In FotRSU, yes you do. In most other mods and stock, you cannot turn-off the SD unless you submerge... However, going by your question, I would be willing to bet that this has not adversely affected your patrols too often... lol - Primary goal is to sink ships. In conducting said goal, number one chore is to not be seen. To minimize that risk, you use radar. However, the enemy can home in on your radar signal, just like they can the radio signals, so if you want to do things the "realistic" manner, you use 1x TC like Front Runner does, and then sparingly use your radars, such that you are aware of your surroundings, but not having a contact "beacon" sounding... Myself, I only do the intermittent stuff occasionally, else you would be out there on the boat for four years...
