Which frequency follows the earth's contours and is less impacted by atmospheric conditions?

Lower frequency waves are characterized by their ability to follow the contours of the Earth, which is often referred to as "ground wave propagation." This type of propagation allows lower frequencies to diffract around obstacles and travel over long distances, especially within the horizon. The lower frequency is also less susceptible to atmospheric conditions such as rain, fog, and other weather phenomena, making them more reliable for communication at longer ranges in various conditions.

In contrast, high frequency and ultra-high frequency waves tend to follow a line-of-sight propagation path, which limits their range and effectiveness in hilly or urban environments. Microwave frequencies also generally require line-of-sight and can be significantly affected by atmospheric conditions, particularly moisture. This highlights why lower frequencies are the best choice for reliable ground wave communication that is not heavily affected by atmospheric variables.