Stable broadband variable noise source for microwave radiometry

A stable broadband microwave reference noise source has been designed using, as radiating elements, carbon-filament indicator lamps mounted in a waveguide. When used as a reference in an accurate radiometer, in place of a gas tube and attenuator, this source has a number of advantages. It is electronically controllable, insensitive to ambient temperature changes and the output may be set to match exactly any hot-load absolute standard of noise.