oh.. i can hear that..
When diving into the periscope depth (Om Uboat type 2 periscop setting is 13m depth), nothing was seen because it was too deep. so than I always dive to 10 meters deep.
Consequently I could not hear anything on the hydrophone.(hydrophone working for more than 12m depth.)
So now i can heard for hydrophone. thank you very much for your help.
