 Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals.Jamming is problematic to radar since the jamming signal only needs to travel one way (from the jammer to the radar receiver) whereas the radar echoes travel two ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver in accordance with inverse-square law.. Jammers therefore can be much less powerful than their jammed radars and still effectively mask targets along the line of sight from the jammer to the radar ("mainlobe jamming").Jammers have an added effect of affecting radars along other lines of sight through the radar receiver's sidelobes ("sidelobe jamming").