Parabolic & dish
Building an antenna
An antenna has three fundamental properties: gain, direction, and polarization.
Gain is term used for measuring of increase in signal power, described in decibels (dB). Antenna with a higher gain is more effective in it's radiation pattern.
Every antenna is designed to raise the power in the wanted direction and reduce it in unwanted directions. Gain of an antenna is reciprocal, meaning it is the same for transmitting and receiving.
Direction is the shape of the wireless signal after leaving the antenna.
Polarization is the orientation of wireless signal relative to the earth. It can be vertical, horizontal, circular or combinations of these. In WiFi networks most signals are vertically polarized.
Objects that reflects signal (metallic, water and glass objects) can affect polarization. Two antennas with similar polarization will inter-operate most effectively.