Can't connect external DAB radio through aux

[sploosh]

Got a mini dab radio for Xmas so I can listen in Saab via aux cable. Uses cable as aerial. Works fine with FM but not dab.

Does anyone know if the aux links into the sharkfin circuit? If so I'm buggered as I swapped the perished rubber fin for a plastic one from the later Saab but this is a dummy as the connections are different. I was told this was only used by satnav so was redundant.

I seems a bit clever for aux to do this.......