What is the primary cause of "fading" in radio signals?

Fading in radio signals primarily occurs due to variations in the ionosphere and atmospheric conditions. As radio waves travel, they can be refracted or scattered by changes in the density of the ionosphere, which can be influenced by factors such as solar activity, time of day, and even weather conditions. This leads to fluctuations in the signal strength as it reaches the receiver, causing it to fade in and out.

The ionosphere can reflect radio waves back to Earth, but as conditions change, the effectiveness of that reflection can vary, leading to more pronounced fading at certain times or under specific conditions. This phenomenon is particularly evident in high-frequency (HF) radio communication, where signals rely heavily on the ionosphere for propagation.

The other factors mentioned, such as interference from other signals or inconsistencies in equipment, can certainly impact the clarity of a received signal, but they do not primarily cause the type of fading associated with environmental variations. High transmission power can enhance signal strength but does not address the underlying issues of atmospheric and ionospheric variability, which are the primary drivers of fading.