The rotary-vane attenuator as an inter-laboratory standard

A comprehensive report is presented on the measurement and the use of the rotary-vane attenuator as an interlaboratory standard. Methods of attenuation measurement developed at NBS are used to supply data for the evaluation of the deviations from theoretical cos squared law due to rotor misalignment, gear eccentricity, resettability, resolution, and insufficient maximum attenuation. A precision rotary-vane attenuator with an optical readout capable of 1 second of arc angular resolution has an effective attenuation resolution of 0.00005db at a 3-db dial setting, and 0.0005db at a 30-db dial setting. This type of precision attenuator is an effective standard for use in the dual detection microwave bridge measurement system.