Sailtron R/T 80
It's not too difficult to make the almost antique marine VHF Sailtron RT80 and the identical Sealine MC5500 suited for the recepton of AIS by adding a discriminator output.
The VHF transceiver uses a conventional discriminator, consisting of a ceramic resonator and two diodes. Usually, the performance of this type of discriminator is less than that of a receiver with a more modern receiver IC. In spite of that, for the R/T 80, the results were quite acceptable.
The unfiltered audio can be found on the cathode of diode CR162. This diode can be found right next to the ceramic resonator.
The cathode of CR162 contains the unfiltered audio
The connection to CR162
Follow the next steps to make the discriminator output:
Of course, it is also possible to use a longer cord and use a 3.5 mm plug to connect the signal directly with your PC's line or microphone input.
The discriminator output: a 'pig tail' with a female cinch plug