The "time" factor is why. Something has to hit the "threshold" for the game to respond for you. Depending upon the mod set, that might be altered from stock. Don't forget also that the game has that confounded "range" dial if you look at the PPI, which can throw you off if looking at the wrong scale... The nice, though non-historical aspect of the game's radar is that you do not get land reflections to interfere with reception and interpretation... Have you read CapnScurvy's "Using Radar_Sonar.pdf"?
