In 1943, enemy radar equipment,was more softicated an was a u-boats had, and the equipment that existed among the Germans was not 100% sure, and while using the equipment, so you reveal your location, so it was under real conditions during WWII,read a little about the real conditions,some links
http://www.uboat.net/technical/radar.htm
http://www.ibiblio.org/hyperwar/USN/...51/ASW-14.html
http://www.historylearningsite.co.uk/u-boats.htm