antenna-theory.com

[messi-d]

TX antenna: input power 20dBm(assume perfect match to antenna) 1MHz Channel Bandwidth
TX antenna gain: 8dBi
TX antenna efficiency:-1dB
path loss LOS: 40dB
RX antenna gain: 0dBi(assume perfect match to antenna).. assume RX antenna efficiency 0dB
polarization mismatch: 0dB(same polarization TX and RX antenna)
if you connect the RX antenna to a spectrum analyzer... what will the power measured in the spectrum analyzer be?

[admin]

Just look at Friis Transmission Equation:
http://www.antenna-theory.com/basics/friis.php

Efficiency does not matter since you already have gain (gain=dir+eff)

assuming your pathless factors in the frequency and distance dependence term of Lambda^2/(4piR)^2, then it is simple

Pr = Pt + Gt + Gr + pathloss

=20 + 8 + 0 - 40 = -12 dBm

the bandwidth does not matter for power, that's only for power spectral density