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General Class Exam Question Pool

effective 7/01/2015 thru 6/30/2019

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2015-G3C: Ionospheric layers; critical angle and frequency; HF scatter; Near Vertical Incidence Sky-wave

2015-G3C01: Which ionospheric layer is closest to the surface of the Earth?

The D layer

The E layer

The F1 layer

The F2 layer



2015-G3C02: Where on the Earth do ionospheric layers reach their maximum height?

Where the Sun is overhead

Where the Sun is on the opposite side of the Earth

Where the Sun is rising

Where the Sun has just set



2015-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



2015-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



2015-G3C05: Why is long distance communication on the 40-meter, 60-meter, 80-meter and 160-meter bands more difficult during the day?

The D layer absorbs signals at these frequencies during daylight hours

The F layer absorbs signals at these frequencies during daylight hours

The F layer is unstable during daylight hours

The E layer is unstable during daylight hours



2015-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



2015-G3C07: What makes HF scatter signals often sound distorted?

Energy is scattered into the skip zone through several different radio wave paths

The ionospheric layer involved is unstable

Ground waves are absorbing much of the signal

The E-region is not present



2015-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 magnetosphere 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



2015-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

Faraday rotation

Sporadic-E skip

Short-path skip



2015-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



2015-G3C11: Which of the following antenna types 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



2015-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



2015-G3C13: What is Near Vertical Incidence Sky-wave (NVIS) propagation?

Short distance MF or HF propagation using high elevation angles

Propagation near the MUF

Long path HF propagation at sunrise and sunset

Double hop propagation near the LUF





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