A method of determining the performance of an open area test site (OATS) or an anechoic chamber is to perform a site attenuation measurement. The process used is to step a signal source at the transmitting antenna and use a receiver or spectrum analyzer at the receiving antenna. The two are stepped together to give a set of data that shows the performance of the test site or chamber. ANSI C63.4 outlines the process for performing normalized site attenuation (NSA) measurements. In these measurements, the spectrum analyzer controls the signal source.
Control of low audio frequency magnetic fields from cables, as required by some spacecraft EMI control standards, is best implemented as a conducted emission measurement, but these may require exceptionally efficient transducers and techniques, which are discussed herein.