Gray Line Map & World Clock

The gray line is the band of twilight that circles the Earth where day meets night. Along that band, low-band HF signals can travel a very long way. This live map shows exactly where the gray line sits right now. It also keeps UTC, Eastern time and the local time at popular DX spots, so you know when a path is about to open.

What is the gray line?

Twice a day, every spot on Earth passes through the gray line, once at sunrise and once at sunset. During the day, the sun builds up the D layer of the ionosphere, and that layer soaks up signals on 160, 80 and 40 meters. At night, the D layer fades away. In the twilight band, however, the D layer is already weak while the higher F layer is still strong. As a result, low-band signals can skip along the line with very little loss.

That is why hams in New Jersey often work Europe or Asia on 40 or 80 meters right around their own sunrise or sunset. When both stations sit on the gray line at the same moment, the path can be remarkably strong.

How to use this map

1. Check the clocks. Logs and DX spots use UTC, so the big amber clock is the one to watch. Eastern time and your own computer time sit beside it.
2. Read the gold band. The glowing gold stripe on the map is the gray line. Darker shading is night, and the bright area is daylight. The sun symbol marks the spot where the sun is directly overhead.
3. Watch the green dot. That is ACURA in Absecon. The box above the map tells you when Absecon reaches its next gray line, or which DX spots share the line with us right now.
4. Drag the time slider. Move it up to 24 hours ahead to plan a session, or 12 hours back to see when a contact happened. Press Back to now to return to the live view.
5. Scan the city cards. Each card shows the local time, whether that place is in daylight, on the gray line or in darkness, and its next sunrise and sunset in UTC.

Tips for working gray line DX

• Get on the air about 30 minutes before your local sunrise or sunset and stay until about 30 minutes after.
• For most gray line contacts, 40 and 80 meters are the best bands. Experienced operators also chase 160 meters this way.
• Morning gray line from New Jersey often favors paths toward Asia and the Pacific. Evening gray line often favors Europe and Africa.
• Around the equinoxes, the line runs nearly north to south and links stations in both hemispheres. Near the solstices it tilts, which opens different paths.
• Pair this map with our DX Propagation page and the NCDXF Beacon Tracker to see which bands are open.

New to HF? Our VE testing schedule lists upcoming license exams, and the practice exams will help you get ready for your General ticket.