1. How antenna gain is related to signal strength & Communication between 2 antennas 2. What will happen if 3dB antenna is put under communication with 12dB antenna? Is there any problem in the communication because of different dB values?
Antennae are bidirectional passive amplifiers. The higher the gain the stronger the signal. They also shape the coverage. Having one at 3dB and one at 12dB should not be a problem so long a you are within the legal transmit powers and are getting the desired rates, much like a weaker mobile device connecting to an AP. Go to YouTube and look up Aerohive's Antenna Basics to watch my video explaining antenna theory.