## 3 Results of Case Study Research
The background RF EMR value was found by subtracting the RF EMR from the mobile antenna at the emitted frequencies from the general RF EMR level investigated. Figure 10 illustrates the contributions to the RF EMR distribution of the GSM-900, GSM-1800, and UMTS-2100 mobile antennas (ERP = 1739 W, height = 14 m) and the background depending on distance. From the figure it is clear that the RF EMR at different frequencies emitted by the directional mobile antenna dominated up to a distance of 90 m. The power density of the background RF EMF contributed approximately 0.01% of the total RF EMR. The biggest part of the RF EMR (up to 72%) consisted of the RF EMF power density created in the radio frequency bands of the GSM-900 MHz and GSM-1800 MHz mobile antenna technologies. The RF EMF power density created in the UMTS-2100 MHz radio frequency bands amounts to about 28% of the general RF EMR. The uneven distribution of the RF EMR of the three technologies depends on each technology's RF EMR effective power: The GSM-900 MHz radio frequency band's ERP is 698 W, the GSM-1800 MHz radio frequency band's ERP is 736 W, and the UMTS-2100 MHz radio frequency band's ERP is 305 W. From the field measurements conducted, it is easy to see that the background RF EMR has an increasing influence at distances of 100 m or more from the mobile antenna: at 100 m distance, the background RF EMR amounts to 7% of the total RF EMR, at 200 m it is 50%, at 300 m it is 58%, at 400 m it is 65%, and at 500 m it is 92%. Background RF EMR consists of television, radio, and telecommunications base station antennas in the vicinity of the investigated area. In order to evaluate the influence of two mobile antennas on the total RF EMR in a particular area, measurements of the RF EMF power density of directional antennas A (ERP = 1329 W, height = 30 m) and B (ERP = 707 W, height = 30 m) were carried out on mobile antennas at a height of 1.5 m above the earth's surface (Figures 11 and 12). The calculated EQ is less than 1 and therefore the environment is considered safe against radio frequency radiation. Figure 10: Contributions of different antenna types to the total exposure. The results plotted in Figure 11 show that the maximum local RF EMF power density created by the mobile antennas are in a 200 m distance, but these exposure guidelines are not as strong as their numerical value (because of the lower ERP and greater height). This influences the form of the mobile antenna's directional diagram in the vertical plane, with the main power density reaching the earth's surface at a distance of 200 m. At distances of 200 m or more from the antenna, the RF EMF power density declines in inverse proportion to the distance from the antenna's geometric centre to the investigated point and fluctuates between 0.25 and 0.03 \(\upmu\)W/cm\({}^{2}\). At greater distances, where the greatest interference by electromagnetic waves, absorption, and reflection occurs, the power density of the RF EMF declines even more intensely. Further away from the mobile antenna's pole axis RF EMF, the power density is distributed gradually at a height of 1.5 m above the earth's surface (this is approximately the height at which mobile telephony are usually used). It is evident that the RF EMR created by mobile antenna A (ERP = 1329 W) is twice as intense as that created by mobile antenna B (ERP = 707 W). It is difficult to evaluate each antenna's influence on the total RF EMR according to a given figure, and therefore each antenna's RF EMF power density distribution layer is presented (Figure 12). Figure 12 shows that in the direction of the main radiation (main lobe) from mobile antenna A (ERP = 1329 W), the RF EMR created by the antenna itself dominates. In the antenna's zone (up to a distance of 50 m), increased background RF EMR clearly dominates comparing to antenna A. This can be explained by the fact that opposite to mobile antenna A (ERP = 1329 W), at a distance of 60 m from it, stands another mobile antenna, whose radiated RF EMF crosses that of the investigated antenna.