________________________________________ 1. What is the frequency swing of an FM broadcast transmitter when modulated 60%? a) ±60 kHz b) ±35 kHz c) ±45 kHz d) ±75 kHz ________________________________________ 2. What produces splatter in an AM transmission? a) Flickering b) Harmonics c) overmodulation d) Clipping ________________________________________ 3. What is an ideal pulse? a) A perfect square wave with zero rise time b) A low duty cycle c) A high amplitude d) A very short duration ________________________________________ 4. (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) Band-pass filter d) High-pass filter ________________________________________ 5. (Apr 1998) Type of modulation used in TV broadcast visual transmitter. a) Pulse modulation b) Vestigial sideband c) SSBFC d) DSBFC ________________________________________ 6. (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 ________________________________________ 7. (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) 144.50 GHz c) 345.00 MHz d) 450.00 MHz ________________________________________ 8. Find the noise voltage for a 1-kohms resistor at 170C “tuned” by an LC circuit with a BW of 1 MHz. a) 50 uV b) 5.01 uV c) 15.01 uV d) 15 uV ________________________________________ 9. With _____, the modulation envelope is an expression of the amplitude and frequency of the modulation signal. a) FM b) PM c) AM d) PCM ________________________________________ 10. (Apr 1998) Term in communication which is referred, “to send out in all direction”. a) Media b) Broadcast c) Transmit d) Announce ________________________________________ 11. (Mar 1996) In AM, the carrier carries _____ intelligence. a) Difference b) Same c) Distorted d) No ________________________________________ 12. What is the frequency of the color burst? a) 60 Hz b) 3.58 MHz c) 30 Hz d) 6 MHz ________________________________________ 13. An FM signal has a frequency deviation of 2000 Hz caused by modulating signal of 500 Hz. What is the modulation index? a) 2 b) 5 c) 8 d) 4 ________________________________________ 14. The major difference between FM and PM a) All of the above b) Lies in the different definition of modulation index c) Is too great to make the two system compatible d) Lies in the poorer audio response of phase modulation index ________________________________________ 15. In what type of transmitters is balanced modulators used? a) PM b) A3E c) F3E d) SSB ________________________________________ 16. In TV system. A picture signals are transmitted by a) PM b) FM c) PCM d) AM ________________________________________ 17. In a TV receiver, what is the horizontal sync frequency? a) 60 Hz b) 30 Hz c) 525 Hz d) 15,750 Hz ________________________________________ 18. Any periodic function is represented by the sum of a number of sinusoidal variations of different amplitudes, frequencies, and phases. a) Fourier’s Theorem b) Nyquist Theorem c) Hartley’s Theorem d) Huygen’s Theorem ________________________________________ 19. What does an FM detector do? a) to convert frequency changes to amplitude changes b) to increase the frequency change c) to convert phase changes to frequency changes d) to extract amplitude variations ________________________________________ 20. What is a device such as the microphone and the headset sometimes called? a) Receiver b) Converter c) Reproducer d) Transmission Medium ________________________________________ 21. 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 ________________________________________ 22. What will the normal AM receiver detect from an unmodulated RF AC wave? a) noise b) Carrier c) AF signal d) Nothing ________________________________________ 23. A duplexer is used to a) Connect two t6ransmitter to the same antenna b) Feed more than one receiver from a single antenna c) Feed more than one transmitter from a single antenna d) Connect a receiver and a transmitter to the same antenna ________________________________________ 24. Receiver ___ is a gauge of the receiver’s capacity to receive weak signals. a) Selectivity b) Dynamic Range c) Sensitivity d) Gain Factor ________________________________________ 25. The term angular velocity as applied to electronic system refers to the number of: a) None of these b) Degrees averaged together c) Degrees subtracted from the radians d) Radian per second a voltage vector rotates ________________________________________ 26. (Nov 1998) Refers to the first symbol in an emission designation with an amplitude modulated main carrier represented by letter A. a) Double sideband b) Independent sideband c) Single sideband suppressed carrier d) Double sideband full carrier ________________________________________ 27. (Nov 1996) Both frequency and phase modulation utilizes _____ modulation. a) angle b) Phase c) Digital d) AM and Fm ________________________________________ 28. A function y = f(t) is even if it has perfect symmetry about the _____. a) z-axis b) x-axis c) y-axis d) w-axis ________________________________________ 29. What is the main problem in receiving a suppressed carrier transmission or a single sideband transmission? a) The receiver needs to reinsert the missing carrier. b) The selectivity of the receiver must be good. c) The gain of the amplifier must be high d) There must be three detectors. ________________________________________ 30. What is the amount of power lost in a device due to its presence in the path of energy flow? a) Wave attenuation b) Phase shift c) Insertion loss d) Gain ________________________________________ 31. 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) Varying b) Constant c) Decreased d) Increased ________________________________________ 32. What other term is essentially synonymous with beating? a) Heterodyning b) Scrambling c) Filtering d) Suppressing ________________________________________ 33. The PM signal produces by an FM circuit is called a) Indirect PM b) Indirect FM c) Direct FM d) Direct PM ________________________________________ 34. The velocity at which energy is transported by a wave of nearly constant frequency. a) Group velocity b) Linear velocity c) Average velocity d) Phase velocity ________________________________________ 35. What is the main difference between an AF amplifier and an RF amplifier? a) The stability b) The amplification factor c) The range of frequencies that they amplify d) The selectivity ________________________________________ 36. Which of the following is not contained in TV tuner? a) VHF oscillator b) Duplexer c) VHF RF amplifier d) VHF mixer ________________________________________ 37. The pre-emphasis network in Europe has a time constant of ___. a) 100 us b) 150 us c) 75 us d) 300 us ________________________________________ 38. Which of the following is not an advantage of vestigial sideband transmission? a) Easy to detect the carrier b) Reduces transmission bandwidth c) Reduces power requirements d) Simple receiver circuitry ________________________________________ 39. What does AFC mean? a) Audio Frequency Camera b) All Filipino Conference c) Automatic Frequency Control d) Anti Firing Countermeasure ________________________________________ 40. It is the representation of a complex waveform in such a way that the sinusoidal components are displayed as a function of time. a) Frequency Domain b) TDR c) Time Domain d) Wave Representation ________________________________________ 41. (Mar 1996) what is the purpose of a beat frequency oscillator (BFO)? a) Aids in the reception of weak voice-modulated signals b) Generates a signal, whose frequency is the same as that of the intermediate frequency c) Generates a 1 kHz tone to Morse reception d) Generates an output, whose frequency differs from that of the intermediate frequency by 1 kHz ________________________________________ 42. What service uses HF CW communications? a) Satellite System b) Telephony c) Police d) Broadcasting ________________________________________ 43. In 1877, _____ invented a method of making a permanent record of sound with his invention of the phonograph. a) Edison b) Marconi c) Morse d) Bell ________________________________________ 44. What is the circuit that changes modulated RF to AF? a) Demodulator b) Modulator c) Synthesizer d) Modem ________________________________________ 45. Any waveform that is not symmetrical in area about the time axis has a (n) _____ component. a) RC b) FC c) DC d) AC ________________________________________ 46. Keyed AGC is AGC that: a) Is used in TV receivers so that transmitted picture brightness does not affect the AGC b) Is used in color TV receivers so that the transmitted color has no effect on the AGC c) Works only with Morse code. Is activated when keyed by the transmitting signal ________________________________________ 47. Which of the following is used in microwave ovens? a) TWT b) BWO c) Magnetron d) Klystron ________________________________________ 48. This noise increases with bias current level and is inversely proportional to the square of frequency. a) burst noise b) shot noise c) thermal noise d) flicker ________________________________________ 49. The three kind of demodulators for AM are: a) simple, suppressed carrier, and single sideband b) simple, medium, and complex c) a and c but not b d) frequency, phase and amplitude ________________________________________ 50. An FM signal with modulation index m is applied to a frequency tripler. The modulation index at the output is _____. a) m / 2 b) m c) 3m d) 0 ________________________________________ ________________________________________ 51. What circuit accompanies a mixer? a) IF Amplifier b) Detector c) LO d) RF Amplifier ________________________________________ 52. The parameter of a high-frequency carrier that may be varied by a low-frequency intelligence signal is _____. a) All of the above b) Frequency c) Phase d) Amplitude ________________________________________ 53. A receiver has a dynamic range of 81 dB. It has 0.55 nW sensitivity. What is the maximum allowable input signal? a) 15 uW b) 5.01 uW c) 0.0692 W d) 5.01 W ________________________________________ 54. What is an application for vestigial sideband transmission? a) TV Broadcast b) Telephony c) FDM d) AM Broadcast ________________________________________ 55. What sweep frequency could be used on a scope to stop an envelope pattern of 600-Hz modulation? a) 600 Hz b) 150 Hz c) 300 Hz d) 1200 Hz ________________________________________ 56. What is the main feature of DSB transmission? a) Carrier is suppressed b) High reliability c) High voltage d) Narrow bandwidth ________________________________________ 57. To make the headset reproduce the original modulating signal, the metal disk mask: a) Vibrate fast enough to keep up with the high frequency radio wave. b) Move in step with the frequency of the received carrier. c) Have a source of energy from a battery. d) Move in step with the changes in amplitude of the received carrier. ________________________________________ 58. 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) 97.2 MHz c) 98.6 MHz d) 99.3 MHz ________________________________________ 59. What is the carrier power transmitted on a 75-Ω antenna if mf=2 and Vc (unmodulated) is 2 kVpk? a) 9 kW b) 12.9 kW c) 1.29 kW d) 10 kW ________________________________________ 60. How many oscillators does black and white TV receiver contain? a) 1 b) 2 c) 3 d) 4 ________________________________________ 61. In a TV picture tube, what is the purpose of the large tube voltage? a) create huge magnetic field b) produce good quality of picture c) repels electrons away from tube d) attracts electrons towards face of tube ________________________________________ 62. Which of the following FM detectors is not used in mobile? a) Quadrature b) Balanced Detector c) Ratio d) Discriminator ________________________________________ 63. 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) Out d) Over ________________________________________ 64. Which of the following limits the performance of a communication system? a) Cost b) Accessibility c) Bandwidth d) Reliability ________________________________________ 65. (Nov 1998) Which of the following is referred to as a radio emission without sidebands? a) Data b) Carrier c) Voice d) Analog ________________________________________ 66. (Nov 1997) Extra-terrestrial noise is observable at frequencies from a) 8 to 1.43 GHz b) Above 2 GHz c) 0 to 20 kHz d) 5 to 8 GHz ________________________________________ 67. When voltages are out-of-phase, the total voltage can be found by adding: a) Vectorially b) Peak values c) Arithmetically d) Average values ________________________________________ 68. It is the ability of a radio receiver to receive weak signal. a) fidelity b) stability c) sensitivity d) selectivity ________________________________________ 69. How many mixers are in an SSB receiver? a) 3 b) 4 c) 2 d) 1 ________________________________________ 70. Another name for burst noise a) flicker b) shot noise c) pink noise d) popcorn noise ________________________________________ 71. Which of the following is not associated with transistors? a) shot noise b) jitter c) transit-time d) flicker noise ________________________________________ 72. 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) 39.3 MHz b) All of the above c) 10.7 MHz d) 110.7 MHz ________________________________________ 73. In SSB transmission, which sideband can be eliminated? a) Lower only b) Either c) Upper only d) Depends upon the use ________________________________________ 74. What constitutes the input to an AM transmitter? a) Mixer and amplifier b) Buffer and IF amplifier c) RF oscillator and/or audio amplifier d) Mixer and local oscillator ________________________________________ 75. How often must remote control instrumentals be calibrated? a) Yearly b) Weekly c) Daily d) Monthly ________________________________________ 76. What is the coupling used in Stoneman transmission bridge? a) Capacitive b) Resistive c) Inductive d) A combination of the above ________________________________________ 77. What determines the selectivity of a receiver? a) the frequency stability b) the bandwidth of the tuned circuits c) the power handling capability d) the gain of the amplifier ________________________________________ 78. It is the ___ that tunes the receiver to different stations. a) Detector b) IF Amplifier c) RF Amplifier d) Local Oscillator ________________________________________ 79. What is the S/N at the output of an amplifier whose NF=10 dB and the input S/N=25 dB? a) 15 dB b) 35 dB c) 10 dB d) 25 dB ________________________________________ 80. What determines the purity of received colors? a) Y and I amplitudes b) Q and I amplitudes c) Q and Y amplitudes d) Y amplitudes ________________________________________ 81. 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) 20% b) 120% c) 67% d) 80% ________________________________________ 82. A subcarrier has a (n) _____ frequency than the main carrier. a) Equal b) Lower c) Good d) Higher ________________________________________ 83. What is the major advantage of a super heterodyne receiver? a) inexpensive b) high amplification factor c) good image rejection d) excellent selectivity and sensitivity ________________________________________ 84. What broadcast station use vertical antennas on flat ground? a) AM b) Shortwave c) FM d) TV ________________________________________ 85. 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 transmitting signal ________________________________________ 86. What is the deviation ratio for commercial FM? a) 10 b) 1 c) 2 d) 5 ________________________________________ 87. What is the main disadvantage of a single-tube transmitted? a) Frequency instability b) High resistivity c) High attenuation d) Low gain ________________________________________ 88. The circuit used for producing a double sideband suppressed carrier type of AM signal is called _____. a) Mixer b) Balances modulator c) PLL d) AGC ________________________________________ 89. An adjustable resonant cavity calibrated if frequency and which undergoes some power absorption at resonance. a) Cavity Resonator b) Frequency Meter c) Ferrite isolator d) Auto Coupler ________________________________________ 90. What is the noise figure of an ideal amplifier? a) unity b) infinity c) zero d) 100 ________________________________________ 91. What is the result of overmodulation of an FM emission? a) Higher power b) Excessive bandwidth distortion c) distortion d) Lower frequency ________________________________________ 92. 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 ________________________________________ 93. What percentage of the primary colors used in color TV are needed to produce the brightest white? a) 30% red, 59% green, 11% blue b) 50% red, 28% green, 22% blue c) 58% red, 20% green, 22% blue d) 33% red, 33% green, 33% blue ________________________________________ 94. (Nov 1998) What connects the front-end circuit of a VHF TV super heterodyne receiver? a) Mixer, RF amplifier and AFC b) Local oscillator, AGC and antenna c) RF amplifier, Band pass filter and mixer d) Local oscillator, mixer and RF amplifier ________________________________________ 95. For an AM signal modulated to a depth of 100% by a pure tone, the power is _____ the power of unmodulated carrier. a) Same as b) twice as c) less than d) 3 / 2 times ________________________________________ 96. To what feature of the modulating tone is FM deviation proportional? a) Phase b) Amplitude c) Frequency d) Harmonics ________________________________________ 97. 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) 200 W c) 100 W d) 1200 W ________________________________________ 98. What is an advantage of series modulation? a) High gain and selectivity b) Low noise and interference c) Capable of modulating very high frequencies d) Capable of generating high power ________________________________________ 99. Which of the following is an advantage of PM over FM? a) A need for several modulators b) Requires a complex circuitry c) Requires a simpler transmitter d) One amplifier is required ________________________________________ 100. (Mar 1996) What is the primary advantage of DSBSC in AM? a) It is simpler to transmit and receive than the standard AM b) No transmitter power is wasted in the carrier c) Reduce bandwidth over standard AM d) All of these ________________________________________ 101. What is the signal, usually of random character, which is always present in a communications system? a) noise b) interference c) spur d) sideband ________________________________________ 102. Amplitude limiting in the IF section eliminates _____ interference from the FM signal. a) Broadband b) FM c) PM d) AM ________________________________________ 103. What type of second detector is used for AM? a) Ratio b) Diode c) PLL d) Lattice ________________________________________ 104. (Nov 1997) A good example of a pilot tone system used in commercial frequency modulation stations. a) Stereo multiplexing b) Time division c) FDM d) Frequency modulation ________________________________________ 105. (Apr 1998) Term for transmission of printed picture by radio. a) ACSSB b) Television c) Xerography d) Facsimile ________________________________________ 106. Two 4Ω speakers connected in series have a total impedance of ____. a) 6Ω b) 2Ω c) 4Ω d) 8Ω ________________________________________ 107. It is the liberation of electrons by thermionic means, used as the principal source of electron emission in microwave vacuum tube devices. a) Bunching b) Secondary Effect c) Edison Effect d) Miller Effect ________________________________________ 108. What does aspect ratio mean? a) Ratio of the screen height to its width b) Ratio of the screen diagonal to its height c) Ratio of the screen width to its height d) Ratio of the screen diagonal to its width ________________________________________ 109. What determine the bandwidth of a transmitted AM signal? a) The lowest frequency component of the intelligence b) The maximum modulation amplitude c) The highest frequency component of the modulating signal d) The lowest modulation amplitude ________________________________________ 110. 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 ________________________________________ 111. _____ frequencies are exact multiples of the fundamental frequency. a) Distortion b) Radio c) Harmonic d) Modulation ________________________________________ 112. What is the approximate efficiency of a class B linear RF AM amplifier? a) 12% b) 50% c) 35% d) 90% ________________________________________ 113. What form of energy is contained in a sound? a) kinetic b) electromagnetic c) acoustic d) elastic ________________________________________ 114. 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) 51% b) 57.9% c) 42.8% d) 67% ________________________________________ 115. Determine the open-circuit noise voltage in 1Hz of bandwidth at 290 K for a diode biased at 1 mA. a) 56 pV b) 65 pV c) 654 pV d) 465 pV ________________________________________ 116. Most of the communications receiver is in the form of ___type. a) High-level b) TRF c) Single-ended d) Super heterodyne ________________________________________ 117. Determine the equivalent noise bandwidth for a single RC low-pass filter if R=20 kohms and C= 0.1 uF a) 250 Hz b) 500 Hz c) 200 Hz d) 125 Hz ________________________________________ 118. What is reduced by rounding off square-wave emissions? a) Amplitude b) energy c) Phase d) Bandwidth ________________________________________ 119. What formula determines sideband power in AM emissions? a) Pc(m2/2) b) Pc(m2/3) c) Pc(m2/5) d) Pc(m2/4) ________________________________________ 120. 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) 75% b) 82% c) 66% d) 30% ________________________________________ 121. What is the frequency for the pilot subcarrier for commercial stereo FM? a) 20 kHz b) 38 kHz c) 19 kHz d) 67.5 kHz ________________________________________ 122. What is the function of an FM limiter? a) to eliminate interference b) to provide image rejection c) to remove amplitude variation d) to increase stability ________________________________________ 123. What is the name of the operation that uses an antenna changeover switch? a) Switching b) Crossover c) Duplex d) Simplex ________________________________________ 124. (Nov 1996) What is the type of emission used by the standard AM radio broadcast? a) A b) D c) C d) F ________________________________________ 125. If a broadcast station is transmitting but not modulating, what is heard in a receiver tuned to its frequency? a) Carrier only b) Hiss c) Nothing d) Audio only ________________________________________ 126. (Nov 1998) In modulation technique, which of the following is referred to audible pitch? a) Harmonic b) Amplitude c) Frequency d) Width ________________________________________ 127. The type of device noise, which is important at high frequencies, is ___ noise. a) flicker b) Johnson c) shot d) Transit-time ________________________________________ 128. (Apr 1997) Unit of noise power of psophometer a) pWp b) dBmo c) dBa d) dBm ________________________________________ 129. (Apr 1997) What particular circuit gets rids of FM noise? a) Limiter b) LPF c) HPF d) Phase Shifter ________________________________________ 130. What are the two emission designations of a TV transmission? a) B8e, C3F b) J3E, C3F c) A3E, ISB d) F3E, C3F ________________________________________ 131. In what classes are SSB linear amplifiers operated? a) C or D b) B or C c) A or AB d) D ________________________________________ 132. What percent of the radiated power is in the sidebands with 50% sinusoidal modulation (AM)? a) 11% b) 20% c) 16.67% d) 33% ________________________________________ 133. (Nov 1997) Noise caused by the thermal agitation of electrons in resistance. a) Johnson’s Noise b) White Noise c) Thermal Noise d) ALL of these ________________________________________ 134. To provide two or more voice circuits with the same carrier, what system must be used? a) Pilot carrier system b) Lincomplex c) Vestigial sideband system d) ISB emission ________________________________________ 135. The signal which is superimposed on a high-frequency sine wave is called _____. a) Square wave b) Information c) Carrier d) Sideband ________________________________________ 136. (Apr 1998) Which of the following refers to a double side band full carrier? a) A3J b) F3 c) R3A d) A3E ________________________________________ 137. How many AM stations can be accommodated in a 150-kHz bandwidth if the highest modulating frequency is 10 kHz? a) 7 b) 14 c) 15 d) 10 ________________________________________ 138. What is the horizontal resolution of a broadcast TV receiver? a) 339 lines b) 500 lines c) 30 lines d) 428 lines ________________________________________ 139. (Apr 1998) What is the period of a wave? a) The number of degrees in tone cycle b) The number of zero crossing in one cycle c) The amplitude of the wave d) The time required to complete one cycle ________________________________________ 140. What causes audio signals to be distorted in a receiver? a) Amplitude b) Interference c) Gain d) Harmonics ________________________________________ 141. (Mar 1996) One-hundred twenty µbars of pressure variation is equal to a) 115.56 dBSPL b) 57.78 dBSPL c) 120 dBSPL d) 41.58 dBSPL ________________________________________ 142. (Nov 1998) Which band does channel 14 of the television channel belongs? a) High VHF band b) Low VHF band c) UHF band d) EHF band ________________________________________ 143. What type of device can be used in balanced modulators? a) AF, IF b) AF, RF c) RF, IF d) AF, PF ________________________________________ 144. A decibel notation relative to a reference noise level. a) dBf b) dBrn c) dBa d) dBpwp ________________________________________ 145. A diode detector: a) Allows current to flow in one direction only. b) Detects the modulating signal. c) Converts AC into pulsating DC. d) Does all of the above. ________________________________________ 146. (Mar 1996) After the IF stages have been aligned, the next state to align in FM receiver is a) local oscillator b) limiter stage c) Mixer stage d) RF Amplifier ________________________________________ 147. Complex number, equal to the ratio of a complex pressure amplitude to the complex amplitude of the volume velocity a) Acoustic Intensity b) Acoustic Impendance c) Air Elasticity d) Acoustic Pressure ________________________________________ 148. What type of coupling discriminates against harmonic transmission a) Inductive b) Transformer c) Capacitive d) Direct ________________________________________ 149. (Apr 1997) channels 2, 4 and 5 are known as a) low band UHF b) low band VHF c) high band VHF d) mid band UHF ________________________________________ 150. The big breakthrough in electric communications came with the invention of the _____ in 1844. a) Phonograph b) Transistor c) Telegraph d) Telephone ________________________________________ 151. (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) Primary b) Experimental c) Tertiary d) Secondary ________________________________________ 152. What is the result if a balanced modulator is not perfectly balanced? a) Both sideband transmitted b) Carrier transmitted c) SB filtered d) Low sideband transmitted ________________________________________ 153. What is the required time constant for an FM broadcast preemphasis and deemphasis network? a) 75 µs b) 50 µs c) 25 µs d) 100 µs ________________________________________ 154. What devise is used to determine phase difference between two broadcast antennas? a) Frequency monitor b) FSM c) OTDR d) Phase monitor ________________________________________ 155. What determines the station that will be selected by a tuner? a) The bandwidth of the amplifier b) The resonant frequency of the tuner c) The sensitivity of the tuner d) The selectivity of the IF ________________________________________ 156. What is the required accuracy of BC station meters? a) 2% b) 5% c) 1% d) 10% ________________________________________ 157. What part of a super heterodyne is responsible for the band pass of the receiver? a) RF Amplifier b) IF Amplifier c) LO d) Detector ________________________________________ 158. (Nov 1996) Noise from random acoustic or electric noise that has equal per cycle over a specified total frequency band. a) All of these b) White noise c) Gaussian noise d) Thermal noise ________________________________________ 159. 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? a) 0.001 W b) 0.1 W c) 0.0001 W d) 0.01W ________________________________________ 160. What factor(s) determine the modulation index of an FM signal? a) Frequency of the modulation signal b) A and b are true c) Amplitude of the carrier d) Frequency deviation ________________________________________ 161. Treble sound corresponds to a) Mid- frequencies b) High frequencies c) Low frequencies d) Radio frequencies ________________________________________ 162. Which of the following is not a continuous wave modulation? a) FM b) AM c) PCM d) PM ________________________________________ 163. (Apr 1998) What is a frequency discriminator? a) An FM generator b) A circuit for detecting FM signals c) A circuit for filtering two closely adjacent signal d) An automatic bandswitching circuit ________________________________________ 164. (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 ________________________________________ 165. What is the ratio of maximum deviation allowed to the modulating frequency being used called? a) Modulation Index b) Modulation Sideband c) Deviation ratio d) Percent Modulation ________________________________________ 166. What is the meaning of the acronym WDM? a) Wap distributed mode b) Wireless data monitoring c) Wide distribution media d) Wavelength division multiplexing ________________________________________ 167. What is the following is not a product of overmodulation? a) Splatter b) Spurious signal c) Buckshot d) Image ________________________________________ 168. What does VOX mean? a) Very onward circuit b) Voice-operated transmission c) Very oxford transmitter d) Voice onward transmission ________________________________________ 169. An amplifier with NF= 6 dB has (S/N), of 25 dB. What is the output S/N? a) 6 dB b) 19 dB c) 31 dB d) 25 dB ________________________________________ 170. (Nov 1997) An antenna that can only receive a television signal? a) Reference Anenna b) Isotropic antenna c) TVRO d) Yagi antenna ________________________________________ 171. (Nov 1998) What is the major cause of atmospheric or static noise? a) thunderstorm b) airplanes c) sunspot d) meteor showers ________________________________________ 172. Which produces greater interference, overmodulated positive or negative peaks? a) Negative b) neither c) either d) Positive ________________________________________ 173. (Nov 1997) Atmospheric noise is less severe at frequencies above a) 1 GHz b) audio level c) 30 MHz d) 10 GHz ________________________________________ 174. What is the major advantage of FM over AM? a) Less noise b) No interference c) High frequency d) Simple circuits ________________________________________ 175. FM system is superior to AM because a) It produces more rock music b) It eliminates most of amplitude variation noise c) It is at VHR band d) It has wider bandwidth ________________________________________ 176. (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) 0.12 W b) 12 W c) 1.2 W d) 0.012 W ________________________________________ 177. If two signals are in quadrature, what is their phase relation? a) 0° b) 90° c) 180° d) 45° ________________________________________ 178. Compute the noise figure of a receiving system with a noise temperature of 2000C. a) 2.4 dB b) 42 dB c) 24 dB d) 4.2 dB ________________________________________ 179. What is the noise current for a diode with a forward bias of 1 mA over a 1 MHz bandwidth? a) 91.5 uA b) 9.15 nA c) 179 nA d) 17.9 nA ________________________________________ 180. (Mar 1996) Cross modulation on a receiver is eliminated at the a) Detector stage b) IF stage c) Mixer stage d) RF stage ________________________________________ 181. What is the advantage of using a high IF? a) improve S/N ratio b) high gain c) better image rejection d) better quality of music ________________________________________ 182. How many cathodes are there in a shadow-mask tube? a) 2 b) 1 c) 4 d) 3 ________________________________________ 183. (Nov 1996) Which determines the number of sideband components in FM? a) All of these b) Modulation frequency c) Modulation index d) Carrier frequency ________________________________________ 184. What is the maximum power that ca be contained in the sideband without distortion? a) 25% b) 50% c) 66.67% d) 16.67% ________________________________________ 185. A type of room whose boundaries absorb effectively all incident sound. a) Acoustic Room b) Production Room c) Live Room d) Anechoic Room ________________________________________ 186. Where is a degaussing coil in a TV set? a) around the IF amp b) inside the CRT c) at the tuner d) around the tube face ________________________________________ 187. What information must be contained in a TV signal? a) Synchronizing signal b) Sound c) Video d) All of these ________________________________________ 188. 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) 1 c) 2 d) 0.5 ________________________________________ 189. (Mar 1996) What is the difference between phase and frequency modulation? a) Is purely theoretical because they are the same in practice b) Os too great to make two systems compatible c) Lies in the different definitions of the modulation index d) Lies in poorer audio response of phase modulation ________________________________________ 190. What is the major requirement of the oscillators used in an SSB receiver? a) Goof feedback b) High frequency c) Selectivity d) stability ________________________________________ 191. Which came first, the invention of the telephone or the invention of the phonograph? a) telephone b) neither c) phonograph d) either ________________________________________ 192. A device which can perform the function of both a transmitter and a receiver. a) Relay b) Repeater c) Transceiver d) Buffer ________________________________________ 193. Does the video transmitter at a TV BC station employ FM or AM? a) AM b) both AM and FM c) FM d) PM ________________________________________ 194. The local FM stereo rock station is at 96.5 MHz. What must be the local oscillator frequency? a) 105.9 MHz b) 112.5 MHz c) 107.2 MHz d) 93.9 MHz ________________________________________ 195. What characteristic of the sound wave determines its pitch? a) frequency b) amplitude c) phase d) harmonics ________________________________________ 196. If the second-harmonic amplitude is 2V and the fundamental is 10V, then the second-harmonic distortion is ___. a) 2 b) 40% c) 4 d) 20% ________________________________________ 197. For an unmodulated carrier of 1000V and a modulated peak value of 1800 V, what is the modulation index? a) 0.8 b) 0.5 c) 0.7 d) 0.9 ________________________________________ 198. Which of the following must not be included? a) solar noise b) atmospheric noise c) galactic noise d) cosmic noise ________________________________________ 199. (Nov 1997) The Tendency for the sound energy to spread. a) Rarefaction b) Refraction c) Reflection d) Diffraction ________________________________________ 200. Which is not true about modulation a) Transmission over longer distances b) More practical antenna c) Narrower bandwidth d) Multiple transmission ________________________________________ 201. (Nov 1996) When was the UHF channels (14-83) of television were added? a) 1952 b) 1904 c) 1852 d) 1947 ________________________________________ 202. The audible pitch refers to a) frequency b) harmonics c) purity d) amplitude ________________________________________ 203. (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) 79.1 dB b) 69.1 dB c) 59.1 dB d) 89.1 dB ________________________________________ 204. Which of the following do not require a tuner? a) TV receiver b) Communications Satellite Receiver c) CB receiver d) None of these ________________________________________ 205. An indirect method of generating FM is a) Reactance tube modulator b) Armstrong modulator c) Reactance transistor modulator d) Varactor diode modulator ________________________________________ 206. For _____ percent modulation in AM, the modulation envelope has a peak value double the unmodulated carrier level. a) 100 b) 66.67 c) 50 d) 83.3 ________________________________________ 207. What happens in standard AM transmission when no modulating signal is being transmitted? a) There are several sidebands. b) There are no sidebands. c) There is no signal. d) There are two carriers ________________________________________ 208. Calculate the thermal noise delivered to a system with a bandwidth of 1 Hz operating at 170C. a) 1.2 x 10-14 W b) 4 x 10-12 W c) 4 x 10-21 W d) 2.1 x 10-14 W ________________________________________ 209. When diode is used as a detector in the simple AM radio, what happens to the waveform of the carrier? a) It is rectified. b) It is amplified. c) It is modulated. d) It is filtered. ________________________________________ 210. A SSB transmitter drives 121 V peak into a 50-Ω antenna. What is the PEP? a) 292 W b) 73 W c) 121 W d) 146W ________________________________________ 211. (Apr 1998) Refers to an emission designation for facsimile. a) J3E and F4E b) R3E and A3E c) A3C and F3C d) A3J and A4E ________________________________________ 212. Which of the following is not an application of PLL? a) FM demodulators b) FSK decoder c) AM Discriminator d) Frequency Synthesizers ________________________________________ 213. When a carrier is frequency-modulated, what is developed on both sides carrier? a) Noise b) Carrier c) Envelope d) sidebands ________________________________________ 214. How many ground radials should a λ/4 vertical AM broadcast antenna use? a) 1 b) 3 – 10 c) 5 – 20 d) 24 or more ________________________________________ 215. What factor determines the modulation index of an FM transmission? a) Modulating signal frequency b) Carrier amplitude c) Carrier frequency d) Carrier phase ________________________________________ 216. What information other than the sound has to be transmitted in TV transmission? a) blanking pulses b) all of the above c) visual signal d) synchronizing signals ________________________________________ 217. Where is a color burst found? a) Blanking pulse b) Synch pulse c) Back porch d) Front porch ________________________________________ 218. (Nov 1997) Operating method in which the transmission is made alternately in each direction of a telecommunication channel. a) Semi-duplex operation b) Half duplex operation c) Simplex operation d) Duplex operation ________________________________________ 219. It refers to the sending, receiving and processing of information by electronic means. a) Telemetry b) Telephony c) Communications d) Broadcasting ________________________________________ 220. Basically, what would be added to a TRF to produce a super heterodyne? a) IF stage b) All of the above c) Local Oscillator d) Mixer stage ________________________________________ 221. In FM, what determines bandwidth? a) Modulation index b) Carrier frequency c) Carrier power d) Modulation phase ________________________________________ 222. A ______ is a resonant circuit tuned to reject an undesired signal by reducing the gain at the trap frequency. a) LC tank b) HPF c) Wave trap d) LPF ________________________________________ 223. What is the power saving in J3E system at 100% modulation? a) 66.67% b) 83.3% c) 33.3% d) 100% ________________________________________ 224. Who is in overall control of a TV production? a) manager b) producer c) director d) actor ________________________________________ 225. Which is not a method of generating single sideband signal? a) Phase-shift b) Balanced modulator c) Weaver d) Filter ________________________________________ 226. Determine the power saving in percent when the carrier is suppressed in an AM signal modulated to 80% a) 75.8% b) 100% c) 80% d) 66.7% ________________________________________ 227. What pattern of modulation must used when neutralizing an operating transmitter? a) 10 % b) 80% c) 100% or over d) 50% ________________________________________ 228. What is the lowest number of sections required by communications receiver? a) 3 b) 4 c) 1 d) 2 ________________________________________ 229. What does ALC mean? a) Automatic Link Circuit b) Asynchronous Link Control c) Automatic Level Control d) All Local Circuits ________________________________________ 230. What is the channel width of an AM BC station? a) 20 kHz b) 5 kHz c) 10 kHz d) 50 kHz ________________________________________ 231. Which type of microphone has a high Z output? a) Ribbon b) Crystal c) Dynamic d) Carbon ________________________________________ 232. In a low-level modulation system, the type of amplifier that follows the modulated stage should be a _____. a) Linear amplifier b) Any of the above c) Harmonic generator d) Class C amplifier ________________________________________ 233. What is the power in each sideband for an AM signal with 80%modulation and a total power of 2500 W? a) 303 W b) 500 W c) 250 W d) 400 W ________________________________________ 234. What is the relative permittivity of air? a) 20 b) 1.26 x 10-6 c) 8.853 x 10-12 d) 1 ________________________________________ 235. (Apr 1997) Sound intensity level is_____. a) 10 log I / ref / I b) 20 log I / ref c) 30 log I / ref d) 10 log I / I ref ________________________________________ 236. (Nov 1997) An AM transmitter is rated 100 W at 100% modulation. How much power is required for the carrier? a) 83.33 W b) 66.66 W c) 100 W d) 33.33 W ________________________________________ 237. (Mar 1996) What is the main purpose of a communications system? a) To provide an acceptable replica of the information at the designation b) To have a frequency assignment c) For modulation d) None of these ________________________________________ 238. How many watts are represented by 40 dBw? a) 10000 W b) 1000 W c) 40000 W d) 40 W ________________________________________ 239. 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) 8 MHz b) 1 kHz c) 12 kHz d) 120 kHz ________________________________________ 240. What is the letter symbol for the luminance signal? a) Y b) Q c) R d) I ________________________________________ 241. (Mar1996) The equivalent noise temperature of the amplifier is 25 K. What is the noise figure? a) 1.086 b) 10.86 c) 0.1086 d) 1.86 ________________________________________ 242. (Apr 1998) How does a SSB transmitter output power normally expressed? a) In term of peak-to-peak power b) Average power c) Peak power d) In term of peak envelope power ________________________________________ 243. The range of frequencies represented in a signal. a) Beamwidth b) Guardband c) Crisp d) Bandwidth ________________________________________ 244. What is the major problem with a very-high-frequency oscillator? a) Poor frequency stability b) Poor image rejection c) No power stability d) Low sensitivity ________________________________________ 245. What distinguishes one electromagnetic wave form another? a) Frequency b) Energy c) Amplitude d) Phase ________________________________________ 246. 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) Limiter b) Discriminator c) AFC d) AGC ________________________________________ 247. Where is the single-button microphone used most? a) Paging system b) Broadcast Studio c) Telephone d) Intercom ________________________________________ 248. For an FM signal in the 88-108-MHz broadcast band with a frequency deviation of 15 kHz, determine the percent modulation. a) 80% b) 40% c) 60% d) 20% ________________________________________ 249. In FM for a given frequency deviation, the modulation index varies _____ with the modulating frequency. a) Independently b) Directly c) Equally d) Inversely ________________________________________ 250. (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 pressure b) Sound intensity c) Loudness d) Pressure variation ________________________________________ Submit ________________________________________ 251. (Nov 1996) The output of a balanced modulator is _____. a) USB b) Carrier c) LSB d) LSB and USB ________________________________________ 252. Calculate the modulating frequency that causes an FM signal to have a bandwidth of 50 kHz when its frequency deviation is 15 kHz. a) 40 kHz b) 20 kHz c) 10 kHz d) 50 kHz ________________________________________ 253. (Nov 1998) In radio regulation. The first symbol in the designation of radio emission is _____. a) Bandwidth b) Type of modulation of the main carrier c) Type of information to be transmitted d) Nature of signal(s) ________________________________________ 254. What is another term meaning “downward modulation”? a) Distortion Modulation b) Negative Carrier Shift c) Harmonic Modulation d) Positive Carrier Shift ________________________________________ 255. (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) 1.14 volts b) 1.88 volts c) 0.88 volt d) 0.12 volt ________________________________________ 256. 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) 0.83 b) 0.94 c) 0.67 d) 1 ________________________________________ 257. What kind of system relays has remote readings? a) Telemetering b) Data gathering c) Broadcasting d) Telecast ________________________________________ 258. What stage in a super heterodyne is aligned first? a) RF Amplifier b) IF Amplifier c) Mixer d) Second Detector ________________________________________ 259. What is the BFO in SSB receiver called? a) Frequency Oscillator b) Carrier Oscillator c) Backward Oscillator d) Local Oscillator ________________________________________ 260. What is the amount of carrier swing necessary to produce an 80% modulation for the audio portion of the TV band? a) 50 kHz b) 20 kHz c) 40 kHz d) 25 kHz ________________________________________ 261. Is the information used to represent a TV picture transmitted at the same time? a) No b) Yes c) Sometimes d) None of the above ________________________________________ 262. What is the disadvantage slope detection of FM? a) low noise reduction b) high level of noise c) no noise discrimination d) complexity ________________________________________ 263. Which of the following services use crystal local oscillators? a) Shortwave listener b) FM c) AM d) Aircraft ________________________________________ 264. (Apr 1997) Which transmit only sideband? a) H3E b) A3E c) 11BE d) 3AJ ________________________________________ 265. The term wolfe number refers to the front-end circuit of a VHF TV super heterodyne receiver? a) X-rays b) Ultraviolet Radiation c) 11-year sunspot cycle d) 27-year solar cycle ________________________________________ 266. What is the wavelength for a frequency of 1 million hertz? a) 300 m b) 3 km c) 30 km d) 30 m ________________________________________ 267. (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) 50% c) 83% d) 115.5% ________________________________________ 268. (Apr 1998) In television broadband vivid strong color are often referred as ____. a) hue b) chrominance c) luminance d) saturation ________________________________________ 269. What is the maximum power output of a CB A3E emission? a) 10 kW b) 10 W c) 3 kW d) 4 W ________________________________________ 270. What type of circuit reduces even-order harmonics? a) Class A b) Push-Pull c) Demodulator d) Armstrong circuit ________________________________________ 271. What do you call a heterodyne frequency changer? a) Frequency translator b) Modulator c) Frequency synthesizer d) Mixer ________________________________________ 272. The SI unit of magnetic field intensity is a) Ampere/square meter b) Ampere c) Ampere/meter d) Volt/meter ________________________________________ 273. The process of impressing information signals to a high frequency carrier is called _____. a) detection b) multiplexing c) scrambling d) modulation ________________________________________ 274. 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 ________________________________________ 275. (Nov 1998) A third symbol emission which represent television. (0 correct answers) a) D b) A c) C d) F ________________________________________ 276. What is the source of wheel static? a) Piston b) Wheel c) Oscillations d) Brakes ________________________________________ 277. A suppressed-carrier synchronous detector requires: a) The presence of a reinserted carrier that has a frequency close to the original carrier. b) A BFO that is at the exact frequency difference between the original carrier and modulating frequency. c) A BFO that is near the frequency difference between the original carrier and modulating frequency. d) The presence of a reinserted carrier of exactly the same frequency and phase as the original. ________________________________________ 278. What AF range is required of the aural transmitter of a TV BC station? a) 20 Hz – 20 kHz b) 20 Hz – 2 kHz c) 5 – 50 kHz d) 50 Hz – 15,000 Hz ________________________________________ 279. 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) ±7.5 Hz d) ±20 Hz ________________________________________ 280. Amplitude distortion results from _____ amplification. a) Indirect b) Nonlinear c) Linear d) Direct ________________________________________ 281. What source of noise is related to system temperature? a) pink noise b) burst noise c) thermal noise d) shot noise ________________________________________ 282. What radio frequencies are most affected by lightning or static waves? a) SHF b) VLF c) UHF d) VHF ________________________________________ 283. If an FM transmitter has two doublers and one tripler, what is the carrier swing when the oscillator deviates 2 kHz? a) 36 kHz b) 2 kHz c) 48 kHz d) 24 kHz ________________________________________ 284. What happens to the spectrum of a repetitive pulse as the pulse width decreases? a) More harmonics of the same phase b) decreases c) Remain constant d) Less harmonics of the same phase ________________________________________ 285. (Apr 1997) 100% modulation inn AM means a corresponding increase in total power by _____. a) 100% b) 50% c) 75% d) 25% ________________________________________ 286. In single-gun color CRT, what electron beam travels straight through the tube? a) blue b) green c) red d) yellow ________________________________________ 287. What is the frequency of the VCR control signal? a) 60 Hz b) 15625 Hz c) 30 Hz d) 15750 Hz ________________________________________ 288. (Apr 1998) A carrier signal has _____. a) Constant peak amplitude b) A varying amplitude c) Frequency range 20-20000 Hz d) The information ________________________________________ 289. A type of microphone which has a permanent magnet a) ribbon b) crystal c) carbon d) electret ________________________________________ 290. Sound is a wave motion of varying air____. a) Pressure b) Resistance c) Viscosity d) Density ________________________________________ 291. (Nov 1997) What is the effect in over modulated amplitude modulated radio broadcasting transmission? a) Higher audio signal b) Increase noise c) Higher fidelity d) Interference to adjacent channel ________________________________________ 292. During 100% modulation, what percentage of the average output power is in the sidebands? a) 66.67% b) 16.67% c) 33.3% d) 100% ________________________________________ 293. FM has a major disadvantage of _____. a) High voltage b) Greater coverage c) Greater bandwidth d) Low efficiency ________________________________________ 294. What is the greatest possible modulation value without distortion? a) 50% b) 100% c) 99.9% d) 66.67% ________________________________________ 295. It describe the acoustic energy flowing per unit area and per unit time. a) Acoustic Pressure b) Sound Reflection c) Sound Absorption d) Acoustic Intensity ________________________________________ 296. For an FM signal a) The amplitude of any sideband depends on the modulation index b) The carrier frequency cannot disappear c) The carrier frequency disappears when the modulation index is large d) The total number of sidebands depends on the modulation frequency the carrier frequency ________________________________________ 297. An SSB contains 30 kW. The power content of the carrier is _____ kW. a) 30 b) 0 c) 20 d) 10 ________________________________________ 298. (Nov 1997) A large speaker having diameter (15 cm. and above) a) Woofer b) Coaxial speaker c) Tweeter d) Triaxial speaker ________________________________________ 299. What is the standard intermediate frequency for FM radio? a) 112 kHz b) 4.5 kHz c) 10.7 kHz d) 455 kHz ________________________________________ 300. (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) Full carrier single sideband emission b) Half carrier single sideband emission c) Reduced carrier single sideband emission d) Double sideband emission ________________________________________ 301. (Apr 1998) Best describes as an amplifier used in radio telephony. a) Magnifier b) Class B c) Class C d) Class A ________________________________________ 302. What are the le7tter-number designations of carrier and one SB? a) H3E b) A3E c) J3E d) F3E ________________________________________ 303. What is the purpose of AFC in an FM receiver? a) to increase the sensitivity b) to provide good selectivity c) to stabilize the gain d) to help maintain a steady local oscillator frequency ________________________________________ 304. (Apr 1997) The random and unpredictable electric signal from natural causes, both internal and external to the system is known as ___. a) attenuation b) interference c) distortion d) noise ________________________________________ 305. (Apr 1997) Tendency of sound energy to spread. a) Reflection b) Diffraction c) Rarefaction d) Refraction ________________________________________ 306. What is the sound carrier for channel 10? a) 193.25 MHz b) 197.75 MHz c) 196.83 MHz d) 192 MHz ________________________________________ 307. In a transmitted AM wave, state where the information is contained? a) Modulating signal b) Sidebands c) Envelope d) Carrier ________________________________________ 308. The modulated carrier power in FM a) All of the above b) Is independent of modulating signal power c) Increases with modulating signal power d) Decreases with modulating signal power ________________________________________ 309. What is the highest video frequency set by the FCC for commercial TV? a) 6 MHz b) 4.2 MHz c) 5.5 MHz d) 15 kHz ________________________________________ 310. What is another name for AF volume control? a) AMC b) ARC c) Gain d) AFC ________________________________________ 311. What electrical device inside a communication receiver selects one station and rejects all others? a) Tuner b) Local Oscillator c) AGC d) Detector ________________________________________ 312. In an AM transmitter, after the modulation stage, _____ amplifier cannot be used. a) Linear b) Class B c) Class C d) Class A ________________________________________ 313. (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) 4.78 uV b) 4278 uV c) 0.4782 uV d) 47.8 uV ________________________________________ 314. The maximum swing of the sound carrier in TV system is ______. a) ±75 kHz b) ±25 kHz c) ±15 kHz d) ±10 kHz ________________________________________ 315. (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) Standard single sideband emission b) Reduce carrier single sideband emission c) Half carrier single sideband emission d) Full carrier single band emission ________________________________________ 316. (Nov 1998) In amplitude modulation technique the unmodulated carrier is referred as having _____. a) 50% modulated b) over modulated c) 100% modulation d) 0% modulation ________________________________________ 317. When did the first transatlantic radio communications take place? a) 1876 b) 1888 c) 1901 d) 1942 ________________________________________ 318. Where is ISB primarily used? a) FM Broadcast b) Telemetry c) Radar d) Telephone and Telegraph Communications ________________________________________ 319. The purpose of the balances modulator circuits is to eliminate the _____. a) Carrier b) Noise c) Distortion d) Sidebands ________________________________________ 320. (Apr 1998) With which emission type is the capture-effect most pronounced? a) CW b) AM c) SSB d) FM ________________________________________ 321. (Nov 1998) The third symbol radio emission which represent telephone transmission including sound broadcasting. a) E b) F c) C d) W ________________________________________ 322. (Nov 1996)Multiplexing in a time division multiplexer occurs based upon a) The position of a frame within a group of frames b) The activity of a connected device c) The positioning of data within a frame d) The priority assigned to a connected device ________________________________________ 323. A super heterodyne is tuned to 2738 kHz. The IF is 475 kHz. What is the image frequency? a) 4385 kHz b) 3688 kHz c) 3.09 MHz d) 4.5 kHz ________________________________________ 324. (Nov 1997) In the designation of bandwidth and emission, what letter in the symbol represents a double-sideband of modulation? a) A b) C c) H d) B ________________________________________ 325. How often should BC stations be identified? a) every ten minutes b) at least once an hour c) at least once a day d) every thirty minutes ________________________________________ 326. What is the small amount of the signal applied to the input port that leaks through to the output port? a) Regenerative loss b) Reflection loss c) Insertion loss d) Feedthrough loss ________________________________________ 327. He was the one who developed the mathematical solution to a complex repetitive waveform. a) Y. Uda b) Carson c) J. Fourier d) P.H Smith ________________________________________ 328. (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) 5 b) 3 c) 4 d) 2 ________________________________________ 329. (Apr 1998) Considered as the main source of an internal noise. a) Device imperfection b) Temperature change c) Flicker d) Thermal agitation ________________________________________ 330. Which of the following items need not be checked with receivers? a) Sensitivity b) Gain c) Distortion d) Squelch ________________________________________ 331. The input power to a 50-Ω receiver is 200 pW. Determine the receiver gain required to produce 3 dBm at the detector. a) 70 dB b) 40 dB c) 20 dB d) 7 dB ________________________________________ 332. What do you call the combining circuit used in TV? a) Matrix b) Adder c) Multiplier d) Synthesizer ________________________________________ 333. A relatively rigid extended surface surrounding an acoustic source. a) Panel Board b) Baffle c) Dash Board d) Screen ________________________________________ 334. The entire range of _____ of electromagnetic radiation is called the frequency spectrum. a) Frequencies b) Phases c) Energies d) Amplitudes ________________________________________ 335. What device can be used to make a modulated envelope visible? a) Synthesizer b) Calibrator c) Oscilloscope d) Spectrum Analyzer ________________________________________ 336. 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) 80 kHz b) 100 kHz c) 40 kHz d) 200 kHz ________________________________________ 337. What TV signal are amplified by the video IF amplifier? a) Sound carriers b) Color burst c) Sync pulse d) Sound the picture carriers ________________________________________ 338. What is the bandwidth of a narrowband FM signal generates by a 2 kHz audio signal a 110-MHz FM carrier? a) 5 kHz b) 2 kHz c) 1 kHz d) 4 kHz ________________________________________ 339. If a 7-A carrier is modulated 100% by a sinusoidal tone, how much does the antenna current increase? a) 66.7% b) 44.8% c) 33.3% d) 22.5% ________________________________________ 340. (Nov 1998) The extremely high frequency (EHF) band is in the radio spectrum range of _____. a) 30 to 300 GHz b) 3 to 30 GHz c) 3 to 30 MHz d) 30 to 300 kHz ________________________________________ 341. What is the process where some of the medium through which it impinges? a) refraction b) diffraction c) reflection d) absorption ________________________________________ 342. What is the oldest and simplest form of multiplexing? a) Time-division multiplexing b) Frequency-division multiplexing c) Space-division multiplexing d) Hybrid-division multiplexing ________________________________________ 343. What is the magnitude of the frequency component at seven times the fundamental frequency for a square wave amplitude 1 V? a) 0.18 b) 0.2 c) 0.14 d) 0.7 ________________________________________ 344. An AM transmission of 1000 W is fully modulated. Calculate the power transmitted as a SSB signal. a) 1000 W b) 167 W c) 667 W d) 333 W ________________________________________ 345. What is meant by amplitude modulation? a) The carrier frequency is varied b) The carrier phase is varied c) The carrier sign is varied d) The carrier amplitude is varied ________________________________________ 346. Pilot carrier transmission, means a) Only two sidebands are transmitted b) Only one sideband is transmitted c) One sideband and carrier are transmitted d) Two sidebands as well as a trace of carrier are transmitted ________________________________________ 347. (Apr 1998) What is emission C3F? a) Television b) Facsimile c) Modulated CW d) RTTY ________________________________________ 348. (Apr 1997) Modulation means a) transmit pulse in DC form on a copper wire b) varying of information c) utilization of a single transmission channels to carry multiple signals d) varying of some parameters of a carrier such as its amplitude to transmit information ________________________________________ 349. The power of thermal noise is ___ of resistance. a) equal b) a function c) dependent d) independent ________________________________________ 350. 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) Will burn out the tuner. d) Produces sound in the headset. ________________________________________ 351. (Apr 1998) The final power amplifier in an FM y=transmitter usually operates class _____. a) A b) C c) B d) AB ________________________________________ 352. 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) 0.2 b) 0.5 c) 0.7 d) 0.1 ________________________________________ 353. What BC service must used directional antennas? a) FM BC b) AM BC c) TV BC d) International broadcasting ________________________________________ 354. 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 ________________________________________ 355. A 1500-kHz carrier and 2 kHz intelligence signal are combined in anon-liner device. What component is present at the output? a) 1500 kHz b) all of the above c) 1502 kHz d) 1492 kHz ________________________________________ 356. (Nov 1996) Which symbol indicates that only one sideband is transmitted? a) A3E b) B8E c) C3F d) H3E ________________________________________ 357. What is the device designed to display the signal state of many lines simultaneously? a) Logic analyzer b) Oscilloscope c) OTDR d) Spectrum analyzer ________________________________________ 358. The noise figure of a system is 12 and its input signal-to-noise ratio is 60. What is the output signal-to-noise ratio? a) 0.2 b) 5 c) 720 d) 72 ________________________________________ 359. A type of information signal which is made up of rapid and unpredictable variations in amplitude and frequency. a) digital b) bits c) speech d) pulses ________________________________________ 360. (Nov 1996) What is the equivalent output of a circuit in dBm , if it has an output of 10 watts? a) 10 dBm b) 40 dBm c) 30 dBm d) 20 dBm ________________________________________ 361. Where is telemetering used in BC stations? a) At the receiver b) At the studio c) Within the transmitter d) Remote position to transmitter ________________________________________ 362. The value of a resistor creating thermal noise is halved. The noise power generated is a) unchanged b) quadrupled c) halved d) doubled ________________________________________ 363. 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) 30 kHz c) 15 kHz d) 60 kHz ________________________________________ 364. A method of generating SSB signal; that utilizes only one balanced modulator circuit. a) Weaver method b) Third method c) Filter method d) Phase-Shift method ________________________________________ 365. The device that prevents aural RF from entering the video transmitter and vice versa is called____. a) tuner b) diplexer c) coupler d) duplexer ________________________________________ 366. What is the aspect ratio in commercial TV receivers? a) 4:3 b) 2:3 c) 3:4 d) 16:9 ________________________________________ 367. The color phasor has what phase for the I signal? a) 37º b) 57º c) 180º d) 90º ________________________________________ 368. (Nov 1998) Frequencies above _____ kHz, are referred to as the radio frequencies. a) 20 b) 100 c) 10 d) 2 ________________________________________ 369. When do BC stations make equipment tests? a) Sunday only b) experimental period c) day time d) night time ________________________________________ 370. The modulation index of an AM wave is changes from 0 to 1. The transmitter power is? a) Halved b) Increased by 50% c) Unchanged d) Doubled ________________________________________ 371. Quantization noise is produced in a) FSK b) PCM c) All modulation system d) All pulse modulation system ________________________________________ 372. He was the one who developed the wireless telegraph. a) Marconi b) Armstrong c) Edison d) Bell ________________________________________ 373. (Nov 1997) Which of the following falls under the high frequency band of the radio spectrum? a) 8.2345 MHz b) 35.535 MHz c) 2.4555 MHz d) 150.50 MHz ________________________________________ 374. A mirror that reflects one color but passes all other are called ____. a) Monochroic b) Concave c) Convex d) Dichroic ________________________________________ 375. The all-encompassing noise associated with a give environment, being usually composite of sounds from many sources near and far. a) Average Noise b) Nominal Room c) Ambient Noise d) Relative Noise ________________________________________ 376. Determine the noise power delivered to a receiver input at 300 K and noise bandwidth of 20 kHz. a) -25 dBm b) 131dBm c) -120 dBm d) -130.8 dBm ________________________________________ 377. Name a periodic waveform that consists of only odd harmonics. a) Sine wave b) Square wave c) Spikes d) Cosine wave ________________________________________ 378. What method can be used to invert speech? a) Frequency multiplier b) Frequency translation c) Inverter d) AGC ________________________________________ 379. Which of the following is not commonly used in the LO? a) Colpitts b) Hartley c) Armstrong d) Crystal ________________________________________ 380. The information carrying capacity of a signal is _____ to its bandwidth. a) Equal b) Not related c) Directly proportional d) Inversely proportional ________________________________________ 381. (Apr 1998) The signal to noise ratio that is required for a satisfactory television reception. a) 10 dB b) 20 dB c) 40 dB d) 30 dB ________________________________________ 382. A device used for abating the noise accompanying the flow of gas through a pipe. a) Acoustic Chamber b) Muffler c) Acoustic Filter d) Helmholtz Resonator ________________________________________ 383. (April 1997) Industrial noise frequency is between ___. a) 15 to 160 MHz b) 0 to 10 kHz c) 20 GH d) 200 to 3000 MHz ________________________________________ 384. What type of microphone has the lowest power output? a) Carbon b) Ribbon c) Condenser d) Dynamic ________________________________________ 385. What major principle prevents the TV viewer from observing flicker? a) persistence of the picture tube and human eye b) light reflections c) drowsiness d) scanning ________________________________________ 386. The typical output voltage from a magnetic microphone is a) 5 mV b) 50 mV c) 1 mV d) 10 mV ________________________________________ 387. What class of bias should produce least harmonics? a) Class D b) Class A c) Class B d) Class C ________________________________________ 388. What determines the maximum number of vertical picture element? a) Number of lines on the screen b) Number of pixel c) Number of frames per second d) Number of fields per second ________________________________________ 389. What is the color subcarrier for channel 5? a) 76 MHz b) 81.75 MHz c) 76.25 MHz d) 80.83 MHz ________________________________________ 390. What id the purpose of a conversion frequency oscillator? a) To increase stability b) To produce the IF c) To provide a conversion frequency d) To provide good selectivity ________________________________________ 391. Which is better, an NF of 20 or 10 dB? a) Either b) 10 dB c) 20 dB d) Neither ________________________________________ 392. 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) 315 K c) 25 K d) 290 K ________________________________________ 393. What is the interference due to single tone or complex periodic waveforms? a) Insertion b) Tone interference c) Harmonic Distortion d) Inter-modulation Distortion ________________________________________ 394. A modulation technique commonly used for low-cost digitization of voice signals. a) A5C b) F3 c) A0 d) A3 ________________________________________ 395. (Apr 1997) The final amplifier of either FM or AM transmitter operates as a) Class B b) Class A c) Class C d) Class D ________________________________________ 396. (Nov 1997) The third symbol in the designation of radio emission under the IYU rules refers to a) bandwidth b) nature of signal(s)modulating the main carrier c) type of modulation of the main carrier d) type of information to be transmitted ________________________________________ 397. What is a hybrid transmitter? a) Combination of metal and plastic b) part metal, part liquid c) Part semiconductor, part vacuum tube d) Multiple transmitter ________________________________________ 398. (Nov 1996) Which stands for dB relative level? a) dBr b) dBm c) dBa d) dBm ________________________________________ 399. How many times more bandwidth does the UHF band have than VHF band? a) 1 b) 100 c) 10 d) 1000 ________________________________________ 400. What is the most common application of carbon microphone? a) telephone b) TV transmitter c) Am radio d) FM radio ________________________________________ 401. Determine the open-circuit noise voltage in 1 Hz of bandwidth at 290 K for a 26 ohms resistor. a) 645 pV b) 45 pV c) 145 pV d) 65 pV ________________________________________ 402. (Apr 1997) The most common unit of noise measurement in white noise testing. a) NPR b) dBm c) dBw d) dBk ________________________________________ 403. It is the representation of a waveform in such a way that its amplitude is displayed as a function of frequency. a) Frequency Domain b) OTDR c) Wave Shape d) Time Domain ________________________________________ 404. A 100-V carrier is amplitude modulated by a 1-kHz sine wave. What is the side-frequency amplitude when m=0.75? a) 18.75 V b) 37.5 V c) 100 V d) 75 V ________________________________________ 405. (Nov 1997) The first symbol in the designation of radio emission under the ITU rules refers to a) bandwidth b) type of modulation of the main carrier c) type of information to be transmitted d) nature of signal(s) modulating the main carrier ________________________________________ 406. It is the interference of a signal from one channel into another channel. a) Spur b) Sideband splatter c) Inter-modulation distortion d) Crosstalk ________________________________________ 407. (Apr 1998) Quantity that do not change when a beam of light enters one medium to another. a) Wavelength b) Speed c) Frequency d) Direction ________________________________________ 408. What type of field does a Faraday shield stop? a) Electrostatic b) Common c) Magnetostatic d) Array ________________________________________ 409. Which of the following is not a type of log used in BC stations? a) Program b) Maintenance c) Operating d) Period ________________________________________ 410. (Nov 1998) What is the first symbol of radio signal emission having an amplitude modulated main carrier, double sideband? a) A b) B c) C d) H ________________________________________ 411. A system has 150 kHz of bandwidth available for a 10-kHz modulating signal. What is the approximate deviation? a) 65 kHz b) 70 kHz c) 100 kHz d) 75 kHz ________________________________________ 412. What is the seventh harmonic of 360 kHz? a) 5040 kHz b) 1260 kHz c) 2520 kHz d) 7000 kHz ________________________________________ 413. The value(s) associated with sine waves of voltages are: a) All of the above b) Average c) Maximum d) Instantaneous ________________________________________ 414. A type of device noise whose intensity decreases with frequency. a) flicker b) popcorn noise c) thermal noise d) shot noise ________________________________________ 415. What type of wave trap is connected in series with a line? a) Parallel b) Asynchronous c) Series d) Synchronous ________________________________________ 416. In Phase Modulation (PM), the modulation index represents ______. a) The maximum phase shift b) The total number of sidebands c) The maximum frequency deviation d) The ratio of the modulation amplifier to the carrier amplitude ________________________________________ 417. (Apr 1997) Lowest frequency produced by musical instrument. a) Midrange b) Fundamental c) Harmonic d) Period ________________________________________ 418. A mixer is tuned to 2000 kHz and the local oscillator is on 1300 kHz. What frequency would cause an image? a) 1100 kHz b) 700 kHz c) 600 kHz d) 3300 kHz ________________________________________ 419. How many horizontal lines are used to develop a TV raster? a) 525 b) 615 c) 15750 d) 750 ________________________________________ 420. What kind of crystal is used in oscillators? a) Galena b) Carborundum c) Quartz d) Salt ________________________________________ 421. (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 ________________________________________ 422. (Nov 1998) What is meant by the term deviation ratio? a) The ratio of the audio modulating frequency to the center carrier frequency b) The ratio of the carrier center frequency to the audio modulating frequency c) The ratio of the maximum carrier frequency deviation to the highest audio modulation frequency d) The ratio of the highest audio modulating frequency to the average audio modulating frequency ________________________________________ 423. 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) 328 b) 1000 c) 1.6 d) 14.14 ________________________________________ 424. What does the acronym VIR mean? a) Vertical Interval Reference b) Video Interval Recording c) Vertical Interface Relay d) Video Interface Relay ________________________________________ 425. What stage in an AM transmitter creates its own sine wave? a) Oscillator b) Buffer c) Modulator d) Amplifier ________________________________________ 426. The bandwidth in _____ depends on the number of significant sidebands. a) Frequency Modulation b) QAM c) Delta Modulation d) FCM ________________________________________ 427. What frequencies are considered to be in the AF range? a) 15 Hz – 10 kHz b) 20 Hz – 20 kHz c) 50 Hz – 50 kHz d) 300 Hz – 3000 kHz ________________________________________ 428. 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) 0.6 b) .05 c) 0.75 d) 0.8 ________________________________________ 429. The total power content of an AM signal is 600 W. What is the percentage modulation if each sideband contains 100 W? a) 100% b) 66.7% c) 33.3% d) 83.3% ________________________________________ 430. (Nov 1996) The unit of pitch. a) Decibel b) Sone c) Mel d) Phon ________________________________________ 431. What portion of the TV signal is used to synchronize the video information on the recording tape? a) the vertical deflection coil b) the raster lines c) the horizontal sync d) the vertical sync ________________________________________ 432. For an IF frequency of 455 kHz, what must be the LO frequency when receiving a 580 kHz transmission? a) 1.035 MHz b) 3.51 MHz c) 351 kHz d) 1035 MHz ________________________________________ 433. A 2-kW RF carrier is sinusoidally modulated 100% . Haw much power is in one sideband? a) 250 W b) 500 W c) 125 W d) 2000 W ________________________________________ 434. Modulating two waves of the same frequency but with _____. a) 360° b) 90° c) 45° d) 180° ________________________________________ 435. What section of a TV receiver determines the bandwidth and produces the signal gain? a) Mixer b) Local oscillator c) IF Amplifier d) RF Amplifier ________________________________________ 436. In FM, what produces the sidebands? a) Carrier and its harmonics b) RF signal c) Modulating signal d) Carrier signal ________________________________________ 437. In Frequency Modulation ______. a) The frequency of carrier varies according to the frequency of the modulating signal b) The frequency of carrier varies according to the amplitude 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 phase of the modulating signal ________________________________________ 438. What is the percent modulation of a signal in the FM broadcast band at 92 MHz with 20 kHz frequency deviation? a) 72% b) 60% c) 27% d) 12% ________________________________________ 439. What is a radio carrier? a) A lower amplitude signal b) A lower frequency signal c) A higher amplitude signal d) A higher frequency signal ________________________________________ 440. What is the power saving when the carrier is suppressed in a regular AM signal modulated to an index of 100%? a) 33.3% b) 100% c) 16.7% d) 66.7 % ________________________________________ 441. The audio is reconstructed from the radio wave by: a) None of the above. b) Having the audio removed from the carrier c) The action of a filter capacitor connected across the headset d) The action of the headset ________________________________________ 442. The circuit that performs the suppression of the carrier signal. a) Balanced modulator b) LPF c) Carrier synthesizer d) Pre-emphasis ________________________________________ 443. In an FM receiver, the circuit that keeps the receiver tuned exactly to the desired station is ___. a) AFC b) Discriminator c) AGC d) Limiter ________________________________________ 444. (Mar 1996) Atmospheric condition is controlled by a) Temperature b) All of these c) Humidity d) Pressure ________________________________________ 445. What are the frequency limits of the AM BC band? a) 88 – 108 MHz b) 500 – 1600 kHz c) 300 – 3000 kHz d) 535 – 1605 kHz ________________________________________ 446. (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) 250 Hz b) 245 Hz c) 240 Hz d) 255 Hz ________________________________________ 447. What is the power requirement for international BC stations? a) 100 W b) 15 W c) 50 kW d) 5 kW ________________________________________ 448. (Nov 1997) A method of expressing the amplitude of complex non-periodic signals such as speech. a) Volume b) Pitch c) Frequency d) Wavelength ________________________________________ 449. (Apr 1997) _____ used to measure speech volume. a) Audio frequency meter b) Volume unit meter c) Volume meter d) Speech meter ________________________________________ 450. If the 500-Hz modulation of a 1-MHz carrier has 3rd harmonic distortion, what is the emission bandwidth? a) 1 kHz b) 3 kHz c) 1 MHz d) 1500 Hz ________________________________________ 451. (Apr 1997) Reference noise temperature. a) 250C b) 300C c) 700F d) 290 K ________________________________________ 452. The noise power generated by a resistor depends upon a) none of the above b) its resistance value c) its operating temperature d) both a and b ________________________________________ 453. What happens to noise when you increase the bandwidth of an amplifier? a) Remain constant b) fluctuates c) it decreases d) it increases ________________________________________ 454. Who hears high audio frequency best? a) young people b) old people c) 40 years old d) all of the above ________________________________________ 455. What is the allowable bandwidth of commercial AM radio in the United States? a) 30 kHz b) 10 kHz c) 15 kHz d) 10 MHz ________________________________________ 456. What was the first BC PM system called? a) Fourier b) Wienbridge c) Weaver d) Armstrong ________________________________________ 457. (Apr 1998) An instrument for recording waveforms of audio frequency. a) Phonoscope b) Radioscope c) Oscilloscope d) Audioscope ________________________________________ 458. What holds the horizontal oscillator on frequency? a) AFC b) AGC c) ECL d) ALC ________________________________________ 459. What is the letter-number designation for an FM facsimile? a) F3E b) A3E c) C3C d) F3C ________________________________________ 460. (Mar 1996) The letter-number designation B8E is a form of modulation also known as _____. a) Vestigial sideband transmission b) Pilot-carrier system c) Lincompex d) Independent sideband emission ________________________________________ 461. (Mar 1996) In the phase shift method, how many circuits must be balanced? a) 4 b) None of these c) 2 d) 1 ________________________________________ 462. (Nov 1996) The wavelength of light has no role in a) Diffraction b) Polarization c) Resolving power d) Interference ________________________________________ 463. Normally, for how long must logs be kept for the FCC? a) 1 week b) 1 month c) 1 year d) 2 years ________________________________________ 464. A diagram which shows the relationship between RF signal phase and maximum bunching of the electron beam in velocity-modulated devices. a) Smith Chart b) Venn Diagram c) S-parameters Diagram d) Applegate Diagram ________________________________________ 465. (Nov 1996) The maximum power suggested by the KBP on 919 – 1312 kHz AM broadcast station I Metro Manila is a) 15 kW b) 20 kW c) 10 kW d) 5 kW ________________________________________ 466. What determines the rate of frequency swing for an FM broadcast transmitter? a) Carrier amplitude b) Modulation frequency c) Carrier frequency d) Modulation amplitude ________________________________________ 467. An unmodulated carrier is 300 VP-P. Calculate %m when its maximum p-p value reaches 400 V. a) 100% b) 83.3% c) 33.3% d) 66.67% ________________________________________ 468. Noise is most problematic at the___. a) communication channel b) receiver c) source d) transmitter ________________________________________ 469. (Nov 1997) Modulation in which the modulated wave is always present. a) Carrier modulation b) Front-end c) Log-periodic modulation d) Continues modulation ________________________________________ 470. (Apr 1997) What is the reference frequency of CCITT psophometric noise measurement? a) 1500 Hz b) 3400 Hz c) 800 Hz d) 1000 Hz ________________________________________ 471. What is the shape of a trapezoidal pattern at 100% modulation? a) Square b) Circle c) Rectangle d) Triangle ________________________________________ 472. Which of the following is not normally tested in a transmitter? a) Modulation b) Power c) Frequency d) Amplitude ________________________________________ 473. In AM, maximum desirable output of a transmitter is obtained when its modulation is _____%. a) less than 100 b) greater than 100 c) 50 d) 100 ________________________________________ 474. What is the blanking level for negative transmission? a) 66.6% b) 12.5% c) 50% d) 75% ________________________________________ 475. What is the meaning of kinescope? a) Wide screen CRT b) Enhanced CRT c) TV picture tube d) Color CRT ________________________________________ 476. (Nov 1997) Background noise is the same as the following except a) impulse noise b) white noise c) gaussian noise d) thermal noise ________________________________________ 477. What is usually transmitted by facsimile? a) Video signal b) Voice c) Bits d) Pictures ________________________________________ 478. A radio receiver is called ___ if the local oscillator frequency is made equal to the wanted RF signal frequency. a) homodyne b) Up-conversion c) TRF d) Single-conversion ________________________________________ 479. Most household radio receiver uses ___ detector. a) envelope b) synchronous c) phase d) asynchronous ________________________________________ 480. (Mar 1996) Power is always _____. a) A definite amount of energy b) The rate at which energy is used c) Expressed in watts d) All of these ________________________________________ 481. (Nov 1996) Speaker is a device that ____. a) none of these b) convert sound waves into current and voltage c) convert electrical energy to mechanical energy d) convert current variations into sound waves ________________________________________ 482. Which stages in a broadcast transmitter are normally class C? a) AF amplifier b) oscillator c) modulated amplifier d) buffer amplifier ________________________________________ 483. What does ANSI mean? a) American national standards institute b) Auxiliary non station identifier c) American non stop information d) Auxiliary net system interconnection ________________________________________ 484. (Nov 1997) Nominal voice channel a) 20 to 20 kHz b) 3 to 3 kHz c) 16 to 16 kHz d) 4 kHz ________________________________________ 485. Which subcarrier leads by 90º in TV system? a) Q b) Y c) I d) R ________________________________________ 486. The super heterodyne circuit uses local oscillator to ___ with the RF signal of the station and convert the carrier to the intermediate frequency. a) heterodyne b) mix c) beat d) all of the above ________________________________________ 487. What produces the dark spots on fax receiving paper? a) Low impedance b) Excessive heat c) Burning due to electric current flow between helix wire and blade d) High current ________________________________________ 488. A major disadvantage of the vacuum tube is its need for a _____ to give energy to the electrons. a) Voltage source b) Heater c) Line equalizer d) Limiter ________________________________________ 489. Which of the following is not an advantage of FM over AM? a) The transmitted power is mote useful b) Less modulating power is required c) Better noise immunity is provided d) Lower bandwidth is required ________________________________________ 490. In what way would a program may be received at BC stations? a) Telephone Lines b) Satellite c) All of the above d) Radio Relay ________________________________________ 491. Which of the following is not a requirement for a color TV signal? a) good raster reproduction b) within 6 MHz bandwidth c) simulate a width variety of colors d) compatibility with B/W receivers ________________________________________ 492. Is SSB, voice compression is better in the AF or Rf section? a) RF b) Intermediate c) SB d) AF ________________________________________ 493. What is the main function of a balanced modulator? a) Produce balanced modulation of a carrier wave b) Suppress carrier signal in order to create a SSB or DSB c) Limit noise picked by a receiver d) Produce 100% modulation ________________________________________ 494. 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) 2.5 kW b) 15 kW c) 50 kW d) 5 kW ________________________________________ 495. What is gained by operating an oscillator on some subharmonic of the transmission frequency? a) Frequency sensitivity b) Frequency stability c) Good selectivity d) High sensitivity ________________________________________ 496. The power in FM _____ as the modulation index increases. a) Fluctuates b) Decreases c) Increases d) Remain constant ________________________________________ 497. In free-space, the phase velocity of a TEM wave is _____ the group velocity. a) Greater than b) Less than c) None of the above d) Equal to ________________________________________ 498. Which of the following is not a major difference between FM and AM receivers? a) Limiter b) deemphasis c) IF frequency d) AGC ________________________________________ 499. (Mar 1996) The _____ filter attenuates signals but passes frequencies below and above the band. a) High pass b) Band stop c) Low pass d) Band pass ________________________________________ 500. (Nov 1996) Which frequency band is the standard AM radio broadcast? a) HF b) MF c) VHF d) UHF ________________________________________ 501. What is an NO RY? a) Non organic relay b) Non operational relay c) Normally open relay d) Normally ready ________________________________________ 502. (Mar 1996) In an FM receiver, which circuit removes amplitude variations? a) Exciter b) Limiter c) Mixer d) Discriminator ________________________________________ 503. How many electron beans actually leave the electron gun of a single-gun color CRT? a) 3 b) 1 c) 4 d) 2 ________________________________________ 504. What is the picture carrier frequency for channel 7? a) 179.75 MHz b) 175.25 MHz c) 174 MHz d) 178.83 MHz ________________________________________ 505. Which of the following is not a type of external noise? a) Pink Noise b) Solar Noise c) Galactic Noise d) Atmospheric Noise ________________________________________ 506. (Apr 1997) If a voltage is equal to twice its original value, what is its corresponding change in dB? a) 6 dB b) 9 dB c) 10 dB d) 3 dB ________________________________________ 507. (Mar 1996) Which of the following pulse modulation systems is analog? a) PCM b) Delta c) PWM d) Differential PCM ________________________________________ 508. What is the waveform of sweep voltage? a) Sawtooth b) Square wave c) Spikes d) Rectangular wave ________________________________________ 509. How much time is allocated for horizontal retrace? a) 76 µs b) 63.5 µs c) 10.2 µs d) 7.5 µs ________________________________________ 510. In communications systems, demodulation ______. a) Is performed at the transmitting station b) Removes sidebands c) Is opposite of modulation d) Rectifies modulated signal 511. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth? a) 230 kHz b) 200 kHz c) 215 kHz d) 115 kHz 512. What circuit is used to create vestigial transmission? a) HPF b) LPF c) Diplexer d) Duplexer 513. When the loop in a PLL is locked, what is the difference in frequency detected by the phase detector? a) 900 b) 450 c) 00 d) 1800 ________________________________________ 514. (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) 20 kW b) 5 kW c) 15 kW d) 8.36 kW ________________________________________ 515. High-frequency distortion occurs when the _____ harmonic components of a digital square wave are lost. a) Sub b) Cut-off frequency c) High frequency d) Low frequency