I am trying to analyze all components in one home-made GPS receiver and I am stuck with figuring out how to determine Noise Figure at the mixer output.
If we are going from the input - ground noise level is at -174dBm and LNA amplifies it with 28dB of gain and adding 0.8dB more, so by now we have: -174+0,8+28.OK, going further - since SAW, COAX and MIXER are attenuating signals they are also attenuating the noise therefore their sign is negative(-174+0,8+28-1,5-3,9-6). What is confusing me is why after RF amplifier MGA-86563 we are not adding +20(GAIN)+2(NF)?
Instead we have: -174+0,8+28-1,5-3,9+20-6+10*log(BANDWITH)=-73dBm.
Why is this wrong: -174+0,8+28-1,5-3,9+20+2-6+10*log(BANDWITH)
What is wrong in my analysis? Did I misunderstood what NF is?
EDIT: I forgot to write +28 in the last expression.