In Data\Menu\cfg\Maps.cfg set the SymbolZoom value for which zoom level you want to "activate" the bearing tool.
If you want a bearing tool mod, try Patos Bearing Tools.
1500m and 3000m can be found here:
http://www.subsim.com/radioroom/down...o=file&id=1601
http://www.subsim.com/radioroom/down...o=file&id=1597
Some notes reg. bearing tools:
http://www.subsim.com/radioroom/show...earing+%2Btool
Note: size of tool depends of your screen resolution.
If it doesn't show up correctly, you'll have to find another one scaled to your screenresolution or do it yourself...
I use Patos 3000m Bearing Tool scaled to 1600x1200, if you want it.