The CCEM comparison of microwave attenuation at 60 MHz and 5000 MHz in Type N connected 7 mm coaxial line involved 20 participants with NPL (UK) acting as the pilot laboratory. Two commercial switched attenuators were used as the comparison artefacts, one being selected for having good port matches and the second having matches more representative of a good quality commercial device.

Participants were asked to measure attenuation steps up to a nominal 110 dB, but some were unable to measure over the full range due to the limitations of their facilities. The report contains all reported measurements but, due to size constraints, only a subset are presented for analysis. This analysis covers measurements of the 20 dB, 60 dB and 100 dB steps, these values being chosen to provide measurements at low, medium and high values of incremental attenuation.

It is interesting to note that while there was generally very good agreement (within the reported uncertainties) between the measurements, there was a large variation in the reported uncertainties. Generally, participants with dedicated attenuation measurement facilities reported much lower uncertainties than those who performed measurements using commercial equipment such as vector network analysers. This was particularly noticeable at the higher attenuation steps.

Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).