Radar sets have clocks and timers in them to ensure things happen when they should and so you can convert time to distance. A radar mile is 12.36 microseconds. "Something" is putting noise on the screen between 60 and 120 microseconds [a guesstimate] after every transmitter pulse regardless of where the antenna is pointing.
You have the choice of being practical, like me, and say that is most likely to be internally generated or can be a whacko conspiracy theorist, like you, and believe what you wish to believe.
