Grey Line Map

A greyline map is valuable for identifying the best times and locations for DX (long-distance) contacts, especially on low-frequency bands (160m, 80m, and 40m). It shows the twilight zones (dawn and dusk) around the Earth, where radio propagation conditions are enhanced.
Using a Greyline Map for DX Contacts

Understand the Greyline Effect
At sunrise and sunset, the D-layer of the ionosphere weakens, reducing the absorption of low-frequency signals.
The F-layer remains ionized, allowing signals to travel further with lower attenuation.
This significantly improves long-distance propagation on bands like 40m, 80m, and 160m.

Find Your Location on the Map
Identify when your station is entering or exiting the greyline.
The best time to operate is right before sunrise or right after sunset at your QTH.

Identify Potential DX Locations
Look for other regions in the greyline at the same time.
If a distant station is also in the greyline, there’s a high probability of enhanced propagation between both locations.

Target Specific DX Locations
If you want to work in a specific country or region, determine when you and that location share greyline conditions.
Example: If you’re in North America and want to contact Australia, check when both locations experience dawn or dusk simultaneously.

Monitor Propagation on 40m
Since you operate CW on 40m, expect stronger DX signals along the greyline path.
Try calling CQ DX or tuning around the CW portions (7.000–7.100 MHz) at sunrise/sunset.

Use Real-Time Greyline Tools
Websites and apps like VOACAP, DX Maps, and DX Heat provide real-time greyline overlays.
Some logging software also includes live greyline tracking.