Page 82 - Сигурност и отбрана - брой 1 - 2025

Сигурност и отбрана, брой 1, 2025 г. Научно списание

GHz), RFD900+ (900 MHz), and TBS Crossfire (868 MHz) (see Table 6,
Table 7, Table 8).

Table 6. Path Loss and SNR Calculations for the XBee PRO S2C (2.4
GHz) Telemetry Module

S/S Distance (m) Path Loss (dB) SNR (dB)
1. 100 80.05 37.95
2. 200 86.07 31.93
3. 300 89.60 28.40
4. 400 92.10 25.90

5. 500 94.03 23.97

Table 7. RFD900+ (900 MHz) path loss and SNR calculations for the
telemetry module

S/S Distance (m) Path Loss (dB) SNR (dB)
1. 100 71.22 46.78
2. 200 77.24 40.76
3. 300 80.76 37.24
4. 400 83.26 34.74
5. 500 85.20 32.80

Table 8. TBS Crossfire (868 MHz) path loss and SNR calculations for the
telemetry module

S/S Distance (m) Path Loss (dB) SNR (dB)
1. 100 71.22 46.78
2. 200 77.24 40.76
3. 300 80.76 37.24
4. 400 83.26 34.74

5. 500 85.20 32.80

3. Visualization of Distance-Dependent Changes in Path Loss and
SNR in UAVs Using Python
The distance-dependent variation of Path Loss and SNR is illustrated in
the graphs below. These graphs represent real calculations obtained for the
telemetry modules XBee PRO S2C (2.4 GHz), RFD900+ (900 MHz), and
TBS Crossfire (868 MHz). The results show that as the distance increases,
Path Loss also increases, while SNR decreases. Modules operating at lower
frequencies (RFD900+ and TBS Crossfire) are able to maintain signal
quality over longer distances.

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