I have aftermarket DAB in A6, to start with I was running on OEM roof aerial with amp/filter removed. Coverage was patchy aroud Buckingham and Rugby.
I have since switched to this aerial
https://www.dabonwheels.co.uk/produc...-car-aerial-3/ and reception is great everywhere when weather is good even in areas that did not have any reception around Rugby/Buckingham but is seems to be affected quite often by thick clouds/fog even in areas with good reception. I never experienced any difference in poor weather with old aerial.
To sum it up it works a lot better in good weather but in basd weather sometimes it's OK but often it is **** with new aerial.