Abstract: A method of measuring the reflectivity of a region of an article to electromagnetic radiation, in particular for the characterisation of the radio-frequency (RF) properties of wind turbine blades. The article (10) is arranged in the near-field of a transceiver antenna (4), which performs both illumination and measurement of reflected radiation from the region of the article the article undergoing measurement. The method is beneficial in that it can be used with an antenna in close proximity (or in contact) to the article to be measured, for example for use in on site measurement of specific regions of a turbine blade.