Sporadic-E on 6 m, 4 m and 2 m: when it happens and how to catch an opening

Updated 2026-10-27 · SQ3SWG

Sporadic-E (Es) is caused by dense, patchy clouds of ionisation in the E layer, about 100–120 km up. When a cloud is dense enough, it reflects VHF signals over distances of roughly 500 to 2300 km on a single hop, sometimes for hours, with strong signals from stations that are normally far out of reach.

When

In Europe the main season runs from May to August, with the peak in June and July, and a much smaller season around the turn of the year. Openings are most common from late morning to the evening. 6 m opens on most days in the peak season; 4 m less often; 2 m only a few times a year, because the cloud has to be dense enough to reflect 144 MHz.

The Es MUF

The maximum usable frequency (MUF) for a 2000 km hop is about five times the critical frequency (foEs) measured by ionosondes. When the Es MUF over a point between you and the other station reaches 50, 70 or 144 MHz, that band can open over that path. Our propagation page shows the current Es MUF from European ionosondes, and the band pages show where spots suggest Es right now, which also catches clouds between the ionosondes.

Catching an opening

• Watch the lower bands: when 10 m and 6 m show short skip (500–1000 km), the MUF is rising.
• The reflection point is about halfway along the path, so watch the area halfway to where you want to work.
• Listen on the activity frequencies – FT8 on 50.313 MHz, CW and SSB around 50.100–50.150 MHz, and on 2 m SSB around 144.300 MHz – and for beacons.
• Openings on 2 m are short, often minutes. Be ready, keep contacts short, and don't wait for a sked: call CQ.

Skeds still help: arrange to be on during the peak hours with stations in the right distance range, and let the chat know when you hear something.