## 3 Results of Case Study Research  
Field measurements of the directional mobile antenna (ERP = 1739 W) at a height of 12 m above the ground showed that the electric field strength rapidly declined with increasing distance from the antenna (Figure 7). An intense decrement of the strength of the electric field is noticeable at 15 m distance from the mobile antenna, where its values are decreased almost by half, from 20 to 11.4 V/m. At 20 m or more from the antenna, the strength of the electric field is not so intense and fluctuates between 10.5 and 7.5 V/m. The maximum electric field strength was measured as 20 V/m and was half of the ICNIRP exposure guidelines. The investigation of the directional mobile antenna (ERP = 1329 W, at 31 m height above the ground) revealed that a more intense and stronger fluctuation of the electric field strength occurred at the height of the mobile antenna's geometric centre: the values of the electric field strength at distances between 1 and 7 m were distributed in the interval ranging between 161 and 35 V/m. On comparing the values of the electric field strength of the directional mobile antenna (geometric centre height = 14 m, ERP = 1739 W) at a height of 12 m above the ground with those of the directional  
Figure 6: The bearing support for the mast: 1. mast; 2. height of fastening system; 3. brace; 4. bearing support branch; 5. length of fastening system; 6. concrete blocks. Figure 7: Distribution of the RF electric field strength of mobile telephony base station antenna (ERP = 1739 W) at different distances. mobile antenna (geometric centre height = 31 m, ERP = 1329 W) at a height of 31 m above the ground, it is noticed that the intensity of the RF EMF parameters varied by a factor of approximately 10 (Figures 7 and 8). The field measurements conducted clearly show that the RF EMF intensity parameters depend directly on the vertical distance from the height of the antenna's geometric centre. The maximum electric field strength was measured as 160 V/m, which was 2.6 times higher than the reference level. Figure 9 shows that the maximum local RF EMF power density (0.98 \(\mu\)W/cm\({}^{2}\)) created by the directional mobile antenna (ERP = 1739 W, height = 12.7 m) in the direction of the main radiation (main lobe) occurs at a height of 1.5 m above the ground and a distance of 50 m. At distances greater than 50 m, the RF EMF power density begins to decrease: at 60 m distance it reaches 0.74 \(\mu\)W/cm\({}^{2}\), at 70 m it is 0.15 \(\mu\)W/cm\({}^{2}\), at 80 m it is 0.13 \(\mu\)W/cm\({}^{2}\), at 90 it is 0.11 \(\mu\)W/cm\({}^{2}\), and at 100 m it is 0.1 \(\mu\)W/cm\({}^{2}\). At a distance of more than 100 m, the electromagnetic power density fluctuates very marginally and is distributed in the interval between 0.05 and 0.1 \(\mu\)W/cm\({}^{2}\). The field measurements showed that the antenna diagram in the vertical plane has a relatively narrow radiation-width radiation slope of 6.8\({}^{\circ}\), which is directed downwards because of the mechanical and electrical downtilt. Accordingly, the greatest power density appears where the main antenna's diagram slip reaches the earth's surface (in this case at a distance of 50 m from the antenna). Obviously, the created exposure limit of the mobile antenna depends on the antenna's ERP and its height above the earth's surface. Figure 8: Distribution of the RF electric field strength at different distances from the mobile telephony base station antenna (ERP = 1329 W). Figure 9: Distribution of the RF power density at different distances from the mobile telephony base station antenna (ERP = 1739 W) and other radio engineering objects (background). In order to determine the influence on the total RF EMF power density values of each mobile antenna technology and the general RF EMR background (radio, TV broadcasting, and other telecommunication antennas are included under \"background\"), investigations were carried out at particular mobile antenna frequencies.