From the other thread, it seems you already have your game patched with TDW SH5Patcher... the sonarguy still cannot hear a ship at 1.250? Is it out of the deaf zone (I think 20º bow and 40º stern)? Even if you can hear them, the sonarguy will usually lose their track.
(if not using the patch:
http://174.123.69.202/~subsimc/radio...d.php?t=181433)