A Critique on Traceability in Site Validation Measurements

Site validation measurement procedures are specified in ANSI C63.4 and ANSI C63.5 in the US, and CISPR 16 internationally. The metrics for site performance for both standards are the site attenuation deviation (DeltaSA) or normalized site attenuation deviation (DeltaNSA). However, DeltaSA or DeltaNSA measured according to these standards for the same site-under-test are non-unique, leading to ambiguities in the reference for traceability. Because the antennas used for site-attenuation measurements are not specified, the variety of allowed antennas have a non-negligible effect on DeltaSAs. The main variable antenna characteristics which directly influence the apparent site response are differing antenna balun impedances, different near-field coupling effects for different antenna elements, and differing far-field radiation patterns. Results are presented for these influencing factors to show that several dB variations in DeltaSAs can be obtained for the same site. Consequently, it is suggested that standards development organizations (re-)consider specifying and adopting some type(s) of reference antenna(s).