Antenna Gain...What does it mean???
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Yagi Antenna 
YAGI Antenna:
Yagi-8: 8 dBi gain, Multi Element 50 Ohm Co-Phased Yagi assembly,
compact 550 x 108 x 85 mm in size excluding Clamps, weighing only 800 grams.
Fitted with a 600mm 50 Ohm down lead terminating in an 'SMA' male plug.

Technical Specs: Frequency 2.4 to 2.485 GHz, Horizontal Beamwidth of 31.1 degrees,
Mechanical tilt 90 degrees azimuth +20 degrees, Maximum power input 2 Watts.

Can also be used for wireless networking!