The noise figure of an amplifier is defined as the ratio of the S/N ratio at the its input to the S/N ratio at its output. In other words, the noise figure is a measure of the degree by which an LNB degrades the signal-to-noise ratio of the satellite signal as it passes through the device. Noise temperature, is also expressed in degrees Kelvin. This scale is based on the fact that at a temperature known as absolute zero, 0°K (equal to minus 273.16°C or minus 459.72°F), molecular motion ceases and consequently noise disappears.