GROL - General Radiotelephone Operator License Radio Wave Propagation Questions and Answers

Question 1

A ship is attempting to communicate with a shore station 40 nautical miles away using a VHF marine radio in the 156-162 MHz range.
The signal is blocked by a large coastal mountain range between them.
What is the primary propagation path for these signals, and why is communication failing?

Accepted Answer

Space wave (line-of-sight), because VHF signals are blocked by significant physical obstructions.

Answer

Skywave, because the frequency is too high for ionospheric refraction.

Answer

Groundwave, because the signal's energy is being absorbed by the terrain.

Answer

Tropospheric scatter, because the required atmospheric conditions are not present.

Question 2

In HF skywave propagation, what is the term for the region between the farthest reach of the groundwave and the point where the first refracted skywave returns to Earth, where the signal cannot be received?

Accepted Answer

The skip zone

Answer

The Fresnel zone

Answer

The absorption region

Answer

The multipath area

Question 3

Which layer of the ionosphere is the highest in altitude, the most heavily ionized, and is primarily responsible for the long-distance propagation of HF radio signals, especially during transcontinental communication?

Accepted Answer

The F2 layer

Answer

The D layer

Answer

The E layer

Answer

The troposphere

Question 4

A radio signal is received via two or more distinct paths, causing the signals to interfere with each other at the receiver. This results in rapid fluctuations in signal strength, sometimes causing deep fades. What is this phenomenon called?

Accepted Answer

Multipath fading

Answer

Doppler shift

Answer

Faraday rotation

Answer

Atmospheric absorption

Question 5

Under certain weather conditions, such as a temperature inversion where a layer of warm air sits above cooler air, VHF and UHF signals can become trapped and travel far beyond their normal line-of-sight horizon. What is this propagation mode called?

Accepted Answer

Tropospheric ducting

Answer

Ionospheric skip

Answer

Sporadic E

Answer

Groundwave propagation

Question 6

Which of the following frequency bands is most reliant on groundwave propagation for effective communication over seawater for distances up to a few hundred miles?

Accepted Answer

MF (300-3000 kHz)

Answer

UHF (300-3000 MHz)

Answer

VHF (30-300 MHz)

Answer

SHF (3-30 GHz)