G9D: Specialized antennas
G9D01:
What does the term "NVIS" mean as related to antennas?
Near Vertical Incidence Skywave
Nearly Vertical Inductance System
Non-Visible Installation Specification
Non-Varying Impedance Smoothing
G9D02:
Which of the following is an advantage of an NVIS antenna?
High vertical angle radiation for short skip during the day
Low vertical angle radiation for DX work
High forward gain
All of these choices are correct
G9D03:
At what height above ground is an NVIS antenna typically installed?
Between 1/10 and 1/4 wavelength
As close to one-half wave as possible
As close to one wavelength as possible
Height is not critical as long as significantly more than 1/2 wavelength
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?
Approximately 3 dB higher
Approximately 1.5 dB higher
Approximately 6 dB higher
Approximately 9 dB higher
G9D05:
What is the advantage of vertical stacking of horizontally polarized Yagi antennas?
Narrows the main lobe in elevation
Allows quick selection of vertical or horizontal polarization
Allows simultaneous vertical and horizontal polarization
Narrows the main lobe in azimuth
G9D06:
Which of the following is an advantage of a log periodic antenna?
Wide bandwidth
Higher gain per element than a Yagi antenna
Harmonic suppression
Polarization diversity
G9D07:
Which of the following describes a log periodic antenna?
Length and spacing of the elements increases logarithmically from one end of the boom to the other
Impedance varies periodically as a function of frequency
Gain varies logarithmically as a function of frequency
SWR varies periodically as a function of boom length
G9D08:
Why is a Beverage antenna generally not used for transmitting?
It has high losses compared to other types of antennas
Its impedance is too low for effective matching
It has poor directivity
All of these choices are correct
G9D09:
Which of the following is an application for a Beverage antenna?
Directional receiving for low HF bands
Directional transmitting for low HF bands
Portable Direction finding at higher HF frequencies
Portable Direction finding at lower HF frequencies
G9D10:
Which of the following describes a Beverage antenna?
A very long and low receiving antenna that is highly directional
A vertical antenna constructed from beverage cans
A broad-band mobile antenna
A helical antenna for space reception
G9D11:
Which of the following is a disadvantage of multiband antennas?
They have poor harmonic rejection
They present low impedance on all design frequencies
They must be used with an antenna tuner
They must be fed with open wire line
G9D12:
What is the primary purpose of traps installed in antennas?
To permit multiband operation
To notch spurious frequencies
To provide balanced feed-point impedance
To prevent out of band operation
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