Why does my radio sometimes lose its pre-set stations?

Some DAB radios have a backup battery that powers a memory chip. When the radio is switched off or unplugged from the mains, this chip remembers the stations you have stored as pre-sets. If the battery runs down, the data is lost. In addition, if the radio is moved to a new location, or signal strength is very low, some radios will automatically erase existing pre-sets and scan for new stations.