Diffraction plays an important role in determining the RCS of a body. At some frequencies, typically low frequencies, diffraction can dominate the scattering process. This work examines the effects of diffraction on ultrawide band (UWB) radar pulses. We measured the RCS of three different size square aluminum plates using a UWB pulse and broadband sampling oscilloscope. We used a bistatic measurement configuration with a bistatic angle of 10.58 deg. The plates were rotated from -90 deg to +90 deg in 2 deg increments (angles relative to the center line of the bistatic configuration). Diffraction patterns for each plate are plotted and the time domain wave forms are analyze. We find that the smallest plate has a significant amount of diffracted energy even in its specular reflection lobe. The largest plate is relatively free from diffraction. Travelling waves and late time resonances are observed for the plates.