FCC Technician Class Exam Study Guide - 2014-2018/Subelement T3 Group C

Propagation modes: line of sight; sporadic E; meteor and auroral scatter and reflections; tropospheric ducting; F layer skip; radio horizon

The Question Pool

Question 1

Why are direct (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?

A. They are too weak to go very far

B. FCC regulations prohibit them from going more than 50 miles

C. UHF signals are usually not reflected by the ionosphere

D. They collide with trees and shrubbery and fade out

The correct answer is C.

Question 2

Which of the following might be happening when VHF signals are being received from long distances?

A. Signals are being reflected from outer space

B. Signals are arriving by sub-surface ducting

C. Signals are being reflected by lightning storms in your area

D. Signals are being refracted from a sporadic E layer

The correct answer is D.

Question 3

What is a characteristic of VHF signals received via auroral reflection?

A. Signals from distances of 10,000 or more miles are common

B. The signals exhibit rapid fluctuations of strength and often sound distorted

C. These types of signals occur only during winter nighttime hours

D. These types of signals are generally strongest when your antenna is aimed west

The correct answer is B.

Question 4

Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?

A. Backscatter

B. Sporadic E

C. D layer absorption

D. Gray-line propagation

The correct answer is B.

Question 5

Which of the following effects might cause radio signals to be heard despite obstructions between the transmitting and receiving stations?

A. Knife-edge diffraction

B. Faraday rotation

C. Quantum tunneling

D. Doppler shift

The correct answer is A.

Question 6

What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?

A. Tropospheric scatter

B. D layer refraction

C. F2 layer refraction

D. Faraday rotation

The correct answer is A.

Question 7

What band is best suited for communicating via meteor scatter?

A. 10 meters

B. 6 meters

C. 2 meters

D. 70 cm

The correct answer is B.

Question 8

What causes tropospheric ducting?

A. Discharges of lightning during electrical storms

B. Sunspots and solar flares

C. Updrafts from hurricanes and tornadoes

D. Temperature inversions in the atmosphere

The correct answer is D.

Question 9

What is generally the best time for long-distance 10 meter band propagation via the F layer?

A. From dawn to shortly after sunset during periods of high sunspot activity

B. From shortly after sunset to dawn during periods of high sunspot activity

C. From dawn to shortly after sunset during periods of low sunspot activity

D. From shortly after sunset to dawn during periods of low sunspot activity

The correct answer is A.

Question 10

What is the radio horizon?

A. The distance over which two stations can communicate by direct path

B. The distance from the ground to a horizontally mounted antenna

C. The farthest point you can see when standing at the base of your antenna tower

D. The shortest distance between two points on the Earth's surface

The correct answer is A.

Question 11

Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?

A. Radio signals move somewhat faster than the speed of light

B. Radio waves are not blocked by dust particles

C. The Earth seems less curved to radio waves than to light

D. Radio waves are blocked by dust particles

The correct answer is C.

Question 12

Which of the following bands may provide long distance communications during the peak of the sunspot cycle?

A. Six or ten meters

B. 23 centimeters

C. 70 centimeters or 1.25 meters

D. All of these choices are correct

The correct answer is A.