What is generally the best time for long-distance 10 meter band propagation?

The best time for long-distance communication on the 10 meter band is generally during daylight hours. This is primarily due to the way ionospheric propagation works. During the day, the sun's ultraviolet radiation ionizes the Earth's upper atmosphere, particularly the F-layer of the ionosphere. This layer reflects radio waves back to Earth, allowing for long-distance communication.

As the sun rises, the ionization increases, enhancing propagation conditions. The key frequency range for the 10 meter band thrives on these favorable conditions, enabling signals to travel much farther than they would during lower ionization times, such as at night.

At nighttime, ionization decreases, which typically leads to poorer propagation conditions on higher frequencies like those in the 10 meter band. Coronal mass ejections can momentarily enhance propagation but are less predictable and do not guarantee good conditions for long-distance communication, while low solar flux usually correlates with reduced ionospheric activity, thus limiting the range of propagation.