G9C: Directional antennas
G9C01:
How can the SWR bandwidth of a Yagi antenna be increased?
Use larger diameter elements
Use closer element spacing
Use traps on the elements
Use tapered-diameter elements
G9C02:
What is the approximate length of the driven element of a Yagi antenna?
1/2 wavelength
1/4 wavelength
3/4 wavelength
1 wavelength
G9C03:
Which statement about a three-element single-band Yagi antenna is true?
The director is normally the shortest parasitic element
The reflector is normally the shortest parasitic element
The driven element is the longest parasitic element
Low feed-point impedance increases bandwidth
G9C04:
Which statement about a Yagi antenna is true?
The reflector is normally the longest parasitic element
The director is normally the longest parasitic element
The reflector is normally the shortest parasitic element
All of the elements must be the same length
G9C05:
What is one effect of increasing the boom length and adding directors to a Yagi antenna?
Gain increases
SWR increases
Weight decreases
Wind load decreases
G9C06:
Which of the following is a reason why a Yagi antenna is often used for radio communications on the 20 meter band?
It helps reduce interference from other stations to the side or behind the antenna
It provides excellent omnidirectional coverage in the horizontal plane
It is smaller, less expensive and easier to erect than a dipole or vertical antenna
It provides the highest possible angle of radiation for the HF bands
G9C07:
What does "front-to-back ratio" mean in reference to a Yagi antenna?
The power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction
The number of directors versus the number of reflectors
The relative position of the driven element with respect to the reflectors and directors
The ratio of forward gain to dipole gain
G9C08:
What is meant by the "main lobe" of a directive antenna?
The direction of maximum radiated field strength from the antenna
The magnitude of the maximum vertical angle of radiation
The point of maximum current in a radiating antenna element
The maximum voltage standing wave point on a radiating element
G9C09:
What is the approximate maximum theoretical forward gain of a 3 Element Yagi antenna?
9.7 dBi
7.3 dBd
5.4 times the gain of a dipole
All of these choices are correct
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?
All of these choices are correct
The physical length of the boom
The number of elements on the boom
The spacing of each element along the boom
G9C11:
What is the purpose of a "gamma match" used with Yagi antennas?
To match the relatively low feed-point impedance to 50 ohms
To match the relatively high feed-point impedance to 50 ohms
To increase the front to back ratio
To increase the main lobe gain
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?
None of these answers are correct. No insulation is needed
Support the driven element with ceramic standoff insulators
Insert a high impedance transformer at the driven element
Insert a high voltage balun at the driven element
G9C13:
Approximately how long is each side of a cubical-quad antenna driven element?
1/4 wavelength
1/2 wavelength
3/4 wavelength
1 wavelength
G9C14:
How does the forward gain of a 2-element cubical-quad antenna compare to the forward gain of a 3 element Yagi antenna?
About the same
2/3
3/2
Twice
G9C15:
Approximately how long is each side of a cubical-quad antenna reflector element?
Slightly more than 1/4 wavelength
Slightly less than 1/4 wavelength
Slightly less than 1/2 wavelength
Slightly more than 1/2 wavelength
G9C16:
How does the gain of a two element delta-loop beam compare to the gain of a two element cubical quad antenna?
About the same
3 dB higher
3 dB lower
2.54 dB higher
G9C17:
Approximately how long is each leg of a symmetrical delta-loop antenna Driven element?
1/3 wavelengths
1/4 wavelengths
1/2 wavelengths
2/3 wavelengths
G9C18:
Which of the following antenna types consists of a driven element and some combination of parasitically excited reflector and/or director elements?
A Yagi antenna
A collinear array
A rhombic antenna
A double-extended Zepp antenna
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 cubical quad antenna
A stacked dipole array
A collinear array
An Adcock array
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?
The polarization of the radiated signal changes from horizontal to vertical
The polarization of the radiated signal changes from vertical to horizontal
The direction of the main lobe is reversed
The radiated signal changes to an omnidirectional pattern
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?
The reflector element must be approximately 5% longer than the driven element
The driven element must be fed with a balun transformer
The driven element must be open-circuited on the side opposite the feed-point
The reflector element must be approximately 5% shorter than the driven element
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