Hi.
I have just bought a 2016 custom and had problems with the dab signal dropping out and I searched the forum and could not find a definitive answer so I thought I would write this solution in case any one else was having the same problem
I had a Mk 7 before with an after market dab radio and the signal was fantastic, anywhere in the country, so I bought myself the same aerial from Halfords that I had with my mk7, photo attached.
I took off the passenger pillar trim and inside is a fakra connector/fitting for the dab/fm aerial, so I bought a fakra extension cable and cut one end of the extension cable (the same end that comes from the aerial) and cut the end off the new aerial as it had a different connector on it and joined the fakra connector to the new aerial.
I disconnected the fakra connector/fitting for the dab/fm aerial in the passenger pillar and connected the fakra connection of the new aerial that I had made and if it didn't work I could still use my ford aerial.
I did an 80 mile trip with a 25 mile drive through the country with a national dab station on and it only started to drop out when I got into the town, where as before it would drop out every journey, no station available, I did the return 80 miles with the fm on and the signal was fine.
I have attached 2 photos of the aerial, the first one with no cover over the aerial and the second photo of a balloon over the aerial, to stop the whistling when driving.
I hope this is not too confusing and that someone finds a fix for their poor signal.