What is the noise figure of a receiver?

All electronic components naturally generate a certain amount of thermal noise. The noise figure of a receiver is a vital metric that describes exactly how much internal noise the receiver's components add to the incoming signal. Technically, it is the ratio, expressed in decibels (dB), of the actual noise generated by the receiver compared to the theoretical minimum thermal noise at a standard room temperature. A lower noise figure means the receiver is 'quieter' and better at hearing weak signals. Distractors often incorrectly compare this to atmospheric noise. Atmospheric noise varies wildly by frequency and weather, making it useless as a standard benchmark for measuring internal receiver hardware performance.