TRANSMISSION LINES

Communications Engineering part 4TRANSMISSION LINES

Multiple Choice. Encircle the letter which corresponds to your answer.

1. In practice, the transmission lines are almost connected to antennas that have a _________.

a. resistive load whose resistance is greater than the characteristic impedance of the lineb. resistive load whose resistance is less than the characteristic impedance of the linec. resistive load at the resonant frequencyd. capacitive load

2. When the transmission line is matched to the load, it

a. transfers maximum current to the loadb. transfers maximum voltage to the loadc. transfers maximum power to the loadd. reduces the load current

3. Conventional transmission media include

a. twisted cable pairb. waveguidec. fiber optic cabled. all of these

4. To couple a coaxial line to a parallel wire line, it is best to use a _____

a. slotted lineb. directional couplerc. balund. quarter wavelength transformer

5. Impedance inversion may be obtained with

a. an open circuited stubb. a short circuited stubc. a quarterwave lined. a half-wave line

6. To be properly matched, the ratio of maximum to minimum voltage along a transmission line should be equal to

a. 50b. 10c. 2d. 1

7. When ZL Zo, the power sent down the line toward the load is called the

a. the incident powerb. the reflected powerc. the power dissipationd. the carrier power

8. For transmission line load matching over a range of frequencies, it is best to use a

a. balunb. broadband directional couplerc. double stubd. single adjustable stub

9. A short section of a transmission line, open or shorted that is used to match the impedance of the line to that of an antenna or transmitter.

a. slotted lineb. stubc. wavetrapd. lecher wire

10. The property of a material that determines how much electrostatic energy can be stored per unit volume when voltage is applied.

a. permeabilityb. magnetic effectc. capacitanced. permittivity

11. The value of the total opposition of the transmission media to the flow of electromagnetic field energy is called

a. characteristic impedanceb. velocity factorc. standing wavesd. reflected waves

12. When mismatch is great, this power actually cause damage to the transmitter or the line itself.

a. the incident powerb. the reflected powerc. the power dissipationd. the carrier power

13. What is the velocity factor for non-foam dielectric 50 or 75 ohm flexible coaxial cable such as RG 8, 11, 58 and 59?

e. 270f. 0.10g. 0.66h. 0.30

14. The measure of the superiority of a material over vacuum as a path for magnetic lines of force is

a. permitivityb. permeabilityc. conductivityd. resistivity

15. The number of standing waves on the wire is equal to the length of the wire divided by a half wavelength. The principle which allows antennas to operate at different frequencies which are integral multiples of the fundamental frequency is called __________.

a. harmonic operationb. decimonic operationc. electromagnetic reverberationd. asynchronous operation

16. A coax line has an attenuation of 2.4 dB per 100 ft. The attenuation for 2.75 ft. is ____ dB.

a. 2.4b. 4.8c. 3.3d. 6.6

17. When a quarter wave stub is used to match a 600 ohm antenna to a line of 52 ohms, the impedance of the matching stub must be ________ ohms.

a. 176b. 200c. 150d. 300

18. The characteristic impedance of a transmission line is determined by

a. its lengthb. its height above groundc. its physical constructiond. the operating frequency

19. When the diameter of two conductors of a two-wire transmission line is held constant, the effect of decreasing the distance between the conductors is to

a. decrease the impedanceb. increase the surge impedancec. increase radiation resistanced. decrease SWR

20. Considering a coaxial transmission line, maximum voltage on the line divided by the minimum voltage equals the

a. characteristic impedanceb. ISWRc. VSWRd. inductive reactance

21. In a transmission line, if the SWR or maximum current to a minimum current ratio of 2:1, the ratio of the maximum voltage to the minimum voltage is

a. 1:4b. 4:1c. 1:2d. 2:1

22. Transmission lines are either balanced or unbalanced with respect to

a. negative terminalb. inputc. groundd. positive terminal

23. The load is properly matched with the transmission line if the standing wave ratio is equal to

a. 50b. 10c. 5d. 1

24. The radiation resistance of a quarterwave antenna is

a. 49 ohmsb. 288 ohmsc. 72 ohmsd. 144 ohms

25. A radio transmission line of 500 ohms impedance is to be connected to an antenna having an impedance of 200 ohms. What is the impedance of a quarter wave matching line?

a. 300b. 316c. 316.5d. 361

26. The VSWR for a line terminated in its Zo is

a. 0b. 1c. 1.5d. infinity

27. Which of the following is used to measure SWR?

a. multimeterb. reflectometerc. spectrum analyzerd. oscilloscope

28. A 75-j50 ohm load is connected to a coaxial transmission line of Z0 = 75 ohms at 10GHz. The best method of matching consists in connecting

a. a short-circuited stub at the loadb. a capacitance at some specific distance from the loadc. an inductance at the loadd. a short-circuited stub at some specific distance from the load

29. For a two-wire line, Zo is higher when

a. the wire size is small with respect to the spacing of the conductorsb. the spacing is varied in accordance with the frequencyc. the D:d ratio is smallerd. the wire is large with respect to the spacing of the conductors.

30. A resultant wave due to the combination of incident and reflected wave.

a. electromagnetic waveb. sine wavec. standing waved. current

31. For transmission line load matching over a range of frequencies, it is best to use a

a. balunb. broadband directional couplerc. double stubd. single stub

32. If the load impedance matches the characteristic impedance of the line, there are __________ standing waves.

a. moreb. lessc. nod. ten (10)

33.VSWR stands for

a. Voltage sending wave ratiob. Voltage Receiving Wave Ratioc. Very Small Wave Radiationd. Voltage Standing Wave Ratio

34.Reflections on a transmission line can occur when

a. impedance of the source and load are matchedb. impedance of the source and the load are mismatchedc. resonance conditions are obtainedd. power transfer between source and load is maximum

35.A transmission line with a characteristic impedance (Zo) of 300 ohms is terminated in a resistance load (Rl). If by measurement, the minimum and maximum voltages through the load are 12 and 20 microvolts, respectively, what is the SWR?

a. 1.67b. 0.6c. 6.7d. 3.67

36. A measure of the mismatch between line and load impedance is called as

a. reflection coefficientb. standing wave ratioc. lossd. standing waves

37. Transmission lines when connected to antenna have

a. capacitive loadb. resistive load whose resistance is less than characteristic impedancec. resistive load at the resonant frequencyd. resistive load whose resistance is greater than the characteristic impedance of the line

38. At matched condition, SWR is equal to

a. zerob. onec. 100d. infinite

39.An HF transmission line has a characteristic impedance of 600 ohms and is terminated by an antenna. The SWR along the line when the antenna impedance is 500 ohms is

a. 1.2:1b. 1:2.1c. 2:1d. 1:2

40.A characteristic of an infinite transmission line is that

a. the impedance in equals impedance outb. it carries waves at the velocity of lightc. it can be connected to mismatched loadsd. the impedance varies with the length of the line

41. A quarter wave transmission line shorted at the end:

a. has the characteristics of parallel tuned circuitb. has the characteristics of a series tuned circuitc. has a minimum current at the endd. reflects a low impedance to the supply

42.The outer conductor of a coaxial transmission line is usually grounded at the:

a. input and outputb. output onlyc. input onlyd. point of infinite resistance

43.A certain feedline has a high SWR. It can be caused by:

a. an impedance mismatchb. use of non-resonant linec. matching the load to the lined. excessive transmitter output

44.If the input impedance of an antenna is 300 ohms and it is fed with a 600 ohm balanced transmission line, the SWR on the line is

a. 4b. 3c. 2d. 0.5

45.A radio transmission line of 300 ohms impedance is to be connected to an antenna having an input impedance of 150 ohms. The impedance of a quarter wave matching line is _______ ohms.

a. 212b. 450c. 600d. 150

46. The ratio of the reflected voltage to the incident voltage on the transmission line is termed as

a. reflection coefficientb. standing wave ratioc. lossd. standing waves

47.Indicate the three types of transmission line energy losses

a. Radiation, I(squared) R and Dielectric Heatingb. Conductor Heating, dielectric heating and radiation resistancec. I(squared)R, RL and Temperatured. Dielectric Separation, Insulation breakdown and radiation

48.Termination means

a. load connected to the output end of a transmission lineb. result of disconnecting a line from a transmitterc. looking back impedance of a line with no loadd. result of cutting both ends of a conductor

49.When transmission line uses ground return, it is called a/n _______ line.

a. ungroundedb. unbalancedc. groundedd. balanced

50.Permeability is the measure of superiority of a material over vacuum as a path of magnetic lines of force. The permeability of free space is equal to ______ henry/meter

a. 1.257 x 10exp-6b. 1.527 x 10exp 6c. 7.251 x 10exp-6d. 5.217 x 10exp-6

51.The most commonly used transmission line is a ________.

a. two-wire balanced lineb. single linec. three-wire lined. coax

52.The characteristic impedance of a transmission line does not depend upon its

a. lengthb. conductor diameterc. conductor spacingd. thickness of armor

53.What is the impedance of a balance 4-wire with a diameter of 0.25 cm and spaced 2.5 cm apart using an insulator with a dielectric constant of 2.56?

a. 100 ohmsb. 65 ohmsc. 75 ohmsd. 50 ohms

54.It is required to match a 73-ohm antenna to a 600 ohm polyethylene coaxial feeder line, with a velocity factor of 0.66 by means of a quarter wave matching transformer. At a frequency of 150 MHz, the impedance of the matching section is ________ ohms.

a. 209.28b. 310.5c. 150.28d. 450.82

55.If the terminating impedance is exactly equal to the characteristic impedance of the transmission line, the return loss is ________.

a. zerob. infinityc. oned. negative

56.The characteristic impedance of a transmission line is the impedance measured at the _____ when its length is infinite.

a. shorted end of the lineb. midsectionc. inputd. output

57.The characteristic impedance of a transmission line is 70 ohms and has a load of 35 ohms. The SWR and reflection coefficient are _____ and ______ respectively.

a. 2 and 0.333b. 1 and 0.666c. 2 and 0.666d. 1 and 0.333

58.It is required to match a 200 ohm load to a 300 ohm transmission line to reduce the SWR and attain resonance. A quarter wave transformer used, directly connected to the load has a Zo of ______ ohms.

a. 245b. 425c. 524d. 254

59.What quarter wave transformer will match a 100 ohm-line to an antenna whose value is 175 ohms?

a. 150 ohmsb. 137.5 ohmsc. 132.29 ohmsd. 16.58 ohms

60.The mismatch between antenna and transmission line impedances cannot be corrected by

a. using an LC networkb. adjusting antenna lengthc. using a balund. adjusting the length of the transmission line

61.A pattern of voltage and current variation along a transmission line not terminated in its characteristic impedance is called a. an electric fieldb. radio wavesc. standing wavesd. magnetic field

62.The most desirable value of SWR on a transmission line is

a. 0b. 1c. 2d. infinity

63.In transmission lines, the most desirable reflection coefficient is

a. zerob. 0.5c. 1.d. Infinity

64.At very high frequencies, transmission lines are used as ________

a. tuned circuitsb. antennasc. insulatorsd. resistors

65. What is the reflection coefficient of a 100 ohm characteristic impedance line and a 300 ohm load?

a. 0. 25b. 0.3c. 0.5d. 0.75

66.The minimum voltage along a transmission line is 260 volts, while the maximum is 390 volts. The SWR is

a. 0.67b. 1.0c. 1.2d. 1.5

67. A single conductor running from the transmitter to the antenna.

a. RG-8/Ub. Single line wirec. Twin-leadd. Microstrip

68. What characteristic impedance is needed to match a 50-ohm line to a 300 ohm-load?

a. 221 ohmsb. 122 ohmsc. 212 ohmsd. 112 ohms69.Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in

a. a short circuitb. a complex impedancec. an open circuitd. a pure reactance

70.A (75 j50) - load is connected to a coaxial transmission line of Zo = 75 , at 10 GHz. The best method of matching consists in connecting

a. a short-circuited stub at the loadb. an inductance at the loadc. a capacitance at some specific distance from the loadd. a short-circuited stub at some specific distance from the load

71.The velocity factor of a transmission line

a. depends on the dielectric constant of the material usedb. increases the velocity along the transmission linec. is governed by the skin effectd. is higher for a solid dielectric than for air

72.What is the characteristic impedance of a single wire with diameter d = 0.25 mm placed at the center between grounded parallel planes separated by 1 mm apart. The wire is held by a material with a velocity factor of 0.75.

a. 85 ohmsb. 63 ohmsc. 50 ohmsd. 75 ohms

73.Coaxial lines are used on those system operating __________.

a. below 2 GHzb. at 300 MHzc. above 10 kHzd. above 10 GHz

74.Referred to the dielectric constant of a transmission line material

a. Inductance and capacitanceb. Velocity factorc. Characteristic impedanced. Propagation velocity

75.The main disadvantage of the two-hole directional coupler is

a. low directional couplingb. poor directivityc. high SWRd. narrow bandwidth

76. To couple a coaxial line to a parallel-wire line, it is best to use a

a. slotted lineb. balunc. directional couplerd. quarter-wave transformer

77.What is the meaning of the term velocity factor of a transmission line?

a. The index of shielding for coaxial cableb. The velocity of the wave on the transmission line multiplied by the velocity of light in vacuumc. The ratio of the characteristic impedance of the line to the terminating impedanced. The velocity of the wave on the transmission line divided by the velocity of light in a vacuum

78. A transmission line consisting of two conductors that have equal resistance per unit length.

a. Unbalanced lineb. Open-wire linec. Balanced lined. Coaxial line

79.Which of the following is not a common transmission line impedance?

a. 50 b. 75 c. 120 d. 300

80.For maximum absorption of power at the antenna, the relationship between the characteristic impedance of the line Zo and the load impedance Zl should be

a. Zo = ZLb. Zo > Zlc. Zo < Zld. Zo = 0

81.Which of the following determines the characteristics of a transmission line?

a. Inductanceb. Capacitancec. Physical dimensionsd. Length

82.In the study of transmission cable, twin lead is also referred to as a __________.

a. Twisted pairb. Double cablec. Ribbon cabled. Open pair

83.A 50- coax is connected to a 73- antenna. The SWR is

a. 0.685b. 1c. 1.46d. 2.92

84.A ratio expressing the percentage of incident voltage reflected on a transmission line is known as the

a. Velocity factorb. Standing-wave ratioc. Reflection coefficientd. Line efficiency

85.Three feet is one wavelength at a frequency of

a. 100 MHzb. 164 MHzc. 300 MHzd. 328 MHz

86.An open quarter-wave line at the operating frequency acts like a(n)

a. Series resonant circuitb. Parallel resonant circuitc. Capacitord. Inductor

87.A shorted half-wave line at the operating frequency acts like a(n)

a. Capacitorb. Inductorc. Series resonant circuitd. Parallel resonant circuit

88. At UHF and microwave frequencies, transmission lines are commonly used as

a. antennab. couplerc. resonant circuitd. transformer

89.The transmission medium subjects the transmitted signal to be

a. Modulatedb. Amplifiedc. Attenuatedd. Boosted

90.Transmission line is a two-wire cable that connects the transmitter to the antenna or the antenna to the receiver. The purpose of the transmission line is to

a. Amplify the RF signalb. Modulate the signalc. Carry the RF energy for the desired distanced. All of the above91.These conductors are uniformly spaced by insulators. They have low losses at low and medium frequencies and are economical to construct and maintained.

a. Coaxial cablesb. Open-wire transmission linesc. Optical cablesd. Waveguides

92.To prevent radiation losses and interference from external sources, the inner conductor of this transmission line is completely enclosed with a metal sheath or braid.

a. Coaxial cableb. Open-wire transmission linesc. Optical cablesd. Waveguides

93.The term balance line means that

a. Both conductors carry currents that flow in opposite directionsb. Conductors present equal capacitance to groundc. One conductor is connected to groundd. Both A and B

94.The characteristic impedance of a transmission line is determined by:

a. Its operating frequencyb. Its lengthc. Its physical size and arrangementd. The signal applied at the input terminal

95.The distributed parameters of the transmission line are: the series resistance; the series inductance; the shunt capacitance and the shunt conductance. What parameter was determined due to dielectric losses?

a. Series resistanceb. Series inductancec. Shunt capacitanced. Shunt conductance

96.Shunt capacitance was determined due to:

a. Conductors were closed to each otherb. The length and diameter of the conductorsc. Dielectric lossesd. Flux linkages

97.Series resistances was determined due to:

a. Conductors were closed to each otherb. The length and diameter of the conductorsc. Dielectric lossesd. Flux linkages

98.At radio frequencies, a line is considered lossless because:

a. Characteristic impedance is determined by its physical structureb. Inductive reactance is much more than the resistancec. Capacitive reactance is much larger than the shunt conductanced. Both B and C

99.Determine the characteristic impedance of a transmission line which has a capacitance of 30 pF/m and an inductance of 75 nH/m.

a. 5 b. 50 c. 500 d. 5 K

100.If a change in the dielectric material decreases the capacitance, the characteristic impedance is

a. Kept constantb. Decreasedc. Increasedd. halved

COMMUNICATIONS ENGINEERING PART 5WAVE PROPAGATION

1. Whether or not polarization of an antenna is linear depends on changes in direction in which:

a. The direction in which the electric plane is radiatedb. The horizontal or vertical plane of the electric wavec. The direction in which magnetic wave is radiatedd. None of these

2. The D, E and F layers of the ionosphere are called

a. Mark-Space Layersb. Davidson-Miller Layersc. Kenelly Heaviside Layersd. Maxwell Layers

3. __________ refers to the ratio of an electric field component to a magnetic field component at the same point of the wave.

a. characteristic impedanceb. load impedancec. intrinsic impedanced. wave impedance

4. The field strength of a radio signal varies according to the output or transmitted power and the distance of the receiver from the transmitter. This wave behavior is described by

a. The Field Strengthb. Huygens Principlec. Faradays Lawd. Inverse Square Law

5. The antenna theory which states that reception and transmission functions are interchangeable is

a. Poynting Theoremb. Snells Lawc. Huygens Principled. Law of Reciprocity6. The frequency band where electromagnetic waves travel in straight path or in a direct line of sight between the transmitter and receiver antenna is

a. ELFb. HFc. VLFd. VHF and above

7. This mode of electromagnetic wave propagation uses the earths surface or curvature as a guide to transmit vertically polarized waves.

a. Sky Waveb. Tropospheric Wavec. Transionospheric Waved. Ground Wave

8. Frequencies in the UHF range propagate by means of

a. Ground Wavesb. Surface Wavesc. Sky Wavesd. Space Waves

9. The ground wave eventually disappear as it moves farther away from the transmitter, because of

a. Tiltingb. Reflectionc. Refractiond. Diffraction

10.As electromagnetic waves travel in free space, only one of the following can happen

a. Absorptionb. Attenuationc. Refractiond. Reflection

11. In polarization diversity, two signals are

a. Both polarized at one specific location.b. Vertically and horizontally polarized separately.c. Polarized in the same mannerd. Vertically and horizontally polarized using a common antenna.

12.If the direction of the electric field of a radio wave is horizontal, that wave is known to be __________ polarized.

a. Negativelyb. Verticallyc. Positivelyd. Horizontally

13.The property of a material that determines how much electrostatic energy can be stored per unit volume when voltage is applied.

a. Miller Effectb. Permeability c. Capacitanced. Permitivity

14.According to this law or principle, a wavefront may be considered to consist of an infinite number of isotropic radiators, each one sending out wavelets, always away from the source.

a. Snells Lawb. Maxwells Lawc. Huygens Principled. Archimedes Principle

15.A number, which when multiplied by the speed of light in free space gives the speed of light in the medium in question is

a. Fibonacci Numberb. Fermats numberc. Velocity Factord. K-factor

16.The ability of a radio wave to be bent slightly over the edge of a sharp obstacle such as a steep hill or mountain top is

a. Diffractionb. Reflectionc. Refractiond. Attenuation

17. A space wave is a

a. Sky waveb. Radio wavec. Surface waved. Line-of-sight propagation wave18.It is a diagram indicating the intensity in volts/meter, in all directions, of the radiated filed of an antenna as it would occur under actual operating conditions.

a. Constellation diagramb. Argand Diagramc. Funicular Diagramd. Radiation Pattern

19. Equivalent to capacitance in electrical circuits

a. Inductanceb. Permitivityc. Permeabilityd. Power density

20. All of these cause attenuation except

a. Tiltingb. Ground absorptionc. Atmospheric absorptiond. Surface wave propagation

21.The transmission of radio waves far beyond line of sight distances by using high power and large transmitting antennas to beam the signal upward into the atmosphere and a similar large receiving antenna to pick up a small portion of the signal scattered by the atmosphere is called

a. Forward Scatter Propagationb. Beyond the Horizon Propagationc. Either a or bd. Meteoric Scatter Propagation

22.The apparent height of an ionized layer of the atmosphere; as determined from the time interval between the transmitted signal and the ionospheric echo at vertical incidence. This height is the maximum height reached if the actual paths are projected forming straight lines from the ascent to the descent of waves.

a. Optimum heightb. Virtual heightc. Complex heightd. Critical height

23. The highest frequency whereby a wave will be returned back to earth by an ionospheric layer after having been beamed up at it and ranges from 5 to 12 MHz. For F2 Layers. This frequency is directly proportional to the secant function of the smallest angle, which allows reflection of sky waves.

a. Apex frequencyb. Critical frequencyc. Carrier frequencyd. Baseband frequency

24.The distance at which sky-wave signals are reflected back to earth depends on

a. height of the reflecting layer.b. The takeoff angle of the wavesc. Both a and bd. Conductivity of the soil

25.Perfect reflection of waves occur when

a. The magnitude of the incident is equal to the reflected wavesb. The magnitude of the incident is less than the reflected wavesc. The magnitude of incident is greater than reflected wavesd. Both a and b

26.The process by which a radio wave is bent and returned to earth from one medium to another after striking them is

a. Reflectionb. Refractionc. Diffractiond. Absorption

27.An incident, traveling obliquely from one medium to another, will undergo a change in direction if the velocity of the wave in one medium is different from that in the other and the ratio of the sine of the angle of incidence to the sine of the angle of refraction is the same ratio of respectively wave velocities in these media. This law is called

a. Snells lawb. Fishers Lawc. Hookes lawd. Newtons Law

28.The lowest layer of the ionosphere which exists between 50 to 90 km from the earths surface and reflects VLF and LF waves while absorbing MF and HF waves during daytime is the

a. D layerb. E layerc. F layerd. Vantress layer

29.This phenomenon occurs when the thicker air is on top instead of being at the bottom when the temperature or water vapor gradient is lesser or greater than the standard rate.

a. Thermal Inversionb. Horizontal Ductingc. Elevated Ductingd. Sporadic E30.An ionospheric layer, which exists between 90 to 120 km above the earths surface and is about 25 km thick. It aids MF surface propagation while reflecting some HF during daytime.

a. D-layerb. E-layerc. F layerd. Vantress layer

31. Atmospheric condition is controlled by

a. Pressureb. Temperaturec. Humidityd. All of these

32.This ionospheric layer forms at night at about 300 kms from the earths surface and is responsible for long distance HF wave propagation due to reflection and refraction. It splits during daytime due to the ionizing energy from ultraviolet rays of the sun.

a. D layerb. E layerc. F layerd. Vantress layer

33. When the transmitting and receiving antennas are line-of-sight of each other, the mode of propagation is __________ wave.

a. Space or directb. Skyc. Surfaced. ground

34.Power density is inversely proportional to the square of the distance from the source or transmitter to the destination or receiver. This law is called:

a. Coulombs Lawb. Law of Universal Gravitationc. Inverse Square Lawd. Lenzs Law

35. A one-hop, full duplex, microwave system is in a space diversity arrangement. Determine how many receivers in all are used?

a. 6b. 2c. 8d. 4

36.__________ is the extra ionization of the E-layer resulting to irregular and intermittent reflection of frequencies of up to 80 MHz in temperate and lower latitudes. It is variable in time of occurrence, height, geographical distribution, penetration frequency and ionization density.

a. Sporadic Eb. Dillinger Effectc. Faraday Rotationd. Scintillations

37.The derease in signal strength as a result of absorption or scattering of energy along a transmission path is called:

a. attenuationb. microbendingc. dispersiond. multipath fading

38.The transfer of electromagnetic waves or acoustical energy from one place to another through a suitable transmission medium is

a. Wave propagationb. RF Inductionc. Radio Frequency Interferenced. Forward Scatter

39.The upper limit of frequencies that can be used at a specified time for radio transmissions between two points and involving propagation by reflection from regular ionized layers of the ionosphere is

a. maximum usable frequencyb. optimum traffic frequencyc. minimum usable frequencyd. carrier frequency

40.Waves whose oscillations are perpendicular to the direction of propagation are called

a. Huygens wavesb. Transverse wavesc. Longitudinal Wavesd. Fraunhoffer Waves

41.Indicate which one of the following terms applies to troposcatter propagation:

a. SIDsb. Fadingc. Atmospheric stormsd. Faraday rotation

42.VLF waves are used for some types of services because

a. Of the low powers requiredb. The transmitting antennas are of convenient sizec. They are very reliabled. They penetrate the ionosphere easily

43.High-frequency waves are

a. Absorbed by the F2 layerb. Reflected by the D layerc. Capable of use for long-distance communications on the moond. Affected by the solar cycle

44.Distances near the skip distance should be used for sky-wave propagation

a. To avoid tiltingb. To prevent sky-wave and upper ray interferencec. To avoid the Faraday effectd. So as not to exceed the critical frequency

45.The ground wave eventually disappears, as one moves away from the transmitter, because of

a. Interference from the sky waveb. Loss of line-of-sight conditionsc. Maximum single-hop distance limitationd. Tilting

46.In electromagnetic waves, polarization

a. Is caused by reflectionb. Is due to the transverse nature of the wavesc. Results from the longitudinal nature of the wavesd. Is always vertical in an isotropic medium

47. Radio fading resulting from obstruction losses.

a. Log normal fadingb. Rayleigh fadingc. Multi-path fadingd. None of these

48.The absorption of radio waves by the atmosphere depends on

a. Their frequencyb. Their distance from the transmitterc. The polarization of the wavesd. The polarization of the atmosphere

49.Electromagnetic waves are refracted when they

a. Pass into a medium of different dielectric constantb. Are polarized at right angles to the direction of propagationc. Encounter a perfectly conducting surfaced. Pass through a small slot in a conducting plane

50.Diffraction of electromagnetic waves

a. Is caused by reflection from the groundb. Arises only with spherical wavefrontsc. Will occur when the waves pass through a large slotb. May occur around the edge of a sharp obstacle

51.What do you call of the travel of electromagnetic waves through a medium at the speed of light?

a. RF propagationb. Radio propagationc. Wave propagationd. All of these52.Electromagnetic waves are

a. Consist of electric and magnetic component that are parallel to each otherb. Oscillations that propagate through free spacec. Irregular oscillationsd. Oscillations that are produced by an oscillating circuit

53.The region around an electrically charged body in which other charged bodies are acted on by an attracting or repelling force.

a. Electric fieldb. Radiation fieldc. Magnetic fieldd. Electromagnetic field

54.What are the two components of electromagnetic field?

a. Ray and wavefrontb. Magnet and electricityc. Polar electrons and magnetic fieldd. Electric field (E-field) and magnetic field

55.Shows a surface of constant phase of a wave and is formed when points of equal phase on rays propagated from the same source are joined together.

a. Rayb. Wavefrontc. Point sourced. Isotropic source

56.It is a line drawn along the direction of propagation of an electromagnetic wave used to show the relative direction of electromagnetic wave propagation.

a. Rayb. Wavefrontc. Point sourced. Isotropic source

57.Refers to the rate at which energy passes through a given surface area in free space.

a. Field instensityb. Power densityc. Refractive indexd. Absorption coefficient

58.It is the intensity of the electric and magnetic fields of an electromagnetic wave propagating in free space.

a. Field intensityb. Power densityc. Refractive indexd. Absorption coefficient

59.In a lossless transmission medium, __________ of free space is equal to the square root of the ratio of its magnetic permeability to its electric permitivity.

a. Resistanceb. Field intensityc. Characteristic impedanced. A or C is correct

60.Electromagnetic wave measures all of these except

a. Inductanceb. Power densityc. Magnetic field intensityd. Permitivity of the medium

61.A reduction in power density due to the inverse-square law presumes free-space propagation is called

a. Absorptionb. Wave attenuationc. Space attenuation of the waved. B or C is correct

62.Which of the following are optical effects of radio waves?

a. Refraction and reflectionb. Diffraction and interferencec. Induction and diffractiond. A and B

63.What is diffraction?

a. Is the change in direction of a ray as it passes obliquely from one medium to another with different velocities or propagation.b. Refers to the modulation or redistribution of energy within a wavefront when it passes near the edge of an opaque object.c. Is the phenomenon that allows light or radio waves to travel (peek) around corners of an obstacle.d. A or C is right

64.A rare refracting medium has

a. Smaller value of dielectric constantb. Higher value for dielectric constantc. Variable value for dielectric constantd. A dielectric constant dependent on the medium

65.Refractive index refers to

a. The ratio of velocity of light in free space to the velocity of light in a given materialb. The ratio of the light in free space towards the light in a given mediumc. The ratio of the angle of refractiond. The amount of bending or refraction that occurs at the interface of two materials of different densities

66.Whay is it that rays traveling near the top of the medium travel faster than those at the bottom?

a. The medium is more dense near the bottomb. The medium is less dense at the topc. A and B are incorporatedd. The medium is less dense near the bottom and more dense at the top

67.When does reflection of wave occur?

a. When an incident wave strikes a boundary of two media, and some of the incident power does not enter the second material.b. When the reflective surface is irregular or rough

c. When two or more electromagnetic waves combine in such a way that the system performance is degraded.d. A and B

68.What is meant by specular reflection?

a. Is a reflection from a perfectly smooth surfaceb. Is an incident wavefront striking an irregular surface, randomly scattered in many directionsc. Reflection of surfaces that fall between smooth and irregulard. Is a combination of diffused and semirough surfaces

69.__________ states that a semirough surface will reflect as if it were a smooth surface whenever the cosine of the angle of incidence is greater than /8d, where d is the depth of the surface irregularity and is the wavelength of the incident wave.

a. Rayleigh criterionb. Huygens principlec. Linear superpositiond. Reflection coefficient

70. Energy that has neither been radiated into space nor completely transmitted.

a. Modulated wavesb. Captured wavesc. Standing wavesd. Incident waves

71.What property of radio waves occurs whenever two or more waves simultaneously occupy the same point in space?

a. Reflectionb. Refractionc. Diffractiond. Interference

72.Pertains to a source which radiates equally in all directions.

a. Isobaric sourceb. Isotropic sourcec. Isentropic sourced. Isothermal source

73. Electromagnetic waves travel at __________ in free space.

a. 300,000 km/secb. 200 km/secc. 400,000 km/secd. 100,000 km/sec

74.Any space or region wherein a magnetic force is exerted on moving electric charges.

a. Electric fieldb. Radiation fieldc. Magnetic fieldd. Electromagnetic field

75.Which of the following is a characteristic of electromagnetic wave?

a. Measures power, voltage, capacitance and impedance of a systemb. Measures power density, voltage, and inductancec. Measures power density, magnetic field intensity, and electric field intensityd. All of the above

76.Reflection of waves

a. Should take place at one medium b. Does not necessarily take place at one mediumc. Occurs at any other medium at the same timed. Is not possible

77. Way(s) of propagating electromagnetic waves:

a. Ground-wave propagationb. Space-wave propagationc. Sky-wave propagationd. All of these78.At frequencies below 1.5 MHz, what propagation provides the best coverage?

a. Ground waveb. Space wavec. Sky waved. All of these

79.Which of these causes the wavefront to tilt progressively forward?

a. Gradient densityb. Electric field intensityc. Absorption coefficientd. Magnetic field intensity

80.Which of the following must be taken into consideration to ensure proper ground-wave propagation?

a. Powerb. Terrainc. Frequencyd. B and C

81.What are the applications of ground-wave propagation?

a. Ship-to-ship and ship-to-shore communicationsb. Maritime mobile communicationsc. Radio navigationd. All of these

82.The curvature of the earth presents a horizon to space wave propagation which is approximately 4/3 that of the optical horizon.

a. Standard atmosphereb. Optical horizonc. Radio horizond. All of these

83.Refraction is caused by what factors?

a. Changes in tropospheres density and temperatureb. Water vapor contentc. Relative conductivityd. All of the above84.Any of the following can be used to lengthen radio horizon:

a. Elevating the transmit or receive antennas above Earths surfaceb. Elevating both antennasc. Installing the transmit and/or receive antennas on top of mountains or high buildingsd. All of these

85.A special condition which occurs when the density of the lower atmosphere is such that electromagnetic waves are trapped between it and Earths surface.

a. Duct propagationb. Sky-wave propagationc. Space-wave propagationd. Ground-wave propagation

86.The vibrating electrons at the ionosphere decrease current which is equivalent to reducing the dielectric constant, which in turn, will also cause the velocity of propagation to __________.

a. Increaseb. Decreasec. Remain constantd. Decrease by a factor of 2

87.Increasing the velocity of propagation causes a/an __________ of the electromagnetic waves.

a. Increasing refractionb. Decreasing reflectionc. Increasing diffractiond. Decreasing interference

88.What layer has its maximum density at approximately 70 mi at noon, when the sun is at its highest point?

a. D layerb. E layerc. Kennelly-Heaviside layerd. B or C

89.The sporadic E layer is a thin layer with a very high ionization density. It is considered separately from the other layers and when it appears, gives an unexpected improvement in long-distance radio transmissions. What cause(s) its unpredictable appearance?

a. Sunspot activityb. Sunspot cyclec. Solar flaresd. A and C

90.The region in the ionosphere with a very high ionization density at roughly 55 to 90 miles and is used for frequencies up to about 20 MHz. It is gone completely by midnight.

a. D layerb. E layerc. F layerd. G layer

91.A layer in the ionosphere which is the most important reflecting medium for HF radio waves. It has 2 sublayers, at 90 to 250 mi height.

a. A layerb. D layerc. E layerd. F layer

92.The apparent height of the ionized layer and is always greater than the actual height.

a. Critical heightb. Virtual heightc. Maximum heightd. Imaginary height

93.Refers to the shortest distance in which a sky-wave signal will be returned to the earth. It includes the maximum ground-wave range and the width of the skip zone.

a. Hopb. Skip distancec. Actual distanced. Critical distance94.Concerns to the highest frequency that is able to return to earth when beamed at a certain angle of incidence.

a. Relative frequencyb. Optimum frequencyc. Resonant frequencyd. Maximum usable frequency, muf

95.In __________, the distance of each succeeding hop from earth to ionosphere and back is also the skip distance.

a. Hop transmissionb. Single transmissionc. Unihop transmissiond. Multihop transmission

96.Concerns to the single reflection of a radio wave from the ionosphere back to earth.

a. Jogb. Hopc. Skipd. Fading

97.The fluctuation of signal strength at the receiver that are caused by changes in the transmission medium.

a. Fadingb. Hoppingc. Skippingd. Diversity

98.Gradual variation in the field strength of a radio signal is compensated by

a. Fading techniquesb. Diversity techniquesc. Transverse techniquesd. Transmission techniques

99. A modulation of two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination.

a. Diversityb. Space diversityc. Frequency diversityd. Polarization diversity

100.To increase the availability of the system, a method in which the output of a transmitter is fed to two or more antennas that are physically separated by an appreciable number of wavelengths.

a. Space diversityb. Frequency diversityc. Polarization diversityd. Space wave propagation