#### Example 4.1 | #### Question 4.2 Question 4.3

## Sources of noise – thermal noise

#### The average power attributable to thermal noise is: #### Thermal noise Nav = kTB #### where k is Boltzmann's constant = 1.38 x 10–23 watts/Hz/oK, T is the absolute temperature in oK, and B is the bandwidth in which the measurement is made.

#### Thermal noise can clearly be reduced by cooling the noise source and this very principle is being applied in some radio receivers using cryogenic coolers, to improve the receiver sensitivity. |