yagi yuda (88Mhz,1reflector,4director)

Hi every body
i want to Simulate a yagi yuda antenna (one reflector and 4 director)with hfss and unfortunately i dont know what are the differences between reflector and director !
such as materials ...
and until know just i could simulate a Dipole.
please guide me.

read this
http://en.wikipedia.org/wiki/Yagi_antenna

and use this calculator
http://vk5dj.mountgambier.org/Yagi/Yagi.html
from
http://www.educypedia.be/electronics...ulatorsant.htm

pl