BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 1._____ frequencies exact multiples of fundamental frequency. a) Harmonic b) Distortion c) Radio d) Modulation
are the
2.The signal which is superimposed on a highfrequency sine wave is called _____. a) Sideband b) Square wave c) Carrier d) Information 3.(Mar 1996) Power is always _____. a) A definite amount of energy b) Expressed in watts c) The rate at which energy is used d) All of these 4.He was the one who developed the mathematical solution to a complex repetitive waveform. a) P.H Smith b) J. Fourier c) Carson d) Y. Uda 5.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) 14.14 d) 1.6 6.The entire range of _____ of electromagnetic radiation is called the frequency spectrum. a) Phases b) Frequencies c) Amplitudes d) Energies
7.(Mar 1996) What is the main purpose of a communications system? a) To have a frequency assignment b) For modulation c) To provide an acceptable replica of the information at the designation d) None of these 8.What is an NO RY? a) Normally open relay b) Non organic relay c) Non operational relay d) Normally ready 9.Which is not true about modulation a) Transmission over longer distances b) More practical antenna c) Multiple transmission d) Narrower bandwidth 10.What class of bias should produce least harmonics? a) Class C b) Class B c) Class D d) Class A 11.What is the approximate efficiency of a class B linear RF AM amplifier? a) 35% b) 50% c) 12% d) 90% 12.When did the first transatlantic radio communications take place? a) 1901 b) 1942 c) 1876 d) 1888
13.A duplexer is used to a) Feed more than one receiver from a single antenna b) Connect two t6ransmitter to the same antenna c) Feed more than one transmitter from a single antenna d) Connect a receiver and a transmitter to the same antenna 14.(Apr 1998) A carrier signal has _____. a) Constant peak amplitude b) Frequency range 2020000 Hz c) The information d) A varying amplitude 15.High-frequency distortion occurs when the _____ harmonic components of a digital square wave are lost. a) Cut-off frequency b) Low frequency c) High frequency d) Sub 16.What is the magnitude of the frequency component at seven times the fundamental frequency for a square wave amplitude 1 V? a) 0.14 b) 0.2 c) 0.18 d) 0.7 17.(Mar 1996) Atmospheric condition is controlled by a) Humidity b) Temperature c) All of these d) Pressure 18.Which of the following items need not be checked with receivers? a) Gain b) Squelch c) Sensitivity d) Distortion
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 19.Amplitude results from amplification. a) Direct b) Nonlinear c) Indirect d) Linear
distortion _____
20.The term angular velocity as applied to electronic system refers to the number of: a) Radian per second a voltage vector rotates b) None of these c) Degrees averaged together d) Degrees subtracted from the radians 21.What is an ideal pulse? a) A very short duration b) A low duty cycle c) A perfect square wave with zero rise time d) A high amplitude 22.The noise figure of a system is 12 and its input signal-to-noise ratio is 60. What is the output signal-tonoise ratio? a) 720 b) 5 c) 72 d) 0.2 23.It is the representation of a complex waveform in such a way that the sinusoidal components are displayed as a function of time. a) Wave Representation b) Time Domain c) TDR d) Frequency Domain 24.A function y = f(t) is even if it has perfect symmetry about the _____. a) z-axis b) y-axis c) w-axis d) x-axis
25.What sweep frequency could be used on a scope to stop an envelope pattern of 600-Hz modulation? a) 300 Hz b) 600 Hz c) 1200 Hz d) 150 Hz 26.The audio is reconstructed from the radio wave by: a) The action of a filter capacitor connected across the headset b) The action of the headset c) Having the audio removed from the carrier d) None of the above. 27.(Apr 1997) The final amplifier of either FM or AM transmitter operates as a) Class C b) Class A c) Class D d) Class B 28.Where is ISB primarily used? a) Telemetry b) Radar c) FM Broadcast d) Telephone and Telegraph Communications 29.Which of the following limits the performance of a communication system? a) Cost b) Bandwidth c) Reliability d) Accessibility 30.What is the device designed to display the signal state of many lines simultaneously? a) Oscilloscope b) Spectrum analyzer c) Logic analyzer
31.(Nov 1996) When was the UHF channels (14-83) of television were added? a) 1947 b) 1904 c) 1852 d) 1952 32.Which of the following is used in microwave ovens? a) TWT b) Magnetron c) BWO d) Klystron 33.What is meant by amplitude modulation? a) The carrier sign is varied b) The carrier amplitude is varied c) The carrier frequency is varied d) The carrier phase is varied 34.What determines the station that will be selected by a tuner? a) The selectivity of the IF b) The bandwidth of the amplifier c) The sensitivity of the tuner d) The resonant frequency of the tuner 35.(Nov 1998) Frequencies above _____ kHz, are referred to as the radio frequencies. a) 10 b) 20 c) 100 d) 2 36.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) AGC b) Discriminator c) AFC d) Limiter
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 37.It is the representation of a waveform in such a way that its amplitude is displayed as a function of frequency. a) OTDR b) Frequency Domain c) Time Domain d) Wave Shape 38.What does ALC mean? a) Asynchronous Link Control b) Automatic Level Control c) Automatic Link Circuit d) All Local Circuits 39.What radio frequencies are most affected by lightning or static waves? a) UHF b) SHF c) VHF d) VLF 40.Which of the following is not normally tested in a transmitter? a) Modulation b) Power c) Frequency d) Amplitude 41.(Nov 1998) Which of the following is referred to as a radio emission without sidebands? a) Voice b) Data c) Carrier d) Analog 42.In an AM transmitter, after the modulation stage, _____ amplifier cannot be used. a) Class C b) Class A c) Linear d) Class B 43.What type of wave trap is connected in series with a line? a) Series b) Asynchronous c) Parallel d) Synchronous
44.What is a radio carrier? a) A lower frequency signal b) A lower amplitude signal c) A higher frequency signal d) A higher amplitude signal 45.(Nov 1996) Which stands for dB relative level? a) dBm b) dBa c) dBm d) dBr 46.What is the standard intermediate frequency for FM radio? a) 112 kHz b) 455 kHz c) 4.5 kHz d) 10.7 kHz 47.What is the circuit that changes modulated RF to AF? a) Modulator b) Synthesizer c) Modem d) Demodulator 48.(Apr 1998) An instrument for recording waveforms of audio frequency. a) Phonoscope b) Radioscope c) Oscilloscope d) Audioscope 49.How many times more bandwidth does the UHF band have than VHF band? a) 1000 b) 10 c) 100 d) 1 50.Which is not a method of generating single sideband signal? a) Filter b) Weaver c) Balanced modulator d) Phase-shift
51.In 1877, _____ invented a method of making a permanent record of sound with his invention of the phonograph. a) Morse b) Edison c) Marconi d) Bell 52.(Nov 1997) A method of expressing the amplitude of complex non-periodic signals such as speech. a) Volume b) Wavelength c) Frequency d) Pitch 53.What is a hybrid transmitter? a) Multiple transmitter b) Combination of metal and plastic c) Part semiconductor, part vacuum tube d) part metal, part liquid 54.Which of the following services use crystal local oscillators? a) Aircraft b) Shortwave listener c) AM d) FM 55.(Mar 1996) The _____ filter attenuates signals but passes frequencies below and above the band. a) Band stop b) Low pass c) Band pass d) High pass 56.Any waveform that is not symmetrical in area about the time axis has a (n) _____ component. a) AC b) DC c) RC d) FC
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 57.What is the major problem with a very-high-frequency oscillator? a) Poor frequency stability b) Poor image rejection c) Low sensitivity d) No power stability 58.What distinguishes one electromagnetic wave form another? a) Frequency b) Amplitude c) Phase d) Energy 59.What other term is essentially synonymous with beating? a) Filtering b) Heterodyning c) Scrambling d) Suppressing 60.A ______ is a resonant circuit tuned to reject an undesired signal by reducing the gain at the trap frequency. a) HPF b) LC tank c) LPF d) Wave trap 61.(Nov 1996) The wavelength of light has no role in a) Polarization b) Diffraction c) Interference d) Resolving power 62.What is the coupling used in Stoneman transmission bridge? a) Inductive b) A combination of the above c) Resistive d) Capacitive
63.The parameter of a highfrequency carrier that may be varied by a low-frequency intelligence signal is _____. a) Phase b) All of the above c) Amplitude d) Frequency 64.What is the amount of power lost in a device due to its presence in the path of energy flow? a) Wave attenuation b) Insertion loss c) Phase shift d) Gain 65.(Nov 1998) The extremely high frequency (EHF) band is in the radio spectrum range of _____. a) 3 to 30 MHz b) 3 to 30 GHz c) 30 to 300 GHz d) 30 to 300 kHz 66.What produces the dark spots on fax receiving paper? a) High current b) Low impedance c) Burning due to electric current flow between helix wire and blade d) Excessive heat 67.What is the purpose of a conversion frequency oscillator? a) To provide a conversion frequency b) To provide good selectivity c) To produce the IF d) To increase stability 68.(Apr 1998) What is the period of a wave? a) The amplitude of the wave b) The number of zero crossing in one cycle c) The number of degrees in tone cycle d) The time required to complete one cycle
69.The range of frequencies represented in a signal. a) Guardband b) Beamwidth c) Bandwidth d) Crisp 70.(Nov 1998) Determine from the following radio frequency that falls under the Very High Frequency band of the radio spectrum. a) 450.00 MHz b) 235.5 MHz c) 144.50 GHz d) 345.00 MHz 71.What is reduced by rounding off square-wave emissions? a) Bandwidth b) Phase c) energy d) Amplitude 72.When an operator wishes to indicate that he has received all of the last transmission, he will transmit the word _____. a) Out b) Over c) Ok d) Roger 73.(Apr 1998) Term in communication which is referred, “to send out in all direction”. a) Announce b) Transmit c) Media d) Broadcast 74.(Nov 1996) Which of the following filters block FM radio band for TV channels (2 to 13)? a) Low-pass filter b) Band-pass filter c) Band-reject filter d) High-pass filter
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 75.Which of the following do not require a tuner? a) TV receiver b) Communications Satellite Receiver c) None of these d) CB receiver
81.What type of coupling discriminates against harmonic transmission a) Transformer b) Direct c) Inductive d) Capacitive
76.(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
82.He was the one who developed the wireless telegraph. a) Armstrong b) Bell c) Marconi d) Edison
88.What type of field does a Faraday shield stop? a) Common b) Electrostatic c) Array d) Magnetostatic
77.What is the result if a balanced modulator is not perfectly balanced? a) Carrier transmitted b) SB filtered c) Both sideband transmitted d) Low sideband transmitted
83.When voltages are out-ofphase, the total voltage can be found by adding: a) Peak values b) Arithmetically c) Vectorially d) Average values
89.What is a device such as the microphone and the headset sometimes called? a) Reproducer b) Receiver c) Transmission Medium d) Converter
78.In TV system. A picture signals are transmitted by a) PCM b) FM c) PM d) AM
84.What kind of crystal is used in oscillators? a) Quartz b) Galena c) Salt d) Carborundum
90.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
79.(Nov 1997) Which of the following falls under the high frequency band of the radio spectrum? a) 35.535 MHz b) 150.50 MHz c) 2.4555 MHz d) 8.2345 MHz
85.(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) 4 c) 3 d) 2 86.(Apr 1998) What is a frequency discriminator? a) A circuit for filtering two closely adjacent signal b) An FM generator c) An automatic bandswitching circuit d) A circuit for detecting FM signals
80.An adjustable resonant cavity calibrated if frequency and which undergoes some power absorption at resonance. a) Frequency Meter b) Ferrite isolator c) Cavity Resonator d) Auto Coupler
87.What is gained by operating an oscillator on some subharmonic of the transmission frequency? a) High sensitivity b) Good selectivity c) Frequency sensitivity d) Frequency stability
91.A subcarrier has a (n) _____ frequency than the main carrier. a) Higher b) Good c) Lower d) Equal 92.(Apr 1998) With which emission type is the captureeffect most pronounced? a) AM b) SSB c) CW d) FM 93.What does VOX mean? a) Very onward circuit b) Voice onward transmission c) Voice-operated transmission d) Very oxford transmitter
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 94.The maximum swing of the sound carrier in TV system is ______. a) ±10 kHz b) ±75 kHz c) ±15 kHz d) ±25 kHz 95.Is SSB, voice compression is better in the AF or Rf section? a) AF b) SB c) RF d) Intermediate 96.The process of impressing information signals to a high frequency carrier is called _____. a) scrambling b) detection c) modulation d) multiplexing 97.A type of information signal which is made up of rapid and unpredictable variations in amplitude and frequency. a) digital b) pulses c) bits d) speech 98.Keyed AGC is AGC that: a) Works only with Morse code. Is activated when keyed by the transmitting signal b) Is used in color TV receivers so that the transmitted color has no effect on the AGC c) Is used in TV receivers so that transmitted picture brightness does not affect the AGC
99.Pilot carrier transmission, means a) Only one sideband is transmitted b) Two sidebands as well as a trace of carrier are transmitted c) Only two sidebands are transmitted d) One sideband and carrier are transmitted
105.It is the liberation of electrons by thermionic means, used as the principal source of electron emission in microwave vacuum tube devices. a) Secondary Effect b) Miller Effect c) Edison Effect d) Bunching
100.What is the source of wheel static? a) Wheel b) Brakes c) Oscillations d) Piston
106.What does ANSI mean? a) American non stop information b) Auxiliary non station identifier c) American national standards institute d) Auxiliary net system interconnection
101.The SI unit of magnetic field intensity is a) Ampere b) Ampere/square meter c) Volt/meter d) Ampere/meter 102.(Nov 1997) voice channel a) 4 kHz b) 16 to 16 kHz c) 3 to 3 kHz d) 20 to 20 kHz
Nominal
103.If two signals are in quadrature, what is their phase relation? a) 0° b) 45° c) 180° d) 90° 104.(Apr 1997) If a voltage is equal to twice its original value, what is its corresponding change in dB? a) 10 dB b) 6 dB c) 3 dB d) 9 dB
107.What is the oldest and simplest form of multiplexing? a) Hybrid-division multiplexing b) Space-division multiplexing c) Frequency-division multiplexing d) Time-division multiplexing 108.What device can be used to make a modulated envelope visible? a) Spectrum Analyzer b) Calibrator c) Synthesizer d) Oscilloscope 109.To provide two or more voice circuits with the same carrier, what system must be used? a) Pilot carrier system b) Vestigial sideband system c) Lincomplex d) ISB emission
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 110.The value(s) associated with sine waves of voltages are: a) All of the above b) Maximum c) Instantaneous d) Average
115.What is the main disadvantage of a single-tube transmitted? a) High attenuation b) High resistivity c) Frequency instability d) Low gain
111.What causes audio signals to be distorted in a receiver? a) Harmonics b) Amplitude c) Gain d) Interference
116.In free-space, the phase velocity of a TEM wave is _____ the group velocity. a) Greater than b) Equal to c) None of the above d) Less than
112.The circuit that performs the suppression of the carrier signal. a) Pre-emphasis b) Balanced modulator c) Carrier synthesizer d) LPF
117.What type of circuit reduces even-order harmonics? a) Demodulator b) Push-Pull c) Armstrong circuit d) Class A
113.(Mar 1996) what is the purpose of a beat frequency oscillator (BFO)? a) Generates a signal, whose frequency is the same as that of the intermediate frequency b) Generates an output, whose frequency differs from that of the intermediate frequency by 1 kHz c) Generates a 1 kHz tone to Morse reception d) Aids in the reception of weak voice-modulated signals 114.The input power to a 50Ω receiver is 200 pW. Determine the receiver gain required to produce 3 dBm at the detector. a) 40 dB b) 7 dB c) 20 dB d) 70 dB
118.What is the name of the operation that uses an antenna changeover switch? a) Switching b) Simplex c) Crossover d) Duplex 119.(Apr 1998) Best describes as an amplifier used in radio telephony. a) Class C b) Magnifier c) Class A d) Class B 120.(Apr 1998) Term for transmission of printed picture by radio. a) ACSSB b) Xerography c) Television d) Facsimile 121.What service uses HF CW communications? a) Broadcasting b) Telephony c) Satellite System d) Police
122.What kind of system relays has remote readings? a) Telecast b) Telemetering c) Data gathering d) Broadcasting 123.(Nov 1996)Multiplexing in a time division multiplexer occurs based upon a) The priority assigned to a connected device b) The activity of a connected device c) The positioning of data within a frame d) The position of a frame within a group of frames 124.A diagram which shows the relationship between RF signal phase and maximum bunching of the electron beam in velocity-modulated devices. a) S-parameters Diagram b) Venn Diagram c) Applegate Diagram d) Smith Chart 125.What is the small amount of the signal applied to the input port that leaks through to the output port? a) Insertion loss b) Regenerative loss c) Feedthrough loss d) Reflection loss 126.What is the wavelength for a frequency of 1 million hertz? a) 30 km b) 3 km c) 30 m d) 300 m 127.What does the acronym VIR mean? a) Video Interface Relay b) Video Interval Recording c) Vertical Interface Relay d) Vertical Interval Reference
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 128.Any periodic function is represented by the sum of a number of sinusoidal variations of different amplitudes, frequencies, and phases. a) Hartley’s Theorem b) Fourier’s Theorem c) Huygen’s Theorem d) Nyquist Theorem 129.What is another name for AF volume control? a) AFC b) Gain c) ARC d) AMC 130.A major disadvantage of the vacuum tube is its need for a _____ to give energy to the electrons. a) Limiter b) Heater c) Line equalizer d) Voltage source 131.What happens to the spectrum of a repetitive pulse as the pulse width decreases? a) Remain constant b) Less harmonics of the same phase c) decreases d) More harmonics of the same phase 132.What does AFC mean? a) All Filipino Conference b) Automatic Frequency Control c) Audio Frequency Camera d) Anti Firing Countermeasure 133.What is an advantage of series modulation? a) High gain and selectivity b) Capable of modulating very high frequencies c) Capable of generating high power d) Low noise and interference
134.What is the permittivity of air? a) 8.853 x 10-12 b) 20 c) 1.26 x 10-6 d) 1
relative
141.What is the seventh harmonic of 360 kHz? a) 1260 kHz b) 2520 kHz c) 5040 kHz d) 7000 kHz
135.A device which can perform the function of both a transmitter and a receiver. a) Transceiver b) Relay c) Buffer d) Repeater
142.In a low-level modulation system, the type of amplifier that follows the modulated stage should be a _____. a) Any of the above b) Harmonic generator c) Linear amplifier d) Class C amplifier
136.Which came first, the invention of the telephone or the invention of the phonograph? a) either b) telephone c) neither d) phonograph 137.What is usually transmitted by facsimile? a) Voice b) Bits c) Pictures d) Video signal 138.Amplitude limiting in the IF section eliminates _____ interference from the FM signal. a) AM b) FM c) Broadband d) PM 139.Name a periodic waveform that consists of only odd harmonics. a) Cosine wave b) Spikes c) Square wave 140.The information carrying capacity of a signal is _____ to its bandwidth. a) Directly proportional b) Inversely proportional c) Equal
143.What method can be used to invert speech? a) AGC b) Frequency translation c) Frequency multiplier d) Inverter 144.It refers to the sending, receiving and processing of information by electronic means. a) Telemetry b) Telephony c) Broadcasting d) Communications 145.(Nov 1996) What is the equivalent output of a circuit in dBm , if it has an output of 10 watts? a) 20 dBm b) 30 dBm c) 10 dBm d) 40 dBm 146.What is the main difference between an AF amplifier and an RF amplifier? a) The range of frequencies that they amplify b) The stability c) The amplification factor d) The selectivity
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BSECE Board Examination Reviewer in Communications Engineering Principles of Communications 147.What circuit is used to create vestigial transmission? a) Diplexer b) Duplexer c) HPF d) LPF 148.What is the meaning of the acronym WDM? a) Wavelength division multiplexing b) Wireless data monitoring c) Wide distribution media d) Wap distributed mode 149.The big breakthrough in electric communications came with the invention of the _____ in 1844. a) Phonograph b) Telegraph c) Transistor d) Telephone 150.How many watts are represented by 40 dBw? a) 1000 W b) 10000 W c) 40000 W d) 40 W
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