An update on comparison of site-to-site measurement reproducibility using HP site reference source

In this paper, the authors report the results to date of the current round of reproducibility testing that started in August 2000 and is expected to finish by July 2002. A total of 33 sites have participated in this study, which includes nine 10 M semi-anechoic chambers, sixteen 10 M OATS, and eight 3 M sites. Of the eight 3 M sites, five are 3 M semi-anechoic chambers, and three are 3 M measurements on 10 M sites. The reference site chosen for this year was Liberty Labs in Kimbleton, Iowa, USA. Of the 33 sites, 25 performed at least 4 measurements, with two completing 20 measurements over several days. Statistically, 95% of the standard deviations of the 10 M sites was within +/- 1.6 dB as a maximum from 30 MHz to 1 GHz, with greater than 80% falling in the 0.3 to 0.6 dB deviation for measurements made on the same site over a period of days. Test result differences in repeated EMC tests are partially caused by physical characteristics of the measurement sites and changes or differences in the measurement chain. This program meets the requirements of A2LA and NVLAP for site-to-site comparisons.