1. How many electron beans actually leave the electron gun of a single-gun color CRT? a) 3 b) 2 c) 4 d) 1 2. What is the oldest and simplest form of multiplexing? a) Space-division multiplexing b) Time-division multiplexing c) Hybrid-division mu multiplexing d) Frequency-division mu multiplexing 3. What is the required time constant for an FM broadcast preemphasis and deemphasis network? a) 50 µs b) 100 µs c) 25 µs d) 75 µs 4. High-frequency distortion occurs when the _____ harmonic components of a digital square wave a re lost. a) Sub b) Cut-off frequency c) High frequency d) Low frequency 5. What produces the dark spots on fax receiving paper? a) Burn Burnin ing g due due to to ele elect ctri ric c cur curre rent nt flow flow betw betwee een n hel helix ix wire wire and and bla blade de b) Excessive heat c) Low impedance d) High current 6. To make the headset reproduce the original modulating signal, the metal disk mask: a) Move Move in step step with with the the cha chang nges es in ampl amplit itud ude e of of the the rec recei eive ved d car carri rier er.. b) Have a source of energy from a battery. c) Move Move in step step wit with the the freq freque uen ncy of the the rec recei eive ved d car carri rier er.. d) Vibr Vibrat ate e fas fastt eno enoug ugh h to to kee keep p up up with with the the hig high h fre frequ quen ency cy radi radio o wav wave. e. 7. Treble sound corresponds to a) Low frequencies b) High frequencies c) Radio frequencies d) Mid- frequencies 8. What is the source of wheel static? a) Brakes b) Piston c) Oscillations d) Wheel 9. Which of the following services use crystal local oscillators? a) AM b) FM c) Shortwave listener d) Aircraft 10. (Nov 1998) What connects the front-end circuit of a VHF TV super heterodyne receiver? a) Mixer, RF amplifier and AFC b) Local os oscillator, mi mixer an and RF RF am amplifier c) Local oscillator, AGC and antenna d) RF amplifier, Band pass filter an and mixer 11. (Mar 1996) The _____ filter attenuates signals but passes frequencies below and above the band. a) Band stop b) High pass c) Low pass d) Band pass 12. What BC service must used directional antennas? a) International broadcasting b) FM BC c) AM BC d) TV BC 13. (Nov 1996) What is the maximum color TV bandwidth? a) 1.0 MHz b) 1.6 MHz c) 0.5 MHz d) 1.3 MHz 14. What type of second detector is used for AM? a) Diode b) PLL c) Lattice d) Ratio 15. What sweep frequency could be used on a scope to stop an envelope pattern of 600-Hz modulation? a) 300 Hz b) 1200 Hz c) 150 Hz d) 600 Hz 16. A DSB-SC system must suppress the carrier by 50 dB from its original value of 10 W. To what value must the carrier be reduced? 1
a) 0.01W b) 0.0001 W c) 0.001 W d) 0.1 W 17. A double conversion receiver uses a first IF of 10.7 MHz and a second of 455 kHz, both with high tracking. If a signal is received at 50 MHz, what signal/s will go into the second mixer? a) 10.7 MHz b) All of the above c) 110.7 MHz d) 39.3 MHz 18. What are the le7tter-number designations of carrier and one SB? a) F3E b) J3E c) H3E d) A3E 19. (Nov 1996) When was the UHF channels (14-83) of television were added? a) 1852 b) 1952 c) 1904 d) 1947 20. What is an ideal pulse? a) A high amplitude b) A low duty cycle c) A perfect square wave with zero rise time d) A very short duration 21. What pattern of modulation must used when neutralizing an operating transmitter? a) 50% b) 10 % c) 100% or over d) 80% 22. Two 4Ω speakers connected in series have a total i mpedance of ____. a) 4Ω b) 2Ω c) 8Ω d) 6Ω 23. (Mar 1996) After the IF stages have been aligned, the next state to align in FM receiver is a) RF Amplifier b) limiter stage c) local oscillator d) Mixer stage 24. (Mar 1996) Power is always _____. a) A definite amount of energy b) Expressed in watts c) All of these d) The rate at which energy is used 25. A device used for abating the noise accompanying the flow of gas through a pipe. a) Helmholtz Resonator b) Acoustic Filter c) Muffler d) Acoustic Chamber 26. (Apr 1998) Which of the following refers to a double side band full carrier? a) A3E b) A3J c) F3 d) R3A 27. How many cathodes are there in a shadow-mask tube? a) 4 b) 1 c) 2 d) 3 28. What is the coupling used in Stoneman transmission bridge? a) A combination of the above b) Inductive c) Resistive d) Capacitive 29. A decibel notation relative to a reference noise level. a) dBa b) dBpwp c) dBrn d) dBf 30. (Nov 1997) Operating method in which the transmission is made alternately in each direction of a telecommunication channel. a) Semi-duplex op operation b) Duplex operation c) Half duplex operation d) Simplex operation 31. What AF range is required of the aural transmitter of a TV BC station? a) 50 Hz – 15,000 Hz 2
a) 0.01W b) 0.0001 W c) 0.001 W d) 0.1 W 17. A double conversion receiver uses a first IF of 10.7 MHz and a second of 455 kHz, both with high tracking. If a signal is received at 50 MHz, what signal/s will go into the second mixer? a) 10.7 MHz b) All of the above c) 110.7 MHz d) 39.3 MHz 18. What are the le7tter-number designations of carrier and one SB? a) F3E b) J3E c) H3E d) A3E 19. (Nov 1996) When was the UHF channels (14-83) of television were added? a) 1852 b) 1952 c) 1904 d) 1947 20. What is an ideal pulse? a) A high amplitude b) A low duty cycle c) A perfect square wave with zero rise time d) A very short duration 21. What pattern of modulation must used when neutralizing an operating transmitter? a) 50% b) 10 % c) 100% or over d) 80% 22. Two 4Ω speakers connected in series have a total i mpedance of ____. a) 4Ω b) 2Ω c) 8Ω d) 6Ω 23. (Mar 1996) After the IF stages have been aligned, the next state to align in FM receiver is a) RF Amplifier b) limiter stage c) local oscillator d) Mixer stage 24. (Mar 1996) Power is always _____. a) A definite amount of energy b) Expressed in watts c) All of these d) The rate at which energy is used 25. A device used for abating the noise accompanying the flow of gas through a pipe. a) Helmholtz Resonator b) Acoustic Filter c) Muffler d) Acoustic Chamber 26. (Apr 1998) Which of the following refers to a double side band full carrier? a) A3E b) A3J c) F3 d) R3A 27. How many cathodes are there in a shadow-mask tube? a) 4 b) 1 c) 2 d) 3 28. What is the coupling used in Stoneman transmission bridge? a) A combination of the above b) Inductive c) Resistive d) Capacitive 29. A decibel notation relative to a reference noise level. a) dBa b) dBpwp c) dBrn d) dBf 30. (Nov 1997) Operating method in which the transmission is made alternately in each direction of a telecommunication channel. a) Semi-duplex op operation b) Duplex operation c) Half duplex operation d) Simplex operation 31. What AF range is required of the aural transmitter of a TV BC station? a) 50 Hz – 15,000 Hz 2
b) 20 Hz – 2 kHz c) 20 Hz – 20 kHz d) 5 – 50 kHz 32. It is the representation of a waveform in such a way that its amplitude is displayed as a function of frequency. a) OTDR b) Frequency Domain c) Time Domain d) Wave Shape 33. What is the major advantage of FM over AM? a) Simple circuits b) High frequency c) No interference d) Less noise 34. A 100-V carrier is amplitude modulated by a 1-kHz sine wave. What is the side-frequency amplitude when m=0.75? a) 75 V b) 37.5 V c) 100 V d) 18.75 V 35. Determine the open-circuit noise voltage in 1 Hz of bandwidth at 290 K for a 26 ohms resistor. a) 65 pV b) 145 pV c) 645 pV d) 45 pV 36. Which of the following is not a type of log used in BC stations? a) Maintenance b) Period c) Program d) Operating 37. What kind of crystal is used in oscillators? a) Carborundum b) Galena c) Quartz d) S a lt 38. The audio is reconstructed from the radio wave by: a) The action of the headset b) None of the above. c) The The ac action tion of a fil filte terr ca capac pacitor itor conne onnec cted ted acr acros oss s the the head headse sett d) Having th the au audio re removed from th the ca carrier 39. (Nov 1998) What is meant by the term deviation ratio? a) The The rat ratio io of of the the carr carrie ierr cen cente terr fre frequ quen ency cy to the the aud audio io modu modula lati ting ng freq freque uenc ncy y b) The The rati ratio o of the the hig highe hest st audi audio o mod modul ulat atin ing g fre frequ quen ency cy to to the the aver averag age e audi audio o modu modulat latin ing g freq freque uenc ncy y c) The The rati ratio o of the the max maxim imum um carri carrier er fre frequ quen ency cy dev devia iati tion on to to the the hig highe hest st audi audio o mod modul ulat ation ion freq freque uenc ncy y d) The The rati ratio o of the the aud audio io mod modul ulat atin ing g fre frequ quen ency cy to the the cen cente terr car carri rier er fre frequ quen ency cy 40. A radio receiver is called ___ if the local oscillator frequency is made equal to the wanted RF signal frequency. a) T RF b) Up-conversion c) homodyne d) Single-conversion 41. (Apr 1998) Considered as the main source of an internal noise. a) Temperature ch change b) Flicker c) Device imperfection d) Thermal agitation 42. A modulation technique commonly used for low-cost digitization of voice signals. a) A3 b) F3 c) A0 d) A5C 43. He was the one who developed the mathematical solution to a complex r epetitive waveform. a) J. Fourier b) P.H Smith c) Y . Ud a d) Carson 44. What is the device designed to display the signal state of many lines simultaneously? a) Spectrum analyzer b) Logic analyzer c) Oscilloscope d) OTDR 45. What is the result if a balanced modulator is not perfectly balanced? a) Both sideband transmitted b) Carrier transmitted c) Low sideband transmitted d) SB filtered 46. (Nov 1998) What is the first symbol of radio signal emission having an amplitude modulated main carrier, double sideband? 3
a) H b) C c) B d) A 47. Find the noise voltage for a 1-kohms resistor at 170C “tuned” by an LC circuit with a BW of 1 MHz. a) 15.01 uV b) 5.01 uV c) 50 uV d) 15 uV 48. (Nov 1997) Which of the following falls under the high frequency band of the radio spectrum? a) 150.50 MHz b) 2.4555 MHz c) 8.2345 MHz d) 35.535 MHz 49. Which of the following is not an application of PLL? a) FM demodulators b) Frequency Synthesizers c) FSK decoder d) AM Discriminator 50. What is an application for vestigial sideband transmission? a) AM Broadcast b) TV Broadcast c) FDM d) Telephony 51. In a TV picture tube, what is the purpose of the large tube voltage? a) attracts electrons towards face of tube b) create huge magnetic field c) repels electrons away from tube d) produce good quality of picture 52. (Apr 1998) A form of single sideband emission where the degree of carrier suppression enables the carrier to be reconstituted and be used for demodulation. a) Reduced carrier single sideband emission b) Double sideband emission c) Half carrier single sideband emission d) Full carrier single sideband emission 53. (Nov 1998) Refers to the first symbol i n an emission designation with an amplitude modulated main carrier represented by letter A. a) Double sideband full carrier b) Independent sideband c) Single sideband suppressed carrier d) Double sideband 54. An SSB contains 30 kW. The power content of the carrier is _____ kW. a) 30 b) 0 c) 10 d) 20 55. What is the reason for using pre-emphasis? a) increase selectivity b) reduce S/N ratio c) to increase noise figure d) reduce noise reception 56. What is the carrier power transmitted on a 75-Ω antenna if mf=2 and Vc (unmodulated) is 2 kVpk? a) 1.29 kW b) 12.9 kW c) 10 kW d) 9 kW 57. What is the circuit that changes modulated RF to AF? a) Synthesizer b) Demodulator c) Modulator d) Modem 58. What circuit accompanies a mixer? a) RF Amplifier b) LO c) Detector d) IF Amplifier 59. (Nov 1997) A good example of a pilot tone system used in commercial frequency modulation stations. a) FDM b) Stereo multiplexing c) Frequency modulation d) Time division 60. (Apr 1997) Sound intensity level is_____. a) 10 log I / ref / I b) 10 log I / I ref c) 20 log I / ref d) 30 log I / ref 61. Modulating two waves of the same frequency but with _____. a) 90° 4
b) 45° c) 360° d) 180° 62. A super heterodyne is tuned to 2738 kHz. The IF is 475 kHz. What is the image frequency? a) 3.09 MHz b) 3688 kHz c) 4385 kHz d) 4.5 kHz 63. What is the greatest possible modulation value without distortion? a) 99.9% b) 66.67% c) 100% d) 50% 64. What determine the bandwidth of a transmitted AM signal? a) The lowest modulation amplitude b) The maximum modulation amplitude c) The highest frequency component of the modulating signal d) The lowest frequency component of the intelligence 65. With _____, the modulation envelope is an expression of the amplitude and frequency of the modulation signal. a) PM b) AM c) FM d) PCM 66. Which of the following must not be included? a) atmospheric noise b) cosmic noise c) galactic noise d) solar noise 67. What would be produce by weak blue, weak green, and weak red signals on a color CRT? a) Black b) White c) Weak white d) Gray 68. A device which can perform the function of both a transmitter and a receiver. a) Transceiver b) Relay c) Repeater d) Buffer 69. What frequencies are considered to be in the AF range? a) 50 Hz – 50 kHz b) 20 Hz – 20 kHz c) 300 Hz – 3000 kHz d) 15 Hz – 10 kHz 70. (Nov 1997) The first symbol in the designation of radio emission under the ITU rules re fers to a) bandwidth b) nature of si gnal(s) modul ating the main ca rrie r c) type of information to be transmitted d) type of modulation of the main carrier 71. Where is a degaussing coil in a TV set? a) around the IF amp b) around the tube face c) at the tuner d) inside the CRT 72. What is the color subcarrier for channel 5? a) 76.25 MHz b) 80.83 MHz c) 76 MHz d) 81.75 MHz 73. Where is telemetering used in BC stations? a) Within the transmitter b) Remote position to transmitter c) At the receiver d) At the studio 74. The total power content of an AM signal is 600 W. What is the percentage modulation if each sideband contains 100 W? a) 33.3% b) 100% c) 83.3% d) 66.7% 75. What is the main function of a balanced modulator? a) Suppress carrier signal in order to create a SSB or DSB b) Produce 100% modulation c) Limit noise picked by a receiver d) Produce bala nced modulation of a car rier wave 76. (Nov 1998) In radio regulation. The first symbol in the designation of radio emission is _____. a) Nature of signal(s) b) Bandwidth 5
c) Type of modulation of the main carrier d) Type of information to be transmitted 77. (Apr 1997) The most common unit of noise measurement in white noise testing. a) NPR b) dBw c) dBk d) dBm 78. (Mar 1996) Cross modulation on a receiver is eliminated at the a) RF stage b) Mixer stage c) IF stage d) Detector stage 79. Which of the following is not a major component of a color TV receiver? a) color reference oscillator b) sync analyzer c) color signal amplifier d) color demodulator circuit 80. How many ground radials should a λ/4 vertical AM broadcast antenna use? a) 5 – 20 b) 1 c) 24 or more d) 3 – 10 81. What is the process where some of the medium through which it impinges? a) reflection b) diffraction c) refraction d) absorption 82. What is the main problem in receiving a suppressed carrier transmission or a single sideband transmission? a) T he receiver needs to reinsert the mi ssing carrier . b) T he selecti vity of the receiver must be goo d. c) The gain of the amplifier must be high d) There must be three detectors. 83. What does an FM detector do? a) to conve rt pha se change s to frequency change s b) to increase the frequency change c) to extract amplitude variations d) to convert frequency changes to amplitude changes 84. Compute the modulation index of an FM signal with a carrier swing of 10 kHz when the modulating signal is 5 kHz. a) 4 b) 0.5 c) 2 d) 1 85. What circuit is used to create vestigial transmission? a) Diplexer b) LPF c) HPF d) Duplexer 86. The major difference between FM and PM a) Lies in the poorer audio response of phase modulation index b) All of the above c) I s to o great to make the two system compa ti ble d) Lies in the different definition of modulation index 87. (Apr 1997) Tendency of sound energy to spread. a) Reflection b) Rarefaction c) Diffraction d) Refraction 88. (Mar 1996) What is the main purpose of a communications system? a) None of these b) For modulation c) To provide an acceptable replica of the information at the designation d) To have a frequency assignment 89. In what type of transmitters is balanced modulators used? a) PM b) SSB c) A3E d) F3E 90. What is the aspect ratio in commercial TV receivers? a) 16:9 b) 4:3 c) 3:4 d) 2:3 91. Determine the power saving in percent when the carrier is suppressed in an AM signal modulated to 80% a) 100% b) 80% c) 75.8% 6
d) 66.7% 92. In AM, increasing the amplitude of the modulating signal, the amount of power in the information part of the transmitted signal is _____ relative to the power used for the carrier. a) Increased b) Varying c) Constant d) Decreased 93. To what feature of the modulating tone is FM deviation proportional? a) Phase b) Harmonics c) Amplitude d) Frequency 94. The maximum swing of the sound carrier in TV system is ______. a) ±75 kHz b) ±10 kHz c) ±15 kHz d) ±25 kHz 95. (Apr 1997) If a voltage is equal to twice its original value, what is its corresponding change in dB? a) 3 dB b) 10 dB c) 6 dB d) 9 dB 96. Which is not true about modulation a) More practical antenna b) Transmission over longer distances c) Multiple transmission d) Narrower bandwidth 97. What determines the purity of received colors? a) Y and I amplitudes b) Y amplitudes c) Q and Y amplitudes d) Q and I amplitudes 98. What is the power saving when the carrier is suppressed in a regular AM signal modulated to an index of 100%? a) 100% b) 16.7% c) 66.7 % d) 33.3% 99. What is the advantage of using a high IF? a) better image rejection b) improve S/N ratio c) better quality of music d) high gain 100. Which of the following is not associated with transistors? a) transit-time b) jitter c) flicker noise d) shot noise 101. What is a device such as the microphone and the headset sometimes called? a) Reproducer b) Converter c) Receiver d) Transmission Medium 102. (Nov 1997) An antenna that can only receive a television signal? a) Yagi antenna b) TVRO c) Reference Anenna d) Isotropic antenna 103. What might cause a 120-MHz aircraft transmission to be received on an FM broadcast band receiver with a 10.7-MHz IF? a) 96.3 MHz b) 98.6 MHz c) 99.3 MHz d) 97.2 MHz 104. (Nov 1996) The maximum power suggested by the KBP on 919 – 1312 kHz AM broadcast station I Metro Manila is a) 20 kW b) 10 kW c) 5 kW d) 15 kW 105. How many horizontal lines are used to develop a TV raster ? a) 525 b) 15750 c) 615 d) 750 106. What does AFC mean? a) Anti Firing Countermeasure b) Audio Frequency Camera 7
c) Automatic Frequency Control d) All Filipino Conference 107. A relatively rigid extended surface surrounding an acoustic source. a) Dash Board b) Baffle c) Panel Board d) Screen 108. What happens to noise when you increase the bandwidth of an amplifier? a) it increases b) it decreases c) fluctuates d) Remain constant 109. (Mar 1996) In AM, the carrier carries _____ intelligence. a) Distorted b) No c) Same d) Difference 110. Which of the following is not commonly used in the LO? a) Crystal b) Armstrong c) Hartley d) Colpitts 111. The bandwidth in _____ depends on the number of significant sidebands. a) Delta Modulation b) Frequency Modulation c) QAM d) FCM 112. (Nov 1996) Which stands for dB relative level? a) dBm b) dBr c) dBa d) dBm 113. In what way would a program may be received at BC stati ons? a) Radio Relay b) Telephone Lines c) All of the above d) Satellite 114. (Apr 1998) What is a frequency discriminator? a) A circuit for filtering two closely adjacent signal b) An automatic bandswitching circuit c) A circuit for detecting FM signals d) An FM generator 115. Which of the following do not require a tuner? a) CB receiver b) TV receiver c) None of these d) Communications Satellite Receiver 116. What produces splatter in an AM transmission? a) Clipping b) Flickering c) overmodulation d) Harmonics 117. (Nov 1998) Which band does channel 14 of the television channel belongs? a) EHF band b) Low VHF band c) UHF band d) High VHF band 118. (Mar 1996) The letter-number designation B8E is a form of modulation also known as _____. a) Lincompex b) Independent sideband emission c) Vestigial sideband transmission d) Pilot-carrier system 119. What service uses HF C W communications? a) Broadcasting b) Police c) Satellite System d) Telephony 120. Which came first, the invention of the telephone or the invention of the phonograph? a) phonograph b) telephone c) either d) neither 121. A 1500-kHz carrier and 2 kHz intelligence signal are combined in anon-liner device. What component is present at the output? a) 1502 kHz b) 1492 kHz c) all of the above d) 1500 kHz 8
122. (Apr 1998) Refers to an emission designation for facsimile. a) A3J and A4E b) R3E and A3E c) J3E and F4E d) A3C and F3C 123. What is the picture carrier frequency for channel 7? a) 174 MHz b) 179.75 MHz c) 178.83 MHz d) 175.25 MHz 124. The typical output voltage from a magnetic microphone is a) 50 mV b) 10 mV c) 5 mV d) 1 mV 125. What is usually transmitted by facsimile? a) Video signal b) Voice c) Bits d) Pictures 126. What type of device can be used in balanced modulators? a) AF, IF b) AF, PF c) RF, IF d) AF, RF 127. The power in FM _____ as the modulation index increases. a) Increases b) Remain constant c) Fluctuates d) Decreases 128. FM has a major disadvantage of _____. a) High voltage b) Greater bandwidth c) Greater coverage d) Low efficiency 129. For an AM signal modulated to a depth of 100% by a pure tone, the power is _____ the power of unmodulated carrier. a) less than b) 3 / 2 times c) Same as d) twice as 130. (Apr 1998) If a transmitter supplies 8 kW to the antenna when it is unmodulated, determine the total radiated power when modulated at 30%. a) 8.36 kW b) 15 kW c) 5 kW d) 20 kW 131. (Nov 1997) Two resistor, 20 kohms and 50 kohms are at ambient temperature. Calculate for a bandwidth equal to 100 kHz, the thermal noise voltage for the two resistors connected in parallel. a) 4278 uV b) 4.78 uV c) 0.4782 uV d) 47.8 uV 132. Which of the following FM detectors is not used in mobile? a) Discriminator b) Ratio c) Quadrature d) Balanced Detector 133. (Nov 1996) What is the equivalent output of a circuit in dBm , if it has an output of 10 watts? a) 30 dBm b) 20 dBm c) 10 dBm d) 40 dBm 134. What is the purpose of AFC in an FM receiver? a) to stabilize the gain b) to provide good selectivity c) to increase the sensitivity d) to help maintain a steady local oscillator frequency 135. (Mar 1996) Which of the follo wing pulse modulation systems is analog? a) Delta b) PCM c) PWM d) Differential PCM 136. What information must be contained in a TV signal? a) Video b) All of these c) Sound d) Synchronizing signal 9
137. (Nov 1997) Nominal voice channel a) 3 to 3 kHz b) 4 kHz c) 20 to 20 kHz d) 16 to 16 kHz 138. Most of the communications receiver is in the form of ___type. a) High-level b) TRF c) Single-ended d) Super heterodyne 139. What is the S/N at the output of an amplifier whose NF=10 dB and the input S/N=25 dB? a) 35 dB b) 15 dB c) 10 dB d) 25 dB 140. (Nov 1998) In amplitude modulation technique the unmodulated carrier is referre d as having _____. a) over modulated b) 0% modulation c) 50% modulated d) 100% modulation 141. What is the maximum power output of a CB A3E emission? a) 10 kW b) 3 kW c) 4W d) 10 W 142. What does ANSI mean? a) American national standards institute b) American non stop information c) Auxiliary net system interconnection d) Auxiliary non station identifier 143. The antenna current of an AM transmitter is 6.2 A when unmodulated and rises to 6.7 A when modulated. What is the %m? a) 67% b) 42.8% c) 57.9% d) 51% 144. When did the first transatlantic radio communications take place? a) 1876 b) 1888 c) 1942 d) 1901 145. What is another name for AF volume control? a) ARC b) Gain c) AFC d) AMC 146. (Nov 1996) A loudspeaker cabinet has an internal volume of 5,184 in³ (84,950 cm³). If has a port area on the on the baffle of 50 in² (323cm²) and the thickness of 0.75 in (19mm). What is the Helmholtz resonance, in hertz, of this loudspeaker enclosure? a) 255 Hz b) 240 Hz c) 250 Hz d) 245 Hz 147. (Nov 1998) In modulation technique, which of the following is referred to audible pitch? a) Amplitude b) Width c) Frequency d) Harmonic 148. (Apr 1997) Modulation means a) varying of information b) utilization of a single transmission channels to carry multiple signals c) varying of some parameters of a carrier such as its amplitude to transmit information d) transmit pulse in DC form on a copper wire 149. What is the frequency of the color burst? a) 6 MHz b) 3.58 MHz c) 60 Hz d) 30 Hz 150. What distinguishes one electromagnetic wave form another? a) Frequency b) Phase c) Amplitude d) Energy 151. (Apr 1997) 100% modulation inn AM means a corresponding increase in total power by _____. a) 25% b) 75% c) 50% d) 100% 10
152. (Nov 1996) Which of the following filters block FM radio band for TV channels (2 to 13)? a) Low-pass filter b) Band-reject filter c) High-pass filter d) Band-pass filter 153. (Apr 1997) What particular circuit gets rids of FM noise? a) Phase Shifter b) HPF c) Limiter d) LPF 154. What is the percent modulation of a signal in the FM broadcast band at 92 MHz with 20 kHz frequency deviation? a) 12% b) 27% c) 60% d) 72% 155. Sound is a wave motion of varying air____. a) Viscosity b) Resistance c) Pressure d) Density 156. (Apr 1998) How does a SSB transmitter output power normally expressed? a) In term of peak-to-peak power b) Peak power c) Average power d) In term of peak envelope power 157. In communications systems, demodulation ______. a) Is performed at the transmitting station b) Is opposite of modulation c) Removes sidebands d) Rectifies modulated signal 158. It describe the acoustic energy flowing per unit area and per unit time. a) Sound Absorption b) Sound Reflection c) Acoustic Pressure d) Acoustic Intensity 159. Any waveform that is not symmetrical in area about the time axis has a (n) _____ component. a) DC b) RC c) FC d) AC 160. What is the highest video frequency set by the FCC for commercial TV? a) 5.5 MHz b) 15 kHz c) 4.2 MHz d) 6 MHz 161. What does aspect ratio mean? a) Ratio of the screen diagonal to its height b) Ratio of the screen width to its height c) Ratio of the screen diagonal to its width d) Ratio of the screen height to its width 162. Compute the noise figure of a receiving system with a noise temperature of 2000C. a) 24 dB b) 2.4 dB c) 4.2 dB d) 42 dB 163. The input power to a 50-Ω receiver is 200 pW. Determine the receiver gain required to produce 3 dBm at the detector. a) 40 dB b) 70 dB c) 20 dB d) 7 dB 164. The big breakthrough in electric communications came with the invention of the _____ in 1844. a) Phonograph b) Telegraph c) Telephone d) Transistor 165. What is the standard intermediate frequency for FM radio? a) 4.5 kHz b) 10.7 kHz c) 455 kHz d) 112 kHz 166. What type of wave trap is connected in series with a line? a) Synchronous b) Series c) Parallel d) Asynchronous 167. A method of generating SSB signal; that utilizes only one balanced modulator circuit. 11
a) Phase-Shift method b) Weaver method c) Filter method d) Third method 168. In 1877, _____ invented a method of making a permanent record of sound with his invention of the phonograph. a) Morse b) Marconi c) Bell d) Edison 169. The noise power generated by a resistor depends upon a) its resistance value b) both a and b c) none of the above d) its operating temperature 170. (Nov 1996) Both frequency and phase modulation utilizes _____ modulation. a) Phase b) Digital c) angle d) AM and Fm 171. How many times more bandwidth does the UHF band have than VHF band? a) 1 b) 1000 c) 10 d) 100 172. What method can be used to invert speech? a) Frequency translation b) Inverter c) Frequency multiplier d) AGC 173. In a low-level modulation system, the type of amplifier that follows the modulated stage should be a _____. a) Class C amplifier b) Linear amplifier c) Harmonic generator d) Any of the above 174. For an FM transmitter, the initial carrier frequency is 8 MHz with a frequency deviation of 1 kHz. If the total frequency multiplication of the transmitter is 12, determine the final; frequency deviation. a) 12 kHz b) 1 kHz c) 120 kHz d) 8 MHz 175. What is the sound carrier for channel 10? a) 193.25 MHz b) 197.75 MHz c) 196.83 MHz d) 192 MHz 176. (Mar 1996) what is the purpose of a beat frequency oscillator (BFO)? a) Generates a signal, whose frequency is the same as that of the intermediate frequency b) Generates a 1 kHz tone to Morse reception c) Aids in the reception of weak voice-modulated signals d) Generates an output, whose frequency differs from that of the intermediate frequency by 1 kHz 177. (Nov 1996) Speaker is a device that ____. a) conver t electrical energy to me chani cal ener gy b) conver t curr ent var iations into sound wave s c) conver t sound waves i nto curre nt and voltage d) none of these 178. A microwave antenna at an earth station has Tant=25 K. If the receiver has Tr=290 K (3 dB NF), then the resultant equivalent system noise temperature is ___. a) 300 K b) 290 K c) 25 K d) 315 K 179. Determine the noise power delivered to a receiver input at 300 K and noise bandwidth of 20 kHz. a) -130.8 dBm b) -25 dBm c) 131dBm d) -120 dBm 180. For a 75-MHz FM carrier modulated by 5-kHZ audio tone that causes a frequency deviation of 15 kHz, determine the FM signal bandwidth. a) 40 kHz b) 200 kHz c) 80 kHz d) 100 kHz 181. What is the result of overmodulation of an FM emission? a) distortion b) Lower frequency c) Higher power d) Excessive bandwidth distortion 12
182. What TV signal are amplified by the video IF amplifier? a) Sound carriers b) Sound the picture carriers c) Sync pulse d) Color burst 183. (Apr 1997) What is the reference frequency of CCITT psophometric noise measurement? a) 800 Hz b) 1000 Hz c) 3400 Hz d) 1500 Hz 184. (Nov 1997) A single sideband emission in which the degree of carrier suppression enables the carrier to be reconstituted and to be used for demodulation. a) Full carrier single band emission b) Standard single sideband emission c) Reduce carrier single sideband emission d) Half carrier single sideband emission 185. Basically, what would be added to a TRF to produce a super heterodyne? a) Mixer stage b) IF stage c) All of the above d) Local Oscillator 186. (Nov 1997) Atmospheric noise is less severe at frequencies above a) audio level b) 10 GHz c) 30 MHz d) 1 GHz 187. What broadcast station use vertical antennas on flat ground? a) FM b) TV c) Shortwave d) AM 188. (Apr 1997) If you have an available number of power amplifiers with a gain of 100 each, how many such amplifiers do you need to cascade to give an overall gain of 60 dB? a) 3 b) 4 c) 5 d) 2 189. How many watts are represented by 40 dBw? a) 40000 W b) 40 W c) 10000 W d) 1000 W 190. For _____ percent modulation in AM, the modulation envelope has a peak value double the unmodulated carrier level. a) 50 b) 83.3 c) 100 d) 66.67 191. Which produces greater interference, overmodulated positive or negative peaks? a) Negative b) Positive c) either d) neither 192. A suppressed-carrier synchronous detector requires: a) The presence of a reinserted carrier of exactly the same frequency and phase as the original. b) A BFO that is near the frequency difference between the original carrier and modulating frequency. c) The presence of a reinserted carrier that has a frequency close to the original carrier. d) A BFO that is at the exact frequency difference between the original carrier and modulating frequency. 193. (Mar 1996) One-hundred twenty µbars of pressure variation is equal to a) 57.78 dBSPL b) 41.58 dBSPL c) 120 dBSPL d) 115.56 dBSPL 194. What is reduced by rounding off square-wave emissions? a) energy b) Phase c) Bandwidth d) Amplitude 195. The circuit used for producing a double sideband suppressed carrier type of AM signal is called _____. a) Balances modulator b) AGC c) Mixer d) PLL 196. What is the maximum power that ca be contained in the sideband without distortion? a) 66.67% b) 25% 13
c) 16.67% d) 50% 197. (Apr 1998) What is emission C3F? a) Modulated CW b) Facsimile c) RTTY d) Television 198. (Nov 1997) Noise caused by the thermal agitation of electrons in resistance. a) Johnson’s Noise b) Thermal Noise c) ALL of these d) White Noise 199. Determine the equivalent noise bandwidth for a single RC low-pass filter if R=20 kohms and C= 0.1 uF a) 500 Hz b) 250 Hz c) 125 Hz d) 200 Hz 200. For an unmodulated carrier of 1000V and a modulated peak value of 1800 V, what is the modulation index? a) 0.7 b) 0.8 c) 0.9 d) 0.5 201. In TV system. A picture signals are transmitted by a) PCM b) FM c) AM d) PM 202. What happens to the spectrum of a repetitive pulse as the pulse width decreases? a) More harmonics of the same phase b) Remain constant c) Less harmonics of the same phase d) decreases 203. In what classes are SSB linear amplifiers operated? a) B or C b) A or AB c) D d) C or D 204. The power of thermal noise is ___ of resistance. a) a function b) equal c) dependent d) independent 205. (Apr 1998) Best describes as an amplifier used in radio telephony. a) Magnifier b) Class C c) Class A d) Class B 206. Quantization noise is produced in a) PCM b) FSK c) All modulation system d) All pulse modulation system 207. What is the frequency for the pilot subcarrier for commercial stereo FM? a) 20 kHz b) 67.5 kHz c) 19 kHz d) 38 kHz 208. What do you call the combining circuit used in TV? a) Synthesizer b) Matrix c) Adder d) Multiplier 209. What characteristic of the sound wave determines its pitch? a) harmonics b) amplitude c) phase d) frequency 210. What electrical device inside a communication receiver selects one station and rejects a ll others? a) Local Oscillator b) Detector c) AGC d) Tuner 211. What is the wavelength for a frequency of 1 million hertz? a) 30 m b) 300 m c) 30 km d) 3 km 14
212. Connecting a headset directly across the tuner in a simple AM radio receiver: a) Will not produce sound in the headset. b) Will not work until a battery is added. c) Produces sound in the headset. d) Will burn out the tuner. 213. Does the video transmitter at a TV BC station employ FM or AM? a) FM b) both AM and FM c) PM d) AM 214. In FM for a given frequency deviation, the modulation index varies _____ with the modulating frequency. a) Independently b) Directly c) Inversely d) Equally 215. A radio transmitter is rated as having a frequency accuracy of ±0.2 parts per million. What is the maximum frequency error at 150 MHz? a) ±30 Hz b) ±150 Hz c) ±20 Hz d) ±7.5 Hz 216. Amplitude limiting in the IF section eliminates _____ interference from the FM signal. a) PM b) AM c) Broadband d) FM 217. Calculate the modulating frequency that causes an FM signal to have a bandwidth of 50 kHz when its frequency deviation is 15 kHz. a) 50 kHz b) 20 kHz c) 40 kHz d) 10 kHz 218. What is a radio carrier? a) A lower frequency signal b) A higher amplitude signal c) A higher frequency signal d) A lower amplitude signal 219. What is the disadvantage slope detection of FM? a) complexity b) high level of noise c) no noise discrimination d) low noise reduction 220. What devise is used to determine phase difference between two broadcast antennas? a) Phase monitor b) FSM c) Frequency monitor d) OTDR 221. In single-gun color CRT, what electron beam travels straight through the tube? a) yellow b) blue c) green d) red 222. What information other than the sound has to be transmitted in TV transmission? a) visual signal b) all of the above c) synchronizing signals d) blanking pulses 223. What type of coupling discriminates against harmonic transmission a) Direct b) Inductive c) Capacitive d) Transformer 224. Which is better, an NF of 20 or 10 dB? a) 20 dB b) 10 dB c) Neither d) Either 225. An adjustable resonant cavity calibrated if frequency and which undergoes some power absorption at resonance. a) Auto Coupler b) Cavity Resonator c) Frequency Meter d) Ferrite isolator 226. (Apr 1998) Type of modulation used i n TV broadcast visual transmitter. a) SSBFC b) Vestigial sideband c) Pulse modulation d) DSBFC 15
227. What happens in standard AM transmission when no modulating signal is being transmitted? a) There is no signal. b) There are two carriers c) There are several sidebands. d) There are no sidebands. 228. (Nov 1998) A third symbol emission which represent television. (0 correct answers) a) F b) A c) C d) D 229. What is the major advantage of a super heterodyne receiver? a) inexpensive b) high amplification factor c) excellent selectivity and sensitivity d) good image rejection 230. What is the frequency of the VCR control signal? a) 60 Hz b) 15625 Hz c) 30 Hz d) 15750 Hz 231. What is the interference due to single tone or complex periodic waveforms? a) Insertion b) Inter-modulation Distortion c) Harmonic Distortion d) Tone interference 232. (Nov 1998) Determine from the following radio frequency that falls under the Very High Frequency band of the radio spectrum. a) 235.5 MHz b) 345.00 MHz c) 450.00 MHz d) 144.50 GHz 233. Another name for burst noise a) popcorn noise b) shot noise c) pink noise d) flicker 234. (Mar 1996) If the percentage of modulation of an AM amplifier is 88% and the modulation signal is 1 volt, the carrier has an amplitude of _____. a) 0.12 volt b) 1.14 volts c) 1.88 volts d) 0.88 volt 235. What is the seventh harmonic of 360 kHz? a) 1260 kHz b) 5040 kHz c) 2520 kHz d) 7000 kHz 236. In a transmitted AM wave, state where the information is contained? a) Modulating signal b) Carrier c) Envelope d) Sidebands 237. A duplexer is used to a) Connect a receiver and a transmitter to the same antenna b) Fee d more tha n one receiver from a single antenna c) C onnect two t6r ansmitter to the same antenna d) Feed more than one transmitter from a single antenna 238. (Mar 1996) In an FM receiver, which circuit removes amplitude variations? a) Exciter b) Mixer c) Limiter d) Discriminator 239. Which of the following items need not be checked with receivers? a) Squelch b) Gain c) Distortion d) Sensitivity 240. What is the horizontal resolution of a broadcast TV receiver? a) 500 lines b) 30 lines c) 428 lines d) 339 lines 241. What is the noise figure of an ideal amplifier? a) unity b) 100 c) zero d) infinity 242. (Mar1996) The equivalent noise temperature of the amplifier is 25 K. What is the noise figure? 16
a) 1.086 b) 1.86 c) 10.86 d) 0.1086 243. What is the circuit that automatically holds the level or strength of a signal at a predetermined level used to compensate for variations due to fading? a) Discriminator b) AFC c) Limiter d) AGC 244. What is the main disadvantage of a single-tube transmitted? a) Low gain b) High attenuation c) Frequency instability d) High resistivity 245. When do BC stations make equipment tests? a) day time b) experimental period c) night time d) Sunday only 246. What is the major requirement of the oscillators used in an SSB receiver? a) Goof feedback b) stability c) Selectivity d) High frequency 247. A subcarrier has a (n) _____ frequency than the main carrier. a) Good b) Equal c) Higher d) Lower 248. What percent of the radiated power is in the sidebands with 50% sinusoidal modulation (AM)? a) 33% b) 16.67% c) 20% d) 11% 249. What is the meaning of kinescope? a) Color CRT b) Wide screen CRT c) TV picture tube d) Enhanced CRT 250. When a carrier is frequency-modulated, what is developed on both sides carrier? a) Noise b) Carrier c) sidebands d) Envelope 251. What are the two emission designations of a TV transmission? a) J3E, C3F b) B8e, C3F c) F3E, C3F d) A3E, ISB 252. (Nov 1997) A large speaker having diameter (15 cm. and above) a) Woofer b) Coaxial speaker c) Triaxial speaker d) Tweeter 253. An AM transmission of 1000 W is fully modulated. Calculate the power transmitted as a SSB signal. a) 667 W b) 333 W c) 167 W d) 1000 W 254. How guardbands are allocated in commercial FM stations? a) 15 kHz modulation b) 75 kHz deviation c) 50 kHz on each side of the carrier d) 25 kHz on either side of the transmi tti ng si gnal 255. For an IF frequency of 455 kHz, what must be the LO frequency when receiving a 580 kHz transmission? a) 1035 MHz b) 3.51 MHz c) 351 kHz d) 1.035 MHz 256. What is the main feature of DSB transmission? a) High voltage b) High reliability c) Narrow bandwidth d) Carrier is suppressed 257. (Nov 1996) Which frequency band is the standard AM radio broadcast? a) VHF b) HF 17
c) UHF d) MF 258. (Nov 1997) What is the effect in over modulated amplitude modulated radio broadcasting transmission? a) Interference to adjacent channel b) Higher audio signal c) Higher fidelity d) Increase noise 259. (Nov 1997) In the designation of bandwidth and emission, what letter in the symbol represents a doublesideband of modulation? a) A b) B c) C d) H 260. The audible pitch refers to a) harmonics b) amplitude c) purity d) frequency 261. (Nov 1996) Which symbol indicates that only one sideband is transmitted? a) B8E b) A3E c) C3F d) H3E 262. It is the representation of a complex waveform in such a way that the sinusoidal components are displayed as a function of time. a) Time Domain b) TDR c) Frequency Domain d) Wave Representation 263. Where is ISB primarily used? a) Telemetry b) Telephone and Telegraph Communications c) Radar d) FM Broadcast 264. What is a hybrid transmitter? a) \part metal, part liquid b) Combination of metal and plastic c) Multiple transmitter d) Part semiconductor, part vacuum tube 265. What is the power in each sideband for an AM signal with 80%modulation and a total power of 2500 W? a) 500 W b) 400 W c) 250 W d) 303 W 266. What is gained by operating an oscillator on some subharmonic of the transmission frequency? a) Frequency stability b) Good selectivity c) High sensitivity d) Frequency sensitivity 267. (Apr 1997) _____ used to measure speech volume. a) Speech meter b) Volume unit meter c) Volume meter d) Audio frequency meter 268. What source of noise is related to system temperature? a) thermal noise b) burst noise c) pink noise d) shot noise 269. What is the function of an FM limiter? a) to eliminate interference b) to increase stability c) to provide image rejection d) to remove amplitude variation 270. (Apr 1997) The final amplifier of either FM or AM transmitter operates as a) Class A b) Class B c) Class C d) Class D 271. The rms antenna current for an AM transmitter increases by 15% over the unmodulated value when sinusoidal modulation is applied. Find the daepth of modulation. a) 0.8 b) .05 c) 0.75 d) 0.6 272. Determine the open-circuit noise voltage in 1Hz of bandwidth at 290 K for a diode biased at 1 mA. a) 465 pV b) 56 pV 18
c) 654 pV d) 65 pV 273. The SI unit of magnetic field intensity is a) Ampere b) Ampere/square meter c) Volt/meter d) Ampere/meter 274. An AM signal displayed on an oscilloscope has a maximum span of 5 V and a minimum of 1 V. What is the modulation index? a) 120% b) 80% c) 67% d) 20% 275. It is the interference of a signal from one channel into another channel. a) Sideband splatter b) Crosstalk c) Inter-modulation distortion d) Spur 276. FM system is superior to AM because a) I t eli minates most of amplitude var iation noise b) It has wider bandwidth c) It is at VHR band d) It produces more rock music 277. (Nov 1996) Which determines the number of sideband components in FM? a) All of these b) Modulation index c) Carrier frequency d) Modulation frequency 278. The velocity at which energy is transported by a wave of nearly constant frequency. a) Linear velocity b) Average velocity c) Phase velocity d) Group velocity 279. Keyed AGC is AGC that: a) Works only with Morse code. Is activated when keyed by the transmitting signal b) Is used in color TV receivers so that the transmitted color has no effect on the AGC c) Is used in TV receivers so that transmitted picture brightness does not affect the AGC 280. Which stages in a broadcast transmitter are normally class C? a) AF amplifier b) oscillator c) buffer amplifier d) modulated amplifier 281. What id the purpose of a conversion frequency oscillator? a) To increase stability b) To produce the IF c) To provide good selectivity d) To provide a conversion frequency 282. What form of energy is contained in a sound? a) elastic b) electromagnetic c) kinetic d) acoustic 283. What will the normal AM receiver detect from an unmodulated RF AC wave? a) Carrier b) noise c) Nothing d) AF signal 284. A type of device noise whose intensity decreases with frequency. a) shot noise b) flicker c) popcorn noise d) thermal noise 285. (Nov 1998) The extremely high frequency (EHF) band is in the radio spectrum range of _____. a) 30 to 300 kHz b) 3 to 30 GHz c) 3 to 30 MHz d) 30 to 300 GHz 286. Where is the single-button microphone used most? a) Telephone b) Broadcast Studio c) Intercom d) Paging system 287. (Nov 1997) A method of expressing the amplitude of complex non-periodic signals such as speech. a) Wavelength b) Frequency c) Pitch d) Volume 19
288. An earth station receiver has a signal of 4 x 10-12 W across 50 Ω input. What is the signal level in microvolts? a) 1000 b) 1.6 c) 14.14 d) 328 289. Complex number, equal to the ratio of a complex pressure amplitude to the complex amplitude of the volume velocity a) Acoustic Intensity b) Acoustic Pressure c) Air Elasticity d) Acoustic Impendance 290. What determines the rate of frequency swing for an FM broadcast transmitter? a) Modulation frequency b) Carrier amplitude c) Carrier frequency d) Modulation amplitude 291. (Apr 1998) The final power amplifier in an FM y=transmitter usually operates class _____. a) A b) B c) AB d) C 292. Which of the following is not a continuous wave modulation? a) AM b) PCM c) FM d) PM 293. (April 1997) Industrial noise frequency is between ___. a) 20 GH b) 15 to 160 MHz c) 0 to 10 kHz d) 200 to 3000 MHz 294. In a TV receiver, what is the horizontal sync frequency? a) 15,750 Hz b) 525 Hz c) 30 Hz d) 60 Hz 295. Amplitude distortion results from _____ amplification. a) Direct b) Linear c) Indirect d) Nonlinear 296. What determines the selectivity of a receiver? a) the frequency stability b) the power handling capability c) the gain of the amplifier d) the bandwidth of the tuned circuits 297. Which of the following is used in microwave ovens? a) Klystron b) TWT c) Magnetron d) BWO 298. A function y = f(t) is even if it has perfect symmetry about the _____. a) w-axis b) z-axis c) x-axis d) y-axis 299. When voltages are out-of-phase, the total voltage can be found by adding: a) Arithmetically b) Average values c) Peak values d) Vectorially 300. What type of microphone has the lowest power output? a) Dynamic b) Carbon c) Condenser d) Ribbon 301. If a broadcast station is transmitting but not modulating, what is heard in a receiver tuned to its frequency? a) Audio only b) Nothing c) Hiss d) Carrier only 302. What is the signal, usually of random character, which is always present in a communications system? a) interference b) sideband c) noise d) spur 20
303. This noise increases with bias current level and is inversely propor tional to the square of frequency. a) flicker b) shot noise c) burst noise d) thermal noise 304. Which of the following is an advantage of PM over FM? a) Requires a complex circuitry b) A need for several modulators c) Requires a simpler transmitter d) One amplifier is required 305. A mixer is tuned to 2000 kHz and the local oscillator is on 1300 kHz. What frequency would cause an image? a) 600 kHz b) 1100 kHz c) 700 kHz d) 3300 kHz 306. The information carrying capacity of a signal is _____ to its bandwidth. a) Inversely proportional b) Equal c) Directly proportional d) Not related 307. The modulated carrier power in FM a) Increases with modulating signal power b) Decreases with modulating signal power c) Is independent of modulating signal power d) All of the above 308. (Nov 1996) Noise from random acoustic or electric noise that has equal per cycle over a specified total frequency band. a) Gaussian noise b) All of these c) White noise d) Thermal noise 309. When the modulating frequency is halved, the modulation index is doubled and the modulating voltage remains constant. The type of modulation is a) PCM b) FM c) AM d) PM 310. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth? a) 215 kHz b) 115 kHz c) 230 kHz d) 200 kHz 311. Which of the following is not a major difference between FM and AM receivers? a) AGC b) IF frequency c) deemphasis d) Limiter 312. (Apr 1997) The sound power level of a jet plane flying at a height of 1 km is 160 dB (ref = 10-12 W). What is the maximum sound pressure level on the ground directly below the plane assuming that the aircraft radiates sound equality in all directions? a) 59.1 dB b) 69.1 dB c) 79.1 dB d) 89.1 dB 313. The process of impressing information signals to a high frequency carrier is called _____. a) modulation b) detection c) scrambling d) multiplexing 314. Calculate the thermal noise delivered to a system with a bandwidth of 1 Hz operating at 170C. a) 2.1 x 10-14 W b) 4 x 10-12 W c) 4 x 10-21 W d) 1.2 x 10-14 W 315. Name a periodic waveform that consists of only odd harmonics. a) Cosine wave b) Square wave c) Sine wave d) Spikes 316. A type of information signal which is made up of rapid and unpredictable variations in amplitude and frequency. a) pulses b) digital c) speech d) bits 317. What is the channel width of an AM BC station? 21
a) 50 kHz b) 20 kHz c) 5 kHz d) 10 kHz 318. (Mar 1996) In the phase shift method, how many circuits must be balanced? a) 1 b) None of these c) 2 d) 4 319. What determines the maximum number of vertical picture element? a) Number of fields per second b) Number of lines on the screen c) Number of frames per second d) Number of pixel 320. What type of circuit reduces even-order harmonics? a) Armstrong circuit b) Push-Pull c) Class A d) Demodulator 321. If the second-harmonic amplitude is 2V and the fundamental is 10V, then the second-harmonic distortion is ___. a) 40% b) 2 c) 20% d) 4 322. How often should BC stations be identified? a) every thirty minutes b) every ten minutes c) at least once an hour d) at least once a day 323. A receiver has a dynamic range of 81 dB. It has 0.55 nW sensitivity. What is the maximum allowable input signal? a) 5.01 uW b) 15 uW c) 0.0692 W d) 5.01 W 324. What holds the horizontal oscillator on frequency? a) AFC b) ECL c) AGC d) ALC 325. (Apr 1997) The random and unpredictable electric signal from natural causes, both internal and external to the system is known as ___. a) distortion b) attenuation c) noise d) interference 326. What does the acronym VIR mean? a) Vertical Interface Relay b) Video Interval Recording c) Vertical Interval Reference d) Video Interface Relay 327. What is the frequency swing of an FM broadcast transmitter when modulated 60%? a) ±75 kHz b) ±45 kHz c) ±35 kHz d) ±60 kHz 328. He was the one who developed the wireless telegra ph. a) Edison b) Armstrong c) Marconi d) Bell 329. A ______ is a resonant circuit tuned to reject an undesired signal by reducing the gain at the trap frequency. a) LPF b) Wave trap c) HPF d) LC tank 330. In AM, maximum desirable output of a transmitter is obtained when its modulation is _____%. a) 50 b) greater than 100 c) less than 100 d) 100 331. Normally, for how long must logs be kept for the FCC? a) 1 month b) 2 years c) 1 week d) 1 year 22
332. (Nov 1998) What do you call the service area of a standard AM broadcast where fading is allowed but no objectionable co-channel interference? a) Secondary b) Experimental c) Primary d) Tertiary 333. A type of microphone which has a permanent magnet a) crystal b) ribbon c) electret d) carbon 334. An FM signal with modulation index m is applied to a frequency tripler. The modulation index at the output is _____. a) 0 b) m c) m/2 d) 3m 335. If an FM transmitter has two doublers and one tripler, what is the carrier swing when the oscillator deviates 2 kHz? a) 2 kHz b) 24 kHz c) 48 kHz d) 36 kHz 336. (Apr 1998) With which emission type is the capture-effect most pronounced? a) SSB b) AM c) FM d) CW 337. What class of bias should produce l east harmonics? a) Class A b) Class D c) Class C d) Class B 338. (Nov 1997) Background noise is the same as the following except a) white noise b) gaussian noise c) thermal noise d) impulse noise 339. Which of the following is not contained in TV tuner? a) VHF mixer b) VHF oscillator c) VHF RF amplifier d) Duplexer 340. What stage in a super heterodyne is aligned first? a) RF Amplifier b) IF Amplifier c) Mixer d) Second Detector 341. What is the meaning of the acronym WDM? a) Wavelength division multiplexing b) Wide distribution media c) Wap distributed mode d) Wireless data monitoring 342. (Mar 1996) Three audio waves with 100, 200 and 300 volts amplitude respectively, simultaneously modulate a 450 volts carrier. What is the total percent of modulation of the Am wave? a) 69% b) 83% c) 50% d) 115.5% 343. (Apr 1998) What is the period of a wave? a) The amplitude of the wave b) The number of zero crossing in one cycle c) The time required to complete one cycle d) The number of degrees in tone cycle 344. Who is in overall control of a TV production? a) manager b) actor c) producer d) director 345. What is another term meaning “downward modulation”? a) Negative Carrier Shift b) Distortion Modulation c) Harmonic Modulation d) Positive Carrier Shift 346. The pre-emphasis network in Europe has a time constant of ___. a) 75 us b) 150 us c) 100 us 23
d) 300 us 347. In free-space, the phase velocity of a TEM wave is _____ the group velocity. a) Greater than b) Equal to c) Less than d) None of the above 348. The type of device noise, which is important at high frequencies, is ___ noise. a) Johnson b) Transit-time c) flicker d) shot 349. What is the letter symbol for the luminance signal? a) R b) Y c) Q d) I 350. The all-encompassing noise associated with a give environment, being usually composite of sounds from many sources near and far. a) Nominal Room b) Ambient Noise c) Relative Noise d) Average Noise 351. It is the ___ that tunes the receiver to different stations. a) IF Amplifier b) Local Oscillator c) RF Amplifier d) Detector 352. What is the amount of power lost in a device due to its presence in the path of energy flow? a) Insertion loss b) Wave attenuation c) Phase shift d) Gain 353. Which of the following is not a type of external noise? a) Pink Noise b) Solar Noise c) Galactic Noise d) Atmospheric Noise 354. A type of room whose boundaries absorb effectively all incident sound. a) Live Room b) Production Room c) Acoustic Room d) Anechoic Room 355. What is an NO RY? a) Normally ready b) Non organic relay c) Non operational relay d) Normally open relay 356. It is the liberation of electrons by thermionic means, used as the principal source of electron emission in microwave vacuum tube devices. a) Secondary Effect b) Miller Effect c) Edison Effect d) Bunching 357. What kind of system relays has remote readings? a) Telemetering b) Telecast c) Data gathering d) Broadcasting 358. (Nov 1998) Which of the following is referred to as a radio emission without sidebands? a) Data b) Carrier c) Analog d) Voice 359. What major principle prevents the TV viewer from observing flicker? a) scanning b) drowsiness c) light reflections d) per si stence of the picture tube and human eye 360. A 2-kW RF carrier is sinusoidally modulated 100% . Haw much power is in one sideband? a) 2000 W b) 250 W c) 125 W d) 500 W 361. For an FM signal a) The total number of sidebands depends on the modulation frequency the carrier frequency b) The carrier frequency disappears when the modulation index is large c) The carrier frequency cannot disappear d) The amplitude of any sideband depends on the modulation index 24
362. (Nov 1996) The wavelength of light has no role in a) Resolving power b) Interference c) Polarization d) Diffraction 363. What other term is essentially synonymous with beating? a) Heterodyning b) Suppressing c) Scrambling d) Filtering 364. It refers to the sending, receiving and processing of information by electronic means. a) Telemetry b) Communications c) Broadcasting d) Telephony 365. How many oscillators does black and white TV receiver contain? a) 4 b) 1 c) 3 d) 2 366. What is the name of the operation that uses an antenna changeover switch? a) Crossover b) Switching c) Duplex d) Simplex 367. Which type of microphone has a high Z output? a) Ribbon b) Carbon c) Crystal d) Dynamic 368. (Nov 1998) Frequencies above _____ kHz, are referred to as the radio frequencies. a) 20 b) 10 c) 100 d) 2 369. What radio frequencies are most affected by lightning or static waves? a) SHF b) VLF c) VHF d) UHF 370. (Nov 1997) The third symbol in the designation of radio emission under the IYU rules refers to a) type of modulation of the main carrier b) type of information to be transmitted c) bandwidth d) nature of si gnal(s)modulating the ma in carrier 371. What is the magnitude of the frequency component at seven times the fundamental frequency for a square wave amplitude 1 V? a) 0.2 b) 0.18 c) 0.14 d) 0.7 372. _____ frequencies are exact multiples o f the fundamental frequency. a) Modulation b) Harmonic c) Radio d) Distortion 373. (Nov 1996)Multiplexing in a time division multiplexer occurs based upon a) The positioning of data within a frame b) T he po si tion of a frame wi thin a gro up of frames c) T he pr iori ty assi gned to a connected device d) The activity of a connected device 374. (Apr 1998) Quantity that do not change when a beam of light enters one medium to another. a) Frequency b) Direction c) Wavelength d) Speed 375. Which of the following is not an advantage of FM over AM? a) Lower bandwidth is required b) Better noise immunity is provided c) The transmitted power is mote useful d) Less modulating power is required 376. (Apr 1997) What is the local oscillator frequency range in commercial AM broadcast if IF is equal to 455 kHz? a) 955 to 2055 kHz b) 540 to 1600 kHz c) 0 to 1600kHz d) 0 to 455 kHz 377. Who hears high audio frequency best? 25
a) young people b) old people c) all of the above d) 40 years old 378. A major disadvantage of the vacuum tube is its need for a _____ to give energy to the electrons. a) Limiter b) Heater c) Line equalizer d) Voltage source 379. What part of a super heterodyne is responsible for the band pass of the receiver? a) LO b) IF Amplifier c) Detector d) RF Amplifier 380. The term angular velocity as applied to electronic system refers to the number of: a) Radian per second a voltage vector rotates b) Degrees subtracted from the radians c) None of these d) Degrees averaged together 381. What is the allowable bandwidth of commercial AM radio in the United States? a) 10 MHz b) 30 kHz c) 15 kHz d) 10 kHz 382. A diagram which shows the relationship between RF signal phase and maximum bunching of the electron beam in velocity-modulated devices. a) S-parameters Diagram b) Smith Chart c) Applegate Diagram d) Venn Diagram 383. Which of the following is not normally tested in a transmitter? a) Modulation b) Power c) Amplitude d) Frequency 384. In Phase Modulation (PM), the modulation index represents ______. a) The maximum frequency deviation b) The maximum phase shift c) The ratio of the modulation amplifier to the carrier amplitude d) The total number of sidebands 385. A mirror that reflects one color but passes all other are called ____. a) Concave b) Monochroic c) Convex d) Dichroic 386. (Mar 1996) What is the primary advantage of DSBSC in AM? a) Reduce bandwidth over standard AM b) N o tra nsmitter power is wasted in the ca rri er c) All of these d) It is simpler to transmit and receive than the standard AM 387. What causes audio signals to be distorted in a receiver? a) Amplitude b) Gain c) Harmonics d) Interference 388. Which is not a method o f generating single sideband signal? a) Balanced modulator b) Filter c) Weaver d) Phase-shift 389. The color phasor has what phase for the I signal? a) 180º b) 90º c) 57º d) 37º 390. The three kind of demodulators for AM are: a) simple, medium, and complex b) si mple, suppressed carr ier, and single sideband c) a and c but not b d) frequency, phase and amplitude 391. (Mar 1996) The signal in a channel is measured to be 23 dB while noise in the same channel is measured to be 9 dB. The signal to noise ratio therefore is ____. a) 23/9 b) 14-dB c) 32-dB d) 9/23 392. What device can be used to make a modulated envelope visible? a) Spectrum Analyzer 26
b) Synthesizer c) Calibrator d) Oscilloscope 393. Where is a color burst found? a) Back porch b) Blanking pulse c) Synch pulse d) Front porch 394. (Nov 1997) Extra-terrestrial noise is observable a t frequencies from a) 5 to 8 GHz b) 8 to 1.43 GHz c) Above 2 GHz d) 0 to 20 kHz 395. What is the amount of carrier swing necessary to produce an 80% modulation for the audio portion of the TV band? a) 20 kHz b) 50 kHz c) 25 kHz d) 40 kHz 396. What was the first BC PM system called? a) Fourier b) Wienbridge c) Armstrong d) Weaver 397. What portion of the TV signal is used to synchronize the video information on the recording tape? a) the horizontal sync b) the vertical sync c) the raster lines d) the vertical deflection coil 398. The PM signal produces by an FM circuit is called a) Direct FM b) Direct PM c) Indirect PM d) Indirect FM 399. What is an advantage of series modulation? a) Capable of generating high power b) C apa ble of mo dulating ve ry hi gh frequencies c) Low noise and interference d) High gain and selectivity 400. What is the bandwidth of a narrowband FM signal generates by a 2 kHz audio signal a 110-MHz FM carrier? a) 4 kHz b) 2 kHz c) 1 kHz d) 5 kHz 401. (Apr 1997) Lowest frequency produced by musical instrument. a) Midrange b) Harmonic c) Fundamental d) Period 402. What is the required accuracy of BC station meters? a) 1% b) 5% c) 2% d) 10% 403. How many mixers are in an SSB receiver? a) 2 b) 3 c) 4 d) 1 404. A SSB transmitter drives 121 V peak into a 50-Ω antenna. What is the PEP? a) 121 W b) 73 W c) 146W d) 292 W 405. What is the noise current for a diode with a forward bias of 1 mA over a 1 MHz bandwidth? a) 17.9 nA b) 9.15 nA c) 91.5 uA d) 179 nA 406. How often must remote control instrumentals be calibrated? a) Daily b) Weekly c) Monthly d) Yearly 407. Which of the following is not an advantage of vestigial sideband transmission? a) Easy to detect the carrier b) Reduces power requirements 27
c) Reduces transmission bandwidth d) Simple receiver circuitry 408. Noise is most problematic at the___. a) communication channel b) receiver c) source d) transmitter 409. The purpose of the balances modulator circuits is to eliminate the _____. a) Noise b) Distortion c) Sidebands d) Carrier 410. Which of the following limits the performance of a communication system? a) Accessibility b) Bandwidth c) Cost d) Reliability 411. (Nov 1997) An AM transmitter is rated 100 W at 100% modulation. How much power is required for the carrier? a) 33.33 W b) 66.66 W c) 100 W d) 83.33 W 412. Is SSB, voice compression is better in the AF or Rf section? a) RF b) SB c) Intermediate d) AF 413. What factor determines the modulation index of an FM transmission? a) Modulating signal frequency b) Carrier amplitude c) Carrier phase d) Carrier frequency 414. (Mar 1996) A car horn outdoors, produces a sound intensity level of 90 dB at ft away. At this distance, what is the sound power in watt? a) 1.2 W b) 12 W c) 0.012 W d) 0.12 W 415. The entire range of _____ of electromagnetic radiation is called the frequency spectrum. a) Amplitudes b) Phases c) Frequencies d) Energies 416. (Apr 1997) Which transmit only sideband? a) 3AJ b) A3E c) H3E d) 11BE 417. What is the approximate efficiency of a class B linear RF AM amplifier? a) 90% b) 12% c) 35% d) 50% 418. What is the most common application of carbon microphone? a) telephone b) FM radio c) Am radio d) TV transmitter 419. When the loop in a PLL is locked, what is the difference in frequency detected by the phase detector? a) 900 b) 1800 c) 450 d) 00 420. What is the power requirement for international BC stations? a) 100 W b) 15 W c) 50 kW d) 5 kW 421. When diode is used as a detector in the simple AM radio, what happens to the waveform o f the carrier? a) It is modulated. b) It is amplified. c) It is filtered. d) It is rectified. 422. What is the main difference between an AF amplifier and an RF amplifier? a) The stability b) The range of frequencies that they amplify c) The amplification factor 28
d) The selectivity 423. Which of the following is not an advantage of SSB over AM? a) Simple receiver circuit b) Less spectrum c) None of these d) Power saving 424. In an FM receiver, the circuit that keeps the r eceiver tuned exactly to the desired station is ___. a) Limiter b) AGC c) Discriminator d) AFC 425. What is the ratio of maximum deviation allowed to the modulating frequency being used called? a) Percent Modulation b) Deviation ratio c) Modulation Index d) Modulation Sideband 426. In an AM transmitter, after the modulation stage, _____ amplifier cannot be used. a) Class C b) Linear c) Class A d) Class B 427. The local FM stereo rock station is at 96.5 MHz. What must be the local oscillator frequency? a) 112.5 MHz b) 93.9 MHz c) 105.9 MHz d) 107.2 MHz 428. (Apr 1998) Term in communication which is referred, “to send out in all direction”. a) Transmit b) Broadcast c) Media d) Announce 429. (Apr 1997) Unit of noise power of psophometer a) dBm b) dBa c) dBmo d) pWp 430. What factor(s) determine the modulation index of an FM signal? a) Amplitude of the carrier b) Frequency of the modulation signal c) A and b are true d) Frequency deviation 431. How much time is allocated for horizontal retrace? a) 63.5 µs b) 7.5 µs c) 10.2 µs d) 76 µs 432. For an FM signal in the 88-108-MHz broadcast band with a frequency deviation of 15 kHz, determine the percent modulation. a) 40% b) 60% c) 20% d) 80% 433. The term wolfe number refers to the front-end circuit of a VHF TV super heterodyne receiver? a) 27-year solar cycle b) 11-year sunspot cycle c) Ultraviolet Radiation d) X-rays 434. The value of a resistor creating thermal noise is halved. The noise power generated is a) unchanged b) quadrupled c) doubled d) halved 435. What constitutes the input to an AM transmitter? a) RF oscillator and/or audio amplifier b) Buffer and IF amplifier c) Mixer and amplifier d) Mixer and local oscillator 436. An indirect method of generating FM is a) Reactance tube modulator b) Reactance transistor modulator c) Armstrong modulator d) Varactor diode modulator 437. During 100% modulation, what percentage of the average output power is in the sidebands? a) 100% b) 33.3% c) 16.67% d) 66.67% 438. Which subcarrier leads by 90º in TV system? 29
a) Y b) Q c) R d) I 439. (Apr 1998) Term for transmission of printed picture by radio. a) Television b) Xerography c) Facsimile d) ACSSB 440. An amplifier with NF= 6 dB has (S/N), of 25 dB. What is the output S/N? a) 31 dB b) 19 dB c) 6 dB d) 25 dB 441. (Nov 1997) Modulation in which the modulated wave is always present. a) Carrier modulation b) Continues modulation c) Front-end d) Log-periodic modulation 442. The total transmitted power for an AM signal is 1200 W at 100% modulation. What is the power for each sideband? a) 1000 W b) 100 W c) 1200 W d) 200 W 443. (Nov 1996) The unit of pitch. a) Phon b) Decibel c) Sone d) Mel 444. The range of frequencies represented in a signal. a) Guardband b) Beamwidth c) Bandwidth d) Crisp 445. A system has 150 kHz of bandwidth available for a 10-kHz modulating signal. What is the approximate deviation? a) 70 kHz b) 100 kHz c) 75 kHz d) 65 kHz 446. The modulation index of an AM wave is changes from 0 to 1. The transmitter power is? a) Doubled b) Increased by 50% c) Halved d) Unchanged 447. (Apr 1998) The signal to noise ratio that is required for a satisfactory television reception. a) 20 dB b) 40 dB c) 10 dB d) 30 dB 448. In FM, what determines bandwidth? a) Modulation phase b) Carrier power c) Carrier frequency d) Modulation index 449. Any periodic function is represented by the sum of a number of sinusoidal variations of different amplitudes, frequencies, and phases. a) Nyquist Theorem b) Fourier’s Theorem c) Huygen’s Theorem d) Hartley’s Theorem 450. What is the percent modulation of an AM wave that has a power content of 12 kW in each sideband when modulated by a single tone? a) 82% b) 75% c) 66% d) 30% 451. What is the power saving in J3E system at 100% modulation? a) 83.3% b) 100% c) 33.3% d) 66.67% 452. Is the information used to represent a TV picture transmitted at the same time? a) Sometimes b) None of the above c) Yes d) No 30
453. When an operator wishes to indicate that he has received all of the last transmission, he will transmit the word _____. a) Roger b) Ok c) Over d) Out 454. What determines the station that will be selected by a tuner? a) The sensitivity of the tuner b) The bandwidth of the amplifier c) The selectivity of the IF d) The resonant frequency of the tuner 455. What is the major problem with a very-high-frequency oscillator? a) Poor frequency stability b) No power stability c) Poor image rejection d) Low sensitivity 456. What is the deviation ratio for commercial FM? a) 5 b) 10 c) 1 d) 2 457. The super heterodyne circuit uses local oscillator to ___ with the RF signal of the station and convert the carrier to the intermediate frequency. a) beat b) all of the above c) heterodyne d) mix 458. (Nov 1996) ____ is the average rate of transmission of sound energy in a given direction through a cross sectional area of 1 sq. m. at right angle to the direction. a) Sound intensity b) Sound pressure c) Loudness d) Pressure variation 459. What percentage of the primary colors used in color TV are needed to produce the brightest white? a) 58% red, 20% green, 22% blue b) 30% red, 59% green, 11% blue c) 33% red, 33% green, 33% blue d) 50% red, 28% green, 22% blue 460. How many AM stations can be accommodated in a 150-kHz bandwidth if the highest modulating frequency is 10 kHz? a) 10 b) 15 c) 14 d) 7 461. A diode detector: a) Detects the modulating signal. b) Converts AC into pulsating DC. c) Does all of the above. d) Allo ws curr ent to flo w in one dire ction only. 462. (Nov 1998) The third symbol radio emission which represent telephone transmission including sound broadcasting. a) W b) E c) F d) C 463. What are the frequency limits of the AM BC band? a) 500 – 1600 kHz b) 300 – 3000 kHz c) 88 – 108 MHz d) 535 – 1605 kHz 464. What is the relative permittivity of air ? a) 1.26 x 10-6 b) 20 c) 8.853 x 10-12 d) 1 465. An FM signal has a frequency deviation of 2000 Hz caused by modulating signal of 500 Hz. What is the modulation index? a) 5 b) 4 c) 8 d) 2 466. The noise figure of a system is 12 and its input signal-to-noise ratio is 60. What is the output signal-tonoise ratio? a) 720 b) 0.2 c) 72 d) 5 467. What type of field does a Faraday shield stop? 31
a) Magnetostatic b) Electrostatic c) Common d) Array 468. To provide two or more voice circuits with the same carrier, what system must be used? a) Lincomplex b) Pilot carrier system c) ISB emission d) Vestigial sideband system 469. If two signals are in quadrature, what is their phase relation? a) 180° b) 90° c) 45° d) 0° 470. In Frequency Modulation ______. a) The frequency of carrier varies according to the phase of the modulating signal b) The frequency of carrier varies according to the frequency of the modulating signal c) The amplitude of the carrier according to the amplitude of the modulating signal d) The frequency of carrier varies according to the amplitude of the modulating signal 471. A carrier wave is amplitude modulated by two sine waves of different frequencies with modulation indices of 0.3 and 0.4. What is the overall modulation index? a) 0.7 b) 0.2 c) 0.1 d) 0.5 472. Most household radio receiver uses ___ detector. a) asynchronous b) phase c) synchronous d) envelope 473. What is the waveform of sweep voltage? a) Spikes b) Rectangular wave c) Sawtooth d) Square wave 474. (Mar 1996) What is the difference between phase and frequency modulation? a) Lies in the different definitions of the modulation index b) L ies in poor er audio response of phase modulati on c) Os too great to make two systems compatible d) Is purely theoretical because they are the same in practice 475. Receiver ___ is a gauge of the receiver’s capacity to receive weak signals. a) Selectivity b) Sensitivity c) Dynamic Range d) Gain Factor 476. What formula determines sideband power i n AM emissions? a) Pc(m2/4) b) Pc(m2/3) c) Pc(m2/5) d) Pc(m2/2) 477. What do you call a heterodyne frequency changer? a) Mixer b) Frequency synthesizer c) Modulator d) Frequency translator 478. In SSB transmission, which sideband can be eliminated? a) Either b) Depends upon the use c) Upper only d) Lower only 479. What is the blanking level for negative transmission? a) 50% b) 12.5% c) 66.6% d) 75% 480. (Nov 1996) What is the type of emission used by the standard AM radio broadcast? a) F b) C c) D d) A 481. (Nov 1998) What is the major cause of atmospheric or static noise? a) airplanes b) thunderstorm c) sunspot d) meteor showers 482. What is the following is not a product of overmodulation? a) Buckshot b) Splatter 32
c) Image d) Spurious signal 483. What does ALC mean? a) Asynchronous Link Control b) All Local Circuits c) Automatic Link Circuit d) Automatic Level Control 484. An unmodulated carrier is 300 VP-P. Ca lculate %m when its maximum p-p value reaches 400 V. a) 83.3% b) 100% c) 66.67% d) 33.3% 485. (Apr 1998) A carrier signal has _____. a) Constant peak amplitude b) Frequency range 20-20000 Hz c) A varying amplitude d) The information 486. What does VOX mean? a) Very oxford transmitter b) Voice onward transmission c) Voice-operated transmission d) Very onward circuit 487. (Apr 1998) An instrument for recording waveforms of audio frequency. a) Audioscope b) Oscilloscope c) Phonoscope d) Radioscope 488. What is the BFO in SSB receiver called? a) Backward Oscillator b) Carrier Oscillator c) Local Oscillator d) Frequency Oscillator 489. The value(s) associated with sine waves of voltages are: a) Average b) All of the above c) Instantaneous d) Maximum 490. If the 500-Hz modulation of a 1-MHz carrier has 3rd harmonic distortion, what is the emission bandwidth? a) 1 kHz b) 1500 Hz c) 1 MHz d) 3 kHz 491. The device that prevents aural RF from entering the video transmitter and vice versa is called____. a) diplexer b) coupler c) tuner d) duplexer 492. In a 5-kW AM transmitter high-level modulation is used. What is the value of the audio signal power needed for 100 percent modulation? a) 50 kW b) 15 kW c) 5 kW d) 2.5 kW 493. (Apr 1998) In television broadband vivid strong color are often referred as ____. a) luminance b) saturation c) chrominance d) hue 494. What stage in an AM transmitter creates its own sine wave? a) Amplifier b) Modulator c) Buffer d) Oscillator 495. Which of the following is not a requirement for a color TV si gnal? a) compatibility with B/W receivers b) good raster reproduction c) simulate a width variety of colors d) within 6 MHz bandwidth 496. The circuit that performs the suppression of the carrier signal. a) Balanced modulator b) Carrier synthesizer c) Pre-emphasis d) LPF 497. What section of a TV receiver determines the bandwidth and produces the signal gain? a) IF Amplifier b) RF Amplifier c) Local oscillator d) Mixer 33
498. (Mar 1996) Atmospheric condition is controlled by a) All of these b) Humidity c) Pressure d) Temperature 499. An 88-MHz carrier is modulated by an audio tone that caused a frequency deviation of 15 kHz. What is the carrier swing of this FM signal? a) 45 kHz b) 60 kHz c) 15 kHz d) 30 kHz 500. The parameter of a high-frequency carrier that may be varied by a low-frequency intelligence signal is _____. a) All of the above b) Amplitude c) Frequency d) Phase 501. What is the letter-number designation for an FM facsimile? a) A3E b) C3C c) F3E d) F3C 502. The rms antenna current of a radio transmitter is 10 A when unmodulated, rising to 12 A when the carrier is sinusoidally modulated. What is the modulation factor? a) 0.94 b) 1 c) 0.67 d) 0.83 503. What is the lowest number of sections required by communications receiver? a) 3 b) 1 c) 4 d) 2 504. (Nov 1996) The output of a balanced modulator is _____. a) LSB and USB b) USB c) LSB d) Carrier 505. (Nov 1997) The Tendency for the sound energy to spread. a) Rarefaction b) Refraction c) Diffraction d) Reflection 506. What is the shape of a trapezoidal pattern at 100% modulation? a) Rectangle b) Circle c) Square d) Triangle 507. What is the small amount of the signal applied to the input port that leaks through to the output port? a) Regenerative loss b) Feedthrough loss c) Reflection loss d) Insertion loss 508. What is meant by amplitude modulation? a) The carrier sign is varied b) The carrier amplitude is varied c) The carrier frequency is varied d) The carrier phase is varied 509. If a 7-A carrier is modulated 100% by a sinusoidal tone, how much does the antenna current increase? a) 44.8% b) 33.3% c) 66.7% d) 22.5% 510. In FM, what produces the sidebands? a) Modulating signal b) Carrier signal c) RF signal d) Carrier and its harmonics 511. The signal which is superimposed on a high-frequency sine wave is called _____. a) Information b) Square wave c) Sideband d) Carrier 512. Pilot carrier transmission, means a) Only one sideband is transmitted b) One sideband and carrier are transmitted c) Two sidebands as well as a trace of carrier are transmitted d) Only two sidebands are transmitted 34
