I have a Sony DAB player with an external magnetic aerial. AT present this is jammed up against the windscreen (inside the van) but i don't get a great reception - today I had to listen to all the Thatcher funeral carp on radio 5 instead of Hawksbee and Jacobs on talksport

Two questions for the gurus of all knowledge;
1. Are windscreen (stick on) aerials any good?
2. Can anyone recommend an aerial they use?
Cheers
Chris