 Clutter may also be returned from man-made objects such as buildings and, intentionally, by radar countermeasures such as chaff.Some clutter may also be caused by a long radar waveguide between the radar transceiver and the antenna.In a typical plan position indicator (PPI) radar with a rotating antenna, this will usually be seen as a "sun" or "sunburst" in the centre of the display as the receiver responds to echoes from dust particles and misguided RF in the waveguide.