Parabolic & dish
Building an antenna
WiFi antenna emits radio frequency electromagnetic energy that can harm human safety. Because of that, there are standards that limits Equivalent Isotropic Radiated Power (EIRP). EIRP is sometimes defined in mW and sometimes in dBm.
Standard or permitted EIRP vary form country to country. There are three main organizations that regulates use of wireless network:
Federal Communications Commission (FCC)
for United States of America
European Telecommunications Standards Institute (ETSI)