Analyses of data obtained by high-precision observations at 9.55, 3.33 and 2.0 nm of 18 radio sources, including the sun, the moon, the planets, planetary satellites, asteroids, H II regions, planetary nebulae, and a quasar, provide accurate flux densities for the interpretation of source spectra and the calibration of other astronomical observations. A tabulation of absolute flux densities is presented, and the observational techniques employed are described as consisting of dual-beam observations with an 11-m paraboloid telescope, low-noise beamswitching with a nutating subreflector, and absolute and relative thermal calibrations.