i don’t wan’t to be rude but please consider Google first next time.
It really takes us a lot of time to answer such really simple questions that are not at all Specific to othernet. At least that is my standpoint.
I linked the Wikipedia article about LNBs to you above (26 days ago) that answers a lot of questions regarding LNBs, inlcuding noise figures. Quote wikipedia: “The ideal LNB, effectively a perfect amplifier, would have a noise figure of 0 dB…”