulation index of an AM wave is changed from 0 to 1, the transmitted power is
- A. Unchanged
- B. Halved
- C. Doubled
- D. Increased by 50%
86. Which of the following is not a baseband signal of modulation?
- A. Audio signal
- B. Video signal
- C. RF carrier
- D. Binary coded pulses
87. If the unmodulated level peak carrier amplitude is doubled in an AM signal, the perfect modulation is ________.
- A. 20
- B. 50
- C. 100
- D. 200
88. Balanced modulator circuit when inserted in the equivalent suppresses the ___________
- A. Carrier
- B. Upper sideband
- C. Lower sideband
- D. Baseband signal
89. The carrier of a 100% modulated AM wave is suppressed, the percentage power saving is __.
- A. 100 %
- B. 50 %
- C. 83 %
- D. 66.66 %
90. If the modulation index if an AM wave is doubled, the antenna current is also doubled, the AM system being used is
- A. H3E
- B. J3E
- C. C3F
- D. A3E
91. 100% modulation in AM means a corresponding increase in total power by _______.
- A. 100 %
- B. 50 %
- C. 75 %
- D. 25 %
92. A single-tone amplitude modulated wave has _______.
- A. 2 components
- B. 3 components
- C. 4 components
- D. 2n + 1 components
93. A carrier signal has ________.
- A. Constant peak amplitude
- B. Frequency range of 20 – 20,000 Hz
- C. A varying amplitude
- D. The information
94. The modulating system is _________ if the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant.
- A. Amplitude modulation
- B. Phase modulation
- C. Frequency modulation
- D. Pulse modulation
95. What is the modulation index of an FM signal if its modulating frequency is doubled?
- A. No effect
- B. Twice the original index
- C. Four times the original index
- D. One-half the original index
96. An AM transmitter is rated 1000 W at 100% modulation. How much power required for the carrier?
- A. 1000 W
- B. 666.6 W
- C. 333.3 W
- D. 866.6 W
97. Standard way of designating AM
- A. A3E
- B. B3E
- C. AHE
- D. C3F
98. _____ is the circuit used to detect frequency modulated signal.
- A. Discriminator
- B. Modulator
- C. Modem
- D. Detector
99. _____ is an information signal that is sent directly without modulating any carrier.
- A. C-band
- B. Q-band
- C. Baseband
- D. Broadband
100. Both frequency and phase modulation utilize ______ modulation.
- A. Digital
- B. Phase
- C. Amplitude
- D. Angle
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