ARRL Technician Practice Exam

What might be happening when VHF signals are being received from long distances?

1. Signals are being absorbed by the atmosphere

2. Signals are being refracted from a sporadic E layer

3. Signals are being weakened by atmospheric noise

4. Signals are being reflected by buildings

The correct answer is: Signals are being refracted from a sporadic E layer

When VHF signals are received from long distances, one likely explanation is that they are being refracted from a sporadic E layer. This phenomenon occurs when a layer of the atmosphere, specifically the E layer of the ionosphere, becomes ionized under certain conditions, allowing radio waves to be bent or refracted back to Earth. This refraction enables signals that would typically only travel in line of sight to cover much greater distances, facilitating communications over hundreds or even thousands of miles. The sporadic E layer can form irregularly and is known for causing unexpected long-distance VHF propagation, particularly during certain times of the year and under specific atmospheric conditions. Understanding this effect is crucial for amateur radio operators, as taking advantage of these propagation conditions can significantly enhance their communication capabilities.