## 3 Results
### Test 5  
For this test, a directional antenna was used. The ground station antenna was at a height of 3 m and directed towards the UAV with a transmitter module. The parameter setup for the pMDLL2450 modules was the same as that used in Test 4. The measurement location was flat, karst terrain around Konjsko--about 10 km north of Split, Croatia (Figure 12).  
Figure 11: Test 4—The best measured results at ML1, ML2, ML3 and ML4.  
Figure 12: Test 5—Ground station and four measurement locations (MLs).  
Throughput was measured for various distances, UAV altitudes and yaw angles. The measurement results for six different measurement location points are shown in Table 5. From the data presented in Table 5, it can be concluded that this system can satisfy the required throughput for the search and rescue scenario that we presented in this paper. The last measured distance was 6 km from the ground station. Even at that distance, the result obtained for 0\({}^{\circ}\) UAV yaw angle was marginally acceptable. The UAV flight altitude has a significant impact on the throughput. At greater distances from the ground station, the altitude should be higher due to different obstacles and terrain curvatures. The throughput for various distances and UAV flight altitudes is shown in Figure 13. For the targeted 5-km range, the measured optimal height is 90 m. The UAV antenna yaw angle related to the ground station antenna is also an important factor for throughput.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Measurement Location** & **Altitude (m)** & **Throughput (MBps)** & **Angle (\({}^{\circ}\))** \\ \hline \hline \multirow{6}{*}{ML51 (1800 m distance from GS)} & 30 & 1.45 & 0 \\  & 50 & 1.5 & 0 \\  & 50 & 1.9 & 90 \\  & 90 & 1.9 & 0 \\  & 90 & 2.2 & 90 \\ \hline \multirow{6}{*}{ML52 (2590 m distance from GS)} & 30 & 1.65 & 0 \\  & 30 & 2 & 90 \\  & 50 & 1.9 & 0 \\ \cline{1-1}  & 50 & 2.1 & 90 \\ \cline{1-1}  & 50 & 1.9 & \(-\)90 \\ \cline{1-1}  & 90 & 1.9 & 0 \\ \cline{1-1}  & 90 & 2.05 & 90 \\ \cline{1-1}  & 90 & 1.9 & \(-\)90 \\ \hline \multirow{6}{*}{ML53 (3850 m distance from GS)} & 50 & 1.5 & 0 \\  & 50 & 1.7 & 90 \\ \cline{1-1}  & 50 & 1.8 & \(-\)90 \\ \cline{1-1}  & 90 & 1.8 & 0 \\ \cline{1-1}  & 90 & 2.15 & 90 \\ \cline{1-1}  & 90 & 1.75 & \(-\)90 \\ \hline \multirow{6}{*}{ML54 (4550 m distance from GS)} & 50 & 0.75 & 0 \\  & 50 & 0.4 & 90 \\ \cline{1-1}  & 50 & 0.95 & \(-\)90 \\ \cline{1-1}  & 90 & 1.3 & 0 \\ \cline{1-1}  & 90 & 1.3 & 0 \\ \cline{1-1}  & 90 & 1.4 & \(-\)90 \\ \hline \multirow{6}{*}{ML55 (5300 m distance from GS)} & 50 & 1.4 & 0 \\ \cline{1-1}  & 50 & 0.7 & 90 \\ \cline{1-1}  & 50 & 1.1 & \(-\)90 \\ \cline{1-1}  & 50 & 0.9 & 45 \\ \cline{1-1}  & 50 & 1.2 & \(-\)45 \\ \cline{1-1}  & 90 & 1.3 & 0 \\ \cline{1-1}  & 90 & 1.4 & 90 \\ \cline{1-1}  & 90 & 1.2 & \(-\)90 \\ \hline \multirow{6}{*}{ML56 (6000 m distance from GS)} & 140 & 1.3 & 0 \\ \cline{1-1}  & 140 & 0.8 & 90 \\ \cline{1-1}  & 140 & 0.5 & \(-\)90 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Test 5—Measured throughput at six locations for different UAV yaw angles.  
Although the results for all measured location points were not always consistent, in most cases, a UAV antenna yaw angle of 90\({}^{\circ}\) yielded the best results (Figure 14).