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You will need to consult a local professional aerial installation company as DAB reception (especially) can vary from street to street.
Get it professionally installed on the roof for best reception.
You will probably need a DAB folded dipole (with balun) or a DAB 3 element (again with balun) for best DAB only reception. Other aerial types can be used for FM/DAB combined.
But like I said, get the pro's in.
If you have to ask on a forum then you will need them. (No disrespect, I am not a pro either and I would not dream of doing this stuff myself.)
As a rough idea of cost I had the mast and digital TV aerial and an FM and DAB aerial and new double-screened downleads all professionally installed for £190 just over a year ago.
It will cost much less if you are only having DAB fitted to an existing rig (although if your rig is quite old and still has an analogue optimised TV aerial then it may pay you to get the whole lot done at once.)