Ham Radio General Class Practice Test

What effect do high sunspot numbers have on radio communications?

1. High-frequency radio signals become weak and distorted

2. Frequencies above 300 MHz become usable for long-distance communication

3. Long-distance communication in the upper HF and lower VHF range is enhanced

4. Microwave communications become unstable

The correct answer is: Long-distance communication in the upper HF and lower VHF range is enhanced

High sunspot numbers indicate periods of increased solar activity, which can greatly enhance the propagation of high-frequency (HF) radio signals. Specifically, during times of high sunspot activity, there is an increase in ionization in the Earth's ionosphere. This added ionization allows for better reflection of radio waves in the upper HF band (typically 10 MHz to 30 MHz) and can even improve conditions for lower VHF frequencies (such as 30 MHz to 300 MHz). As a result, radio operators often experience improved long-distance communication capabilities, allowing signals to travel farther than they would during periods of low sunspot activity. In contrast, with low sunspot numbers, the ionosphere is less ionized, which can lead to weaker signals and reduced ranges for HF communication. High sunspot activity, therefore, is crucial for operators seeking to make contact over far distances, particularly through the use of skip propagation, where signals bounce off the ionosphere to reach distant locations. This phenomenon is especially beneficial during contests or events where effective long-range communication is desired.