ARRL Technician Practice Exam

Why do VHF and UHF radio signals generally travel farther than the visual line of sight distance?

1. The signals bounce off the ionosphere

2. The Earth appears less curved to radio waves than to light

3. Radio waves are unaffected by terrain

4. VHF and UHF can utilize multiple paths

The correct answer is: The Earth appears less curved to radio waves than to light

VHF and UHF radio signals are able to travel farther than the visual line of sight distance primarily because the Earth appears less curved to radio waves than it does to light. This phenomenon occurs due to the characteristics of electromagnetic waves compared to light waves. Radio waves can diffract or bend around obstacles and follow the curvature of the Earth, allowing them to propagate beyond what a person can see with the naked eye. While light is a straight-line wave that doesn't easily bend around obstructions, radio waves have the ability to reflect and bend, giving them an extended range. In contrast, the other options refer to different principles or are not applicable in this scenario. For example, while bouncing off the ionosphere can help extend radio signal range at HF (high frequency) bands, VHF (very high frequency) and UHF (ultra high frequency) signals primarily travel the way described above. The notion that radio waves are unaffected by terrain is misleading, as terrain does impact signal propagation, although radio waves can navigate some of those terrains better than light. Lastly, while multiple paths can enhance signal reception in some cases, this does not inherently explain the phenomenon of signal propagation distance compared to visual line of sight.