The STEREO WAVES spectrum demonstrates the directionality of type III radiation. Frequently, the radiation recorded by the Ahead and Behind observatories is quite different.
Reiner et al., 2009 discuss possible beaming patterns, as shown above in a detail of their Fig. 1, for a December 7 2007 type III event. Note that the axis of the type III beam is generally tangent to the Parker magnetic field spiral at the source location.