Hello Experts!
What is meaning of Antenna gain in wireless devices in the sense that antenna is actually a passive device without any external power?
Anything between 1dBi and 17 dBi.
Not concerned with values.
Just trying to understand how antenna can amplify signal without any external power supply?
That gain is not terms of power.
Generally an antenna is omni directional, but whenever you make it directional it shows gain since 1 major lobe is formed and rest lobes gets reduced.
In this sense we are calling it as gain.
Ok… directional gain.
Thanks for clarifying. 
Gain in terms of an isotropic antenna, unit dBi.
Antenna does not amplify signal.
It is just that in some directions of space signal will sum up from multiple antenna elements adding it cumulative.constructively to a high signal whereas in other directions signals from different antenna elements will act destructively will not add up.
Kepp in mind that an antenna can have multiple elements (dipole usually).
Ok. In an omni directional antenna, antenna gain would be almost 0 dB, right?
