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Ham General 2015-2019 > SUBELEMENT G9 – ANTENNAS AND FEED LINES > Flashcards

SUBELEMENT G9 – ANTENNAS AND FEED LINES Flashcards

1
Q

G9A01 (A)

Which of the following factors determine the characteristic impedance of a parallel conductor antenna feed line?

A

A. The distance between the centers of the conductors and the radius of the conductors

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2
Q

G9A02 (B)

What are the typical characteristic impedances of coaxial cables used for antenna feed lines at amateur stations?

A

B. 50 and 75 ohms

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3
Q

G9A03 (D)

What is the characteristic impedance of flat ribbon TV type twinlead?

A

D. 300 ohms

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4
Q

G9A04 (C)

What might cause reflected power at the point where a feed line connects to an antenna?

A

C. A difference between feed line impedance and antenna feed point impedance

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5
Q

G9A05 (B)

How does the attenuation of coaxial cable change as the frequency of the signal it is carrying increases?

A

B. Attenuation increases

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6
Q

G9A06 (D)

In what units is RF feed line loss usually expressed?

A

D. Decibels per 100 feet

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7
Q

G9A07 (D)

What must be done to prevent standing waves on an antenna feed line?

A

D. The antenna feed point impedance must be matched to the characteristic impedance of the feed line

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8
Q

G9A08 (B)
If the SWR on an antenna feed line is 5 to 1, and a matching network at the transmitter end of the feed line is adjusted to 1 to 1 SWR, what is the resulting SWR on the feed line?

A

B. 5 to 1

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9
Q

G9A09 (A)

What standing wave ratio will result when connecting a 50 ohm feed line to a non-reactive load having 200 ohm impedance?

A

A. 4:1

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10
Q

G9A10 (D)

What standing wave ratio will result when connecting a 50 ohm feed line to a non-reactive load having 10 ohm impedance?

A

D. 5:1

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11
Q

G9A11 (B)

What standing wave ratio will result when connecting a 50 ohm feed line to a non-reactive load having 50 ohm impedance?

A

B. 1:1

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12
Q

G9A12 (A)

What standing wave ratio will result when connecting a 50 ohm feed line to a non-reactive load having 25 ohm impedance?

A

A. 2:1

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13
Q

G9A13 (C)
What standing wave ratio will result when connecting a 50 ohm feed line to an antenna that has a purely resistive 300 ohm feed point impedance?

A

C. 6:1

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14
Q

G9A14 (B)

What is the interaction between high standing wave ratio (SWR) and transmission line loss?

A

B. If a transmission line is lossy, high SWR will increase the loss

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15
Q

G9A15 (A)

What is the effect of transmission line loss on SWR measured at the input to the line?

A

A. The higher the transmission line loss, the more the SWR will read artificially low

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16
Q

G9B01 (B)

What is one disadvantage of a directly fed random-wire HF antenna?

A

B. You may experience RF burns when touching metal objects in your station

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17
Q

G9B02 (B)
Which of the following is a common way to adjust the feed point impedance of a quarter wave ground plane vertical antenna to be approximately 50 ohms?

A

B. Slope the radials downward

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18
Q

G9B03 (B)
What happens to the feed point impedance of a ground plane antenna when its radials are changed from horizontal to sloping downward?

A

B. It increases

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19
Q

G9B04 (A)

What is the radiation pattern of a dipole antenna in free space in the plane of the conductor?

A

A. It is a figure-eight at right angles to the antenna

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20
Q

G9B05 (C)

How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?

A

C. If the antenna is less than 1/2 wavelength high, the azimuthal pattern is almost omnidirectional

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21
Q

G9B06 (C)

Where should the radial wires of a ground-mounted vertical antenna system be placed?

A

C. On the surface of the Earth or buried a few inches below the ground

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22
Q

G9B07 (B)
How does the feed point impedance of a 1/2 wave dipole antenna change as the antenna is lowered below 1/4 wave above ground?

A

B. It steadily decreases

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23
Q

G9B08 (A)
How does the feed point impedance of a 1/2 wave dipole change as the feed point is moved from the center toward the ends?

A

A. It steadily increases

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24
Q

G9B09 (A)

Which of the following is an advantage of a horizontally polarized as compared to a vertically polarized HF antenna?

A

A. Lower ground reflection losses

25
Q

G9B10 (D)

What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz?

A

D. 32 feet

26
Q

G9B11 (C)

What is the approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz?

A

C. 131 feet

27
Q

G9B12 (A)

What is the approximate length for a 1/4 wave vertical antenna cut for 28.5 MHz?

A

A. 8 feet

28
Q

G9C01 (A)

Which of the following would increase the bandwidth of a Yagi antenna?

A

A. Larger diameter elements

29
Q

G9C02 (B)

What is the approximate length of the driven element of a Yagi antenna?

A

B. 1/2 wavelength

30
Q

G9C03 (B)

Which statement about a three-element, single-band Yagi antenna is true?

A

B. The director is normally the shortest element

31
Q

G9C04 (A)

Which statement about a three-element, single-band Yagi antenna is true?

A

A. The reflector is normally the longest element

32
Q

G9C05 (A)

How does increasing boom length and adding directors affect a Yagi antenna?

A

A. Gain increases

33
Q

G9C06 (D)
What configuration of the loops of a two-element quad antenna must be used for the antenna to operate as a beam antenna, assuming one of the elements is used as a reflector?

A

D. The reflector element must be approximately 5 percent longer than the driven element

34
Q

G9C07 (C)

What does “front-to-back ratio” mean in reference to a Yagi antenna?

A

C. The power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction

35
Q

G9C08 (D)

What is meant by the “main lobe” of a directive antenna?

A

D. The direction of maximum radiated field strength from the antenna

36
Q

G9C09 (B)
How does the gain of two 3-element horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single 3-element Yagi?

A

B. Approximately 3 dB higher

37
Q

G9C10 (D)
Which of the following is a Yagi antenna design variable that could be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth?

A

A. The physical length of the boom
B. The number of elements on the boom
C. The spacing of each element along the boom
D. All of these choices are correct

38
Q

G9C11 (A)

What is the purpose of a gamma match used with Yagi antennas?

A

A. To match the relatively low feed point impedance to 50 ohms

39
Q

G9C12 (A)
Which of the following is an advantage of using a gamma match for impedance matching of a Yagi antenna to 50 ohm coax feed line?

A

A. It does not require that the elements be insulated from the boom

40
Q

G9C13 (A)

Approximately how long is each side of the driven element of a quad antenna?

A

A. 1/4 wavelength

41
Q

G9C14 (B)

How does the forward gain of a two-element quad antenna compare to the forward gain of a three-element Yagi antenna?

A

B. About the same

42
Q

G9C15 (B)

Approximately how long is each side of the reflector element of a quad antenna?

A

B. Slightly more than 1/4 wavelength

43
Q

G9C16 (D)

How does the gain of a two-element delta-loop beam compare to the gain of a two-element quad antenna?

A

D. About the same

44
Q

G9C17 (B)

Approximately how long is each leg of a symmetrical delta-loop antenna?

A

B. 1/3 wavelength

45
Q

G9C18 (A)
What happens when the feed point of a quad antenna of any shape is moved from the midpoint of the top or bottom to the midpoint of either side?

A

A. The polarization of the radiated signal changes from horizontal to vertical

46
Q

G9C19 (B)

How does antenna gain stated in dBi compare to gain stated in dBd for the same antenna?

A

B. dBi gain figures are 2.15 dB higher than dBd gain figures

47
Q

G9C20 (A)

What is meant by the terms dBi and dBd when referring to antenna gain?

A

A. dBi refers to an isotropic antenna, dBd refers to a dipole antenna

48
Q

G9D01 (D)

What does the term NVIS mean as related to antennas?

A

D. Near Vertical Incidence sky-wave

49
Q

G9D02 (B)

Which of the following is an advantage of an NVIS antenna?

A

B. High vertical angle radiation for working stations within a radius of a few hundred kilometers

50
Q

G9D03 (D)

At what height above ground is an NVIS antenna typically installed?

A

D. Between 1/10 and 1/4 wavelength

51
Q

G9D04 (A)

What is the primary purpose of antenna traps?

A

A. To permit multiband operation

52
Q

G9D05 (D)

What is an advantage of vertical stacking of horizontally polarized Yagi antennas?

A

D. It narrows the main lobe in elevation

53
Q

G9D06 (A)

Which of the following is an advantage of a log periodic antenna?

A

A. Wide bandwidth

54
Q

G9D07 (A)

Which of the following describes a log periodic antenna?

A

A. Length and spacing of the elements increase logarithmically from one end of the boom to the other

55
Q

G9D08 (B)

Why is a Beverage antenna not used for transmitting?

A

B. It has high losses compared to other types of antennas

56
Q

G9D09 (B)

Which of the following is an application for a Beverage antenna?

A

B. Directional receiving for low HF bands

57
Q

G9D10 (D)

Which of the following describes a Beverage antenna?

A

D. A very long and low directional receiving antenna

58
Q

G9D11 (D)

Which of the following is a disadvantage of multiband antennas?

A

D. They have poor harmonic rejection

Ham General 2015-2019 (10 decks)

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