The heatmap shows the activity as reported by the RBN (CW/digital modes) of the last 12 months. You can scroll back to January 2015.
Daily activity is measured by the number of active hour slots (24) times band slots (10, 160m - 10m incl. WARC and 60m) and the number of continents in which a skimmer spotted the station in the respective hour, for a maximum daily score of 24 * (10 + 6) = 384. When filtering by band, the continent information is omitted, because it's only saved once per slot, not per band.
Click a single day on the heatmap to see its details.
<a href="https://foc.dj1yfk.de/activity/UN7NFD"><img src="https://foc.dj1yfk.de/activity/image/UN7NFD"></a>