Campbell RF451, Инструкция по эксплуатации

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Appendix D. Distance vs. Antenna Gain, Terrain, and Other Factors
D-8
Using the Lpath values from TABLE D-8 , gives:
TABLE D-9. Fade Margin (dB) vs. Distance for 2-Ray Propagation Model in Example #1
Path Type 2 mi. 4 mi. 6 mi. 8 mi. 10 mi. 14 mi. 18 mi. 22 mi. 26 mi. 30 mi.
2-Ray 24 12 5 0 –4 –10 –14 –17 –20 –23
From TABLE D-9 we see that this link should be very reliable up to a distance
of 4 miles and reasonably reliable at a distance of 6 miles. LOS
MAX
for this link
is approximately 9 miles, so it would be possible to increase distance by
substituting higher gain antennas.
Example #2
Base has MaxRad BMOY8905 Yagi, with 50 ft of LMR195 cable on a 30 ft
tower, also a surge suppressor (lightning protection device) with a 0.34 dB
loss; remote also has a MaxRad BMOY8905 Yagi with 5 ft of LMR195 cable
on a 4 ft pole. Terrain is mostly flat, with sagebrush. How far can I go?
Pt = 30 dBm
Lt = 50 ft • (11.1 dB/100 ft) = 5.55 dB
Gt = 9 dBd = 11.15 dBi
Lr = 5 ft • (11.1 dB/100 ft) = 0.55 dB
Gr = 9 dBd = 11.15 dBi
Need to include an additional loss from the surge suppressor:
Lss = 0.34 dB loss.
From Appendix D.3 , Real World Distance Estimates
(p. D-5)
, we know:
Lpath (2-Ray) = 120 – 20log (h
tx
• h
rx
) + 40Log (d) (h in meters, d in km)
Lpath (2-Ray) = 120 – 20log (9.14 • 1.22) + 40Log (1.609 • d in mi)
Lpath (2-Ray) = 120 – 20.95 + 40Log (1.609 • d in mi)
Lpath (2-Ray) = 99.05 + 40Log (1.609 • d in mi)
Using the above equation to calculate Lpath at different distances, gives:
TABLE D-10. Lpath vs. Distance for 2-Ray Propagation Model in Example #2
Distance 2 mi. 4 mi. 6 mi. 8 mi. 10 mi. 14 mi. 18 mi. 22 mi. 26 mi. 30 mi.
Lpath 119 131 138 143 147 153 157 161 164 166
Now we will calculate the fade margin for each distance:
Fade margin = Prx – (–108 dBm)
Fade margin = Ptx – Ltx + Gtx – Lpath + Grx – Lrx – Lss+ 108 dBM
Fade margin = 30 – 5.55 + 11.15 – Lpath + 11.15 – 0.55 – 0.34 + 108