For the purposes of Microwave Active Radiometry (1), three noise radiators were developed and tested. One is a conventional noise diode source in a rectangular R-100 waveguide with a 6-dB horn attached, other two noise radiators are made as half-wave dipoles with noise diodes installed. Excess noise ratio and polarization ratio was estimated for the three designs, and the 3-D radiation pattern determined for the dipole models. For evaluation, radiometers operating at 11.5 GHz and 12.5 GHz were used, but some response was also determined with a radiometer operating at 4 GHz.