Hello,In the antenna datasheet attached we have gain as dbi which mean measured as referenced to isotropic antenna.
how exactly we get from friis fromula in wats into dBi can you show on a numerical example of the antenna below?
Thanks.

 

I don't exactly understand what you are asking. Do you want to know how to convert between dB and scalar gain to be applied to the Friis equation? If so, dB to scalar power is:

\[ G_{dBi} = 10 \times Log( G_{scalar}) \]