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848 Airport Road, Walla Walla, Washington 99362 U.S.A.
Tel: +1 509.525.7660 / Fax: +1 509.525.7907
twigwirelesscontrols.com
7.4 TOOlS TO ASSURE lInE-Of-SIGhT (vIEw ShED):
When laying out the field wireless network there are some tools that will save you time and trouble.
1) Simply take a TWIG and a controller to the field and get a signal strength reading. Look at the valve locations at the
farthest distance away and check any area where the TWIG may have some signal obstructions. Be sure the TWIG
signal number is 20 or more.
2) The aerial views and topographic map
data can be used in good mapping pro-
grams to view areas that the antennas can
see. Here are two methods:
Example of view shed: The red area is
shadowed from the controller antenna and
some things can be done to make that area
get the signal better. Options are (a) install
higher antennas (b) locate the controller and
antenna at a higher site or (c) use repeaters.
Controller antenna loca-
tion. Orgin of line of sight
Profile of field topography
Example: Here is a line-of-sight topography profile graph. Making this graph will show up the field
surface area that could have radio blockage. In this example a repeater should be used at the point
where the line-of-sight is blocked. The shaded region is light red and it will likely have weak signals.
A solution is to add repeaters and elevate the controller antenna.
add repeater here
not visible
from antenna
