I've few doubts in deciding which antenna to use in my project . Please help me 1. How one can know the gain (dB) of an antenna when constructing it & on what basis gain will be calculated? 2. What will happen if two antennas of different gain (dB) are used at Transmitting & Receiving sides.
those are some loaded questions, and I must say that I am not an expert. I think it's one of those Areas where you either have a mentor or learn from trial and error.
A. You must define the scenario that the external Antenna will be used to solve.
2.How one can know the gain (dB) of an antenna when constructing it Assuming you are not building your own Antenna, You must study the datasheets from the antennae provider, gain, polarity, e-plane, h-plane etc... See if you can get loaners to test with from the Antenna provider of choice, Passive gain is added to the transmit power minus the cable loss, connectors etc...., You must review the regulations for your region when comes to frequency, power levels, etc...
2A.on what basis gain will be calculated? Not sure what you mean? But you select the correct tool for the right job. So if you are doing PTP project of several kilometres distance you need to select the correct Antenna for that purpose.
3. What will happen if two antennas of different gain (dB) are used at Transmitting & Receiving sides? For PTP this is often done to align the Antennae. Once the Antennae are lined up then power can be raised.
There are so many factors to take into consideration that it is difficult to cover them all, but that is why they write books.
Might I suggest reading
CWDP: Certified Wireless Design Professional Official Study Guide