REVIEW in ESAT

REVIEW QUESTION SERIES 1

1. The main advantage of SSB over standard AM or DSB is. (Modulation)a. Less power is consumed.b. Less spectrum space is used.c. Simpler equipment is used.d. A higher modulation percentage.

Answer: bThis greatly conserves spectrum space and allows more signals to be tran

smitted in the same frequency range.

2. In a pulse-averaging discriminator, the pulses are produced by an. (Modulation)a. Zero-crossing detector.b. Astable multivibrator.c. One shot.d. Low-pass filter.

Answer: cPulse-averaging discriminator converts an FM signal into a square wave o

f identical frequency variation using a zero-crossing detector, comparator, or limiter circuit. This circuit triggers a one shot that produces pulses that are averaged in a lowpass filter to reproduce the original modulating signal.

3. Permit very long distances, even worldwide, communications. (Radiowave Propagation)a. Single hopb. Double hopsc. Multiple hopsd. Omni hops

Answer: cThe maximum distance of a single hop is usually no more than about 2000

mi, but with multiple hop this extend the communications range by many thousands of miles.

4. Using a small reflector to beam waves to the larger parabolic reflector is known as. (Microwave Comm)a. Focal feed.b. Coax feed.c. Cassegrain feed.d. Horn feed.Answer: cAdvantages in some feed arrangement. The waveguide transmission line is shorter. The radical bends in the waveguide are eliminated. Less signal attenuation. Noise figure is also improved.

5. A microwave diode with an N-type silicon cathode and a metal anode forming a junction is called a(n). (Microwave Communication)a. Varactor b. TRAPATT c. IMPATTd. Schottky

Answer: dPoint-contact and Schottky or hot-carrier diodes are widely uses as mixe

rs in microwave equipment as they have low capacitance and inductance.

6. Using very narrow beamwidth antennas to isolate signals on the same frequency is known as. (Satellite Communication)a. Frequency isolationb. Frequency reusec. Spatial isolationd. Partial isolation

Answer: cSpatial isolation is another technique for frequency sharing. It uses hi

ghly directional spot-beam antennas to prevent interference between stations on the same frequency.

7. All computers share their resources, such as hard drives, printers, and so on, with all the other computers on the network. (Data Communication)a. Peer-to-peer client/serverb. Point-to-point client/serverc. Dedicated client/serverd. Shared client/server

Answer: aSometimes called workgroup, there are no dedicated servers or hierarchy

among the computers.

8. Actually detects and corrects transmission errors when they are received without requiring a retransmission. (Data Communication)a. FECb. ARQc. Continuous ARQd. CRC

Answer: aWith FEC, redundant bits are added to the message before transmission. W

hen an error is detected, the redundant bits are used to determine which bit is in error.

9. A form of amplitude distortion introduced when the positive and negative alterations in the AM modulated signal are not equal. (Modulation)a. Phase shiftb. Amplitude shiftc. Modulating shiftd. Carrier shift

Answer: dCarrier shift may be either positive or negative. If the positive altera

tion of the modulated signal has a larger amplitude than the negative alteration, positive carrier shift results. If the negative alteration is larger than the positive, negative carrier shifts occurs.

10. The adjustment for the center frequency of the preselector and the adjustment for the local oscillator frequency. (Modulation)a. Frequency conversionb. Gang tunedc. Frequency tuningd. Tuned circuit

Answer: bGang tuning means that the two adjustments are mechanically tied togethe

r so that a single adjustment will change the center frequency of the preselector and, at the same time, change the local oscillator frequency.

11. The function of an AM detector is to demodulate the AM signal and recover the original source information. The AM detector sometimes called. (Modulation)a. First detectorb. Second detectorc. Third detectord. Peak detector

Answer: bWith the mixer/converter being the first detector because it precedes th

e AM detector.

12. The ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme. (Digital Communication)a. Bandwidth compressionb. Bandwidth densityc. Bandwidth efficiencyd. Bandwidth average

Answer: c

Bandwidth efficiency sometimes called information density or spectral efficiency is often used to compare the performance of one digital modulation technique to another.

13. Produces a loop error voltage that is proportional to twice the phase error between the incoming signal and the VCO signal. (Digital Communication)a. Squaring loopb. Costas loopc. Remodulatord. Carrier recovery

Answer: cCarrier recovery is the process of extracting a phase-coherent reference

carrier from a receiver signal. Methods of carrier recovery: squaring loop, costas loop, and remodulator. The remodulator has a faster acquisition time than either the two.

14. The phase relationship between signaling elements for BPSK is the optimum signaling format. (Digital Communication)a. Podal signalingb. Antipodal signalingc. Bit signalingd. One signaling

Answer: bOccurs only when two binary signal levels are allowed and when one signa

l is the exact negative of the other. Because no other bit-by-bit signaling scheme is nay better, antipodal performance is often used as a reference for comparison.

15. Most of the more recently developed codec are called. (Digital Communication)a. Combo chipsb. Micro chipsc. Uni chips

d. Vocoders

Answer: a Combo chips include an antialiasing (bandpass) filter, a sample-and-hold

circuit, and an ADC in the transmit section and a DAC, hold circuit.

16. Extracts the most significant portions of speech information directly from the time waveform rather than from the frequency spectrum. (Digital Communication)a. Vocodersb. Linear predictive codersc. Channel vocodersd. Formant vocoders

Answer: bVocoder is to encode the minimum amount of speech information necessary

to reproduce a perceptible message with fewer bits than those needed by a conventional encoder/decoder. Three vocoding technique; channel vocoder, formant vocoder, and linear predictive coders.

17. One common kind of digit-at-a-time coder, uses a successive approximation register (SAR). (Digital Communication)a. Time coderb. Feedback coderc. Sequentially coderd. Level-at-a-time coding

Answer: bDigit-at-a-time coding is a type of coding determines each digit of the

PCM code sequentially. With this type of coder, the entire PCM code word is determined simultaneously

18. One of the primary causes of ISI that the rate of transmission does not conform to the ringing frequency designed into the communications channel. (Digital Communication)a. Insufficient bandwidthb. Timing inaccuraciesc. Phase distortiond. Amplitude distortion

Answer: bISI is intersymbol interference. ISI is an important consideration in th

e transmission of pulses over circuits with a limited bandwidth and a nonlinear phase response. The four primary causes of ISI are Timing inaccuracies, insufficient bandwidth, phase distortion, and amplitude distortion.

19. Mode of propagation in a helical antenna that is electromagnetic radiation is in direction at right angles to the axis of the helix. (Antennas)a. Helix modeb. Axial modec. Normal moded. Circular mode

Answer: c A helical antenna is a broadband VHF or UHF antenna that is ideally suit

ed for application for which radiating circular rather than horizontal or vertical polarized electromagnetic waves are required. Two modes of propagation for helical antenna are normal and axial. In the axial mode, radiation is in the axial direction and produces a broadband, relatively directional pattern.

20. Is caused by valence electrons in the silica material from which fibers are manufactured. (Fiber Optics)a. Infrared absorptionb. Ion resonance absorptionc. Chromatic absorptiond. Ultraviolet absorption

Answer: dAbsorption losses in optical fibers are analogous to power dissipation i

n copper cables; impurities in the fiber absorb the light and convert it to heat. There are three factors that contribute to the absorption losses in optical fibers: Ultraviolet absorption, infrared absorption, and ion resonance absorption.

21. In LEDs, a p-n junction made from two different mixtures of the same types of atoms. (Fiber Optics)a. Homojunction LEDsb. Heterojunction LEDsc. Edge-emitting LEDd. Burrus Etched-well Surface-Emitting LED

Answer: aLEDs emit light by spontaneous emission-light is emitted as a result of

the recombination of electrons and holes. The simplest LED structures are homojunction and epitaxially grown, or they are single-diffused semiconductor devices.

22. Diffraction occurs around the edge of the obstacle. Allows secondary waves to �sneak� around the corner of the obstacle. (Radiowave Propagation)a. Sneak zoneb. Peek zonec. Shadow zoned. Dark zone

Answer: cDiffraction is defined as the modulation or redistribution of energy wit

hin a wavefront when it passes near the edge of an opaque object. Diffraction is the phenomenon that allows light or radio waves to propagate around the corners.

23. Occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial. (Modulation)a. Single spottingb. Double spottingc. Spurious pointd. Double point

Answer: bOne point is the desired location, and the other point is called the spu

rious point. Double spotting is caused by poor front-end selectivity or inadequate image-frequency rejection. Double spotting is harmful because weak stations can be overshadowed by the reception of a nearby strong station at the spurious location in the frequency spectrum.

24. Filters that are made from lead zirconate-titanate, which exhibits the piezoelectric effect. (Modulation � Single-sideband com. system)a. Surface acoustic wave filtersb. Mechanical filtersc. Ceramic filters

d. Crystal filters

Answer: cThree transmitter configurations are commonly used for single-sideband g

eneration: the filter method, the phase-shift method, and the so-called third method. Ceramic filter is one of the filter methods. Ceramic filters operate quite similar to crystal filters that ceramic filters do not have as high a Q-factor. Typical Q values for ceramic filters go up to about 2000.

25. A system provide narrowband voice communications for land-mobile services with nearly the quality achieved with FM systems and do it using less than one-third the bandwidth. (Modulation � Single-sideband com. system)a. ACSSBb. SSBSCc. DSBSCd. IMTS

Answer: aWith Amplitude-compandoring single-sideband (ACSSB), the audio signals a

re compressed before modulation by amplifying the higher-magnitude signals less than the lower-magnitude.

26. The �payload� on communication satellite consists of (Satellite Communication)a. Transpondersb. Batteriesc. Solar cellsd. All of the above

Answer: aAn automatic device that transmits a predetermined message in response to a predefined received signal.

27. Modulator circuit performs what mathematical operation on its two inputs? (Modulation)a. Multiplication b. Division c. Additiond. Subtraction

Answer: aThe carrier waveform multiplied by the modulating signal waveform.

28. What type of propagation is probably occurring if radio signals travel along the terminator between daylight and darkness? (Radio Propagation)a. Grazingb. Sporadic-Ec. Long-Pathd. Grey line

Answer: dThe "grey line" is a band around the Earth that separates daylight from

darkness. Propagation along the grey line is very efficient. One major reason for this is that the D layer, which absorbs HF signals, disappears rapidly on the sunset side of the grey line, and it has not yet built upon the sunrise side.

29. When scheduling EME contacts, which of these conditions will generally result in the least path loss? (Radio Propagation)a. When the moon is fullb. When the MUF is above 30 MHz

c. When the moon is fulld. When the moon is at apogee

Answer: d When the moon is at apogee there is a least path loss.

30. This transmission line is used in microwave circuit. It consists of a narrow, flat conductor sandwiched between dielectric boards whose outside surfaces are coated with conductor.(Transmission lines)a. Fiber opticsb. Waveguide c. Coax d. Stripline

Answer: dA microwave transmission line constructed of a center conductor suspende

d between parallel conductive ground planes.31. Tropospheric scatter is used with frequencies in the following range:.. (Radio Propagation)a. VLFb. UHFc. HFd. ELFAnswer: bThe scattering of distant TV and FM radio stations by the troposphere so that they travel farther than the line of sight.UHF covers TV and FM.

32. The IEEE standard used for high speed wireless Ethernet access known as Wi-Fi�s is _____. (Data Communication)a. 801.11b. 803.116c. 803.12d. 802.116

Answer: aApplies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).

33. What is emission F3F? (Radio Propagation)a. Radiob. Televisionc. Microwaved. Telephone

Answer: bThe 2nd F in F3F is for television (video)

34. When a meteor strikes the earth's atmosphere, a cylindrical region of free electrons is formed at what layer of the ionosphere? (Radio Propagation)a. E Layerb. F1 Layerc. F2 Layerd. D Layer

Answer: aThe vertical structure of the E layer is primarily determined by the competing effects of ionization and recombination. At night the E layer begins to disappear because the primary source of ionization is no longer present.

35. The farthest point a satellite can reach is (Satcom)a. Apogeeb. Perigeec. Altituded. Attitude

Answer: a The highest point of the orbit or it is the point in an earth satellite orbit, which is farthest away from the earth. (lowest velocity)36. How many horizontal lines make up a fast-scan television frame? (Radio Propagation)a. 530b. 525c. 520d. 535

Answer: bNTSC uses 525 horizontal lines of which only about 487 make up the active picture.

37. Manganese ferrite may be used as a (indicate false answer). (Radio Propagation)a. Circulatorb. Isolatorc. Garnetd. Phase shifter

Answer: cGarnet cannot be used for manganese ferrite.

38. The rate of the power radiated by the antenna to the square of the current at the feed point.a. Directive Gainb. Field Intensityc. Radiation Resistanced. Power Gain

Answer: dPower Gain is the rate of power radiated by the antenna to the square of the current at the feed point. Radiation resistance is a part of an antenna's feed point resistance that is caused by the radiation of electromagnetic waves from the antenna.

39. The fiber optic core is surrounded by. (fiber optics)a. Glassb. Wire braid shieldc. Insulationd. Cladding

Answer: dUsed to protect the fiber core from nicks and scratches.

40. According to this criterion, for a feedback circuit to sustain oscillations, the net voltage gain around the feedback loop must be unity or greater, and the net phase shift around the loop must be a positive integer multiple of 360?. (Communication System)a. block criterionb. Barkhausen criterionc. markhausen criteriond. blocker criterion

Answer: bThe Barkhausen stability criterion states that an oscillator will oscillate when the total phase shift from input to output back to input is an integral multiple of 360 degrees and the system gain is equal to 1.41. A device that performs compression and expansion. (Communication Systems)a. Lapandorb. Compandorc. Compressord. ExpandorAnswer: bThe electronic circuit that does this is called a compandor and works by compressing or expanding the dynamic range of an analog electronic signal such as sound. One variety is a triplet of amplifiers: a logarithmic amplifier, followed by a variable-gain linear amplifier and an exponential amplifier. Such a triplet has the property that its output voltage is proportional to the input voltage raised to an adjustable power. Compandors are used in concert audio systems and in some noise reduction schemes such as dbx and Dolby NR (all versions).42. A geographic representation of a satellite radiation pattern, with contour lines representing limits of equal receives power density. (Satellite Communication)a. Lapprintb. Fingerprintc. Handprintd. FootprintAnswer: bThe footprint of a communications satellite is the ground area that its transponders offer coverage, and determines the satellite dish diameter required to receive each transponder's signal. There is usually a different map for each transponder (or group of transponders) as each may be aimed to cover different areas of the ground.Footprint maps usually show either the estimated minimal satellite dish diameter required or the signal strength in each area measured in dBW.43. Voice band channels are assigned on �as needed� basis. It provides more versatility and more efficient use of the frequency spectrum. (Satellite Communication)a. PAMAb. LAMAc. DAMAd. DOTAAnswer: cDemand Assigned Multiple Access (DAMA) is a technology used to assign a bandwidth to clients that don't need to use it constantly. DAMA systems assign communication channels or circuits based on requests issued from user terminals to a network control system. When the circuit is no longer in use, the channels are then returned to the central pool for reuse by others.Channels are typically a pair of carrier frequencies (one for transmit and one for receive), but can be other fixed bandwidth resources such as timeslots in a TDMA burst plan. Once allocated to a pair of nodes this bandwidth is not available to other users in the network until their session is finished.44. Unveiled the most famous mobile telephone to date: the fully mobile shoe phone in 1966 in a television show called Get Smart. (Mobile Communication)a. E.K. Jettb. Don Adamsc. Charles Wheatstoned. George BooleAnswer: bDon Adams (April 13, 1923 � September 25, 2005) was an American actor, comedian, game show panelist, and director. In his five decades on television, he was best

known as Maxwell Smart (Agent 86) in the TV situation comedy Get Smart (1965�1970, 1995), which he also directed and wrote. Adams won three consecutive Emmy Awards for his portrayal of Smart (1967�1969). He provided the voices for the animated series Tennessee Tuxedo (1963-1966) and Inspector Gadget (1983-1986) as their title characters.

45. Communications system used to carry information for relatively short distances such as between cities with the same state. (Microwave Communication)a. Back haulb. Long haulc. Mid hauld. Short haul

Answer: dA short-haul domestic flight is commonly categorized into being no longer than 500 mi (800 km) 1.5 hours in length, meaning that all domestic flights within a country such as the United Kingdom are short-haul. In addition to this criterion, the destination airport must be in the same country as the departure airport. Domestic flights can vary greatly in length due to some countries being larger than others.46. The _______ has an effect on the symbol timing (clock) recovery circuit and, if excessive, may significantly degrade the performance of cascaded regenerative sections. (Modulation)a. Hitterb. Glitterc. Jitterd. LiterAnswer: cJitter is the time variation of a periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals. Jitter is a significant, and usually undesired, factor in the design of almost all communications links (e.g., USB, PCI-e, SATA, OC-48). In clock recovery applications it is called timing jitter.47. In telecommunication, _______ is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines. (Mobile Communication)a. pulse modulationb. Trellis modulationc. amplitude modulationd. code modulationAnswer: b In telecommunication, trellis modulation (also known as trellis coded modulation, or simply TCM) is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines.48. In signal processing, the ______is two times the bandwidth of a bandlimited signal or a band limited channel. a. extream rateb. bypass ratec. pulse rated. Nyquist rateAnswer: dIn signal processing, the Nyquist rate is two times the bandwidth of a bandlimited signal or a band limited channel.

49. A _____ is a specialized beacon used in aviation in conjunction with an instrument landing system (ILS), to give pilots a means to determine distance to the runway. Marker beacons transmit on the dedicated frequency of 75 MHz. (Navigational Aids)

a. Marker beaconb. Long Range Navigation Systemc. short range navigation systemd. line beacon

Answer: aA marker beacon is a specialized beacon used in aviation in conjunction

with an instrument landing system (ILS), to give pilots a means to determine distance to the runway. Marker beacons transmit on the dedicated frequency of 75 MHz.

50. Most widely used camera tube. (Broadcast & Acoustics)a. Siliconb. Vidiconc. Beacond. Limacon

Answer: bA vidicon tube is a video camera tube design in which the target material is a photoconductor. (Broadcast & Acoustics)51. A photoelectric tube used with a rotating wheel punched with small holes spirating in toward the center to scan the picture elements. (Broadcast & Acoustics)a. hard diskb. flask diskc. scanner diskd. Nipkow Disk

Answer: dA Nipkow disk (sometimes Anglicized as Nipkov disk), also known as scanning disk, is a mechanical, geometrically operating image scanning device, invented by Paul Gottlieb Nipkow. This scanning disk was a fundamental component in mechanical television through the 1920s.52. Developed the first file transfer protocol designed to facilitate transferring data between two personal. (Data Communications)a. Charles Wheatstoneb. C.E. Shannonc. Ward Christiansend. Joseph Jacquard

Answer: cChristensen was noted for building software tools for his needs. He wrot

e a cassette-based operating system before floppies and hard disks were common. When he lost track of the source code for some programs he wrote ReSource, an iterative disassembler for the Intel 8080, to help him regenerate the source code. When he needed to send files to Randy Suess he wrote XMODEM. Christensen received two 1992 Dvorak Awards for Excellence in Telecommunications, one with Randy Seuss for developing the first BBS, and a lifetime achievement award "for outstanding contributions to PC telecommunications." In 1993 he received the Pioneer Award from the Foundation. He also was an initial inductee into the Shareware Hall of Fame in 1997. Christensen has been working for IBM as a technical sales specialist since 1968.

53. High-powered, high capacity mainframe computers that support terminals. (Data Communications)a. Ghostsb. Sibilancec. Hostsd. Digital Pipe

Answer: cThe hosts file is a computer file used by an operating system to map hostnames to IP addresses. This method is one of several methods used by an operating system to locate network nodes on a computer network. On many operating systems, the host file content is used preferentially over other methods, such as the Domain Name System (DNS). Unlike DNS, the hosts file is under the control of the local computer's administrator.54. A mathematician who was an early pioneer in the development of error-detection and correction procedures developed the Hamming Code while working at Bell Telephone Laboratories. (Data Communications)a. John Mauchlyb. George C. Devolc. Joseph F. Engelbergerd. Richard W. Hamming

Answer: d Richard Wesley Hamming (was an American mathematician whose work had ma

ny implications for computer science and telecommunications. His contributions include the Hamming code (which makes use of a Hamming matrix), the Hamming window (described in Section 5.8 of his book Digital Filters), Hamming numbers, Sphere-packing (or hamming bound) and the Hamming distance. He was a founder and president of the Association for Computing Machinery. His philosophy on scientific computing appears as preface to his 1962 book on numerical methods:

55. ________are files that are created to accompany data files, and are used to preserve data integrity and assist in data recovery. (Data Communications)a. folder filesb. parity filesc. security filesd. olded files

Answer: bParity files are files that are created to accompany data files, and are

used to preserve data integrity and assist in data recovery. They are useful when data files are transmitted or stored on less-than-perfect mediums such as newsgroup messages, satellite transmission, or optical disk. Parity files are constructed according to algorithms of error detection and correction.

56. Form of redundancy error checking where each character has a numerical value assigned to it. (Data Communications)a. Bucksumb. hash sumc. dash sumd. outsum

Answer: b A checksum or hash sum is a fixed-size datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during its transmission or storage. The integrity of the data can be checked at any later time by recomputing the checksum and comparing it with the stored one. If the checksums do not match, the data was almost certainly altered (either intentionally or unintentionally).

57. The portion of the satellite communications link involving the transmission of traffic from the satellite to the earth terminal. (Satellite Communication)a. Uplinkb. buck linkc. up&downlinkd. Downlink

Answer: dA downlink (DL) is the link from a satellite to a ground station. Pertaining to cellular networks, the radio downlink is the transmission path from a Base Transceiver Station (Cell Site) to the Mobile Station (Cell Phone). Traffic and signalling flows within the BSS and NSS may also be identified as uplink and downlink.58. What is the wavelength of a violet light? (RadioWave Propagation)a. 4 micrometersb. 700nmc. 40nmd. 0.07 micrometers

Answer: aVisible light is the range of .4 - .7 micrometers. Violet light has a short-wavelength of .4um.

59. The unit of a radar set which display the radar information coming from the receiver is (Radar)a. Magnetronb. Indicatorc. Duplexerd. Transmission

Answer: bThe information available from a radar receiver may contain as many as several million separate data bits per second. From these and other data, such as the orientation of the antenna, the indicator should present to the observer a continuous, easily understandable, graphic picture of the relative position of radar targets. It should provide size, shape, and insofar as possible, indications of the type of targets. A cathode-ray tube (crt) fulfills these requirements to an astonishing degree. The cathode-ray tube's principal shortcoming is that it cannot present a true three-dimensional picture.

60. It is the ratio of the transmitted on time or pulse width to pulse repetition time? (Radar)a. Peak Powerb. Duty Cyclec. Pulse widthd. Pulse Interval

Answer: bA decimal number that expresses a ratio in a pulse modulation system of transmit time to total time.

61. It is an operational brevity cope that means an air contact that is unidentified but assumed to be enemy? (Radar)a. Bogeyb. Clarac. Skunkd. Racket

Answer: aBogey is a radar or visual air contact whose identity is unknown.

62. What type of display presents only the range of the target and the relative strength of the echo? (Radar)a. A-Scopeb. RHI Scopec. PPIScope

d. All of the above

Answer: aThe original radar display was the A-scope, which displays the range to

targets along a scale. These displays were also referred to as R-scope, for range scope. To draw the A-scope display, a sawtooth voltage generator was attached to the X-axis to move the oscilloscope spot across the screen at a fixed speed. The start of the "sweep" was triggered to coincide with the start of a radar pulse being sent out of the antenna, and the speed of the sweep was set to make it reach the far end (typically right side) of the display at the end of the pulse's maximum return time. Any reflected signal was amplified and sent directly to the display's Y-axis input, displacing the beam upward, drawing a "blip" (or "pip").

63. Instead of a single bit, a QPSK symbol contains _______. (Data Communication)a. Bit rateb. Dibitc. Baud rated. Tribit

Answer: bThe term "quadrature" implies that there are four possible phases (4-PSK) which the carrier can have at a given time, as shown at right on the characteristic constellation for this moduation type. The four phases are labelled {A,B,C,D} corresponding to one of {0,90,180,270} degrees. In QPSK, information in conveyed through phase variations. In each time period, the phase can change once. Since there are four possible phases, there are 2 bits of information conveyed within each time slot. The rate of change (baud) in this signal determines the signal bandwidth, but the throughput or bit rate for QPSK is twice the baud rate.

64. The area of a cell of a cellular system is further divided, thus creating more cell areas. (Cellular Telephone Concepts)a. Sectoringb. Segmentationc. Cell splittingd. Dualization

Answer: cThe purpose of cell splitting is to increase the channel capacity and im

prove the availability and reliability of a cellular telephone network. Splitting cell areas creates new cells, providing an increase in the degree of frequency reuse, thus increasing the channel capacity of a cellular network.

65. It is like a long transmission line with one lossy conductor (the earth), and one good conductor (the wire). (Antennas)a. Rhombic antennab. V beam antennac. Beverage antennad. Fishbone antenna

Answer: cBeverage antenna is simply wire antenna, at least one wavelength long, s

upported along its length at a fairly low height (close to the ground) and terminated at the far end in its characteristics impedance. Since it is travelling wave antenna, it has no standing waves resulting from radio signals.

66. It is ideally suited to HF transmission and reception and is a very popular antenna in commercial point-to-point communications. (Antennas)

a. Rhombic antennab. V beam antennac. Beverage antennad. Fishbone antenna

Answer: aRhombic antenna is an antenna consisting of four conductors joined to fo

rm a diamond, or rhombus. All sides of the antenna have the same length and the opposite corner angles are equal. It can be considered as being made up of two V antennas placed end-to-end and terminated by a noninductive resistor to produce a unidirectional pattern.

67. The longer the wires in terms of the wavelength, the greater the gain and the sharper the directional pattern. (Antennas)a. Rhombic antennab. V beam antennac. Beverage antennad. Fishbone antenna

Answer: bA V beam antenna is two long wires combined to form a V with an angle th

at is twice that of the major lobes of the wire with the wires excited out of phase. The radiation along the bisector of the V adds and the radiation in the other directions tend to cancel.

68. It is essentially a wave antenna which evolved from the Beverage antenna. (Antennas)a. Rhombic antennab. V beam antennac. Beverage antennad. Fishbone antenna

Answer: dFishbone antenna is an antenna consisting of closely spaced elements tha

t are lightly coupled (capacitively) to a long, terminated transmission line. This antenna provides a higher gain per acre than does a rhombic.

69. This antenna is a wideband array of loop antennas. (Antennas)a. Aperiodic Loop Arrayb. Ferrite Core Loopc. Loop Skywired. Large Loop

Answer: aUnlike most of the loop, the loop elements in an aperiodic array are unt

urned. The antennas is omnidirectional because it is purposely unbalanced, and also because the isolating resistor causes the antenna to appear as two closely-spaced short monopoles.

70. It is simply a loop antenna erected horizontal to the earth. (Antennas)a. Aperiodic Loop Arrayb. Ferrite Core Loopc. Loop Skywired. Large Loop

Answer: cThis antenna is a magnetic version of the open wire, center-fed electric

dipole. The antenna has one wavelength of wire in its parameter at fundamental frequency.

71. It consists of a driven loop, one wavelength in circumference, a reflector loop, and a director loop(Antennas)a. Quad arrayb. Log-yag arrayc. End-fire arrayd. Sterba array

Answer: aA popular type of parasitic array using rectangular or diamond-shaped fu

ll-wave wire loop elements. It is used in much the same way as dipole elements in the Yagi antenna.

72. Its distinctive feature is the method of closing the ends of the system. (Antennas)a. Quad arrayb. Log-yag arrayc. End-fire arrayd. Sterba array

Answer: dIt is a broadside radiator consisting of both collinear and parallel ele

ments with ?/2 spacing between the latter. For direct current and low-frequency AC, the system form a closed loop, which is advantageous in that heating currents can be sent through the wires to melt the ice that forms in cold climates.

73. This array uses the principles of co-phased verticals to produce a broadside, bidirectional pattern.(Antennas)a. Bruce arrayb. Bobtail curtainc. Stubby antennad. Log-yag antenna

Answer: bIt performs as three in-phase top-fed vertical radiators approximately ?

/4 in height and spaced approximately ?/2. Its most effective for low-angle signals and makes an excellent long-distance antenna.

74. A Multi element array that the array should be two or more wavelength long to achieve a worthwhile gain. (Antennas)a. Bruce arrayb. Bobtail curtainc. Stubby antennad. Log-yag antenna

Answer: aIt consists simply of a single wire folded so that the vertical sections

carry large currents in phase wile the horizontal sections carry small currents flowing in opposite directions with respect to the center of that section.

75. Is a short range navigation aid operating in the VHF band which provides the pilot with a track to steer to the VOR beacon. (Navigational Aids)a. ADFb. VORc. DMEd. LRRA

Answer: b

The VOR(VHF Omnidirectional Range) beacon is a ground station that transmits signals in all directions (omnidirectional). These signals are called radials. The VOR beacon transmits on its carrier frequency two modulation signals, a 30 Hz reference and a 30 Hz variable signal.

76. A navigational aid that is used for automatic determination of relative bearing to a transmitting radio station or Non-Directional Beacon (NDB). (Navigational Aids)a. ADFb. VORc. DMEd. LRRA

Answer: aADF (Automatic Direction Finder) is also used for reception of weather i

nformation and other broadcast programs. In an ADF system, the ground station transmits an amplitude modulated signal in an omnidirectional pattern.

77. It measures the distance through air (slant range) from the aircraft to a equipment ground station. (Navigational Aids)a. ADFb. VORc. DMEd. LRRA

Answer: cDME (Distance Measuring Equipment) is used primarily for position fixing

, en route separation, approach to an airport, avoiding protected air space, holding at a given position, or calculating ground speeds. The DME transceiver initiates the distance measuring action by transmitting interrogation pulses to the ground station.

78. The purpose of this system is to alert flight crew of the existence of an unsafe condition due to terrain proximity. (Navigational Aids)a. GPWSb. LRRAc. TCASd. ILS

Answer: aThe GPWS (Ground Proximity Warning System) gives the crew visual and voi

ce warnings when the aircraft�s flight path and position, with respect to the terrain, need immediate attention from the crew.

79. This system alerts the flight crew of potential conflicts with other airplanes in the same area. (Navigational Aids)a. GPWSb. LRRAc. TCASd. ILS

Answer: cTCAS (Traffic Alert and Collision Avoidance System) provides two types o

f collision avoidance alerts: Traffic Advisory (TA) shows the relative position of any intruder airplanes and Resolution Advisory (RA) shows a vertical maneuver to avoid a possible airplane collision.

80. A radio system that gives lateral and vertical guidance in the approach to a runaway. (Navigational Aids)a. GPWS

b. LRRAc. TCASd. ILS

Answer: dILS (Instrument Landing System) is the radio system enabling an aircraft

to locate the selected runway, adopt the correct glideslope and approach in all weather conditions. This system has three distinct elements: the VHF Localizer, the UHF Glideslope, and the Marker Beacons.

81. This type of pulse radar requires no particular cooperation from the target in order to detect and measure the range of the target. (Radar)a. Primary Pulsed Radarb. Secondary Pulsed Radarc. Tertiary Pulsed Radard. Main Pulsed Radar

Answer: aPrimary pulsed radar is the name given to the simple echo system wherein

the target reflects the transmitted energy from the system and the time elapsed between transmission and reception is measured and converted to range information. The target needs to be simply a reflecting object large enough to return a usable a mount of echo signal to the radar.

82. It is the immediate predecessor of AMPS or Analog Cellular System. (Mobile Communications)a. MTSOb. IMTSc. NAMPSd. NMT

Answer: bIMTS (Improved Mobile Telephone Service) makes use of cell sites that ar

e located in geographically high areas with relatively high transmit powers to ensure a range of up to 25 miles. Because the mobile stations are allowed relatively high output powers (between 13 W and 30 W), one cell site location could serve an entire city.

83. In satellite orbits, it is inclined at an angle of 64 degrees with respect to the equatorial plane. (Satellite Communications)a. Ellipticalb. Polarc. Equatoriald. Circular

Answer: aElliptical orbit is particularly stable with respect to irregularities i

n terrestrial gravitational potential. It also enables the satellite to cover regions of high latitude for a large fraction of the orbital period as it passes to the apogee.

84. With near 90 degrees inclination, this type of orbit guarantees that the satellite will pass over region of the earth. (Satellite Communications)a. Ellipticalb. Polarc. Equatoriald. Circular

Answer: bIn this orbit, the altitude of the satellite is constant and equal to se

veral hundreds of kilometer. The period is of the order of one and a half hours.

85. It contains the satellite and all terrestrial facilities for the control and monitoring of the satellite. (Satellite Communications)a. Space segmentb. Ground segmentc. Satellite segmentd. Geo segment

Answer: aSpace includes the tracking, telemetry, and command stations (TT&C) toge

ther with the satellite control center where all the operations associated with station-keeping and checking the vital functions of the satellite are performed.

86. A diode operates from 0.5 to 10 GHz with average power outputs between 1 and 3W. (Microwave Communications)a. IMPATTb. TRAPATTc. BARITTd. LSA

Answer: bTRAPATT (Trapped-Plasma Avalanche Triggered-Transit) diodes have the hig

hest peak power outputs of the semiconductor devices with outputs ranging from 500 W peak power at lower frequencies to 100 W peak powers at the upper frequencies. The efficiency of TRAPATT diodes is as high as 75 percent at the low-frequency end.

87. A avalanche transit-time devices that operates from about 3 to 12 GHz. (Microwave Communications)a. IMPATTb. TRAPATTc. BARITTd. LSA

Answer: cBARITT (Barrier Injected Transit-Time) diodes have much lower noise figu

res than TRAPATT diodes, but they are limited by low efficiency with very low power outputs of less than 1 mW. They are narrow-bandwidth devices.

88. Combines the advantages of the klystron amplifier with the travelling-wave tube. (Microwave Communications)a. Twistronb. Twystronc. Crossed-fieldd. Klystube

Answer: bThe input to the device is located in the klystron, and the output to th

e device is located in the TWT. It is used for high-power applications in which large peak powers of up to 5 MW are required.

89. A magnetron which is a cylindrical structure with a series of resonant cavities around the outside. (Microwave Communications)a. Cyclotron-frequencyb. Split-ringc. Travelling-waved. Ultra magnetron

Answer: c

Travelling-wave magnetron is the most widely used magnetron in the centimeter-to-millimeter microwave region. It has efficiency as high as 70 percent. Average powers are in the kilowatt region with peak powers of up to 40 MW.

90. A magnetron has an anode split into two anodes of different potential. (Microwave Communications)a. Cyclotron-frequencyb. Split-ringc. Travelling-waved. Ultra magnetron

Answer: bSplit-ring also called negative-resistance magnetron. The effect of the

interaction of electric and magnetic fields on the electron causes the so-called negative resistance. Negative resistance effect permits oscillations to occur within the magnetron.

91. A magnetron has an anode that is a cylinder around an axial cathode with a perpendicular dc magnetic field. (Microwave Communications)a. Cyclotron-frequencyb. Split-ringc. Travelling-waved. Ultra magnetron

Answer: aThe cyclotron-frequency magnetron can be used only at the lower end of t

he microwave spectrum. The device will oscillate with a frequency determined by the time of travel of the electron.

92. It is similar to backscatter propagation, except that the ground scatter zone is merely somewhat off the direct line between the participants. (Radiowave Communications)a. Tropospheric scatterb. Ionospheric scatterc. Sidescatterd. Trans-equatorial scatter

Answer: cSidescatter signals are stronger than backscatter signals using the same general area of ground scattering. They have been observed frequently on the 14 MHz band, and can take place on any band where there is a large window between the MUF and the LUF.

93. It is useful mainly above the MUF, so its useful frequency range depends on geography, time of day, season, and the state of the sun. (Radiowave Communications)a. Tropospheric scatterb. Ionospheric scatterc. Sidescatterd. Trans-equatorial scatter

Answer: bIt works much the same as tropospheric scatter, except that the scatteri

ng medium is the E region of the ionosphere, with some help of the D and F layers. The greatest use for this type of transmission has been for printing-telegraph channels.

94. They are caused by particle emissions from the sun, generally Alpha and Beta rays. (Radiowave Propagation)a. Sudden ionospheric disturbance

b. Travelling ionospheric disturbancec. Ionospheric stormsd. Storm disturbance

Answer: cIonospheric storms are one of the ionospheric irregularities. At

these conditions, the ionosphere behaves erratically causing signal strengths to drop and fluctuate rapidly. They take about 36 hrs. to reach the earth.

95. The two-wire connection to the receiving telephone is made by a series of sequential operations of the switch train operating in tandem. (Wire Communications)a. Human controlb. Progressive Controlc. Common controld. Stored control

Answer: bA switching control in which the call is progressively carried o

ut to the desired terminal under the control of the dial pulses produced by the calling telephone.

96. This type of switching control element may be a relay-operated device called a marker. (Wire Communications)a. Human controlb. Progressive Controlc. Common controld. Stored control

Answer: cIt can be assigned to an incoming call as required. It takes in

the dialed digits, and then sets up the path through the switching matrix according to a hard-wired or stored-program rule.

97. An electromechanical version utilizes electromagnets to open and close contacts in the matrix. (Wire Communications)a. Crossbar switchb. Reed switchc. Stepping switchd. Space switch

Answer: aIt depends on the crossing intersection of two points to make a

connection. The switching matrix is called a crosspoint array. Its operation depends on energizing a vertical line and a horizontal line and the point where they intersect represents the connection made.

98. It is a small, glass-encapsulated, electromechanical switching device. (Wire Communications)a. Crossbar switchb. Reed switchc. Stepping switchd. Space switch

Answer: bThis device is actuated by a common control which selects the re

lays to be closed in response to the number dialed, and sends pulses through coils wound around the relay capsules. The pulses change the polarity of magnetization of plates of magnetic material fitted alongside the glass capsules.

99. In stepping switch train, they connect the calling line to the connector group of the called line. (Wire Communications)a. Line-finderb. Selectorsc. Connectorsd. Cord pair

Answer: bA Stepping Switch Train is used in employed in progressive switc

hing control. The selectors connect the calling line to the connector group of the called line. When the first selector is connected, a dial tone is returned to the calling party.

100. In Stepping switch train, it is the first switch in the switch train. (Wire Communications)a. Line-finderb. Selectorsc. Connectorsd. Cord pair

Answer: aThe first switch in the Stepping switch train is the line-finder

. When a calling telephone goes off-hook, current flowing in the local loop operates a relay in the exchange, causing the first switch in the train, the line-finder, to search for the active line.