d : d corresponds to the distance between the device under test and the antennae:

• Industrial environment d=30m
• Domestic environment d=10m

The site where measurements are carried out (Open Area Test Site) must present specific attenuation characteristics :

The ground plane must be at the centre of a free ellipse. The ellipse must present the geometrical characteristics indicated in the graph.

In the site characterisation step, an emitted wave must be measured by the antenna with +/- 4 dB permissible error. The emission antenna must be moved in a given volume during the phase (+/- 0.75m along two directions).

Such measurements are neither possible in the FM (88 to 108MHz) nor in the Television frequency range. Indeed, the levels of these emitters are far higher than the standards.

Another problem in this kind of test site, is the disturbance caused by undesired sources (such as vehicles in the vicinity).

Consequently, measurement can be made in a Anechoic chamber (See chapter 3.3 'Susceptibility'), but distances must be reduced, since a big chamber would be too expensive.