Why are the shortwave frequencies always being altered?

Unlike FM, medium and long wave frequencies, shortwave frequencies have to be changed regularly. The main reason for this is the rather special propagation properties of electromagnetic waves in the shortwave range.

The frequencies change on the day when the clocks are changed in central Europe. The clocks are put forward in the early hours (01:00 UTC) of the last Sunday in March and put back at the same time on the last Sunday in October.

Please find the current DW frequency lists under the link below:

http://www.dw-world.de/reception