The path loss observed over a height scan yields insight into the nature of imperfections in the test environment used for the measurement of emissions

The quality of a test site is determined by conformance of measured normalized site attenuation (NSA) to specifications cited in ANSI C63.4-1992. Celebration is appropriate if the data is within the +/-4 dB limits. More work is required if the site fails to meet the specification. Data which is ignored during the required search for the maximum signal needed to determine the NSA may prove useful in identifying the nature of the problem. The theoretical height scan response is described in this paper. Measured data obtained from an open area test site and three 10 meter absorber lined chambers are presented and analysis of the results leads to a new postulate for the operating principles of absorber lined chambers