G3C: Ionospheric layers; critical angle and frequency; HF scatter; Near Vertical Incidence Sky waves
G3C01:
Which of the following ionospheric layers is closest to the surface of the Earth?
The D layer
The E layer
The F1 layer
The F2 layer
G3C02:
When can the F2 region be expected to reach its maximum height at your location?
At noon during the summer
At midnight during the summer
At dusk in the spring and fall
At noon during the winter
G3C03:
Why is the F2 region mainly responsible for the longest distance radio wave propagation?
Because it is the highest ionospheric region
Because it is the densest ionospheric layer
Because it does not absorb radio waves as much as other ionospheric regions
All of these choices are correct
G3C04:
What does the term "critical angle" mean as used in radio wave propagation?
The highest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions
The long path azimuth of a distant station
The short path azimuth of a distant station
The lowest takeoff angle that will return a radio wave to the Earth under specific ionospheric conditions
G3C05:
Why is long distance communication on the 40, 60, 80 and 160 meter bands more difficult during the day?
The D layer absorbs these frequencies during daylight hours
The F layer absorbs these frequencies during daylight hours
The F layer is unstable during daylight hours
The E layer is unstable during daylight hours
G3C06:
What is a characteristic of HF scatter signals?
They have a wavering sound
They have high intelligibility
They have very large swings in signal strength
All of these choices are correct
G3C07:
What makes HF scatter signals often sound distorted?
Energy is scattered into the skip zone through several radio wave paths
The ionospheric layer involved is unstable
Ground waves are absorbing much of the signal
The E-region is not present
G3C08:
Why are HF scatter signals in the skip zone usually weak?
Only a small part of the signal energy is scattered into the skip zone
Signals are scattered from the troposphere which is not a good reflector
Propagation is through ground waves which absorb most of the signal energy
Propagations is through ducts in F region which absorb most of the energy
G3C09:
What type of radio wave propagation allows a signal to be detected at a distance too far for ground wave propagation but too near for normal sky wave propagation?
Scatter
Ground wave
Sporadic-E skip
Short-path skip
G3C10:
Which of the following might be an indication that signals heard on the HF bands are being received via scatter propagation?
The signal is heard on a frequency above the maximum usable frequency
The communication is during a sunspot maximum
The communication is during a sudden ionospheric disturbance
The signal is heard on a frequency below the maximum usable frequency
G3C11:
Which of the following is true about ionospheric absorption near the maximum usable frequency (MUF)?
Absorption will be minimum
Absorption is greater for vertically polarized waves
Absorption approaches maximum
Absorption is greater for horizontally polarized waves
G3C12:
Which ionospheric layer is the most absorbent of long skip signals during daylight hours on frequencies below 10 MHz?
The D layer
The F2 layer
The F1 layer
The E layer
G3C13:
What is Near Vertical Incidence Sky-wave (NVIS) propagation?
Short distance HF propagation using high elevation angles
Propagation near the MUF
Long path HF propagation at sunrise and sunset
Double hop propagation near the LUF
G3C14:
Which of the following antennas will be most effective for skip communications on 40 meters during the day?
A horizontal dipole placed between 1/8 and 1/4 wavelength above the ground
A vertical antenna
A left-hand circularly polarized antenna
A right-hand circularly polarized antenna
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