RobJ250. The system short-medium-long is very realistic. At least much more realistic than it would be if your hydrophone operator would tell you: "Ahoy, Skipper! Frachter coming close, distance 2581 meters!"
In contacts_cfg (Silent Hunter/Data/Cfg) you can take a look or adjust values in every "category" = short range could be for example up to 2000 meters, medium up to 10 000 meters and long over 10 000 meters.
Greetings,
-RC-