## 4 Application of the Model
### Level 3 Evaluation: Sensitivity of the Receiver  
The reduction in the VHF3 receiver sensitivity in vehicle 1 when it communicates with the VHF4 transmitter in vehicle 2 is evaluated at this level. According to the information listed in Table 5; Table 6, it can be seen that the polarization mismatch loss corresponds to \(L_{\mathrm{C}}=0\) and the feed losses correspond to \(L_{\mathrm{T}}=0.51\) and \(L_{\mathrm{R}}=0.51\). Using remote sensing technology, a satellite map of the area between the two vehicles could be obtained; this is shown in Figure 3. Based on the digital map, a contour map and a topographic profile of the actual communication path between the two vehicles could be \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Device Set** & **FIM** & **TIM** & **RIM** & **SIM** \\ \hline HF1 and VHF3 & Absent & Present & Present & Present \\ VHF2 and VHF3 & Present & Present & Present & Present \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Calculation results. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Device Set** & \begin{tabular}{c} **Fundamental Wave** \\ **Interference** \\ \end{tabular} & \
\begin{tabular}{c} **High-Order Harmonic Wave** \\ **Interference** \\ \end{tabular} &
\begin{tabular}{c} **High-Order Intermediation** \\ **Interference** \\ \end{tabular} \\ \hline HF1 and VHF3 & Absent & Present & / \\ VHF2 and VHF3 & Present & Absent & / \\ HF1,VHF2 and VHF3 & / & Present \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Calculation results. obtained; these are shown in Figures 4 and 5. The model diagram of the actual communication path between the two vehicles is shown in Figure 6. The actual communication distance can be given by the following Equation (26). \[d=\sqrt{\left[(h_{ar}+H_{\mathrm{v1}}+H_{\mathrm{1}})-(h_{at}+H_{\mathrm{v2}}+H_{ \mathrm{2}})\right]^{2}+{D_{t}}^{2}} \tag{30}\]  
Figure 4: Contour map of the actual communication path. Figure 3: Satellite map of the area between the two vehicles. Here, \(H_{\text{v1}}\) is the height of vehicle 1, \(h_{\text{v2}}\) is the receiving antenna's height, \(H_{\text{1}}\) is the altitude at which vehicle 1 is located, \(H_{\text{v2}}\) is the height of vehicle 2, \(h_{\text{at}}\) is the transmitting antenna height, \(H_{\text{2}}\) is the altitude at which vehicle 2 is located, and \(D_{\text{t}}\) is the topographic distance. The radio wave propagation loss in free space was calculated between two vehicles using Equation (12). The Egli model was used to calculate the propagation loss of the two vehicles using Equation (13). Based on the topographic profile, the propagation loss between the two vehicles on real terrain was calculated using Equations (12) and (30); the results are shown in Figure 7.  
The actual power received by receiver VHF3 was measured at different topographic distances, as shown in Table 9.  
Figure 6: Model diagram of the actual communication path. Figure 7: Comparison of propagation loss under three conditions. The received power of the receiver was calculated according to the free-space propagation loss and the actual terrain propagation loss, and the received power was compared with the actual measurements, as shown in Figure 8.  
Figure 8 shows that the error between the calculated power received by the receiver in free space and the real measurement is 3.03%. The error of the calculated power received by the receiver in the actual terrain and the real measurement is 2.06%. The error was reduced by 0.97%. When the communication distance is greater than 20 km, there are large errors, and there are even errors when the Egli model is used to calculate the propagation loss and the received power at the receiver. This is because the Egli model is not suitable for communication regions with large terrain fluctuations.