Thanks for your reply,
that there are huge differences between the boxen became clear after the hauppauge hvr900 just found 12 Channels (and could only display 2) while this no name dual dvb-t gets the whole bouquet (but only shows 4). EPG data is transmitted for most of the channels.
Whether the antenna is digital capable: I have no idea. But I'll ask my landlady.
So the mathead booster might do the trick, even if the antenna is analouge?
thanks a bunch
Edit PS: That's the booster that's currently "working"
http://images.maplin.co.uk/full/RT68Y.jpg