Dantronik RT 408D / Dancom RT925
It's not too difficult to make the Dantronik RT480D and the almost identical Dancom RT925 marine VHF suited for the reception of AIS by adding a discriminator output.
Dantronic RT 480 D
The receiver IC is a TBA120U, which was originally designed for use in TV's. This IC has two audio outputs: pin 8, which is adjustable by the volume potmeter, and pin 12, which carries a signal with a constant level. For AIS, pin 12 is the most suited.
Pin 12 carries the unfiltered audio
The connection to pin 12
Follow the next steps to make the discriminator output:
The 3.5 mm chassis socket