MRV Communications TERESCOPE TS800/155 - Manual (Page 69)

M R V C o m m u n i c a t i o n s , I n c . – I n s t a l l a t i o n M a n u a l
59
Effect of Wind on Terescopes
Introduction
The outdoor environment in which our devices are normally placed exposes the link to wind
pressures that may affect the accuracy of the link’s alignment.
Several factors play a role in the determination of the extent to which the directionality of
a TS device may be affected by the wind:
Wind speed
Wind direction
Surface area of device perpendicular to wind
Mechanical stability of aiming head – device system.
For example, the mechanical stability is greatest along the side-side axis of the device.
Although the surface area along the side of the device is greatest, the resultant wind force
– even at very high wind speeds – will barely have an impact on the beam’s direction, due
to the rigid mechanics along the side-side axis.
Wind Limits for TS Devices
All TS devices have been tested in “worst-case” scenario of the above four factors.
The force necessary to deviate beam was measured from different direction.
From here
1 , the minimum wind speed with maximum effect on beam deviation was
determined.
The following table lists the minimum wind speeds for different TS products that may
cause:
A momentary lapse in the communication.
An extended lapse requiring mechanical repair.
TS Device Momentary Extended
•
10” (E&F models) 110 km/hr 200 km/hr
•
10” with Windproof-L
Accessory
Over 180 km/hr Over 250 km/hr
•
4” (B,C, D models) 150 km/hr Over 250 km/hr
•
4” with Windproof-S 220 km/hr Over 300 km/hr
•
Light (A&C2 models) 150 km/hr Over 250 km/hr
•
PAL (TS1) 180 km/hr Over 250 km/hr
•
8” (Models D2, E2, G) 150 km/hr
1
We include here the formula for calculating the effective wind force on a flat surface, given a known wind
speed:
Wind Force = 0.79 x (Wind Speed)
2
x (Area of Surface)
For instance, assuming a wind speed of 27.78 m/s (equal to 100Km/hr) on a surface area of 0.04m
2
(400cm
2
), the force is equal to 24.4 Newtons.
APPENDIX F