PropagationMediumQuestion 20329
Question
Which statement about ground wave propagation is correct?
- AIt requires ionospheric reflection
- BThe signal amplitude decreases with distance due to ground absorption and geometric spreadingCorrect
- CIt only works above 30 MHz
- DIt travels in a perfectly straight line with no attenuation
Correct answer
The signal amplitude decreases with distance due to ground absorption and geometric spreading
Explanation
Ground waves follow Earth's curvature but are attenuated by ground absorption (energy dissipated as heat in soil/sea) and 1/r geometric spreading. Seawater (high conductivity) supports longer ground-wave range than dry land. Ground wave range at 1 MHz ≈ 500–1000 km over sea, ~100–300 km over land.