Internal dab aerial is pretty good. I have a jvc long one. hal something maybe?
Ive heard them converters can be pretty rubbish as the normal aerial isnt designed to pick up dab signal. It will but it might not be great.
For any exterior aerials they want to drill holes. I asked about using a exterior one in my boot and was told it wouldnt work, same with under the bonnet.
You can hardly see the windscreen aerial as its just a line. I havent had a problem with it yet TBH. if your signal does run out whilst listening to say radio 1 it will switch to radio1 fm but this never really happens. Even on the country roads to Stonehaven I didnt have a DAB drop out.