http://www.gamespot.com/pc/rpg/fallo...044&pid=918428
that might help, other people claim they got the signal when they were OUTDOORS only, and others claim you 100% need to install the patch, otherwise the signal ever happens, seems quite a mess to be honest...
so, check you installed the patch correctly - right click the fallout3.exe, select properties, look at the detals, file version should be 1.6.0.3
then check anchorage is definately checked in the data files
might also be an idea to check that vista thing too, as you haven't mentioned if your copy is from steam, retail etc...