G9 - ANTENNAS [4 exam questions - 4 groups]

1
G9 - ANTENNAS 4 exam questions - 4 groups

• G9A Antenna feedlines characteristic impedance,
  and attenuation SWR calculation, measurement and
  effects matching networks
• G9B Basic antennas
• G9C Directional antennas
• G9D Specialized antennas

2
Feedlines
3
G9A Antenna feedlines

• Characteristic impedance and attenuation
• The distance between the centers of the
  conductors and the radius of the conductors help
  determine the characteristic impedance of a
  parallel conductor antenna feedline
• The typical characteristic impedance of coaxial
  cables used for antenna feelines at amateur
  stations is 50 and 75 ohms

4
G9A Impedance and attenuation contd

• The characteristic impedance of a flat ribbon TV
  type twin lead is 300 ohms
• The attenuation of coaxial cable increases as the
  frequency of the signal it is carrying increases
• RF feedline losses are usually expressed in dB
  per 100 ft

5
G9A SWR calculations, measurement effects

• If the SWR on an antenna feedline is 5 to 1, and
  a matching network at the transmitter end of the
  feedline is adjusted to 1 to 1 SWR, the resulting
  SWR on the feedline will be 5 to 1
• A standing-wave-ration of 41 will result from
  the connection of a 50-ohm feed line to a
  non-reactive load having a 200-ohm impedence
• SWR 20050 -gt 41
• A SWR of 11 will result from the connection of a
  50-ohm feed line to a non-reactive load having
  50-ohm impedance
• SWR 5050 -gt 11

6
G9A SWR contd

• If you feed a vertical antenna that has a 25-ohm
  feed-point impedance with 50-ohm coaxial cable
  the SWR would be 21
• SWR 5025 -gt 21
• If you feed a folded dipole antenna that has a
  300-ohm feed point impedance with 50-ohm coaxial
  cable the SWR would be 61
• SWR 30050 -gt 61

7
G9A Matching networks

• A common reason for the occurrence of reflected
  power at the point where a feed line connects to
  an antenna is a difference between feedline
  impedance and antenna feed point impedance
• The antenna feed point impedance must be matched
  to the characteristic impedance of the feed line
  to prevent standing waves on an antenna feed line
• A reason for using an inductively coupled
  matching network between the transmitter and
  parallel conductor feed line feeding an antenna
  is to match the unbalanced transmitter output to
  the balanced parallel conductor feed line

8
G9A01 Which of the following factors help
determine the characteristic impedance of a
parallel conductor antenna feedline?

• A. The distance between the centers of the
  conductors and the radius of the conductors
• B. The distance between the centers of the
  conductors and the length of the line
• C. The radius of the conductors and the frequency
  of the signal
• D. The frequency of the signal and the length of
  the line

9
G9A01 Which of the following factors help
determine the characteristic impedance of a
parallel conductor antenna feedline?

• A. The distance between the centers of the
  conductors and the radius of the conductors
• B. The distance between the centers of the
  conductors and the length of the line
• C. The radius of the conductors and the frequency
  of the signal
• D. The frequency of the signal and the length of
  the line

10
Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft Coax Cable Signal Loss (Attenuation) in dB per 100ft
Loss RG-174 RG-58 RG-8X RG-213 RG-6 RG-11 9913 LMR-400
1MHz 1.9dB 0.4dB 0.5dB 0.2dB 0.2dB 0.2dB 0.2dB 0.3dB
10MHz 3.3dB 1.4dB 1.0dB 0.6dB 0.6dB 0.4dB 0.4dB 0.5dB
50MHz 6.6dB 3.3dB 2.5dB 1.6dB 1.4dB 1.0dB 0.9dB 0.9dB
100MHz 8.9dB 4.9dB 3.6dB 2.2dB 2.0dB 1.6dB 1.4dB 1.4dB
200MHz 11.9dB 7.3dB 5.4dB 3.3dB 2.8dB 2.3dB 1.8dB 1.8dB
400MHz 17.3dB 11.2dB 7.9dB 4.8dB 4.3dB 3.5dB 2.6dB 2.6dB
700MHz 26.0dB 16.9dB 11.0dB 6.6dB 5.6dB 4.7dB 3.6dB 3.5dB
900MHz 27.9dB 20.1dB 12.6dB 7.7dB 6.0dB 5.4dB 4.2dB 3.9dB
1GHz 32.0dB 21.5dB 13.5dB 8.3dB 6.1dB 5.6dB 4.5dB 4.1dB
Imped 50ohm 50ohm 50ohm 50ohm 75ohm 75ohm 50ohm 50ohm
11
G9A02 What is the typical characteristic
impedance of coaxial cables used for antenna
feedlines at amateur stations?

• A. 25 and 30 ohms
• B. 50 and 75 ohms
• C. 80 and 100 ohms
• D. 500 and 750 ohms

12
G9A02 What is the typical characteristic
impedance of coaxial cables used for antenna
feedlines at amateur stations?

• A. 25 and 30 ohms
• B. 50 and 75 ohms
• C. 80 and 100 ohms
• D. 500 and 750 ohms

13
G9A03 What is the characteristic impedance of
flat ribbon TV type twin lead?

• A. 50 ohms
• B. 75 ohms
• C. 100 ohms
• D. 300 ohms

14
G9A03 What is the characteristic impedance of
flat ribbon TV type twin lead?

• A. 50 ohms
• B. 75 ohms
• C. 100 ohms
• D. 300 ohms

15
Standing Waves
16
G9A04 What is a common reason for the occurrence
of reflected power at the point where a feedline
connects to an antenna?

• A. Operating an antenna at its resonant frequency
• B. Using more transmitter power than the antenna
  can handle
• C. A difference between feedline impedance and
  antenna feed point impedance
• D. Feeding the antenna with unbalanced feedline

17
G9A04 What is a common reason for the occurrence
of reflected power at the point where a feedline
connects to an antenna?

• A. Operating an antenna at its resonant frequency
• B. Using more transmitter power than the antenna
  can handle
• C. A difference between feedline impedance and
  antenna feed point impedance
• D. Feeding the antenna with unbalanced feedline

18
G9A05 What must be done to prevent standing waves
on an antenna feedline?

• A. The antenna feed point must be at DC ground
  potential
• B. The feedline must be cut to an odd number of
  electrical quarter wavelengths long
• C. The feedline must be cut to an even number of
  physical half wavelengths long
• D. The antenna feed point impedance must be
  matched to the characteristic impedance of the
  feedline

19
G9A05 What must be done to prevent standing waves
on an antenna feedline?

• A. The antenna feed point must be at DC ground
  potential
• B. The feedline must be cut to an odd number of
  electrical quarter wavelengths long
• C. The feedline must be cut to an even number of
  physical half wavelengths long
• D. The antenna feed point impedance must be
  matched to the characteristic impedance of the
  feedline

20
G9A06 Which of the following is a reason for
using an inductively coupled matching network
between the transmitter and parallel conductor
feed line feeding an antenna?

• A. To increase the radiation resistance
• B. To reduce spurious emissions
• C. To match the unbalanced transmitter output to
  the balanced parallel conductor feedline
• D. To reduce the feed-point impedance of the
  antenna

21
G9A06 Which of the following is a reason for
using an inductively coupled matching network
between the transmitter and parallel conductor
feed line feeding an antenna?

• A. To increase the radiation resistance
• B. To reduce spurious emissions
• C. To match the unbalanced transmitter output to
  the balanced parallel conductor feedline
• D. To reduce the feed-point impedance of the
  antenna

22
G9A07 How does the attenuation of coaxial cable
change as the frequency of the signal it is
carrying increases?

• A. It is independent of frequency
• B. It increases
• C. It decreases
• D. It reaches a maximum at approximately 18 MHz

23
G9A07 How does the attenuation of coaxial cable
change as the frequency of the signal it is
carrying increases?

• A. It is independent of frequency
• B. It increases
• C. It decreases
• D. It reaches a maximum at approximately 18 MHz

24
G9A08 In what values are RF feed line losses
usually expressed?

• A. ohms per 1000 ft
• B. dB per 1000 ft
• C. ohms per 100 ft
• D. dB per 100 ft

25
G9A08 In what values are RF feed line losses
usually expressed?

• A. ohms per 1000 ft
• B. dB per 1000 ft
• C. ohms per 100 ft
• D. dB per 100 ft

26
G9A09 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 200-ohm impedance?

• A. 41
• B. 14
• C. 21
• D. 12

27
G9A09 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 200-ohm impedance?

• A. 41
• B. 14
• C. 21
• D. 12

28
G9A10 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 10-ohm impedance?

• A. 21
• B. 501
• C. 15
• D. 51

29
G9A10 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 10-ohm impedance?

• A. 21
• B. 501
• C. 15
• D. 51

30
G9A11 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 50-ohm impedance?

• A. 21
• B. 11
• C. 5050
• D. 00

31
G9A11 What standing-wave-ratio will result from
the connection of a 50-ohm feed line to a
non-reactive load having a 50-ohm impedance?

• A. 21
• B. 11
• C. 5050
• D. 00

32
G9A12 What would be the SWR if you feed a
vertical antenna that has a 25-ohm feed-point
impedance with 50-ohm coaxial cable?

• A. 21
• B. 2.51
• C. 1.251
• D. You cannot determine SWR from impedance values

33
G9A12 What would be the SWR if you feed a
vertical antenna that has a 25-ohm feed-point
impedance with 50-ohm coaxial cable?

• A. 21
• B. 2.51
• C. 1.251
• D. You cannot determine SWR from impedance values

34
G9A13 What would be the SWR if you feed a folded
dipole antenna that has a 300-ohm feed-point
impedance with 50-ohm coaxial cable?

• A. 1.51
• B. 31
• C. 61
• D. You cannot determine SWR from impedance values

35
G9A13 What would be the SWR if you feed a folded
dipole antenna that has a 300-ohm feed-point
impedance with 50-ohm coaxial cable?

• A. 1.51
• B. 31
• C. 61
• D. You cannot determine SWR from impedance values

36
G9A14 If the SWR on an antenna feedline is 5 to
1, and a matching network at the transmitter end
of the feedline is adjusted to 1 to 1 SWR, what
is the resulting SWR on the feedline?

• A. 1 to 1
• B. 5 to 1
• C. Between 1 to 1 and 5 to 1 depending on the
  characteristic impedance of the line
• D. Between 1 to 1 and 5 to 1 depending on the
  reflected power at the transmitter

37
G9A14 If the SWR on an antenna feedline is 5 to
1, and a matching network at the transmitter end
of the feedline is adjusted to 1 to 1 SWR, what
is the resulting SWR on the feedline?

• A. 1 to 1
• B. 5 to 1
• C. Between 1 to 1 and 5 to 1 depending on the
  characteristic impedance of the line
• D. Between 1 to 1 and 5 to 1 depending on the
  reflected power at the transmitter

38
G9B Basic Antennas

• Random-wire antenna
• One of the disadvantages of a directly fed
  random-wire antenna is you may experience RF
  burns when touching metal objects in your station
• Groundplane antenna
• An advantage of downward sloping radials on a
  ground-plane antenna is they can be adjusted to
  bring the geed-point impedance closer to 50 ohms
• The feed-point impedance of a ground-plane
  antenna increases when its radials are changed
  from horizontal to downward sloping

39
G9B Basic Antennas contd

• Vertical antenna
• The radial wire of a ground-mounted vertical
  antenna system should be placed on the surface or
  buried a few inches below the ground
• The approximate length of a ¼ - wave vertical
  antenna cut for 28.5 MHz is 8.2 feet
• Length (1/4 wave Vertical) 234
  234/28.5 8.2 feet
• In feet Fx (MHz)

40
G9B Antennas (presenters note)

• Where did you get 234 in that equation?
• Remember these equations
• 300
• Wavelength in meters f (MHz)
• 984 468
• Wavelength in feet f (MHz) ½ wavelength in
  ft f (MHz)
• 234
• ¼ wavelength in ft f (MHz)

41
G9B Antennas contd

• Dipole
• The low angle azimuthal radiation pattern of an
  ideal half-wave dipole antenna installed ½
  wavelength high and parallel to the earth is a
  figure-eight at right angles to the antenna
• The antenna height affects the horizontal
  (azimuthal) radiation pattern of a horizontal
  dipole HF antenna if the antenna is less than ½
  wavelength high and resulting the azimuthal
  pattern is almost omnidirectional

42
G9B Antennas contd

• Dipole contd
• The feed-point impedance of a ½ wave dipole
  antenna steadily
• Decreases as the antenna is lowered from ¼ wave
  above ground
• Increases as the feed-point location is moved
  from the center toward the ends
• An advantage of a horizontally polarized as
  compared to a vertically polarized HF antenna is
  lower ground reflection losses

43
G9B Antennas contd

• Dipole cont
• The approximate length for a ½ wave dipole
  antenna cut for 14.250 MHz is 32.8 feet
• Length ( ½ wave Dipole) 468 468/14.250
  32.8 ft
• fx ( MHz)
• The approximate length for a ½ wave dipole
  antenna cut for 3.550 MHz is 131.8 feet
• Length ( ½ wave Dipole ) 468 468/3.550
  131.8 ft
• fx (MHz)

44
G9B01 What is one disadvantage of a directly fed
random-wire antenna?

• A. It must be longer than 1 wavelength
• B. You may experience RF burns when touching
  metal objects in your station
• C. It produces only vertically polarized
  radiation
• D. It is not effective on the higher HF bands

45
G9B01 What is one disadvantage of a directly fed
random-wire antenna?

• A. It must be longer than 1 wavelength
• B. You may experience RF burns when touching
  metal objects in your station
• C. It produces only vertically polarized
  radiation
• D. It is not effective on the higher HF bands

46
Vertical Antennas(Quarter Wavelength Vertical)
Quarter wavelength
300 F (MHz)
Wavelength (meters)
Meters to inches
¼? vertical length (inches) Wavelength / 4 x 39
47
Vertical Antenna
Standard ¼ wave vertical has a feedpoint
impedance of 35 ohms Sloping ground radials
downward raises feedpoint impedance
48
G9B02 What is an advantage of downward sloping
radials on a ground-plane antenna?

• A. They lower the radiation angle
• B. They bring the feed-point impedance closer to
  300 ohms
• C. They increase the radiation angle
• D. They can be adjusted to bring the feed-point
  impedance closer to 50 ohms

49
G9B02 What is an advantage of downward sloping
radials on a ground-plane antenna?

• A. They lower the radiation angle
• B. They bring the feed-point impedance closer to
  300 ohms
• C. They increase the radiation angle
• D. They can be adjusted to bring the feed-point
  impedance closer to 50 ohms

50
G9B03 What happens to the feed-point impedance of
a ground-plane antenna when its radials are
changed from horizontal to downward-sloping?

• A. It decreases
• B. It increases
• C. It stays the same
• D. It reaches a maximum at an angle of 45 degrees

51
G9B03 What happens to the feed-point impedance of
a ground-plane antenna when its radials are
changed from horizontal to downward-sloping?

• A. It decreases
• B. It increases
• C. It stays the same
• D. It reaches a maximum at an angle of 45 degrees

52
G9B04 What is the low angle azimuthal radiation
pattern of an ideal half-wavelength dipole
antenna installed 1/2 wavelength high and
parallel to the earth?

• A. It is a figure-eight at right angles to the
  antenna
• B. It is a figure-eight off both ends of the
  antenna
• C. It is a circle (equal radiation in all
  directions)
• D. It has a pair of lobes on one side of the
  antenna and a single lobe on the other side

53
G9B04 What is the low angle azimuthal radiation
pattern of an ideal half-wavelength dipole
antenna installed 1/2 wavelength high and
parallel to the earth?

• A. It is a figure-eight at right angles to the
  antenna
• B. It is a figure-eight off both ends of the
  antenna
• C. It is a circle (equal radiation in all
  directions)
• D. It has a pair of lobes on one side of the
  antenna and a single lobe on the other side

54
½ ? Dipole Radiation
Radiation pattern for a dipole placed ½ ? above
ground looking down from above the
antenna. Looks like a doughnut around the wire
in 3D space. Pattern distorts to omnidirectional
when placed low to the ground.
55
G9B05 How does antenna height affect the
horizontal (azimuthal) radiation pattern of a
horizontal dipole HF antenna?

• A. If the antenna is too high, the pattern
  becomes unpredictable
• B. Antenna height has no effect on the pattern
• C. If the antenna is less than 1/2 wavelength
  high, the azimuthal pattern is almost
  omnidirectional
• D. If the antenna is less than 1/2 wavelength
  high, radiation off the ends of the wire is
  eliminated

56
G9B05 How does antenna height affect the
horizontal (azimuthal) radiation pattern of a
horizontal dipole HF antenna?

• A. If the antenna is too high, the pattern
  becomes unpredictable
• B. Antenna height has no effect on the pattern
• C. If the antenna is less than 1/2 wavelength
  high, the azimuthal pattern is almost
  omnidirectional
• D. If the antenna is less than 1/2 wavelength
  high, radiation off the ends of the wire is
  eliminated

57
G9B06 Where should the radial wires of a
ground-mounted vertical antenna system be placed?

• A. As high as possible above the ground
• B. Parallel to the antenna element
• C. On the surface or buried a few inches below
  the ground
• D. At the top of the antenna

58
G9B06 Where should the radial wires of a
ground-mounted vertical antenna system be placed?

• A. As high as possible above the ground
• B. Parallel to the antenna element
• C. On the surface or buried a few inches below
  the ground
• D. At the top of the antenna

59
G9B07 How does the feed-point impedance of a 1/2
wave dipole antenna change as the antenna is
lowered from 1/4 wave above ground?

• A. It steadily increases
• B. It steadily decreases
• C. It peaks at about 1/8 wavelength above ground
• D. It is unaffected by the height above ground

60
G9B07 How does the feed-point impedance of a 1/2
wave dipole antenna change as the antenna is
lowered from 1/4 wave above ground?

• A. It steadily increases
• B. It steadily decreases
• C. It peaks at about 1/8 wavelength above ground
• D. It is unaffected by the height above ground

61
G9B08 How does the feed-point impedance of a 1/2
wave dipole change as the feed-point location is
moved from the center toward the ends?

• A. It steadily increases
• B. It steadily decreases
• C. It peaks at about 1/8 wavelength from the end
• D. It is unaffected by the location of the
  feed-point

62
G9B08 How does the feed-point impedance of a 1/2
wave dipole change as the feed-point location is
moved from the center toward the ends?

• A. It steadily increases
• B. It steadily decreases
• C. It peaks at about 1/8 wavelength from the end
• D. It is unaffected by the location of the
  feed-point

63
G9B09 Which of the following is an advantage of a
horizontally polarized as compared to vertically
polarized HF antenna?

• A. Lower ground reflection losses
• B. Lower feed-point impedance
• C. Shorter Radials
• D. Lower radiation resistance

64
G9B09 Which of the following is an advantage of a
horizontally polarized as compared to vertically
polarized HF antenna?

• A. Lower ground reflection losses
• B. Lower feed-point impedance
• C. Shorter Radials
• D. Lower radiation resistance

65
G9B10 What is the approximate length for a
1/2-wave dipole antenna cut for 14.250 MHz?

• A. 8.2 feet
• B. 16.4 feet
• C. 24.6 feet
• D. 32.8 feet

66
G9B10 What is the approximate length for a
1/2-wave dipole antenna cut for 14.250 MHz?

• A. 8.2 feet
• B. 16.4 feet
• C. 24.6 feet
• D. 32.8 feet

67
G9B11 What is the approximate length for a
1/2-wave dipole antenna cut for 3.550 MHz?

• A. 42.2 feet
• B. 84.5 feet
• C. 131.8 feet
• D. 263.6 feet

68
G9B11 What is the approximate length for a
1/2-wave dipole antenna cut for 3.550 MHz?

• A. 42.2 feet
• B. 84.5 feet
• C. 131.8 feet
• D. 263.6 feet

69
G9B12 What is the approximate length for a
1/4-wave vertical antenna cut for 28.5 MHz?

• A. 8.2 feet
• B. 10.5 feet
• C. 16.4 feet
• D. 21.0 feet

70
G9B12 What is the approximate length for a
1/4-wave vertical antenna cut for 28.5 MHz?

• A. 8.2 feet
• B. 10.5 feet
• C. 16.4 feet
• D. 21.0 feet

71
Beam Antennas(Yagi Antenna)
72
Yagi Radiation Pattern
The yagi antenna focuses RF energy in one
direction, giving the appearance of getting free
power. This free power or Effective Radiated
Power (ERP) can be expressed as antenna Gain in
Decibels (dB) over a dipole (dBd) or isotropic
resonator (dBi).
73
G9C Directional antennas Yagi

• A Yagi antenna consists of a driven element and
  some combination of parasitically excited
  reflector and/or director elements
• The director is normally the shortest parasitic
  element in a three-element single-band Yagi
  antenna
• The reflector is normally the longest parasitic
  element in a Yagi antenna
• The SWR bandwidth of a Yagi antenna can be
  increased by using larger diameter elements
• The approximate length of the driven element of
  a Yagi antenna is ½ wavelength

74
G9C Yagi conts

• Increasing the boom length and adding directors
  to a Yagi antenna will increase Gain
• A Yagi is often used for on the 20 meter band
  because it helps reduce interference from other
  stations to the side or behind the antenna
• In a Yagi antenna, front-to-back ratio means
  the power radiated in the major radiation lobe
  compared to the power radiated in exactly the
  opposite direction
• The main lobe of a directive antenna is the
  direction of maximum radiated field strength from
  the antenna

75
G9C Yagis contd

• The approximate maximum theoretical forward gain
  of a 3 element Yagi antenna is 9.7 dBi
• All of these Yagi antenna design variables could
  be adjusted to optimize forward gain,
  front-to-back ratio, or SWR bandwidth
• The physical length of the boom
• The number of element on the boom
• The spacing of each element along the boom

76
G9C Yagi contd

• The purpose of a gamma match used with Yagi
  antennas is to match the relatively low
  feed-point impedance to 50 ohms
• No insulation is needed for insulating the driven
  element of a Yagi antenna from the metal boom
  when using a gamma match

77
G9C Directional antennas conts

• Quad
• Each side of a cubical-quad antenna driven
  element is approximately ¼ wavelength long
• The forward gain of a 2-element cubicalquad
  antenna is about the same as the forward gain of
  a 3 element yagi
• Each side of a cubical-quad antenna reflector
  element is slightly more than ¼ wavelength
• A cubial quad antenna is a directional antenna
  and is typically constructed from 2 square loops
  of wire each having a circumference of
  approximately one wavelength at the operating
  frequency a separated by approximately 0.2
  wavelength

78
G9C Quads contd

• When the feed-point of a cubical quad antenna
  is changed from the center of the lowest
  horizontal wire to the center of one of the
  vertical wires, the polarization of the radiated
  signal changes from horizontal to vertical
• In order for the cubical-quad antenna to
  operate as a beam antenna, one of the elements is
  used as a reflector and the reflector element
  must be approximately 5 per cent longer than the
  driven element

79
G9C Directional antennas contd

• Delta-loop
• The gain of a two element delta-loop beam is
  about the same as the gain of a two element
  cubical quad antenna
• Each leg of a symmetrical delta-loop antenna
  Driven element is approximately 1/3 wavelengths
  long

80
G9C01 How can the SWR bandwidth of a Yagi antenna
be increased?

• A. Use larger diameter elements
• B. Use closer element spacing
• C. Use traps on the elements
• D. Use tapered-diameter elements

81
G9C01 How can the SWR bandwidth of a Yagi antenna
be increased?

• A. Use larger diameter elements
• B. Use closer element spacing
• C. Use traps on the elements
• D. Use tapered-diameter elements

82
G9C02 What is the approximate length of the
driven element of a Yagi antenna?

• A. 1/4 wavelength
• B. 1/2 wavelength
• C. 3/4 wavelength
• D. 1 wavelength

83
G9C02 What is the approximate length of the
driven element of a Yagi antenna?

• A. 1/4 wavelength
• B. 1/2 wavelength
• C. 3/4 wavelength
• D. 1 wavelength

84
G9C03 Which statement about a three-element
single-band Yagi antenna is true?

• A. The reflector is normally the shortest
  parasitic element
• B. The director is normally the shortest
  parasitic element
• C. The driven element is the longest parasitic
  element
• D. Low feed-point impedance increases bandwidth

85
G9C03 Which statement about a three-element
single-band Yagi antenna is true?

• A. The reflector is normally the shortest
  parasitic element
• B. The director is normally the shortest
  parasitic element
• C. The driven element is the longest parasitic
  element
• D. Low feed-point impedance increases bandwidth

86
G9C04 Which statement about a Yagi antenna is
true?

• A. The reflector is normally the longest
  parasitic element
• B. The director is normally the longest parasitic
  element
• C. The reflector is normally the shortest
  parasitic element
• D. All of the elements must be the same length

87
G9C04 Which statement about a Yagi antenna is
true?

• A. The reflector is normally the longest
  parasitic element
• B. The director is normally the longest parasitic
  element
• C. The reflector is normally the shortest
  parasitic element
• D. All of the elements must be the same length

88
G9C05 What is one effect of increasing the boom
length and adding directors to a Yagi antenna?

• A. Gain increases
• B. SWR increases
• C. Weight decreases
• D. Wind load decreases

89
G9C05 What is one effect of increasing the boom
length and adding directors to a Yagi antenna?

• A. Gain increases
• B. SWR increases
• C. Weight decreases
• D. Wind load decreases

90
G9C06 Which of the following is a reason why a
Yagi antenna is often used for radio
communications on the 20 meter band?

• A. It provides excellent omnidirectional coverage
  in the horizontal plane
• B. It is smaller, less expensive and easier to
  erect than a dipole or vertical antenna
• C. It helps reduce interference from other
  stations to the side or behind the antenna
• D. It provides the highest possible angle of
  radiation for the HF bands

91
G9C06 Which of the following is a reason why a
Yagi antenna is often used for radio
communications on the 20 meter band?

• A. It provides excellent omnidirectional coverage
  in the horizontal plane
• B. It is smaller, less expensive and easier to
  erect than a dipole or vertical antenna
• C. It helps reduce interference from other
  stations to the side or behind the antenna
• D. It provides the highest possible angle of
  radiation for the HF bands

92
G9C07 What does "front-to-back ratio" mean in
reference to a Yagi antenna?

• A. The number of directors versus the number of
  reflectors
• B. The relative position of the driven element
  with respect to the reflectors and directors
• C. The power radiated in the major radiation lobe
  compared to the power radiated in exactly the
  opposite direction
• D. The ratio of forward gain to dipole gain

93
G9C07 What does "front-to-back ratio" mean in
reference to a Yagi antenna?

• A. The number of directors versus the number of
  reflectors
• B. The relative position of the driven element
  with respect to the reflectors and directors
• C. The power radiated in the major radiation lobe
  compared to the power radiated in exactly the
  opposite direction
• D. The ratio of forward gain to dipole gain

94
G9C08 What is meant by the "main lobe" of a
directive antenna?

• A. The magnitude of the maximum vertical angle of
  radiation
• B. The point of maximum current in a radiating
  antenna element
• C. The maximum voltage standing wave point on a
  radiating element
• D. The direction of maximum radiated field
  strength from the antenna

95
G9C08 What is meant by the "main lobe" of a
directive antenna?

• A. The magnitude of the maximum vertical angle of
  radiation
• B. The point of maximum current in a radiating
  antenna element
• C. The maximum voltage standing wave point on a
  radiating element
• D. The direction of maximum radiated field
  strength from the antenna

96
G9C09 What is the approximate maximum theoretical
forward gain of a 3 Element Yagi antenna?

• A. 9.7 dBi
• B. 7.3 dBd
• C. 5.4 times the gain of a dipole
• D. All of these choices are correct

97
G9C09 What is the approximate maximum theoretical
forward gain of a 3 Element Yagi antenna?

• A. 9.7 dBi
• B. 7.3 dBd
• C. 5.4 times the gain of a dipole
• D. All of these choices are correct

98
G9C10 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. 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

99
G9C10 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. 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

100
G9C11 What is the purpose of a "gamma match" used
with Yagi antennas?

• A. To match the relatively low feed-point
  impedance to 50 ohms
• B. To match the relatively high feed-point
  impedance to 50 ohms
• C. To increase the front to back ratio
• D. To increase the main lobe gain

101
G9C11 What is the purpose of a "gamma match" used
with Yagi antennas?

• A. To match the relatively low feed-point
  impedance to 50 ohms
• B. To match the relatively high feed-point
  impedance to 50 ohms
• C. To increase the front to back ratio
• D. To increase the main lobe gain

102
G9C12 Which of the following describes a common
method for insulating the driven element of a
Yagi antenna from the metal boom when using a
gamma match?

• A. Support the driven element with ceramic
  standoff insulators
• B. Insert a high impedance transformer at the
  driven element
• C. Insert a high voltage balun at the driven
  element
• D. None of these answers are correct. No
  insulation is needed

103
G9C12 Which of the following describes a common
method for insulating the driven element of a
Yagi antenna from the metal boom when using a
gamma match?

• A. Support the driven element with ceramic
  standoff insulators
• B. Insert a high impedance transformer at the
  driven element
• C. Insert a high voltage balun at the driven
  element
• D. None of these answers are correct. No
  insulation is needed

104
Quad antenna
105
G9C13 Approximately how long is each side of a
cubical-quad antenna driven element?

• A. 1/4 wavelength
• B. 1/2 wavelength
• C. 3/4 wavelength
• D. 1 wavelength

106
G9C13 Approximately how long is each side of a
cubical-quad antenna driven element?

• A. 1/4 wavelength
• B. 1/2 wavelength
• C. 3/4 wavelength
• D. 1 wavelength

107
G9C14 How does the forward gain of a 2-element
cubical-quad antenna compare to the forward gain
of a 3 element Yagi antenna?

• A. 2/3
• B. About the same
• C. 3/2
• D. Twice

108
G9C14 How does the forward gain of a 2-element
cubical-quad antenna compare to the forward gain
of a 3 element Yagi antenna?

• A. 2/3
• B. About the same
• C. 3/2
• D. Twice

109
G9C15 Approximately how long is each side of a
cubical-quad antenna reflector element?

• A. Slightly less than 1/4 wavelength
• B. Slightly more than 1/4 wavelength
• C. Slightly less than 1/2 wavelength
• D. Slightly more than 1/2 wavelength

110
G9C15 Approximately how long is each side of a
cubical-quad antenna reflector element?

• A. Slightly less than 1/4 wavelength
• B. Slightly more than 1/4 wavelength
• C. Slightly less than 1/2 wavelength
• D. Slightly more than 1/2 wavelength

111
Delta Loop
112
G9C16 How does the gain of a two element
delta-loop beam compare to the gain of a two
element cubical quad antenna?

• A. 3 dB higher
• B. 3 dB lower
• C. 2.54 dB higher
• D. About the same

113
G9C16 How does the gain of a two element
delta-loop beam compare to the gain of a two
element cubical quad antenna?

• A. 3 dB higher
• B. 3 dB lower
• C. 2.54 dB higher
• D. About the same

114
G9C17 Approximately how long is each leg of a
symmetrical delta-loop antenna Driven element?

• A. 1/4 wavelengths
• B. 1/3 wavelengths
• C. 1/2 wavelengths
• D. 2/3 wavelengths

115
G9C17 Approximately how long is each leg of a
symmetrical delta-loop antenna Driven element?

• A. 1/4 wavelengths
• B. 1/3 wavelengths
• C. 1/2 wavelengths
• D. 2/3 wavelengths

116
G9C18 Which of the following antenna types
consists of a driven element and some combination
of parasitically excited reflector and/or
director elements?

• A. A collinear array
• B. A rhombic antenna
• C. A double-extended Zepp antenna
• D. A Yagi antenna

117
G9C18 Which of the following antenna types
consists of a driven element and some combination
of parasitically excited reflector and/or
director elements?

• A. A collinear array
• B. A rhombic antenna
• C. A double-extended Zepp antenna
• D. A Yagi antenna

118
G9C19 What type of directional antenna is
typically constructed from 2 square loops of wire
each having a circumference of approximately one
wavelength at the operating frequency and
separated by approximately 0.2 wavelength?

• A. A stacked dipole array
• B. A collinear array
• C. A cubical quad antenna
• D. An Adcock array

119
G9C19 What type of directional antenna is
typically constructed from 2 square loops of wire
each having a circumference of approximately one
wavelength at the operating frequency and
separated by approximately 0.2 wavelength?

• A. A stacked dipole array
• B. A collinear array
• C. A cubical quad antenna
• D. An Adcock array

120
G9C20 What happens when the feed-point of a
cubical quad antenna is changed from the center
of the lowest horizontal wire to the center of
one of the vertical wires?

• A. The polarization of the radiated signal
  changes from horizontal to vertical
• B. The polarization of the radiated signal
  changes from vertical to horizontal
• C. The direction of the main lobe is reversed
• D. The radiated signal changes to an
  omnidirectional pattern

121
G9C20 What happens when the feed-point of a
cubical quad antenna is changed from the center
of the lowest horizontal wire to the center of
one of the vertical wires?

• A. The polarization of the radiated signal
  changes from horizontal to vertical
• B. The polarization of the radiated signal
  changes from vertical to horizontal
• C. The direction of the main lobe is reversed
• D. The radiated signal changes to an
  omnidirectional pattern

122
G9C21 What configuration of the loops of a
cubical-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. The driven element must be fed with a balun
  transformer
• B. The driven element must be open-circuited on
  the side opposite the feed-point
• C. The reflector element must be approximately 5
  shorter than the driven element
• D. The reflector element must be approximately 5
  longer than the driven element

123
G9C21 What configuration of the loops of a
cubical-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. The driven element must be fed with a balun
  transformer
• B. The driven element must be open-circuited on
  the side opposite the feed-point
• C. The reflector element must be approximately 5
  shorter than the driven element
• D. The reflector element must be approximately 5
  longer than the driven element

124
G9D Specialized antennas

• Near Vertical Incidence Skywave (NVIS)
• An advantage of a NVIS antenna is the high
  vertical angle radiation for short skip during
  the day
• A NVIS antenna is typically installed at a height
  between 1/10 ¼ wavelength above ground
• Horizontally Polarized Yagi
• The gain of a two 3-element horizontally
  polarized Yagi antennas spaced vertically ½
  wavelength apart from each other typically is
  approximately 3 dB higher than the gain of a
  single 3-element Yagi
• The advantage of vertical stacking of
  horizontally polarized Yagi antennas is it
  narrows the main lobe in elevation

125
G9D Specialized antennas contd

• Log Periodic Antenna
• An advantage of a log periodic antenna is wide
  band width
• A log periodic antenna is described by the length
  and spacing of elements increases logarithmically
  from one end of the boom to the other
• Beverage Antenna
• Generally is not used for transmitting because it
  has high losses compared to other types of
  antennas
• One application for a beverage antenna is
  directional receiving for low HF bands
• It is a very long and low receiving antenna that
  is highly directional

126
G9D Specialized antennas contd

• Multi-band Antenna
• A disadvantage of multiband antennas is poor
  harmonic rejection
• The primary purpose of traps installed in
  antennas is to permit multiband operation

127
G9D01 What does the term "NVIS" mean as related
to antennas?

• A. Nearly Vertical Inductance System
• B. Non-Visible Installation Specification
• C. Non-Varying Impedance Smoothing
• D. Near Vertical Incidence Skywave

128
G9D01 What does the term "NVIS" mean as related
to antennas?

• A. Nearly Vertical Inductance System
• B. Non-Visible Installation Specification
• C. Non-Varying Impedance Smoothing
• D. Near Vertical Incidence Skywave

129
G9D02 Which of the following is an advantage of
an NVIS antenna?

• A. Low vertical angle radiation for DX work
• B. High vertical angle radiation for short skip
  during the day
• C. High forward gain
• D. All of these choices are correct

130
G9D02 Which of the following is an advantage of
an NVIS antenna?

• A. Low vertical angle radiation for DX work
• B. High vertical angle radiation for short skip
  during the day
• C. High forward gain
• D. All of these choices are correct

131
G9D03 At what height above ground is an NVIS
antenna typically installed?

• A. As close to one-half wave as possible
• B. As close to one wavelength as possible
• C. Height is not critical as long as
  significantly more than 1/2 wavelength
• D. Between 1/10 and 1/4 wavelength

132
G9D03 At what height above ground is an NVIS
antenna typically installed?

• A. As close to one-half wave as possible
• B. As close to one wavelength as possible
• C. Height is not critical as long as
  significantly more than 1/2 wavelength
• D. Between 1/10 and 1/4 wavelength

133
G9D04 How does the gain of two 3-element
horizontally polarized Yagi antennas spaced
vertically 1/2 wave apart from each other
typically compare to the gain of a single
3-element Yagi?

• A. Approximately 1.5 dB higher
• B. Approximately 3 dB higher
• C. Approximately 6 dB higher
• D. Approximately 9 dB higher

134
G9D04 How does the gain of two 3-element
horizontally polarized Yagi antennas spaced
vertically 1/2 wave apart from each other
typically compare to the gain of a single
3-element Yagi?

• A. Approximately 1.5 dB higher
• B. Approximately 3 dB higher
• C. Approximately 6 dB higher
• D. Approximately 9 dB higher

135
G9D05 What is the advantage of vertical stacking
of horizontally polarized Yagi antennas?

• A. Allows quick selection of vertical or
  horizontal polarization
• B. Allows simultaneous vertical and horizontal
  polarization
• C. Narrows the main lobe in azimuth
• D. Narrows the main lobe in elevation

136
G9D05 What is the advantage of vertical stacking
of horizontally polarized Yagi antennas?

• A. Allows quick selection of vertical or
  horizontal polarization
• B. Allows simultaneous vertical and horizontal
  polarization
• C. Narrows the main lobe in azimuth
• D. Narrows the main lobe in elevation

137
G9D06 Which of the following is an advantage of a
log periodic antenna?

• A. Wide bandwidth
• B. Higher gain per element than a Yagi antenna
• C. Harmonic suppression
• D. Polarization diversity

138
G9D06 Which of the following is an advantage of a
log periodic antenna?

• A. Wide bandwidth
• B. Higher gain per element than a Yagi antenna
• C. Harmonic suppression
• D. Polarization diversity

139
G9D07 Which of the following describes a log
periodic antenna?

• A. Length and spacing of the elements increases
  logarithmically from one end of the boom to the
  other
• B. Impedance varies periodically as a function of
  frequency
• C. Gain varies logarithmically as a function of
  frequency
• D. SWR varies periodically as a function of boom
  length

140
G9D07 Which of the following describes a log
periodic antenna?

• A. Length and spacing of the elements increases
  logarithmically from one end of the boom to the
  other
• B. Impedance varies periodically as a function of
  frequency
• C. Gain varies logarithmically as a function of
  frequency
• D. SWR varies periodically as a function of boom
  length

141
G9D08 Why is a Beverage antenna generally not
used for transmitting?

• A. Its impedance is too low for effective
  matching
• B. It has high losses compared to other types of
  antennas
• C. It has poor directivity
• D. All of these choices are correct

142
G9D08 Why is a Beverage antenna generally not
used for transmitting?

• A. Its impedance is too low for effective
  matching
• B. It has high losses compared to other types of
  antennas
• C. It has poor directivity
• D. All of these choices are correct

143
G9D09 Which of the following is an application
for a Beverage antenna?

• A. Directional transmitting for low HF bands
• B. Directional receiving for low HF bands
• C. Portable Direction finding at higher HF
  frequencies
• D. Portable Direction finding at lower HF
  frequencies

144
G9D09 Which of the following is an application
for a Beverage antenna?

• A. Directional transmitting for low HF bands
• B. Directional receiving for low HF bands
• C. Portable Direction finding at higher HF
  frequencies
• D. Portable Direction finding at lower HF
  frequencies

145
G9D10 Which of the following describes a Beverage
antenna?

• A. A vertical antenna constructed from beverage
  cans
• B. A broad-band mobile antenna
• C. A helical antenna for space reception
• D. A very long and low receiving antenna that is
  highly directional

146
G9D10 Which of the following describes a Beverage
antenna?

• A. A vertical antenna constructed from beverage
  cans
• B. A broad-band mobile antenna
• C. A helical antenna for space reception
• D. A very long and low receiving antenna that is
  highly directional

147
G9D11 Which of the following is a disadvantage of
multiband antennas?

• A. They present low impedance on all design
  frequencies
• B. They must be used with an antenna tuner
• C. They must be fed with open wire line
• D. They have poor harmonic rejection

148
G9D11 Which of the following is a disadvantage of
multiband antennas?

• A. They present low impedance on all design
  frequencies
• B. They must be used with an antenna tuner
• C. They must be fed with open wire line
• D. They have poor harmonic rejection

149
G9D12 What is the primary purpose of traps
installed in antennas?

• A. To permit multiband operation
• B. To notch spurious frequencies
• C. To provide balanced feed-point impedance
• D. To prevent out of band operation

150
G9D12 What is the primary purpose of traps
installed in antennas?

• A. To permit multiband operation
• B. To notch spurious frequencies
• C. To provide balanced feed-point impedance
• D. To prevent out of band operation

151
G9 - ANTENNAS 4 exam questions - 4 groups