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Chapter 3: System planning
ODU and external antenna location
Find a location for the ODU (and external antenna for connectorized units) that meets the following
requirements:
•
The equipment is high enough to achieve the best radio path.
People can be kept a safe distance away from the equipment when it is radiating. The safe separation
•
distances are defined in
•
The equipment is lower than the top of the supporting structure (tower, mast or building) or its lightning
air terminal.
If the ODU is connectorized, select a mounting position that gives it maximum protection from the
•
elements, but still allows easy access for connecting and weatherproofing the cables. To minimize cable
losses, select a position where the antenna cable lengths can be minimized. If diverse or two external
antennas are being deployed, it is not necessary to mount the ODU at the midpoint of the antennas.
ODU wind loading
Ensure that the ODU and the structure on which it is mounted are capable of withstanding the prevalent wind
speeds at a proposed PTP 550/550E site. Wind speed statistics should be available from national
meteorological offices.
The ODU and its mounting bracket are capable of withstanding wind speeds of up to 325 kph (200 mph).
Wind blowing on the ODU will subject the mounting structure to significant lateral force. The magnitude of
the force depends on both wind strength and surface area of the ODU. Wind loading is estimated using the
Force (in newtons) = 0.5 × ρ × V
following formulae:
•
o
"ρ" is the density of air = 1.225 kg/m
"V" is the wind speed in meters per second,
o
o
"A" is the projected surface area of the ODU in square meters, and
o
"C
" is the drag coefficient = 1.385.
d
The drag coefficient has been measured when the cover plate or antenna is perpendicular to the airflow.
Applying these formulae to the PTP 550/550E ODU at different wind speeds, the resulting wind loadings are
shown in
Table
29.
Table 22 ODU wind loading (newtons)
Type of ODU
Integrated (23 dBi)
Connectorized
Equivalent results in US customary units are shown in
Table 23 ODU wind loading (pounds-force )
Type of ODU
Calculated distances
on page 4-65.
2
× A × C
d
3
,
Max surface
area (square
meters)
0.130
0.051
Table
Max surface
area (square
feet)
Page 3-24
Wind speed (kilometers per hour)
225
250
275
308 N
380 N
460 N
169 N
208 N
253 N
30.
Wind speed (miles per hour)
140
155
170
Site planning
300
325
547 N
643 N
300 N
353 N
185
200
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