Further Analysis of the Off-Null Versus Power Ratio Method of Attenuation Measurement (Correspondence)

Analysis of calibration data of a rotary-vane attenuator has yielded closer agreement between the recently developed off-null and the proven power ratio methods of attenuation measurement. A constant bias was discovered in the measured valures of attenuation difference, and a procedure is described to correct for this bias. After the correction is applied, the average agreement between the two methods of measurements is improved an order of magnitude, namely, from a former 2.0 percent to 0.17 percent.