FM Reviewer

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?


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?


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.


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


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.


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 _____________.


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





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.





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.


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


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


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


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.


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


d. pulse-averaging discriminator

122. Which of the frequency demodulator is considered the best overall?

a. ratio detector

b. PLL

c. quadrature


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?


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


c. PLL


149. A variation of Foster-Seeley discriminator widely used in oldr TV receiver designs

a. ratio detector

b. PLL


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


d. stagger-tuned detector

188. Which of the following discriminator circuits has its diodes in series?

a. ratio


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


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?


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?


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

FM Reviewer

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