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A Fourier Transform Spectrometer using a 250 Watt Mercury lamp, a lamellar grating and a pumped He-cooled detector is applied to the millimeter wave spectral region. The pure rotation spectrum of CH2F, the transmission of graphite particles in a cloud chamber, the interference on round copper dots and the absorption of iron whiskers have been observed.

The radiant output of a noise tube (C. P. Clare Model TN-167), designed for the 90–140-GHz (3.3–2.1-mm) frequency range, has been compared with that from mercury lamps over the wavelength region from 0.4 to ~6 mm. Lamellar grating and Michelson Fourier transform spectrometers were used in conjunction with He cooled bolometers of NEP from 10^−12 to 10^−14 W/(H_2)^1/2 to measure relative spectral irradiance. With this instrumental arrangement, the radiant power emitted by the noise tube was observed to be less than that from a mercury lamp, at least to a 3-mm wavelength, but it produced less source noise than an ac operated mercury lamp. When the noise tube operating current was reduced, the spectral irradiance peak shifted to longer wavelengths.