I am trying to figure out why AMES 254, a MRU (Mobile Radio Unit) radar station, did not detect the Japanese aircraft approaching Colombo on 5 April 1942. MRUs had directional antennas, much like the Chain Home stations, so I have to wonder if maybe it was pointed toward the southwest instead of south, which is the direction the Japanese flew in from. Can anyone say how wide an arc a MRU could cover? For example, if oriented to the southwest could it pick up aircraft approaching from the south? Also, to what extent, if any, was range reduced toward the edges of the arc which could be covered?