NCDXF beacons …

The 18 beacons of the International Beacon Project (NCDXF/IARU) take turns on 14.100, 18.110, 21.150, 24.930 and 28.200 MHz: ten seconds each, a three-minute cycle. Their callsign in CW at 100 W, then four dashes at 100, 10, 1 and 0.1 W: the last one still heard tells the margin. Worked out in your browser from UTC time (set your clock).