Helsinki Unriversity of Technology and the Finnish P&T performed 12 GHz radiometer measurements on a satellite link at Kirkkonummi (in Finland) during eleven years 1979-1989. The experimental equipment, measurement theory and different calibrations, for instance the calibration of the effective medium temperature using the attenuation statistics measured with the OTS satellite, are explained. The average annual and worst-month cumulative distributions of atmospheric attenuation and the corresponding conversion factor Q are presented as the longterm results. The standard deviations of the average distributions are also given.