When can I work them on which band? Type your city and your target's city. The planner shows today's sunrise and sunset at both ends, the great-circle path on a live grey-line globe , and ranks bands using current solar conditions .
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Where + who
Type a city or hit "Use my location".
or pick a DXCC entity
Type a city or pick an entity.
Grey line now
UTC time…
Subsolar latitude…
Subsolar longitude…
Solar declination…
Day of year…
Subsolar point (sun overhead)
Twilight band (±0.5 h around terminator)
Terminator line
Your location pin
Target location pin + great-circle path
Drag to rotate. Auto-rotate resumes after a moment.
Path
Distance (short)
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…
Bearing (short)
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…
Long-path distance
…
via the antipode
UTC offset
…
your time vs theirs
Today (UTC) at both ends
You
Target
now
Recommended windows
Current solar conditions: … SFI · K-index … · …(details)
Pick a target above to see windows.
Why the grey line opens HF
Short version: the terminator ray's long horizontal path through the upper atmosphere absorbs UV before it can ionize the D layer, so for roughly thirty minutes on either side of dawn or dusk, low-band HF (160 m, 80 m, 40 m) opens up.
Full reference on the physics and the operator's checklist →