Specifications

MDS 05-3438A01, Rev. E MDS 4790/9790 Series I/O Guide 7
Site Selection
For a successful installation, careful thought must be given to selecting
the site for the master station and the remote radios. Suitable sites should
offer:
• An antenna location that provides an unobstructed path to all the
remote radios in the system
•A source of adequate and stable primary power
• Suitable entrances for antenna, interface or other required
cabling.
These requirements can be quickly determined in most cases. A possible
exception is the first item—verifying that an unobstructed transmission
path exists. UHF radio signals travel primarily by line-of-sight, and
obstructions between the sending and receiving stations will affect
system performance.
If you are not familiar with the effects of terrain and other obstructions
on radio transmission, the following discussion will provide helpful
background.
Terrain and Signal Strength
A line-of-sight path between stations is highly desirable and provides
the most reliable communications link in all cases. A line-of-sight path
can often be achieved by mounting each station antenna on a tower or
other elevated structure that raises it high enough to clear surrounding
terrain and other obstructions.
The requirement for a clear transmission path depends on the distance
to be covered by the system. If the system is to cover only a limited dis-
tance, say 3.1 miles (5 km), then some obstructions in the transmission
path may be tolerable. For longer range systems, any obstruction could
compromise the performance of the system, or block transmission
entirely.
The signal strength at the receiver must exceed the sensitivity limit by
an amount known as the fade margin to provide reliable operation under
various conditions.
Section 10.2, RF Propagation Planning , beginning on Page 95 includes
a detailed discussion of path planning, and should be reviewed before
beginning an installation. Computer software is also available for this
purpose that can greatly simplify the steps involved in planning a path.
On-the-Air Test
If you’ve analyzed the proposed transmission path and feel that it is
acceptable, an on-the-air test of the equipment and path should be con-
ducted. This not only verifies the path study results, but allows you to
see firsthand the factors involved at each installation site.