What is LNB noise figure and what is a good value?
Noise figure measures how much noise the LNB adds to the received signal, expressed in decibels (dB)-the lower the number, the better the LNB's sensitivity. For modern Ku-band LNBs, a good noise figure is around 0.1-0.3 dB, with premium units reaching about 0.1 dB. C-band performance is instead often specified as noise temperature, where a lower Kelvin value (for example 15-25 K) indicates a better LNB.
Because satellite signals are extremely weak by the time they reach the LNB, any noise the first amplifier stage adds directly limits the achievable signal-to-noise ratio and therefore reception quality in marginal conditions or bad weather. A lower noise figure gives you more link margin, which translates to fewer dropouts during rain and better reception at the edges of a satellite's coverage footprint.
Note that noise figure (dB) and noise temperature (K) describe the same property in different units; a 0.3 dB noise figure corresponds to roughly 20 K. For consumer Ku installations the difference between 0.1 dB and 0.3 dB is usually minor, but in weak-signal or large-network deployments, choosing a lower-noise LNB can meaningfully improve reliability.