Instruction Manual

52
SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System Instruction Manual Date Code 20210405
Appendix C: Link Budget Analysis
Equation 5
Equation 6
Equation 7
Link Budget Calculation Example
The SEL-FR12 antenna is mounted half-way up a utility pole and the SEL-FT50
is located 1.61 km (1 mi) away. There is approximately 40 percent obstruction
within the Fresnel zone. There is also another 900 MHz radio nearby that has
moderate interference.
System
SEL-FT50 Average Transmit Power: +16 dBm
SEL-FT50/SEL-FR12 Receive Sensitivity: –97 dBm
SEL-FT50 Antenna Gain: 0 dBi (integrated into transmit power specification)
SEL-FR12 Antenna: +7.15 dBi
3.05 m (10 ft) of LMR-400 Coaxial Cable: –0.39 dB
Radio Surge Protector (SEL part number 200-2004): –0.25 dB
Path
Obstruction Loss: –5 dB
Polarization Loss: 0 dB
Fading Loss: –6 dB
Interference Margin: –6 dB
Free-Space Path Loss (Equation D.3)
FSPL (dB) = 32.51 + 20log915 (MHz) + 20log1.61 (km)
FSPL (dB) = –95.8 (dB)
Path Loss (Equation D.2)
Path Loss (dB) = –95.8 (dB) – 5 (dB) + 0 (dB) – 6 (dB)
Path Loss (dB) = –106.8 (dB)
Receive Signal Strength (Equation D.5)
RX Signal Strength (dBm) = +16 (dBm) – 0.39 (dBi) – 0.25 (dB) + 7.15 (dBi) –
106.8 (dB) – 0 (dBi) + 0 (dB)
Effective RX Sensitivity (dBm) = –84.3 (dBm)
RX Signal Strength (dBm) TX Power (dBm) Line Loss
FLR
(dBi)
Attenuation
FLR
(dB) Antenna Gain
FLR
(dBi)
Path Loss (dB)
–
Antenna Gain
FLT
(dBi) Line Loss
FLT
–
+
+
––=
Effective RX Sensitivity (dBm) RX Sensitivity (dBm) Interference Margin (dBm)–=
Link Margin (dB) RX Signal Strength (dBm) Effective RX Sensitivity (dBm)–=