Acoustic & Broadcasting [MITRC refresher] 1. a. b. c. d. Which best describe the sound wave? It may be longitudinal It is always transverse It is always longitudinal All of the above 2. a. b. c. d. Which of the following can not travel through a vacuum? Electromagnetic wave Radio wave Soundwave Light wave 3. a. b. c. d. Through which medium does sound travel fastest? Air Water Steel Mercury 4. a. b. c. d. Speed that is faster than that of sound. Ultrasonic Supersonic Subsonic Transonic 5. a. b. c. d. What is the speed of sound in air at 20°C? 1087 ft/s 1100 ft/s 1126 ft/s 200 ft/s 6. a. b. c. d. Calculate a half wavelength sound for sound of 16000 Hz 35 ft 10 ft 0.035 ft 100 ft 7. a. b. c. d. The lowest frequency that a human ear can hear is 5 Hz 20 Hz 30 Hz 20 Hz 8. a. b. c. d. Sound that vibrates at frequency too high for the human ear to hear (over 20 kHz) Subsonic Ultrasonic Transonic Stereo 9. a. b. c. d. The frequency interval between two sounds whose frequency ratio is 10 Octave Half octave Third-octave Decade 10. a. b. c. d. A 16 KHz sound is how many octaves higher than a 500 Hz sound 2 5 4 8 11. a. b. c. d. Sound waves composed of but one frequency is a/an Infra sound Pure tone Structure borne Residual sound 12. a. b. c. d. Sound wave has two main characteristics which are Highness and loudness Tone and loudness Pitch and loudness Rarefactions and compressions 13. a. b. c. d. When waves bend away from straight lines of travel, it is called Reflection Diffraction Rarefaction Refraction 14. which a. b. c. d. The amplitude of sound waves, the maximum displacement of each air particle, is the property perceive as _____ of a sound Pitch Intensity Loudness Harmonics 15. a. b. c. d. It is the weakest sound that average human hearing can detect. SPL = 0 dB Threshold of hearing Reference pressure = 2 x 10-5N/m2 A, b, c 16. a. b. c. d. What is a device that is used to measure the hearing sensitivity of a person? Audiometer OTDR SLM Spectrum analyzer 17. What is the device used in measuring sound pressure levels incorporating a microphone, amplification, filtering and a display. a. Audiometer b. OTDR c. SLM d. Spectrum analyzer 18. of the a. b. c. d. 19. What weighted scale in a sound level meter gives a reading that is most closely to the response human ear? Weighted scale A Weighted scale B Weighted scale C Weighted scale D For aircraft noise measurements, the weighting scale that is used is _____. a. b. c. d. Weighted scale A Weighted scale B Weighted scale C Weighted scale D 20. a. b. c. d. It is the device used to calibrate an SLM? Microphone Pistonphone Telephone Filter 21. a. b. c. d. _____ is the sound power measured over the area upon which is received. Sound pressure Sound energy Sound intensity Sound pressure level 22. a. b. c. d. A measure of the intensity of sound in comparison to another sound intensity Phon Decibel Pascal Watts 23. a. b. c. d. Calculate the sound intensity level in dB of a sound whose intensity is 0.007 W/m2. 95 dB 91 dB 98 dB 101 dB 24. a. b. c. d. What is the sound pressure level for a given sound whose RMS pressure is 200/m2? 200 dB 20 dB 140 dB 14 dB 25. a. b. c. d. What is the sound intensity for an RMS pressure of 200 Pascal? 90 W/m2 98 W/m2 108 W/m2 88 W/m2 26. a. b. c. d. The sound pressure level is increased by _____ dB if the pressure is doubled. 3 4 5 6 27. a. b. c. d. The sound pressure level is increased by _____ dB if the intensity is doubled. 3 4 5 6 28. a. b. c. d. If four identical sounds are added what is the increase in level in dB? 3 4 5 6 29. The transmission of sound from one room to an adjacent room, via common walls, floors or ceilings. a. Flanking transmission b. Reflection c. Refraction d. Reverberation 30. a. b. c. d. _____ is the continuing presence of an audible sound after the sound source has stop. Flutter echo Sound concentration Sound shadow Reverberation 31. a. b. c. d. Required time for any sound to decay to 60 dB Echo time Reverberation time Delay time Transient time 32. a. b. c. d. A room containing relatively little sound absorption Dead room Anechoic room Live room Free-field 33. A room in which the walls offer essentially 100% absorption, therefore simulating free field conditions. a. Dead room b. Anechoic room c. Live room d. Closed room 34. Calculate the reverberation time of the room, which has a volume of 8700 ft3 and total sound absorption 140 sabins. a. 0.3 sec b. 3.5 sec c. 3 sec d. 0.53 sec 35. It is an audio transducer that converts acoustic pressure in air into its equivalent electrical impulses a. Loudspeaker b. Amplifier c. Baffle d. Microphone 36. a. b. c. d. _____ is a pressure type microphone with permanent coil as a transducing element. Dynamic Condenser Magnetic Carbon 37. a. b. c. d. A microphone which has an internal impedance of 25 kΩ is _____ type. High impedance Low impedance Dynamic Magnetic a. 4 6 8 10 46. d. 10 dB b. b. -10 dB b. c.38. What is its rated efficiency? a. a. c. a. Tweeter b. d. d. It describes the output of a microphone over a range of frequencies. a. A or C 40. If the rated efficiency of the loudspeaker is -60 dB. _____ is measure of how much sound is produced from the electrical signal. Mid-range d. What is the maximum intensity 300 ft from it? a. b. Sensitivity Distortion Efficiency Frequency response 41. a. b. Directivity Sensitivity Frequency response All of the above 42. b. Woofer c. It is a transducer used to convert electrical energy to mechanical energy. b. A loudspeaker radiates an acoustic power of 1 mW if the electrical input is 10 W. d. c. d. 20 dB c. -20 dB c. c. c. a. a. Speaker is a device that Converts sound waves into current and voltage Converts current variations into sound waves Converts electrical energy to mechanical energy Converts electrical energy to electromagnetic energy 45. An amplifier can deliver 100 W to a loudspeaker. Microphone Baffle Magnetic assemble Driver . A microphone that uses the piezoelectric effect Dynamic Condenser Crystal Carbon 39. 40 dB 44. 30 dB d. d. b. c. -40 dB 43. The impedance of most drivers is about _____ ohms at their resonant frequency. _____ is a type of loudspeaker driver with an effective diameter of 5 inches used at midrange audio frequency. -30 dB d. b. a. What is the unit of loudness? Sone Phon Decibel Mel 53. Dividing network c. d. Navigation b. Dolby DBx dBa dBk 51. b. speech. b. d. _____ is early reflection of sound. a. b. c. Using a microphone at less than the recommended working distance will create a _____ which greatly increases the low frequency signals. a. Roll-off b. Suspension system b. b. What is the loudness level of a 1KHz tone if its intensity is 100 phons 105 phons 110 phons 100 phons 1 x 10-5W/cm2? 55. Echo Pure sound Reverberation Intelligible sound 50. b. What is the process of sending voice. What is the frequency tolerance for the RF carrier in the standard AM radio broadcast band? . a. Noise reduction system used for film sound in movie. Drop out d. a. d. a. Panel board 49. It is an enclosure used to prevent front and back wave cancellation. d.47. d. A circuit that divides the frequency components into separate bands in order to have individual feeds to the different drivers. c. d. A unit of noisiness related to the perceived noise level Noy dB Sone Phon 54. None of the choices 52. Broadcasting d. Telephony c. a. c. Proximity effect c. music or image intended for reception by the general public? a. Mixing 56. c. Loudspeaker Driver Baffle Frame 48. a. c. c. Magnet assembly d. 10 c. AM BC band is ____. How many AM stations can be accommodated in a 150-kHz bandwidth if the highest modulating frequency is 10 kHz? a. d. Artificial Antenna 61. a. c. 5 b. a. a. Primary Service Area Secondary Service Area Intermittent Service Area Quarternary Service Area 60. Zero 20 Hz 10 Hz 20 KHz 57. a. The service area where the signal is not subject to fading and co-channel interference. d. Main Tx c. What are the frequency limits of the MF BC band? 300-3000 kHz 3-30 MHz 535-1605 kHz 88-108 MHz 63. Vertical Horizontal Circular Elliptical 58. a. c. b. 14 65. d. d. 15 c. b. The center to center spacing between two adjacent stations in the Phil. Short wave broadcasting operates in what band? MF HF . 20 62. The operating power of the auxiliary transmitter shall not be less than _____% or never greater than the authorized operating power of the main transmitter. 7 d. b. b. c. c. Secondary Tx d. Auxiliary Tx b. 10 b. 9 kHz 200 kHz 36 kHz 800 kHz 64. c. d.a. b. a. The part of a broadcast day from 6 PM to 6 AM local time Daytime Nighttime Bed time Experimental period 59. c. The transmitting antenna for an AM broadcast station should have a _____ polarization. a. b. d. a. It is a resistive load used in place of an antenna to test a transmitter under normal loaded condition without actually radiating the transmitter’s output signal. b. 15 d. d. c. c. What is the spacing between any two adjacent channels in the FM broadcast band? 20 KHz 36 KHz 200 KHz 800 KHz 70. Stereo system c. a. SCA b. The first channel in the FM BC band has a center frequency of 88 MHz 88. c. d. a. b. d. d. left. Pilot transmission d. d. d. b. b. The carrier frequency tolerance for FM broadcasting is _____. a.c. a. VHF VLF 66. a. used to create a multidimensional effect on the receiver? a. c. b. a. and right. One of the broadcast transmission auxiliary services is: Remote pick-up STL Communication. What is the radio transmission of two separate signals.1 MHz 88. a. a. c. What is the modulation used by the stereophonic subcarrier? FM PM ISB DSB 74. c. What does the acronym STL stand for? Station-to-link Signal-to-loss-ratio Shout-to-live Studio-to-transmitter-link 67. One of the main considerations in the selection of antenna site is (AM) Conductivity of the soil Height of the terrain Elevation of the site Accessibility 68. d. d. What is the pilot signal for stereo FM? 4. c. b. Monophonic transmission 72.25 MHz 10 kHz 19 KHz 38 KHz . 25 kHz 2 kHz 20 kHz 30 kHz 73. Coordination and Control All of the above 69. b. d. b. b.3 MHz 108 MHz 71. c. b. EBS c. L+R L–R Both a & b 67 KHz 80. a. c. A monaural FM receiver receives only the _____ signal of a stereo multiplex transmission. c. 67 76 38 19 79. in what form are the L – R signals? AF DSBSC 19 kHz 38 kHz 81. Class D b. The class of FM station. which has an authorized radiated power not exceeding 125 KW: Class C Class A Class D Class B 83. c. The normal frequency for an SCA subcarrier is _____ KHz. Class A d. b. Class B 84. does a monaural receiver produce all the sounds that a stereo Yes No Either a or b Neither a or b 76. b. An FM broadcast station. a. d. SCA 82. above average terrain . Where is the pre-emphasis added in a stereo FM system? Before the matrix at the TX Before the matrix at the RX After the matrix at the TX After the matrix at the RX 78. a. c. EIA d. An additional channel of multiplex information that is authorized by the FCC for stereo FM radio stations to feed services such as commercial-free programming to selected customers. does? a. d. which has an authorized transmitter power not exceeding 10 KW and ERP not exceeding 30 KW: a. With stereo FM transmission. d. a. A class of FM station which is limited in antenna height of 500 ft.75. c. d. a. d. d. Class C c. STL b. c. Where is de-emphasis added in a stereo FM system? Before the matrix at the TX Before the matrix at the RX After the matrix at the TX After the matrix at the RX 77. When fed to the stereo FM modulator. c. a. d. a. b. b. b. b. a.75 MHz 45. PM b. b.75 MHz.a.25 MHz. b. d. 10 b. Class D Class C Class A Class B 85.25 MHz 45. What type of broadcast service might have their antennas on top of hills? FM AM TV A&C 86. c. What is the main reason why television picture signal uses amplitude modulation. 600 89. 45. Eliminate attenuation of both video and audio c. FM c. Better efficiency b. What kind of modulation is used for the sound portion of a commercial broadcast TV transmission? a.75 MHz 41. 20 c. d. How many international commercial AM broadcast channels can fit into the bandwidth occupied by a commercial TV station? a. 200 c. b. 30 d. d. AM 90. 41. a. To minimize interference between signals at received end 92. d. The picture and sound carrier frequencies in a TV receiver are _____ respectively. c. 25 kHz 800 kHz 80 kHz 200 kHz 91. b. 125 d. How are guardbands allocated in commercial FM stations? 25 kHz on either sides of the transmitting signal 50 kHz on each side of the carrier 75 kHz deviation 15 kHz modulation 87. 41. b. 40 88.25 MHz 93. a. Estimate the bandwidth occupied by the sound portion of a TV transmission in US.25 MHz. d. How many commercial FM broadcast channels can fit into the bandwidth occupied by a commercial TV station? a. C3F d. c. c. c. a.75 MHz. What is the separation between visual and aural carrier in TV broadcasting? . 45. 41. 100 b. while voice is frequency modulated? a. Maintain synchronized scanning between transmit and received video d. 75 MHz 59. c.75 MHz 96. d.25 MHz 55.5 MHz 5. b.25 MHz 175. a.83 MHz 98. what is the frequency of the tuner’s local oscillator. a. If the sound carrier for UHF channel 23 is 529. 571 MHz b. b. d. c.83 MHz 214. c. 11 and 13 are known as _____. b. d. What is the separation between the lower limit of a channel and the aural carrier? 1.5 MHz 5.75 MHz 0. What is the visual carrier for channel 12? 205. b. 498 MHz d. 1. a.25 MHz 4. 500 MHz 99.25 MHz 65. when turned to this channel? a. a.75 MHz 0.a. What is the aural carrier for channel 3? 61.25 MHz 58.75 MHz 97. TV channels 7.25 MHz 94. What is the frequency tolerance in the color carrier of TV broadcasting? 2 kHz 20 Hz 10 Hz 1 kHz 100. a.25 MHz 65. c. b. d. c. What is color subcarrier for channel 2? 68.24 MHz 101.26 MHz 174 MHz 175. c. d. What is eliminated by using interlaced scanning? Noise Excessive BW Frame .25 MHz 95. c. b. Mid band UHF Low band UHF High band VHF low band UHF 102.75 MHz 59.83 MHz 211.25 MHz 4. d. d. a b c d What is the exact picture carrier frequency for frequency for channel 7 offset by – 10 KHz? 175. b. b.25 MHz 55. a. a.75 MHz. c. 511 MHz c. 22% blue 104. d. What percentage of the primary colors used in color TV are needed to produce the brightest white? 30% red. 33% blue 50% red. cyan Black. c. a. where 1 represents the maximum signal possible.4 106. 59% green. 1. Suppose the signal from a color camera has R=0.498 b. d. b.305 0. indigo. 0. a. c.8. Determine the value at the luminance signal a. c. yellow. b.304 0. b. calculate the chrominance signal 0. a. white. Which of the following consist of two of the three primary colors in television signal? a) red. a. 0. Flicker 103. The three complementary colors are: White. c. c. 22% blue 58% red. a. fushcia 108. b. b) c) yellow. d.1325 d. 20% green.4 and B=0. In the previous problem. Brightness variations of the picture information are in which signal? I Q Y Z . d. d. When the colors Magenta and Yellow are mixed the resultant color is: Red White Blue Green 109. c. d. a. 33% green. d. c. cyan Violet. b. Red Yellow Green Blue The color with the most luminance is 105. b. b. The studio camera produces a luminance signal that contains information about The musical content The speech content The brightness of the scene The color content of the scene 111.2. 0. violet. a. b. d. a. 11% blue 33% red. c.498 0.254 c. G=0.d. and d) blue A and B B and C C and D A and D 110. gray Yellow. 28% green. magenta.022 107. b. a. b. c. c. b. d. The signal that will give the exact color wavelength is _____.25 MHz 3.58 MHz 4. d.5 MHz? I signal Q signal Y signal Z signal 114. gain of a. a. Which of the following is the color video signal transmitted as amplitude modulation of the 3. What does aspect ratio mean? Ratio of the screen width to its height Ratio of the screen height to its width Ratio of the screen diagonal to its width Ratio of the screen diagonal to its height 119.112.92 MHz 118. c. a. The _____ affects the difference between black and white on the picture tube and controls the the video amplifier Brightness control Volume control Power control Contrast control 115. a. d. c. b. d.58 signal in quadrature with bandwidth of 0 to 0. a. b. Which of the following is not a requirement for a color TV signal? compatibility with b lack and white receivers Within 6 MHz bandwidth Simulate a wide variety of colors Functional with baron super antenna 116. c. d. MHz C a. c. d.58 signal with bandwidth of 0 to 1. d. Which of the following is the color video signal transmitted as amplitude modulation of the 3. b. c. d. a. b. c. How many electron beams actually leave the electron gun of a single-gun color CRT? 1 2 3 1/3 117. What is the difference between the sound carrier and color subcarrier frequencies? 1. d.5 MHz 0. MHz C a. c. b. Hue Saturation Carrier Monochrome . b. What is the aspect ratio for HDTV system? 4/3 9/7 19/6 16/9 120.3 MHz? I signal Q signal Y signal X signal 113. c. In a TV receiver. What is the North American TV standard video? PAL SECAM NTSC FCC 129. c. a. d. d. 25 kHz b. c. b. b. b. c. b. a. 75 kHz d. a. What is the maximum allowable frequency deviation in the audio section of a TV signal for PAL/SECAM? a. d. 50 kHz c. What scheme is employed to cause the electron beam in the TV receiver and the electron in the studio camera to track identically? Interlacing NTSC Interleaving Transmission of sync pulses 126. c. d.121. c. d. 127. a. The _____ ensures that the electron beam will strike the correct phosphor dot on the TV screen. Which of the following represents the intensity of a given color? Hue Saturation Carrier Monochrome 122. c. a. b. a. Coating Aperture Mask Diplexer Duplexer 123. b. what is the horizontal signal frequency? 30 Hz 60 Hz 15750 Hz 157625 Hz 124. a. what is the vertical signal frequency? 30 Hz 60 Hz 15750 Hz 157625 Hz 125. What is the frame frequency in the US TV system? 30 Hz 60 Hz 15750 Hz . In a TV receiver. d. 100 kHz 130. Equalizing pulses in TV are sent during Horizontal blanking Vertical blanking The serrations Equalizing intervals What is the return of the electron beam in a CRT from right to left or from bottom to top? Relay Flyback Utilization Resolution 128. b. beam a. c. b. a. c. d. b. d. what is the relationship between the amplitude of the signal and the intensity of the electron beam in the receiver picture tube? a. Fitting c. 157625 Hz 131. Vidicon d. a. b.S. c.d. How many horizontal lines are used to develop a TV raster? 615 525 750 15750 134. a. a. The greater the amplitude the lighter the picture d. Interlacing b. c. b. Sneaking d. d. The lower the amplitude the darker the picture c. Interleaving 139. a. b. c. What is the process of placing the chrominance signal in the band space between portions of the luminance signal? a. c. The channel width in the U. Image orthicon b. If there are 625 lines per TV picture then the number of lines per field are: 1250 312. b. d. It is the popular TV camera designed with much smaller package and lower cost than its earlier designs a. c. What determines the maximum number of vertical picture elements? Number of frames per second Number of lines on the screen Number of pixels Number of fields per second 133. What is the highest video frequency set by the FCC for commercial TV? 4. d. b. a. d.2 MHz 15 MHz 6 MHz 5. The greater the amplitude the darker the picture b.5 625 2500 138. a. In a composite video signal. c. TV system is : 2 MHz 6 MHz 7 MHz 8 MHz 135. d.67 μs 100 μs . d.2 μs 63. b. How much time elapses between the start of one horizontal sync pulse and the next? 10. Plumbicon 136. Iconoscope c. No effect 137.5 MHz 132.5 μs 16. Transmitter d. c. b. c. Signal whose physical quantity varies continuously with time a.140. d. a. d. b. b. c. The components of composite video signal are: Chroma signal Blanking pulse Synchronizing pulse All of these 143. d. a. A portion in a communications system. The camera tube that uses selenium. c. which processes the information so that it will become suitable to the characteristic of the transmission medium a. What section of a TV receiver determines the bandwidth and produces the most signal gain? RF amplifier Audio amplifier IF amplifier Tuned circuit Modulation [MITRC refresher] 1.750 Hz for horizontal sync and scanning 60 Hz for vertical sync and scanning 31. b. It is the quality of the TV picture after imperfections Aspect ratio Utilization ratio A1 Monochrome 145. Multiplexer 2. a. Modulation c.500 Hz for the vertical scanning frequency 141. d. c. a. Encoder b. arsenic and tellurium Plumbicon Vidicon Saticon Silicon Vidicon 142. a.500 Hz for the equalizing pulses and serrations in the vertical sync pulse 31. What is the smallest amount of information that can be displayed on a television screen? Blip Burst Pixel Bits 144. b. b. d. Which of the following frequencies is wrong? 15. c. a. d. Digital . – 82 dBm b. dBW b. A 10 db pad has an output level of -3dBm. When the power ratio of the output to input of a circuit is 200. 23 b. Correctness 4. The level at the input is: . dBk c. – 90 dBm c. Information 3. – 85 dBm d. 46 c. Indicate the voltage level in dB with reference to one volt. Digital information is processed with a specified degree of a. What is the reference level for random noise measurement. Discrete d. – 46 6. dBV 5. What is the gain in dB? a.b. FIA weighted? a. This unit is used in video or TV measurement a. Fidelity b. Sensitivity d. Analog c. – 23 d. dBm d. Accuracy c. – 77 dBm 7. 3. 1 dBm d.8 mW has a loss of: a.3 dBm c. Noise b. Noise b. 2. – 4. – 13 dBm 9. A power level of 50 μW could be expressed as: a. 13 dBm b.98 μW d. Attenuation d. Distortion c. A system having an input power of 2 mW an output power of 0. – 7 dBm c.69 dBm b. Aliasing c.98 mW 10.98 dBm b. 3. Signal waveform perturbation or deviation caused by imperfect response of the system to the desired signal a.98 dB c.a. Is the reduction of signal amplitude as it passed over the transmission medium? a. 1 dBm d. 1. Interference . Interface 11. 7 dBm 8. 1. Distortion d. 4. dBm c. A more precise evaluation of the quality of a receiver as far as noise is concerned. Harmonics d. set at – 85 dBm a.5 dB b. S/N b. Distortion c. Amplification 13. other transmitters. VSWR . Which noise figure represents the lowest noise? a. power lines and machinery. such as. Noise b. dBa b.7 dB d. dBa0 d.0 dB c. 2. pWp 16. Signal contamination by extraneous or external sources.1 dB 15. Modulation c. Signal attenuation can be corrected by a. a. Filtering b. a. Denote the interference of noise in dB above an adjusted reference noise. Interference 14. 1. Equalization d. 3.12. The adjusted reference noise level was a 1 kHz tone. Noise limiter c. a. that is inserted in series with the a-c power cord of an electronic device which allow the 60-Hz current to pass and suppressed high frequency noise components. Noise floor d. Extra-terrestrial noise is observable at frequencies from a. Noise figure for an amplifier with noise is always a. 0 dB b.c. A circuit often used in radio receivers that prevents externally generated noise from exceeding certain amplitude. 8 Mhz to 1. 0 to 20 KHz b. 5 to 8 GHz d. Noise clamper 20. Noise limiter d. usually consisting of capacitance and/or inductance.43 GHz c. a. Infinite c. Noise margin 17. Less than 1 d. Noise quieting 19. 15 to 60 MHz . Noise factor d. Noise filter b. Noise floor b. Noise filter c. A passive circuit. Greater than 1 18. They are also called noise clippers. Modulator circuit performs what mathematical operation on its two inputs? a. what happens? a. Addition b.3. Carrier drops to zero c. Carrier variation 25. The values of Vmax and Vmin as read from an AM wave on an oscilloscope are 2. If m is greater than 1. The carrier frequency remains constant. Trace b. Waveshape c. The outline of the peaks of a carrier has the shape of the modulating signal and is called the a. Square root 23. The information signal amplitude changes the carrier amplitude. Carrier frequency shifts d. 41. Multiplication c. b. Division d. c. Envelope d. Information signal is distorted 24. The percentage of the modulation is a.21. d. Which of the following is not true about AM? a. The carrier frequency changes. 22. Normal operation b. The carrier amplitude varies.7 percent b.4 percent .8 and 0. 10. 0 W 29. For 100 percent modulation. 1.c.5 W d. 33.6 percent d. 887 and 873 kHz 27. 873 and 887kHz b.3 percent c.6 amperes.5 kHz d. 0. 50 percent d. The total sideband power is a. 25 percent b. 35 percent b. An AM transmitter antenna current is measured with no modulation and found to be 2. The percentage of modulation is a. The LSB and USB are respectively.5 and 876.8 W b. The percentage of modulation is 80 percent. 100 percent 28. what percentage of carrier power is in each sideband? a. 89 percent 30.3 percent 26.5-kHz sine wave. 883. The typical audio modulating frequency range used in radio and telephone communications is . An AM signal has a carrier power of 5W. 876. A carrier of 880 kHz is modulated by a 3. 93. 4.5 kHz c. a.5 and 883. 70 percent c.6 W c. 42 percent d. 2. 80. 2 MHz c. Lincompex d. An AM signal with a maximum modulating signal frequency of 4. A filter selects the difference signal. 50 Hz to 15 kHz c. 300 Hz to 3 kHz 31. The output is a. 50 Hz to 5 kHz b. Splatter c. 1. The letter-number designation B8E is a form of modulation also known as a. Deviation 34. 3. Independent sideband emission c. 5 MHz d. 18 kHz 32. Envelope d. Vestigial sideband transmission .8 MHz mixed with a local oscillator of 5 MHz.75 kHz c. Sidebands b. 100 Hz t 10 kHz d.5 kHz b. Pilot-carrier system b.a. 4.8 MHz b. An input signal of 1. 9 kHz d. What is produced by over modulation in AM? a. 6.8 MHz 33.5 kHz as a total bandwidth of a. 6. 5 MHz d. The deviation ratio is a. 500 kHz b. 0. 1. Balanced bridge modulator 37. Both a and b 36. 20 39. 2. What is the third character in the emission designation for telephony? a. F b.5 MHz.5 d.35. 5 c. The outputs are a. Full-wave bridge rectifier c. B c. D d. 8 c. Lattice modulator d.2 b. The inputs to a balanced modulator are 1 MHz and a carrier of 1. E 38. 8 . A widely used balanced modulator is called the a. 5 b.5 Mhz c. Diode bridge circuit b. 12. A 100-MHz carrier is deviated 50 kHz by a 4-kHz signal a. The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. 100 d. 66. If the carrier of a 100 percent modulated AM wave is suppressed. the percentage power saving will be a. Class C amplifier d. 50 b. amplifier following the modulated stage must be a. Pre-amplifying the whole audio band d. Linear devices b. 40 40.d. Capture effect b. Dominating syndrome 41. A pre-emphasis circuit provides extra noise immunity by a. R3E . H3E b. Amplifying the higher audio frequencies c. Quieting factor d. Blot out c. One of the following transmits only one sideband a. In a low-level AM system. Converting the phase modulation to FM 44. Harmonic devices c. Boosting the bass frequencies b. 150 c. The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the a.66 43. Nonlinear devices 42. An increase in transmitter power from 25 W to 30 W will cause the antenna current to increase from 700 mA to . A3E d. 56. B8E 45. Oscilloscope c. Load d. Source c. J3E d.25 kHz d. Digital counter d. Spectrum analyzer b. B3E 48. Frequency b. 53. 112. 48 kHz c. What type of emission is frequency modulation? a. What is the carrier swing of an FM transmitter when modulated by 75%? a.5 kHz 49. Modulation 47.2 kHz b. G3E c. F3E b. _____ is an electronic instrument used to show both the carrier and the sidebands of a modulated signal in the frequency domain a. AM transmission power increases with _____ a. Frequency counter 46.c. 4 MHz d.7 MHz is tuned to 98. 88. Receiver quieting . 120. The function which tends to silence the receiver in the absence of transmitted carrier a.1 MHz 52. Intermodulation interference c. AGC d.a.3 MHz b. The term used to refer to the condition where the signals from a very strong station are superimposed on other signals being received a. AGC d. 800 mA b. AFC 53. What is the numerical value of the image frequency? a. Squelch b. AFC 51. 840 mA 50. Muting c. Cross-modulation interference b. Squelch b. 767 mA d.0 MHz c. _____ is the function which tends to maintain the sound volume level of a voice receiver nearly constant for a large signal strength range a. 750 mA c. Muting c. An FM receiver with an I-F of 10. 109.7 MHz. 77. AF amplifier c.5 and a modulating frequency of 10 kHz? . Squelch gain rollback d. detector. IF amplifier. RF amplifier. Tuner. mixer. VHF transmitter d. the deviation ratio is commonly one and the highest audio frequency is generally limited to a. AF amplifier 55. FM receiver c. Desensitizing 58. AF amplifier b.500 Hz 56. In a narrow-band FM system. FM transmitter b. VHF receiver 57. Quieting b. What is the approximate bandwidth of an FM with a modulation factor of 12. 300 Hz b. Cross-modulation interference c. 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. 7. local oscillator. Which of the following contains de-emphasis circuit? a. detector. RF amplifier. 10.000 Hz c. Stages that are common to both AM and FM receivers a. detector d.000 Hz d. Tuner. Capture effect 54. IF amplifier. 3. Local oscillator. frequency discriminator.d. 4 K b. Thermal agitation b.0 μV c. 1. 4.4 b. 0. 3.a. 40 μV b. 174 K c. Auto ignition c. 394 d. 20 kHz b. Which of the following is not a source of external noise? a. The sun . 400 μV d.6 a. What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17°C? a. Calculate the noise figure of the amplifier whose Req equals 2518 Ω (RT = 600 Ω) if it’s driven by a generator whose output impedance is 50Ω a. 250 kHz d.394 61. 17 K 62. 39.94 c. A receiver connected to an antenna whose resistance is 50 Ω has an equivalent noise resistance of 30 Ω. An amplifier operating over the frequency range of 455 to 460 kHz has a 200 kΩ input resistor. 45 kHz 59.0 mV 60. 270 kHz c. Calculate its equivalent noise temperature if the noise figure is equal to 1. 17.74 K d. 4. A network that has an input of 75 dB and an output of 35dB. 2. Distortion c. Fluorescent lights 63. Higher power d. The loss of the network is _____ -40 dB . receiver.3 μV b. a. Not changed b. What is the noise voltage across a 300 Ω input resistance to a TV set with a 6 MHz bandwidth and temperature of 30°C? a. what is the result of over modulation? a. Tripled d. 3.d. What are the basic elements of communications system? a. Excessive bandwidth 66. Lower frequency b.5 μV d. Transmitter. the signal power is _____ a. transmission channel c. 6. Quadrupled c. Source. Doubled 65.4 μV 64.8 μV c. transmitter b. 5. Sender and receiver 67. transmission channel. transmission channel. If bandwidth is doubled. Information. In an FM transmitter. receiver d. Rest frequency d.2 b.b. 320.0 69. Void band 71. -40 dBm d. 2 c. An interfering signal with a frequency equal to the received signal plus twice the IF is called a.1 d. Band gap d. Center frequency c. what voltage ratio does the gain of 50 dB represent? a. 315. 1 b. 316. 40 dB c. 325. 3 . If an amplifier has equal input and output impedances.2 c. Image frequency b. Interference frequency 70. Guard bands b. 40 dBm 68. Subcarriers that are arranged so that the channels occupying adjacent frequency band with some frequency space between them is known as a. What is the lowest number of sections required by communications receiver? a. AM bands c. Detector 75. The superheterodyne circuit uses a local oscillator to _____ with the RF signal of the station and converts the carrier to the intermediate frequency a. Mix c.035 MHz c. RF Amplifier b. 4 72. The power handling capability d. The frequency stability 73. Beat b.51 MHz d. The gain of the amplifier c. IF Amplifier d. LO c. 1. 3. What circuit accompanies a mixer? a.d.5 MHz. What must be the local oscillator frequency? . What determines the selectivity of a receiver? a. The bandwidth of the tuned circuits b. For an IF frequency of 455 kHz. Heterodyne d. All of the above 76. 351 kHz 74. what must be the LO frequency when receiving a 580 kHz transmission? a. The local FM stereo rock station is at 96. 1035 MHz b. 09 MHz b. Band pass filter and mixer c. mixer and RF amplifier . In an FM receiver. 4. Local oscillator.5 kHz c. Mixer. 3688 kHz 78. Limiter 79. which circuit removes amplitude variations? a. In an FM receiver. a. A superheterodyne is tuned to 2738 kHz. RF amplifier. What connects the front-end circuit of a VHF TV superheterodyne receiver? a.9 MHz 77. AFC b. 112.a. Discriminator 80. 107. Limiter d. 4385 kHz d. Exciter b.9 MHz b. Mixer c.5 MHz d. the circuit that keeps the receiver tuned exactly to the desired station is _____ a.2 MHz c. AGC c. Discriminator d. RF amplifier and AFC b. 93. What is the image frequency? 3. 105. The IF is 475 kHz. Local oscillator. d The information signal amplitude changes the carrier amplitude.d. 1 2 3 4 5 6 7 Having an information signal change some characteristic of a carrier signal is called a Multiplexing b Modulation c Duplexing d Linear mixing Which of the following is not true about AM? a The carrier amplitude varies. b The carrier frequency remains constant. c The carrier frequency changes. what happens? a Normal operation b Carrier drops to zero c Carrier frequency shifts d Information signal is distorted . Encircle the letter which corresponds to your answer. AGC and antenna Modulation Multiple choice. The opposite of modulation is a Reverse modulation b Downward modulation c Unmodulation d Demodulation The circuit used to produce modulation is called a Modulator b Demodulator c Variable gain amplifier d Multiplexer A modulator circuit performs what mathematical operation on its two inputs? a Addition b Multiplication c Division d Square root The ratio of the peak modulating signal voltage to the peak carrier voltage is referred to as a The voltage ratio b Decibels c The modulation index d The mix factor If m is greater than 1. respectively. which of the following is true? a m=0 b m=1 c m<1 d m>1 The outline of the peaks of a carrier has the shape of the modulating signal and is called the a Trace b Waveshape c Envelope d Carrier variation Overmodulation occurs when a Vm > Vc b Vm < Vc c Vm = Vc d Vm = Vc = 0 The values of Vmax and Vmin as read from an AM wave on oscilloscope are 2.6 % d 93.5 kHz c 883.5 and 876.3.3 % The new signals produced by modulation are called a Spurious emissions b Harmonics c Intermodulation products d Sidebands A carrier of 880 kHz is modulated by a 3.5 kHz sine wave. the percentage of modulation is a 10.8 and 0. The LSB and USB are. a 873 and 887 kHz b 876.8 9 10 11 12 13 14 For ideal AM.4 % c 80.7 % b 41.5 kH d 887 and 873 kHz A display of signal amplitude versus frequency is called the a Time domain b Frequency Spectrum c Amplitude Spectrum d Frequency Domain 15 Most of the power in an AM signal is in the a Carrier b Upper sideband .5 and 883. The power is 440W. With modulation. the current rises to 2. The percentage of modulation is a 35 % b 70 % c 42 % d 89 % What is the carrier power in the problem above if the antenna resistance is 75 ohms? a 195 W b 631 W c 507 W d 792 W In an AM signal.6 W c 2.8 W b 1. The power in one sideband is a 85 W b 110 W c 170 W d 610 W An AM transmitter antenna current is measured with no modulation and found to be 2. the transmitted information is contained within the a Carrier b Modulating signal c Sidebands d Envelope 22 An AM signal without the carrier is called a(n) a SSB b Vestigial sideband c FM signal d DSB 23 What is the minimum AM signal needed to transmit information? a Carrier plus sidebands .3 % c 50 % d 100 % An AM transmitter has a percentage of modulation of 88. what percentage of power is in each sideband? a 25 % b 33.16 17 18 19 20 21 c Lower sideband d Modulating signal An AM signal has a carrier power of 5 W. the percentage of modulation is 80% the total sideband power is a 0.6 amperes. The carrier power is 440 W.9 amperes.0 W For 100 % modulation.5 W d 4. 5 kHz has a total bandwidth of a 4. which sideband is the best to use? a Upper b Lower c Neither d Depends upon the use The typical audio modulating frequency range used in radio and telephone communication is a 50 Hz to 5 kHz b 50 Hz to 15 kHz c 100Hz to 10kHz d 300 Hz to 3 kHz An AM signal with a maximum modulating signal frequency of 4.5 kHz b 6.75 kHz c 9 kHz d 18 kHz The modulation system used for telegraphy is a Frequency-shift keying b Two-tone modulation c Pulse-code modulation d Single-tone modulation 29 The process of translating a signal. with or without modulation. to a higher or lower frequency for processing is called a Frequency multiplication b Frequency division c Frequency shift d Frequency conversion 30 Frequency translation is carried out by a circuit called a a Translator b Convertor c Balanced modulator d Local oscillator .24 25 26 27 28 b Carrier only c One sideband d Both sideband The main advantage of SSB over standard AM or DSB is a Less spectrum space is used b Simpler equipment is used c Less power is consumed d A higher modulation percentage In SSB. This type of pulse modulation is called a Pulse duration modulation b Pulse amplitude modulation c Pulse code modulation d Pulse position modulation 33 An SSB transmitter produces a 400-V peak to peak signal across a 52-Ω antenna load.2 MHz c 5 MHz d 6. and which vary in number according to the loudness of the voice.8 MHz 32 One type of pulse communications system uses pulse that appear as a group. The output is a 1.8 MHz b 3. the negative half of the AM wave is supplied by a(n) a Tuned circuit b Transformer c Capacitor d Inductor 38 Amplitude modulation can be produced by a Having the carrier vary a resistance b Having the modulating signal vary a capacitance c Varying the carrier frequency d Varying the gain of an amplifier 39 Amplitude modulators that vary the carrier amplitude with the modulating signal by passing it through an attenuator work on the principle of .8 MHz is mixed with a local oscillator of 5 MHz.31 An input signal of 1.2 W d 3077 W 34 The output power of an SSB transmitter is usually expressed in terms of a Average power b RMS power c Peak-to-peak power d Peak envelope power 35 The letter-number designation B8E is a form of modulation also known as a Pilot-carrier system b Independent sideband emission c Lincomlex d Vestigal sideband transmission 36 Amplitude modulation is the same as a Linear mixing b Analog multiplication c Signal summation d Inductor 37 In a diode modulator.5 W c 769. A filter selects the difference signal. The PEP output is a 192.2 W b 384. a Rectification b Resonance c Variable resistance d Absorption 40 The component used to produce AM at very high frequencies is a a Varactor b Thermistor c Cavity resonator d PIN diode 41 Amplitude modulation generated at a very low voltage or power amplitude is known as a High-level modulation b Low-level modulation c Collector modulation d Minimum modulation 42 A collector modulator has a supply voltage of 48 V.5 A. The peak-to-peak amplitude of the modulating signal for 100 percent modulation is a 24 V b 48 V c 96 V d 120 V 43 A collector modulated transmitter has a supply voltage of 24 V and collector current of 0. The modulator power for 100 percent modulation is a 6W b 12 W c 18 W d 24 W 44 The circuit that recovers the original modulating information from an AM signal is known as a a Modulator b Demodulator c Mixer d Crystal set 45 The most commonly used amplitude demodulator is the a Diode mixer b Balanced modulator c Envelope detector d Crystal filter 46 A circuit that generates the upper and lower sidebands but no carrier is called a(n) a Amplitude modulator b Diode detector c Class C amplifier . The outputs are a 500 kHz b 2.d Balanced modulator 47 The inputs to a balance modulator are 1 MHz and a carrier of 1. The bandwidth is approximately a 2 kHz b 3kHz c 27.501 MHz d 55.502 MHz.502 MHz .5 MHz d Both a and b 48 A widely used balanced modulator is called the a Diode bridge circuit b Full-wave bridge rectifier c Lattice Modulator d Balanced bridge modulator 49 In a diode ring modulator.5 and 27.5 MHz. the diodes act like a Variable resistors b Switches c Rectifiers d Variable capacitors 50 The output of a balanced modulator is a AM b FM c SSB d DSB 51 The principal circuit in the popular 1496/1596 IC balanced modulator is a a Differential amplifier b Rectifier c Bridge d Constant current source 52 The most commonly used filter in SSB generators uses a LC network b Mechanical resonators c Crystals d RC networks and op amps 53 The equivalent circuit of a quartz crystal is a a Series resonant circuit b Parallel resonant circuit c Neither a nor b d Both a and b 54 A crystal lattice filter has crystal frequencies of 27.5 MHz c 1. 6 MHz c 2997 and 3003 kHz d 3000 and 3003 kHz 56 In the phasing method of SSB generation. one sideband is canceled due to a Phase shift b Sharp selectivity c Carrier suppression d Phase inversion 57 A balanced modulator used to demodulate a SSB signal is called a(n) a Transporter b Product detector c Converter d Modulator 58 Frequency translation is done with a circuit called a a Summer b Multiplier c Filter d Mixer 59 The inputs to a mixer are fo and fm.7 and 3. To produce both upper and lower sidebands.3 MHz b 3. which of the following mixer output signals is selected? a Fo b Fm c F o – fm d Fo + fm 60 Mixing for frequency conversion is the same as a Rectification b AM c Linear summing d Filtering 61 Which of the following can be used as a mixer? a Balanced modulator b FET c Diode modulator d All the above 62 The desired output from a mixer is usually selected with a a Phase-shift circuit b Crystal filter c Resonant circuit d Transformer .55 An SSB generator has a sideband filter centered at 3. the following carrier frequencies must be produced: a 2. The modulating signal is 3kHz. In down conversion.0 MHz.3 and 3. the sampling rate that can be used in a PCM system is _____ the highest audio frequency a Once . a frequency shift occurs while what characteristic of the modulating signal is changing? a Shape b Phase c Frequency d Amplitude 67 Maximum frequency deviation of a PM signal occurs at a Zero crossing points b Peak positive amplitude c Peak negative amplitude d Peak positive or negative amplitudes 68 A 100-MHz carrier is deviated 50 KHz by a 4 kHz signal. The deviation ratio is a 0.5 d 40 69 The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. the carrier deviation a Increases b Decreases c Remains constant d Both b and c 66 In PM.2 b 5 c 8 d 40 70 According the Nyquist theorem. The modulation index is a 5 b 8 c 12.63 The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal? a Amplitude b Phase c Angle d Duty Cycle 64 Both FM and PM are types of what kind of modulation? a Amplitude b Phase c Angle d Duty Cycle 65 If the amplitude of the modulating signal decreases. amplifiers following the modulated stage must be a Linear devices b Harmonic devices c Class C amplifiers d Nonlinear devices .b c d Eight times Twice Thrice 71 SSB transmission requires only _______ of the bandwidth for a DSBFC a ¼ b 2/3 c ½ d ¾ 72 Which of the following pulse modulation systems is analog? a Delta b Differential PCM c PWM d PCM 73 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 74 The primary disadvantage of FM is it a Higher cost and complexity b Excessive use of spectrum space c Noise susceptibility d Lower efficiency 75 The phenomenon of a strong FM signal dominating weaker signal on a common frequency is referred to as the a Capture effect b Blot out c Quieting factor d Dominating syndrome 76 If the plate supply voltage for a plate-modulated class C amplifier is E. the maximum plate-cathode voltage could be almost as high as a 4E b 3E c 2E d E 77 In a low-level AM system. The transmitted power is a Unchanged b Halved c Doubled d Increased by 50 percent 82 One of the advantages of base modulation over collector modulation of a transistor class C amplifier is a The lower modulating power required b Higher power output per transistor c Better efficiency d Better linearity 83 A carrier simultaneously modulated by two sine waves with modulation indices of 0.7 84 In the stabilized reactance modulator AFC system.78 If the carrier of a 100 percent modulated AM wave is suppressed.3 and 0. the total modulation index a 1 b Cannot be calculated unless the phase relations are known c 0. the percentage power saving will be a 50 b 150 c 100 d 66.4.66 79 Leak-type bias is used in a plate-modulated class C amplifier to a Prevent tuned circuit damping b Prevent excessive grid current c Prevent overmodulation d Increase the bandwidth 80 The output stage of a television transmitter is most likely to be a a Plate-modulated class C amplifier b Grid-modulated class C amplifier c Screen-modulated class C amplifier d Grid-modulated class A amplifier 81 The modulation index of an AM wave is changed from 0 to 1. or the system will fail d Phase modulation is converted into FM by the equalizer circuit 85 In the spectrum of a frequency of a frequency-modulated wave a The carrier frequency disappears when the modulation index is large b The amplitude of any sideband depends on the modulation index c The total number of sidebands depends on the modulation index . a The discriminator must have a fast time constant to prevent demodulation b The higher the discriminator frequency. the better the oscillator frequency stability c The discriminator frequency must not be too low.5 d 0. the noise amplitude a Remains constant b Decreased c Increased d Equalized 92 When the modulating frequency is doubled. as a crystal oscillator is used c Frequency multiplication must be used d Equalization is unnecessary 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/3 b mf c 3 mf d 9mf An FM signal with a deviation δ is passed through a mixer.86 87 88 89 90 91 d The carrier frequency cannot disappear 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 response of phase modulation d Lies in the different definitions of the modulation index Indicate the false statement regarding the Armstrong modulation system. and has its frequency reduced fivefold. as the noise sideband frequency approaches the carrier frequency. a The system is basically phase. modulation b AFC is not needed. the modulation index is halved. and the modulating voltage remains constant. not frequency. The deviation in the output of the mixer is a 5δ b Indeterminate c δ/5 d δ A pre-emphasis circuit provides extra noise immunity by a Boosting the bass frequencies b Amplifying the higher audio frequencies c Pre-amplifying the whole audio band d Converting the phase modulation to FM Since noise phase modulates the FM wave. The modulating system is a Amplitude modulation b Phase modulation c Frequency modulation d Any of the three 93 Indicate which one of the following is not an advantage of FM over AM a Better noise immunity is provided b Lower bandwidth is required . The AM system being used is a A3H b A5C c A3J d A3 97 Indicate which of the following advantages of the phase cancellation method of obtaining SSB over the filter method is false a Switching from one sideband to the other is simpler b It is possible to generate SSB at any requency c SSB with lower audio frequencies present can be generated d There are more balanced modulators. giving better reception c The signal is more noise resistance d Much less power is required for the same signal strength 96 When the modulation index of an AM wave is doubled. a More channel space is available b Transmitter circuits must be more stable. therefore the carrier is suppressed better 98 The most commonly used filter in SSB generation are a Mechanical b RC c LC d Low.c The transmitted power is more useful d Less modulating power is required 94 One of the following is an indirect way of generating FM.pass 99 Indicate in which one of the following only one sideband is transmitter a A3H b A3 c A3B d A5C 100 A3A modulation is sometimes used to a Allow the receiver to have a frequency synthesizer b Simplify the frequency stability problem in reception c Reduce the power that must be transmitted d Reduce the bandwidth required for transmission. fullcarrier AM. . This is the a Reactance FET modulator b Varactor diode modulator c Armstrong modulator d Reactance bipolar transistor modulator 95 Indicate the false statement regarding the advantages of SSB over double-sideband. the antenna current is also doubled.