This report presents details of the performance of broadband radiometers the the southern Great Plains (SGP) cloud and radiation testbed (CART) site to estimate the uncertainties of irradiance observations. Net radiation is observed with net radiometer in the energy balance Bowen ratio station at the central facility and compared with the net radiation computed as the sum of component irradiances recorded by nearby pyranometers and pyrgeometers. This paper observes the uncertainties of readings from net radiometers which are known to be substantial