Skanti TRP 2500
The Skanti TRP-2500 is a rather vintage marine VHF radio. It's spacious layout makes it easy to enable AIS reception by adding a discriminator output.
The receiver IC is an MC3357. The unfiltered audio can be found on pin 9. The output signal has a peak-peak voltage of about 5 V. A voltage divider is used to attenuate the output signal by about 10 times and protect the line- or microphone input of a connected PC.
Pin 9 contains the unfiltered audio
The connection to pin 9
With the following steps, the discriminator output is made:
The shielded wire is led outside