http://server3.realsimulation.com/u-boot/SH3Mods/
Look for 'Radiolog 1233' and 'Radiolog lite'. The difference is the lite version only gives you procedural signals. The full version has many distress calls and u-boat reports. If you have your game set to go to normal time anytime you get a radio message, the full version can get annoying. Me, I love it.