An Emco 1 cm diameter loop probe and an Advantest spectrum analyzer, Model R3361A, were used to measure the near-field energy radiated from three different cellular phones. The probe was connected to the spectrum analyzer with a 3 meter length of coaxial cable.

The phone was placed on a wooden table outside the laboratory, with the probe directly over the speaker holes, the position of the phone operator’s ear, when using the phone. A measurement was recorded on the spectrum analyzer, while the phone was operating. The shield was then put in place and, during the same phone connection, a second measurement is made, superimposed on the first.

The reduction in signal strength is determined graphically, that is, the distance between the traces is visually measured against the grid background.

The phones were powered by their rechargeable batteries for these tests and located outside the lab building. Measurements were taken with each phone.

The following instrumentation is used in the measurement of emissions. All test equipment calibration is N.I.S.T. traceable.