🌅 Grayline & Terminator Map

What is the Grayline?

The grayline (or terminator) is the zone on Earth between daylight and darkness — the sunrise and sunset regions. During these transition periods, the D-layer of the ionosphere (which absorbs low-band signals during the day) has dissipated, while the higher F-layers are still ionized. This creates a unique propagation enhancement for 20m, 30m, and 40m bands.

Grayline propagation is most effective along the terminator itself — stations on opposite sides of the grayline can communicate via long-path or enhanced F-layer propagation. The effect lasts approximately 30–60 minutes before and after sunrise/sunset at each end of the path.

Using Grayline for DX

• Track your sunrise/sunset: Note when the grayline passes your QTH
• Find DX stations in their grayline: When a distant station is at sunrise or sunset, paths to them are enhanced
• Long path: During grayline, signals may take the long way around the Earth, arriving from the opposite direction
• 20m band: Most effective for grayline DX. 40m and 30m also benefit
• Timing: Best results within 30 minutes of sunrise/sunset at either end of the path