Left: DSB receiver noise temperature measured with a power meter as a function of LO frequency. The inset indicates the current-voltage characteristics and IF output power responses for hot (red) and cold (blue) blackbody radiations. Vertical bars indicate the minimum and maximum noise temperatures across the IF frequency range based on the measurements from the SPA. Right: DSB noise temperature and IF output power for the hot load recorded with the SPA at LO frequencies of 315, 400, and 460 GHz as a function of IF.