Time variation of the level of electromagnetic field in urban areas with multiple mobile telephone base stations

On measuring the strength of electromagnetic field at high sampling rates to get the average 6' values according to ENV-50166-2, instantaneous variations were found, which cast doubt on the stability of this average in urban areas. To confirm this observation, continuous measurements were recorded over periods of 24 h and 7 days at different places. Clear evidence of a daily cycle was found only in the 7-day series, with rapid changes superimposed on a slower signal. The cyclic variations suggest the measuring period should longer than the prescribed 6'.