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Amateur Radio - Extra > E9 - ANTENNAS AND FEEDLINES [8 Exam Questions - 8 Groups] > Flashcards

E9 - ANTENNAS AND FEEDLINES [8 Exam Questions - 8 Groups] Flashcards

1
Q

Which of the following describes an isotropic antenna?

A. A grounded antenna used to measure earth conductivity

B. A horizontally polarized antenna used to compare Yagi antennas

C. A theoretical antenna used as a reference for antenna gain

D. A spacecraft antenna used to direct signals toward the earth

A

C. A theoretical antenna used as a reference for antenna gain

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2
Q

How much gain does a 1/2-wavelength dipole in free space have compared to an isotropic antenna?

A. 1.55 dB

B. 2.15 dB

C. 3.05 dB

D. 4.30 dB

A

B. 2.15 dB

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3
Q

Which of the following antennas has no gain in any direction?

A. Quarter-wave vertical

B. Yagi

C. Half-wave dipole

D. Isotropic antenna

A

D. Isotropic antenna

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4
Q

Why would one need to know the feed point impedance of an antenna?

A. To match impedances in order to minimize standing wave ratio on the transmission line

B. To measure the near-field radiation density from a transmitting antenna

C. To calculate the front-to-side ratio of the antenna

D. To calculate the front-to-back ratio of the antenna

A

A. To match impedances in order to minimize standing wave ratio on the transmission line

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5
Q

Which of the following factors may affect the feed point impedance of an antenna?

A. Transmission-line length

B. Antenna height, conductor length/diameter ratio and location of nearby conductive objects

C. Constant feed point impedance

D. Sunspot activity and time of day

A

B. Antenna height, conductor length/diameter ratio and location of nearby conductive objects

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6
Q

What is included in the total resistance of an antenna system?

A. Radiation resistance plus space impedance

B. Radiation resistance plus transmission resistance

C. Transmission-line resistance plus radiation resistance

D. Radiation resistance plus ohmic resistance

A

D. Radiation resistance plus ohmic resistance

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7
Q

What is a folded dipole antenna?

A. A dipole one-quarter wavelength long

B. A type of ground-plane antenna

C. A dipole constructed from one wavelength of wire forming a very thin loop

D. A dipole configured to provide forward gain

A

C. A dipole constructed from one wavelength of wire forming a very thin loop

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8
Q

What is meant by antenna gain?

A. The ratio relating the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna

B. The ratio of the signal in the forward direction to that in the opposite direction

C. The ratio of the amount of power radiated by an antenna compared to the transmitter output power

D. The final amplifier gain minus the transmission-line losses, including any phasing lines present

A

A. The ratio relating the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna

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9
Q

What is meant by antenna bandwidth?

A. Antenna length divided by the number of elements

B. The frequency range over which an antenna satisfies a performance requirement

C. The angle between the half-power radiation points

D. The angle formed between two imaginary lines drawn through the element ends

A

B. The frequency range over which an antenna satisfies a performance requirement

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10
Q

How is antenna efficiency calculated?

A. (radiation resistance / transmission resistance) x 100%

B. (radiation resistance / total resistance) x 100%

C. (total resistance / radiation resistance) x 100%

D. (effective radiated power / transmitter output) x 100%

A

B. (radiation resistance / total resistance) x 100%

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11
Q

Which of the following choices is a way to improve the efficiency of a ground-mounted quarter-wave vertical antenna?

A. Install a good radial system

B. Isolate the coax shield from ground

C. Shorten the radiating element

D. Reduce the diameter of the radiating element

A

A. Install a good radial system

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12
Q

Which of the following factors determines ground losses for a ground-mounted vertical antenna operating in the 3-30 MHz range?

A. The standing-wave ratio

B. Distance from the transmitter

C. Soil conductivity

D. Take-off angle

A

C. Soil conductivity

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13
Q

How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna?

A. 3.85 dB

B. 6.0 dB

C. 8.15 dB

D. 2.79 dB

A

A. 3.85 dB

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14
Q

How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?

A. 6.17 dB

B. 9.85 dB

C. 12.5 dB

D. 14.15 dB

A

B. 9.85 dB

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15
Q

What is meant by the radiation resistance of an antenna?

A. The combined losses of the antenna elements and feed line

B. The specific impedance of the antenna

C. The value of a resistance that would dissipate the same amount of power as that radiated from an antenna

D. The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal

A

C. The value of a resistance that would dissipate the same amount of power as that radiated from an antenna

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16
Q

In the antenna radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth?

A. 75 degrees

B. 50 degrees

C. 25 degrees

D. 30 degrees

A

B. 50 degrees

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17
Q

In the antenna radiation pattern shown in Figure E9-1, what is the front-to-back ratio?

A. 36 dB

B. 18 dB

C. 24 dB

D. 14 dB

A

B. 18 dB

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18
Q

In the antenna radiation pattern shown in Figure E9-1, what is the front-to-side ratio?

A. 12 dB

B. 14 dB

C. 18 dB

D. 24 dB

A

B. 14 dB

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19
Q

What may occur when a directional antenna is operated at different frequencies within the band for which it was designed?

A. Feed point impedance may become negative

B. The E-field and H-field patterns may reverse

C. Element spacing limits could be exceeded

D. The gain may change depending on frequency

A

D. The gain may change depending on frequency

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20
Q

What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

A. The front-to-back ratio increases

B. The front-to-back ratio decreases

C. The frequency response is widened over the whole frequency band

D. The SWR is reduced

A

B. The front-to-back ratio decreases

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21
Q

If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?

A. The gain increases

B. The SWR decreases

C. The front-to-back ratio increases

D. The gain bandwidth decreases rapidly

A

A. The gain increases

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22
Q

How does the total amount of radiation emitted by a directional gain antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?

A. The total amount of radiation from the directional antenna is increased by the gain of the antenna

B. The total amount of radiation from the directional antenna is stronger by its front to back ratio

C. They are the same

D. The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

A

C. They are the same

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23
Q

How can the approximate beamwidth in a given plane of a directional antenna be determined?

A. Note the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference

B. Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna

C. Draw two imaginary lines through the ends of the elements and measure the angle between the lines

D. Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna

A

A. Note the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference

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24
Q

What type of computer program technique is commonly used for modeling antennas?

A. Graphical analysis

B. Method of Moments

C. Mutual impedance analysis

D. Calculus differentiation with respect to physical properties

A

B. Method of Moments

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25
Q

What is the principle of a Method of Moments analysis?

A. A wire is modeled as a series of segments, each having a uniform value of current

B. A wire is modeled as a single sine-wave current generator

C. A wire is modeled as a series of points, each having a distinct location in space

D. A wire is modeled as a series of segments, each having a distinct value of voltage across it

A

A. A wire is modeled as a series of segments, each having a uniform value of current

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26
Q

What is a disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength?

A. Ground conductivity will not be accurately modeled

B. The resulting design will favor radiation of harmonic energy

C. The computed feed point impedance may be incorrect

D. The antenna will become mechanically unstable

A

C. The computed feed point impedance may be incorrect

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27
Q

What is the far-field of an antenna?

A. The region of the ionosphere where radiated power is not refracted

B. The region where radiated power dissipates over a specified time period

C. The region where radiated field strengths are obstructed by objects of reflection

D. The region where the shape of the antenna pattern is independent of distance

A

D. The region where the shape of the antenna pattern is independent of distance

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28
Q

What does the abbreviation NEC stand for when applied to antenna modeling programs?

A. Next Element Comparison

B. Numerical Electromagnetics Code

C. National Electrical Code

D. Numeric Electrical Computation

A

B. Numerical Electromagnetics Code

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29
Q

What type of information can be obtained by submitting the details of a proposed new antenna to a modeling program?

A. SWR vs. frequency charts

B. Polar plots of the far-field elevation and azimuth patterns

C. Antenna gain

D. All of these choices are correct

A

D. All of these choices are correct

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30
Q

What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?

A. A cardioid

B. Omnidirectional

C. A figure-8 broadside to the axis of the array

D. A figure-8 oriented along the axis of the array

A

D. A figure-8 oriented along the axis of the array

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31
Q

What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?

A. A cardioid

B. A figure-8 end-fire along the axis of the array

C. A figure-8 broadside to the axis of the array

D. Omnidirectional

A

A. A cardioid

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32
Q

What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase?

A. Omnidirectional

B. A cardioid

C. A Figure-8 broadside to the axis of the array

D. A Figure-8 end-fire along the axis of the array

A

C. A Figure-8 broadside to the axis of the array

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33
Q

Which of the following describes a basic unterminated rhombic antenna?

A. Unidirectional; four-sides, each side one quarter-wavelength long; terminated in a resistance equal to its characteristic impedance

B. Bidirectional; four-sides, each side one or more wavelengths long; open at the end opposite the transmission line connection

C. Four-sides; an LC network at each corner except for the transmission connection;

D. Four-sides, each of a different physical length

A

B. Bidirectional; four-sides, each side one or more wavelengths long; open at the end opposite the transmission line connection

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34
Q

What are the disadvantages of a terminated rhombic antenna for the HF bands?

A. The antenna has a very narrow operating bandwidth

B. The antenna produces a circularly polarized signal

C. The antenna requires a large physical area and 4 separate supports

D. The antenna is more sensitive to man-made static than any other type

A

C. The antenna requires a large physical area and 4 separate supports

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35
Q

What is the effect of a terminating resistor on a rhombic antenna?

A. It reflects the standing waves on the antenna elements back to the transmitter

B. It changes the radiation pattern from bidirectional to unidirectional

C. It changes the radiation pattern from horizontal to vertical polarization

D. It decreases the ground loss

A

B. It changes the radiation pattern from bidirectional to unidirectional

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36
Q

What type of antenna pattern over real ground is shown in Figure E9-2?

A. Elevation

B. Azimuth

C. Radiation resistance

D. Polarization

A

A. Elevation

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37
Q

What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?

A. 45 degrees

B. 75 degrees

C. 7.5 degrees

D. 25 degrees

A

C. 7.5 degrees

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38
Q

What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?

A. 15 dB

B. 28 dB

C. 3 dB

D. 24 dB

A

B. 28 dB

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39
Q

How many elevation lobes appear in the forward direction of the antenna radiation pattern shown in Figure E9-2?

A. 4

B. 3

C. 1

D. 7

A

A. 4

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40
Q

How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground?

A. The low-angle radiation decreases

B. The high-angle radiation increases

C. Both the high- and low-angle radiation decrease

D. The low-angle radiation increases

A

D. The low-angle radiation increases

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41
Q

When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?

A. Its overall length must not exceed 1/4 wavelength

B. It must be mounted more than 1 wavelength above ground

C. It should be configured as a four-sided loop

D. It should be one or more wavelengths long

A

D. It should be one or more wavelengths long

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42
Q

What is the main effect of placing a vertical antenna over an imperfect ground?

A. It causes increased SWR

B. It changes the impedance angle of the matching network

C. It reduces low-angle radiation

D. It reduces losses in the radiating portion of the antenna

A

C. It reduces low-angle radiation

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43
Q

How does the gain of an ideal parabolic dish antenna change when the operating frequency is doubled?

A. Gain does not change

B. Gain is multiplied by 0.707

C. Gain increases by 6 dB

D. Gain increases by 3 dB

A

C. Gain increases by 6 dB

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44
Q

How can linearly polarized Yagi antennas be used to produce circular polarization?

A. Stack two Yagis, fed 90 degrees out of phase, to form an array with the respective elements in parallel planes

B. Stack two Yagis, fed in phase, to form an array with the respective elements in parallel planes

C. Arrange two Yagis perpendicular to each other with the driven elements at the same point on the boom and fed 90 degrees out of phase

D. Arrange two Yagis collinear to each other, with the driven elements fed 180 degrees out of phase

A

C. Arrange two Yagis perpendicular to each other with the driven elements at the same point on the boom and fed 90 degrees out of phase

45
Q

How does the beamwidth of an antenna vary as the gain is increased?

A. It increases geometrically

B. It increases arithmetically

C. It is essentially unaffected

D. It decreases

A

D. It decreases

46
Q

Why is it desirable for a ground-mounted satellite communications antenna system to be able to move in both azimuth and elevation?

A. In order to track the satellite as it orbits the Earth

B. So the antenna can be pointed away from interfering signals

C. So the antenna can be positioned to cancel the effects of Faraday rotation

D. To rotate antenna polarization to match that of the satellite

A

A. In order to track the satellite as it orbits the Earth

47
Q

Where should a high-Q loading coil be placed to minimize losses in a shortened vertical antenna?

A. Near the center of the vertical radiator

B. As low as possible on the vertical radiator

C. As close to the transmitter as possible

D. At a voltage node

A

A. Near the center of the vertical radiator

48
Q

Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?

A. To swamp out harmonics

B. To maximize losses

C. To minimize losses

D. To minimize the Q

A

C. To minimize losses

49
Q

What is a disadvantage of using a multiband trapped antenna?

A. It might radiate harmonics

B. It radiates the harmonics and fundamental equally well

C. It is too sharply directional at lower frequencies

D. It must be neutralized

A

A. It might radiate harmonics

50
Q

What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

A. It is increased

B. It is decreased

C. No change occurs

D. It becomes flat

A

B. It is decreased

51
Q

What is an advantage of using top loading in a shortened HF vertical antenna?

A. Lower Q

B. Greater structural strength

C. Higher losses

D. Improved radiation efficiency

A

D. Improved radiation efficiency

52
Q

What is the approximate feed point impedance at the center of a two-wire folded dipole antenna?

A. 300 ohms

B. 72 ohms

C. 50 ohms

D. 450 ohms

A

A. 300 ohms

53
Q

What is the function of a loading coil as used with an HF mobile antenna?

A. To increase the SWR bandwidth

B. To lower the losses

C. To lower the Q

D. To cancel capacitive reactance

A

D. To cancel capacitive reactance

54
Q

What is one advantage of using a trapped antenna?

A. It has high directivity in the higher-frequency bands

B. It has high gain

C. It minimizes harmonic radiation

D. It may be used for multiband operation

A

D. It may be used for multiband operation

55
Q

What happens to feed point impedance at the base of a fixed-length HF mobile antenna as the frequency of operation is lowered?

A. The radiation resistance decreases and the capacitive reactance decreases

B. The radiation resistance decreases and the capacitive reactance increases

C. The radiation resistance increases and the capacitive reactance decreases

D. The radiation resistance increases and the capacitive reactance increases

A

B. The radiation resistance decreases and the capacitive reactance increases

56
Q

Which of the following types of conductor would be best for minimizing losses in a station’s RF ground system?

A. A resistive wire, such as a spark plug wire

B. A wide flat copper strap

C. A cable with 6 or 7 18-gauge conductors in parallel

D. A single 12 or 10-gauge stainless steel wire

A

B. A wide flat copper strap

57
Q

Which of the following would provide the best RF ground for your station?

A. A 50-ohm resistor connected to ground

B. An electrically-short connection to a metal water pipe

C. An electrically-short connection to 3 or 4 interconnected ground rods driven into the Earth

D. An electrically-short connection to 3 or 4 interconnected ground rods via a series RF choke

A

C. An electrically-short connection to 3 or 4 interconnected ground rods driven into the Earth

58
Q

What system matches a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places spaced a fraction of a wavelength each side of element center?

A. The gamma matching system

B. The delta matching system

C. The omega matching system

D. The stub matching system

A

B. The delta matching system

59
Q

What is the name of an antenna matching system that matches an unbalanced feed line to an antenna by feeding the driven element both at the center of the element and at a fraction of a wavelength to one side of center?

A. The gamma match

B. The delta match

C. The epsilon match

D. The stub match

A

A. The gamma match

60
Q

What is the name of the matching system that uses a section of transmission line connected in parallel with the feed line at the feed point?

A. The gamma match

B. The delta match

C. The omega match

D. The stub match

A

D. The stub match

61
Q

What is the purpose of the series capacitor in a gamma-type antenna matching network?

A. To provide DC isolation between the feed line and the antenna

B. To cancel the inductive reactance of the matching network

C. To provide a rejection notch to prevent the radiation of harmonics

D. To transform the antenna impedance to a higher value

A

B. To cancel the inductive reactance of the matching network

62
Q

How must the driven element in a 3-element Yagi be tuned to use a hairpin matching system?

A. The driven element reactance must be capacitive

B. The driven element reactance must be inductive

C. The driven element resonance must be lower than the operating frequency

D. The driven element radiation resistance must be higher than the characteristic impedance of the transmission line

A

A. The driven element reactance must be capacitive

63
Q

What is the equivalent lumped-constant network for a hairpin matching system on a

3-element Yagi?

A. Pi network

B. Pi-L network

C. L network

A

C. L network

64
Q

What term best describes the interactions at the load end of a mismatched transmission line?

A. Characteristic impedance

B. Reflection coefficient

C. Velocity factor

D. Dielectric constant

A

B. Reflection coefficient

65
Q

Which of the following measurements is characteristic of a mismatched transmission line?

A. An SWR less than 1:1

B. A reflection coefficient greater than 1

C. A dielectric constant greater than 1

D. An SWR greater than 1:1

A

D. An SWR greater than 1:1

66
Q

Which of these matching systems is an effective method of connecting a 50-ohm coaxial cable feed line to a grounded tower so it can be used as a vertical antenna?

A. Double-bazooka match

B. Hairpin match

C. Gamma match

D. All of these choices are correct

A

C. Gamma match

67
Q

Which of these choices is an effective way to match an antenna with a 100-ohm feed point impedance to a 50-ohm coaxial cable feed line?

A. Connect a 1/4-wavelength open stub of 300-ohm twin-lead in parallel with the coaxial feed line where it connects to the antenna

B. Insert a 1/2 wavelength piece of 300-ohm twin-lead in series between the antenna terminals and the 50-ohm feed cable

C. Insert a 1/4-wavelength piece of 75-ohm coaxial cable transmission line in series between the antenna terminals and the 50-ohm feed cable

D. Connect 1/2 wavelength shorted stub of 75-ohm cable in parallel with the 50-ohm cable where it attaches to the antenna

A

C. Insert a 1/4-wavelength piece of 75-ohm coaxial cable transmission line in series between the antenna terminals and the 50-ohm feed cable

68
Q

What is an effective way of matching a feed line to a VHF or UHF antenna when the impedances of both the antenna and feed line are unknown?

A. Use a 50-ohm 1:1 balun between the antenna and feed line

B. Use the “universal stub” matching technique

C. Connect a series-resonant LC network across the antenna feed terminals

D. Connect a parallel-resonant LC network across the antenna feed terminals

A

B. Use the “universal stub” matching technique

69
Q

What is the primary purpose of a phasing line when used with an antenna having multiple driven elements?

A. It ensures that each driven element operates in concert with the others to create the desired antenna pattern

B. It prevents reflected power from traveling back down the feed line and causing harmonic radiation from the transmitter

C. It allows single-band antennas to operate on other bands

D. It makes sure the antenna has a low-angle radiation pattern

A

A. It ensures that each driven element operates in concert with the others to create the desired antenna pattern

70
Q

What is the purpose of a Wilkinson divider?

A. It divides the operating frequency of a transmitter signal so it can be used on a lower frequency band

B. It is used to feed high-impedance antennas from a low-impedance source

C. It divides power equally among multiple loads while preventing changes in one load from disturbing power flow to the others

D. It is used to feed low-impedance loads from a high-impedance source

A

C. It divides power equally among multiple loads while preventing changes in one load from disturbing power flow to the others

71
Q

What is the velocity factor of a transmission line?

A. The ratio of the characteristic impedance of the line to the terminating impedance

B. The index of shielding for coaxial cable

C. The velocity of the wave in the transmission line multiplied by the velocity of light in a vacuum

D. The velocity of the wave in the transmission line divided by the velocity of light in a vacuum

A

D. The velocity of the wave in the transmission line divided by the velocity of light in a vacuum

72
Q

Which of the following determines the velocity factor of a transmission line?

A. The termination impedance

B. The line length

C. Dielectric materials used in the line

D. The center conductor resistivity

A

C. Dielectric materials used in the line

73
Q

Why is the physical length of a coaxial cable transmission line shorter than its electrical length?

A. Skin effect is less pronounced in the coaxial cable

B. The characteristic impedance is higher in a parallel feed line

C. The surge impedance is higher in a parallel feed line

D. Electrical signals move more slowly in a coaxial cable than in air

A

D. Electrical signals move more slowly in a coaxial cable than in air

74
Q

What is the typical velocity factor for a coaxial cable with solid polyethylene dielectric?

A. 2.70

B. 0.66

C. 0.30

D. 0.10

A

B. 0.66

75
Q

What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz?

A. 20 meters

B. 2.3 meters

C. 3.5 meters

D. 0.2 meters

A

C. 3.5 meters

76
Q

What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically one-half wavelength long at 14.10 MHz?

A. 15 meters

B. 20 meters

C. 10 meters

D. 71 meters

A

C. 10 meters

77
Q

How does ladder line compare to small-diameter coaxial cable such as RG-58 at 50 MHz?

A. Lower loss

B. Higher SWR

C. Smaller reflection coefficient

D. Lower velocity factor

A

A. Lower loss

78
Q

What is the term for the ratio of the actual speed at which a signal travels through a transmission line to the speed of light in a vacuum?

A. Velocity factor

B. Characteristic impedance

C. Surge impedance

D. Standing wave ratio

A

A. Velocity factor

79
Q

What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz?

A. 10 meters

B. 6.9 meters

C. 24 meters

D. 50 meters

A

B. 6.9 meters

80
Q

What impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end?

A. A capacitive reactance

B. The same as the characteristic impedance of the line

C. An inductive reactance

D. The same as the input impedance to the final generator stage

A

C. An inductive reactance

81
Q

What impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end?

A. The same as the characteristic impedance of the line

B. An inductive reactance

C. A capacitive reactance

D. The same as the input impedance of the final generator stage

A

C. A capacitive reactance

82
Q

What impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?

A. The same as the characteristic impedance of the line

B. The same as the input impedance to the generator

C. Very high impedance

D. Very low impedance

A

D. Very low impedance

83
Q

What impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the transmission line

D. The same as the generator output impedance

A

A. Very high impedance

84
Q

What impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the line

D. The same as the output impedance of the generator

A

B. Very low impedance

85
Q

What impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the line

D. The same as the output impedance of the generator

A

A. Very high impedance

86
Q

Which of the following is a significant difference between foam-dielectric coaxial cable and solid-dielectric cable, assuming all other parameters are the same?

A. Reduced safe operating voltage limits

B. Reduced losses per unit of length

C. Higher velocity factor

D. All of these choices are correct

A

D. All of these choices are correct

87
Q

Which of the following can be calculated using a Smith chart?

A. Impedance along transmission lines

B. Radiation resistance

C. Antenna radiation pattern

D. Radio propagation

A

A. Impedance along transmission lines

88
Q

What type of coordinate system is used in a Smith chart?

A. Voltage circles and current arcs

B. Resistance circles and reactance arcs

C. Voltage lines and current chords

D. Resistance lines and reactance chords

A

B. Resistance circles and reactance arcs

89
Q

Which of the following is often determined using a Smith chart?

A. Beam headings and radiation patterns

B. Satellite azimuth and elevation bearings

C. Impedance and SWR values in transmission lines

D. Trigonometric functions

A

C. Impedance and SWR values in transmission lines

90
Q

What are the two families of circles and arcs that make up a Smith chart?

A. Resistance and voltage

B. Reactance and voltage

C. Resistance and reactance

D. Voltage and impedance

A

C. Resistance and reactance

91
Q

What type of chart is shown in Figure E9-3?

A. Smith chart

B. Free-space radiation directivity chart

C. Elevation angle radiation pattern chart

D. Azimuth angle radiation pattern chart

A

A. Smith chart

92
Q

On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?

A. Prime axis

B. Reactance axis

C. Impedance axis

D. Polar axis

A

B. Reactance axis

93
Q

On the Smith chart shown in Figure E9-3, what is the only straight line shown?

A. The reactance axis

B. The current axis

C. The voltage axis

D. The resistance axis

A

D. The resistance axis

94
Q

What is the process of normalization with regard to a Smith chart?

A. Reassigning resistance values with regard to the reactance axis

B. Reassigning reactance values with regard to the resistance axis

C. Reassigning impedance values with regard to the prime center

D. Reassigning prime center with regard to the reactance axis

A

C. Reassigning impedance values with regard to the prime center

95
Q

What third family of circles is often added to a Smith chart during the process of solving problems?

A. Standing-wave ratio circles

B. Antenna-length circles

C. Coaxial-length circles

D. Radiation-pattern circles

A

A. Standing-wave ratio circles

96
Q

What do the arcs on a Smith chart represent?

A. Frequency

B. SWR

C. Points with constant resistance

D. Points with constant reactance

A

D. Points with constant reactance

97
Q

How are the wavelength scales on a Smith chart calibrated?

A. In fractions of transmission line electrical frequency

B. In fractions of transmission line electrical wavelength

C. In fractions of antenna electrical wavelength

D. In fractions of antenna electrical frequency

A

B. In fractions of transmission line electrical wavelength

98
Q

What is the effective radiated power relative to a dipole of a repeater station with 150 watts transmitter power output, 2-dB feed line loss, 2.2-dB duplexer loss and 7-dBd antenna gain?

A. 1977 watts

B. 78.7 watts

C. 420 watts

D. 286 watts

A

D. 286 watts

99
Q

What is the effective radiated power relative to a dipole of a repeater station with 200 watts transmitter power output, 4-dB feed line loss, 3.2-dB duplexer loss, 0.8-dB circulator loss and 10-dBd antenna gain?

A. 317 watts

B. 2000 watts

C. 126 watts

D. 300 watts

A

A. 317 watts

100
Q

What is the effective isotropic radiated power of a repeater station with 200 watts transmitter power output, 2-dB feed line loss, 2.8-dB duplexer loss, 1.2-dB circulator loss and 7-dBi antenna gain?

A. 159 watts

B. 252 watts

C. 632 watts

D. 63.2 watts

A

B. 252 watts

101
Q

What term describes station output, including the transmitter, antenna and everything in between, when considering transmitter power and system gains and losses?

A. Power factor

B. Half-power bandwidth

C. Effective radiated power

D. Apparent power

A

C. Effective radiated power

102
Q

What is the main drawback of a wire-loop antenna for direction finding?

A. It has a bidirectional pattern

B. It is non-rotatable

C. It receives equally well in all directions

D. It is practical for use only on VHF bands

A

A. It has a bidirectional pattern

103
Q

What is the triangulation method of direction finding?

A. The geometric angle of sky waves from the source are used to determine its position

B. A fixed receiving station plots three headings from the signal source on a map

C. Antenna headings from several different receiving locations are used to locate the signal source

D. A fixed receiving station uses three different antennas to plot the location of the signal source

A

C. Antenna headings from several different receiving locations are used to locate the signal source

104
Q

Why is it advisable to use an RF attenuator on a receiver being used for direction finding?

A. It narrows the bandwidth of the received signal to improve signal to noise ratio

B. It compensates for the effects of an isotropic antenna, thereby improving directivity

C. It reduces loss of received signals caused by antenna pattern nulls, thereby increasing sensitivity

D. It prevents receiver overload which could make it difficult to determine peaks or nulls

A

D. It prevents receiver overload which could make it difficult to determine peaks or nulls

105
Q

What is the function of a sense antenna?

A. It modifies the pattern of a DF antenna array to provide a null in one direction

B. It increases the sensitivity of a DF antenna array

C. It allows DF antennas to receive signals at different vertical angles

D. It provides diversity reception that cancels multipath signals

A

A. It modifies the pattern of a DF antenna array to provide a null in one direction

106
Q

Which of the following describes the construction of a receiving loop antenna?

A. A large circularly-polarized antenna

B. A small coil of wire tightly wound around a toroidal ferrite core

C. One or more turns of wire wound in the shape of a large open coil

D. A vertical antenna coupled to a feed line through an inductive loop of wire

A

C. One or more turns of wire wound in the shape of a large open coil

107
Q

How can the output voltage of a multi-turn receiving loop antenna be increased?

A. By reducing the permeability of the loop shield

B. By increasing the number of wire turns in the loop and reducing the area of the loop structure

C. By winding adjacent turns in opposing directions

D. By increasing either the number of wire turns in the loop or the area of the loop structure or both

A

D. By increasing either the number of wire turns in the loop or the area of the loop structure or both

108
Q

What characteristic of a cardioid-pattern antenna is useful for direction finding?

A. A very sharp peak

B. A very sharp single null

C. Broad band response

D. High-radiation angle

A

B. A very sharp single null

109
Q

What is an advantage of using a shielded loop antenna for direction finding?

A. It automatically cancels ignition noise pickup in mobile installations

B. It is electro-statically balanced against ground, giving better nulls

C. It eliminates tracking errors caused by strong out-of-band signals

D. It allows stations to communicate without giving away their position

A

B. It is electro-statically balanced against ground, giving better nulls

Amateur Radio - Extra (10 decks)

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