GROL Radio Wave Propagation 3

Question 1

What is tropospheric ducting in VHF/UHF propagation?

Accepted Answer

Trapping of radio waves in a layer of the atmosphere due to a temperature inversion

Answer

Tropospheric ducting occurs when a temperature inversion creates a waveguide-like layer in the lower atmosphere, trapping VHF/UHF signals and allowing them to travel far beyond normal line-of-sight distances.

Question 2

At what approximate frequency range does ground-wave propagation become most effective for ship-to-shore communications?

Accepted Answer

300 kHz – 3 MHz (MF)

Answer

Medium frequency (MF) ground waves hug the Earth's surface and can propagate hundreds of miles over seawater, making MF ideal for maritime medium-range communications.

Question 3

What is 'sporadic E' propagation?

Accepted Answer

Irregular, intense patches of ionization in the E layer enabling unexpected long-distance VHF contacts

Answer

Sporadic E (Es) consists of localized, dense clouds of ionization in the E layer that appear unpredictably and can reflect signals at frequencies up to 150 MHz or higher over distances of 1,000–2,500 km.

Question 4

How does seawater affect ground-wave propagation compared to dry land?

Accepted Answer

Seawater is a much better conductor and dramatically reduces ground-wave attenuation

Answer

Seawater's high conductivity (approximately 5 S/m) dramatically reduces ground-wave attenuation, allowing MF signals to propagate many hundreds of miles over ocean paths.

Question 5

What is 'multipath propagation' and what problem does it cause?

Accepted Answer

Two or more signal paths arriving at slightly different times, causing fading or distortion

Answer

Multipath propagation occurs when signals arrive via different paths with different delays, and the resulting phase differences can cause signal cancellation (fading) or intersymbol interference in digital systems.

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Radio Wave Propagation 3