Correction to the noise temperature of a waveguide thermal noise generatordue to nonuniform heating of the channel

The correction to the noise temperature of waveguide thermal noise generato rs due to nonuniformity of the heating of the waveguide line is considered. It is shown chat, for a simplified model of a thermal noise generator, the minimum values of the corrections in a copper waveguide with dimensions of 2.4 x 1.2 mm and a waveguide of stainless steel with dimensions of 3.6 x 1 .8 mm amount to 0.05 K and 0.IS K respectively, far a length of the nonunif ormly heated part of the waveguide line of 80 mm.