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We report on the fabrication and testing of antenna-coupled niobium bolometers for 10 μm wavelength radiation detection. We use 20 nm thick Nb films on oxidized Si substrates. The bolometer design consists of a 1 μm×1 μm Nb microbridge embedded in either a dipole or a spiral Au antenna. We have performed dark dc tests on devices in vacuum at 4.2 K. Current biased dark measurements correspond well to established theory. This result allows us to extract an upper limit for the value of thermal conductance g (340 nWK-1)-hence an indirect measure of the device bandwidth (0.2 GHz). Measurements under incident black body radiation show that the radiation perturbs the return switching characteristics of the devices.