Astrid,
In the UK, although technically illegal, many of us monitor ATC on dedicated airband radio receivers. The Radiocommunications Agency is a government department which monitors use of the radio spectrum and it is normal practice for the RA to turn a blind eye to the use of these receivers, as long as us listeners are discrete.
I don't know what the law is on this subject in Sweden. It might be an idea to get in touch with the Swedish Home Affairs Department (if that is what it is called) to determine policy. There are several manufacturers of quality radio receivers out there but I'd better not name any because that would be advertising and the PPRuNE bosses would probably have me shot !
Hope this helps anyway. Good luck.
TGU