The accuracy of ozone measurements in the middle atmosphere is of great importance when determining its diurnal variation. A high time resolution of the measured data is desirable and depends on the sensitivity of the receiver used to detect the ozone. This thesis aims to improve the sensitivity of a groundbased 142 GHz microwave radiometer used for measuring atmospheric ozone data. This is done by replacing the previous receiver components with a series of new components and arranging them in different setups for comparison purposes. Mechanics and wiring were changed in order to install the setups along with changes in the optics. Each test setup could be implemented as a first step towards improving the sensitivity of the radiometer. The result show that the optics contribute with an unexpected addition of noise to the measurements and hence the overall performance and improvement of the radiometer could not be determined. Suggestions are made for further work which include improving the optics and performing cryo-measurements.