The METEK MRR2 Micro Rain Radar is a compact 24 GHz FM-CW-radar for the measurement of profiles of drop size distributions and – derived from this – rain rates, liquid water content and characteristic falling velocity resolved into 30 range gates. Due to the high sensitivity and fine temporal resolution very small amounts of precipitation – below the threshold of conventional rain gauges – are detectable. Due to the large scattering volume (compared to in situ sensors) statistically stable drop size distributions can be derived within few seconds. The droplet number concentration in each drop-diameter bin is derived from the backscatter intensity in each corresponding frequency bin. In this procedure the relation between terminal falling velocity and drop size is exploited. Automatically controlled antenna heating allows operation under icing conditions. Typical applications include the unattended long-term measurement of rain, real time calibration of weather radar, and monitoring of the melting zone.