Just to expand slightly on Werner's point about radar. Your air search radar is NOT represented as a station in your submarine. These types of contacts are announced but the operator/station are essentially "invisible" to you and work in the background. You will by now have noticed a surface search radar station in your sub which initially does not work. This is an oversight in the game in that the station is represented in your submarine but it didn't exist in the early submarines therefore despite it being represented it doesn't work until the technology is actually "installed" in your submarine later in the war. Again, an oversight by the developers but only a minor frustration at the beginning of a campaign.
Hope this makes sense.
