Communications Engineering Mastery Test 1: ECE Pre-Board Flashcards by Gerund Juan

That dielectric material of an optical fiber surrounding the core

A. Cladding
B. Armor
C. Shield
D. Cover

Cladding

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An antenna that is circularly polarized is the ____________.

A. parabolic reflector
B. helical
C. Yagi-uda
D. small circular loop

B. helical

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A word in telegraphy consist of __________ characters plus a word space.

A. 11
B. 7 and ½
C. 8
D. 5

B. 7 and ½

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The number of voice band channels in master group per CCITT standard is __________.

A. 300
B. 480
C. 600
D. 120

A. 300

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The power of standard test tone is normally ____________.

A. 1 dB
B. 0 mW
C. 1 mW
D. 1 W

C. 1 mW

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LORAN is a navigational system used primarily for _____________.

A. blind landing
B. obtaining your fixes location over large distances
C. automatic collision warning
D. approach control

B. obtaining your fixes location over large distances

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The expander in a companding device provides ___________.

A. greater amplification for low signal levels
B. less amplification for low signal levels
C. greater amplification for high signal levels
D. lesser pressure for transmission cables

B. less amplification for low signal levels

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LORAN is a navigation system used primarily for

A. approach control
B. obtaining fixes over large distances
C. blind landing
D. automatic collision warning

B. obtaining fixes over large distances

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At what power level does a 1 kHz tone cause zero interference (144 weighted) ?

A. -90 dB
B. -90 dBm
C. 90 dBm
D. 90 dB

B. -90 dBm

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One character or a sequence of characters forming a part, or the whole of a message with a specific meaning

A. Signs
B. Call sign
C. Code
D. Identifier

C. Code

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The K-factor under normal atmospheric conditions in a microwave radio data profile calculation is equal to ___________.

A. 2/3
B. 0
C. 4/3
D. Infinity

C. 4/3

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What is the IBM’s asynchronous data link protocol designation?

A. 83 B
B. 8A1 / 8B1
C. 93 B
D. 9A1/ 9B1

A. 83 B

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EIRP stands for _______________.

A. effective isotropic refracted power
B. effective and ideal radiated power
C. effective isotropic reflected power
D. effective isotropic radiated power

D. effective isotropic radiated power

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The modulation system used for telegraphy is

A. frequency-shift keying
B. two-tone modulation
C. pulse-code modulation
D. single-tone modulation

A. frequency-shift keying

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The standard that specifies a balanced interface cable that will operate bit rates up to 10 Mbps with in a span distances up to 1200 m.

A. RS-423A
B. RS-422A
C. RS-550A
D. RS-449A

B. RS-422A

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An antenna which is not resonant at a particular frequencies and so can be used over a wide band of frequencies and so can be used over a wide band of frequencies is called

A. aperiodic
B. boresight
C. cassegrain
D. top-loaded

A. aperiodic

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A receiver connected to an antenna whose resistance is 50 ohms has an equivalent noise resistance of 30 ohms. What is the receiver’s noise temperature?

A. 754 K
B. 464 K
C. 174 K
D. 293 K

C. 174 K

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___________ occurs when the microwave beam is at point of grazing over an obstacle.

A. Diffraction
B. Refraction
C. Absorption
D. Reflection

A. Diffraction

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Atmospheric condition is controlled by

A. humidity
B. pressure
C. temperature
D. all of these

D. all of these

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The characteristics impedance of a transmission line does not depend upon its ________.

A. conductor spacing
B. conductor diameter
C. length
D. conductor radius

C. length

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What is the purpose of a beat frequency oscillator (BFO)?

A. Aid 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 note for Morse code reception
D. Generates an output, whose frequency differs from that of the intermediate frequency by 1 kHz

C. Generates a 1 kHz note for Morse code reception

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he point on the satellite orbit, closest to the earth is

A. prograde
B. perigee
C. zenith
D. apogee

B. perigee

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The potential difference between any exposed structured to ground in any electrical installation should not exceed _________ volts RMS.

A. 10
B. 45
C. 0
D. 30

B. 45

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The capture area of an antenna is directly proportional to the

A. frequency of the received signal
B. distance between transmitter and receiver
C. gain of the antenna
D. power density of the signal

C. gain of the antenna

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Modems are required to connect computer to telephone lines because ___________. A. telephone company rules required them B. the telephone network bandwidth is too high C. none of the above D. the telephone network will pass direct current

D. the telephone network will pass direct current

The standard reference antenna for the directive gain is ___________. A. elementary doublet B. isotropic antenna C. half-wave dipole D. infinitesimal dipole

B. isotropic antenna

One hundred twenty µbars of pressure variation is equal to A. 120 dBSPL B. 115.56 dBSPL C. 41.58 dBSPL D. 57.78 dBSPL

B. 115.56 dBSPL

It is a spacecraft placed in orbit around the earth carrying onboard microwave receiver and transmitting equipment. A. Fiber optic equipment B. Communications satellite C. Wireless radio system D. Coaxial cable system

B. Communications satellite

One type of pulse communications system uses pulse that appear as a group, and which vary in number according to the loudness of the voice. This type of pulse modulation is called A. pulse duration modulation B. pulse amplitude modulation C. pulse code modulation D. pulse position modulation

A. pulse duration modulation

A device to be connected across the headset in telephone receivers to reduce the effects of acoustic shock. A. Ground B. Two rectifiers in parallel with opposite polarities C. Protector D. Fuse

B. Two rectifiers in parallel with opposite polarities

Judgment on the case against an ECE shall become final and executory after A. 10 days B. 60 days C. 30 days D. 15 days

C. 30 days

The equivalent noise temperature of the amplifier is 25 K. What is the noise figure? A. 1.86 B. 0.1086 C. 1.086 D. 10.86

C. 1.086

The letter-number designation B8E is a form of modulation also known as ___________. A. pilot carrier system B. independent sideband emission C. lincomplex D. vestigial sideband transmission

B. independent sideband emission

When the transmitting and receiving antennas are in line-of-sight of each other, the mode of propagation is ________ wave. A. space or direct B. ground C. surface D. sky

A. space or direct

Crosstalk coupling is ___________. A. dBm (disturbing pair) minus dBm (disturbed pair) B. the difference between readings on a cable pair with a tone and a cable pair without tone read at the far end of a cable C. signals from one circuit that get into another circuit D. All of these are true

D. All of these are true

According to the Nyquist theorem, the sampling rate that can be used in a PCM system is ________ the highest audio frequency. A. once B. eight times C. twice D. thrice

C. twice

Passive crossover components cause some frequencies to be delayed with respect to the other frequencies at the crossover point. A. Phase shift B. Phase correction C. Phase-error correction D. Time alignment

A. Phase shift

A car horn outdoors produces a sound intensity level of 90 dB at 10 ft away. At this distance, what is the sound power in watt? A. 12 W B. 0.12 W C. 0.012 W D. 1.2 W

B. 0.12 W

What is the one principal difference between synchronous and asynchronous transmission? A. the pulse height are different B. the clocking is derived from the data in synchronous transmission C. the clocking is mixed with the data in asynchronous D. the bandwidth required is different

B. the clocking is derived from the data in synchronous transmission

The lowest layer in the ionosphere A. D B. F2 C. E D. F1

A. D

What is the number of pins in the RS-232C interface? A. 25 B. 15 C. 20 D. 20

A. 25

SSB transmission requires only ______ of the bandwidth for a DSBFC transmission. A. ¼ B. 2/3 C. ½ D. ¾

C. ½

The method of generating FM used by broadcasting station is A. direct B. all of these C. indirect D. insertion

C. indirect

What is the transmission rate of a system for transmitting the output of a microcomputer to a line printer operating at a speed of 30 lines/minute? Assume that the line printer has 8 bits of data per character and prints out 80 characters/line. A. 800 bps B. 400 bps C. 320 bps D. 640 bps

C. 320 bps

Communications code is ____________. A. eight bits per character B. agreed upon in advance between sender and receiver C. the same in all modern computers D. either seven or eight bits per character

B. agreed upon in advance between sender and receiver

What is the reference tone level for dBm? A. -82 dBm B. -85 dBm C. -67 dBm D. -90 dBm

D. -90 dBm

A type of an underground antenna is a/an __________ antenna. A. Hertz B. isotropic C. parabolic D. Marconi

A. Hertz

Which of the following pulse modulation systems is analog? A. Delta B. Differential PCM C. PWM D. PCM

C. PWM

What is the purpose of the receiver’s squelch circuit? A. To overcome fluctuations in the level the RF signal arriving at the receiver antenna B. To prevent fluctuations in the AGC bias level C. To reduce the receiver’s sensitivity to all incoming signals D. To prevent amplified noise from reaching the loudspeaker during the absence of an incoming signal

D. To prevent amplified noise from reaching the loudspeaker during the absence of an incoming signal

TACAN is a navigational aid providing ___________. A. bearing and distance indication B. speed and height indication C. bearing and weather information D. instrument-landing glide paths

A. bearing and distance indication

In __________ transmission, a unique SYNC character is transmitted at the beginning of each message. A. asynchronous B. synchronous C. digital D. analogue

B. synchronous

If the terminating impedance is exactly equal to the characteristic impedance of the transmission line the return loss is ___________. A. zero B. one C. infinite D. None of these

C. infinite

What is the main purpose of a communications system? A. None of these B. To have a frequency assignment C. For modulation D. To provide an acceptable replica of the information at the destination

D. To provide an acceptable replica of the information at the destination

What is meant by antenna gain? A. The final amplifier gain minus the transmission line losses (including any phasing lines present) B. The ratio of the amount of power produced by the antenna compared to the output power of the transmitter C. The ratio of the signal in the backward direction D. The numeric ratio relating the radiated signal strength of an antenna to that of another antenna

D. The numeric ratio relating the radiated signal strength of an antenna to that of another antenna

Binary communications systems are better because A. they can interface directly with the analog telephone network B. the components are simpler, less costly, and more reliable C. people think better in binary D. interstate calls are less costly

B. the components are simpler, less costly, and more reliable

n the phase shift method, How many circuits must be balanced? A. None of these B. 1 C. 4 D. 2

D. 2

The carrier swing necessary to provide 80% modulation in the FM broadcasting band is __________. A. 150 kHz B. 120 kHz C. 60 kHz D. 75 kHz

B. 120 kHz

The correctness and accuracy of the transmitted message content is A. verified by the modem B. communications system C. determined by the sender and receiver D. ensured by use of digital technique

C. determined by the sender and receiver

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. 9/23 B. 23/9 C. 32 dB D. 14 dB

D. 14 dB

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. 115.5 % C. 50% D. 83%

D. 83%

If the percentage modulation of an AM amplifier is 88% and the modulating signal is 1 volt, the carrier has an amplitude of _______________. A. 1.14 volts B. 0.88 volt C. 1.88 volts D. 0.12 volt

A. 1.14 volts

It consists of a number of dipoles of equal size, equally spaced along a straight line with all dipoles fed in the same phase from the same source. A. Log-periodic antenna B. Yagi antenna C. End-fire array D. Broadside array

D. Broadside array

Data switching systems. A. improve the efficiency of data transfer B. are limited to small data networks C. required additional lines D. are not used in data system

A. improve the efficiency of data transfer

A type of array antenna which consists of one half-wave driven dipole, one reflector and one director A. Hertzian dipole B. Yagi-uda C. Broadside collinear D. Log periodic dipole array

B. Yagi-uda

Power is a _____________ amount of energy used in specific period of time A. large B. definite C. electrical D. relative

B. definite

The midrange frequency range of sound is from A. 256 to 2048 Hz B. 2048 to 4096 Hz C. 512 to 2048 Hz D. 16 to 64 Hz

A. 256 to 2048 Hz

To connect coaxial line to a parallel-wire _________ is the best to use. A. directional coupler B. quarter-wave transformer C. balun D. slotted line

C. balun

In AM, the carrier carries ____________ intelligence. A. no B. difference C. distorted D. same

A. no

Characteristics impedance of a transmission line is the impedance measured at the ___________ when its length is infinite. A. input B. shorted end of the line C. output D. midsection

A. input

Cross modulation on a receiver is eliminated at the A. RF stage B. mixer stage C. IF stage D. detector stage

D. detector stage

A speaker cabinet has an internal volume 84,950 cm3. It has a port area on the baffle of 3,230 cm2 and baffle thickness of 19 mm. What is the Helmholtz resonance hertz of this speaker enclosure? A. 260 Hz B. 245 Hz C. 265 Hz D. 250 Hz

B. 245 Hz

What quarterwave transformer will match a 100Ω line to an antenna whose value is 175Ω? A. 132.29 Ω B. 150 Ω C. 16.58 Ω D. 137.5 Ω

A. 132.29 Ω

The local loop of the telephone system is understood to be A. a single piece of wire connecting the subscriber’s telephone set to another telephone set in an adjacent room B. a two-wire or four-wire communication circuit between the customer’s premise and central office C. a four-wire circuit connecting a facsimile machine to a computer D. a group of wires connecting a telephone set to a modem

B. a two-wire or four-wire communication circuit between the customer’s premise and central office

In what region of the world is sporadic-E most prevalent? A. The equatorial regions B. The northern hemisphere C. The arctic regions D. The polar regions

A. The equatorial regions

The process of assigning PCM codes to absolute magnitudes A. Overloading B. All of these C. Quantizing D. Multiplexing

C. Quantizing

It is a measure of the microwave power radiated from an antenna as a function of angular direction from the antenna axis. A. Antenna pattern B. Polarization C. Beamwidth D. Sidelobes

C. Beamwidth

It is the made from semiconductor material such as aluminum-gallium-arsenide or gallium-arsenide-phosphide. A. APD B. Injection laser diode C. Light emitting diode D. Positive-intrinsic-negative

C. Light emitting diode

Which one is not the basic electrical protection measures in the Philippine Electronics Code? A. Voltage/ current limiting and interrupting B. Undergrounding C. Grounding and bonding D. Shielding

B. Undergrounding

What does the noise weighting curve shows? A. Noise signals measured with a 144 handset B. Power levels of noise found in carrier systems C. The interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertz D. Interfering effects of signals compared with a 3-kHz tone

C. The interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertz

What is the difference between phase and frequency modulation? A. Is purely theoretical because they are the same in practice B. Lies in poorer audio response of phase modulation C. Lies in the different definitions of the modulation index D. Is too great to make two systems compatible

C. Lies in the different definitions of the modulation index

When a transmission line uses ground return, it is called a/an __________ line. A. ungrounded B. balanced C. unbalanced D. grounded

C. unbalanced

What is the gain of four identically polarized antennas stacked one above the other and fed in phase? A. 3 dB over the gain of one antenna B. 10 dB over the gain of one antenna C. 4 dB over the gain of one antenna D. 6 dB over the gain of one antenna

D. 6 dB over the gain of one antenna

The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the same bandwidth. A. Reference audio output B. None of these C. Audio frequency response D. Residual noise level

D. Residual noise level

The ___________ filter attenuates signals but passes frequencies below and above that band. A. low pass B. band pass C. band stop D. high pass

C. band stop

in a telephone system, the customer’s telephone directory numbering is from 000 to 999, what is the capacity of the system? A. 1000 lines B. 100,000 lines C. 10,000 lines D. 100 lines

A. 1000 lines

An absorption loss caused by valence electrons in the silica material from which fibers are manufactured. A. Modal dispersion B. Infrared absorption C. Ion resonance absorption D. Ultraviolet absorption

D. Ultraviolet absorption

In an FM receiver, which circuit removes amplitude variations? A. Exciter B. Mixer C. Discriminator D. Limiter

D. Limiter

A one-hop, full duplex, microwave system in a space diversity arrangement. Determine “how many receivers in all are used?” A. 8 B. 2 C. 4 D. 6

B. 2

The frequency spectrum of the stereophonic FM signal. A. 67 kHz B. 59.5 to 74.5 kHz C. 19 to 38 kHz D. 30 to 53 kHz

D. 30 to 53 kHz

Termination means A. result of disconnecting a line from a transmitter B. result of cutting both ends of a conductor C. looking back impedance of a line with no load D. load connected to the output end of a transmission line

D. load connected to the output end of a transmission line

Asynchronous protocol is A. message oriented B. clock oriented C. bit oriented D. character oriented

D. character oriented

Transmission lines are either balanced or unbalanced with respect to _________. A. negative terminal B. input C. ground D. positive terminal

C. ground

What is the velocity factor for non-foam dielectric 50 or 75 ohm flexible coaxial cable such as RG 8, 11, 58 and 59? A. 2.70 B. 0.10 C. 0.66 D. 0.30

C. 0.66

Gain of an isotropic antenna A. -1 dB B. 1 dB C. 0 dB D. 2 dB

C. 0 dB

In measuring noise in a voice channel at a 4 dB test point level, the meter reads -70 dBm (F1A weighted), convert the reading to pWp. A. 53 B. 93 C. 63 D. 83

B. 93

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

D. all of these

Radio fading resulting from obstruction losses. A. Log normal fading B. None of these C. Multi-path fading D. Rayleigh fading

A. Log normal fading

After the IF stages have been aligned, the next stage to align in FM receiver is. A. local oscillator B. limiter stage C. RF amplifier D. mixer stage

A. local oscillator

___________ is a device in data transmission to interface data terminal equipment to an analogue transmission line. A. RS 232 B. Connector C. Modem D. RJ-11 plug

C. Modem

What is the primary advantage of DSBSC in AM? A. Reduce bandwidth over standard AM B. All of these C. It is simpler to transmit and receive than the standard AM D. No transmitter power is wasted in the carrier

D. No transmitter power is wasted in the carrier