MDS 05-2806A01, Rev. A MDS iNET 900 User’s Guide 99
5.1.2 Site Selection
Suitable sites should provide:
• Protection from direct weather exposure
• A source of adequate and stable primary power
• Suitable entrances for antenna, interface or other required
cabling
• Antenna location that provides as unobstructed a transmission
path as possible in the direction of the associated station
(s)
These requirements can be quickly determined in most cases. A possible
exception is the last item—verifying that an unobstructed transmission
path exists. Radio signals travel primarily by line-of-sight, and obstruc-
tions between the sending and receiving stations will affect system per-
formance. If you are not familiar with the effects of terrain and other
obstructions on radio transmission, the discussion below will provide
helpful background.
5.1.3 Terrain and Signal Strength
While the license-free 900 MHz band offers many advantages for data
transmission services, signal propagation is affected by attenuation from
obstructions such as terrain, foliage or buildings in the transmission
path.
A line-of-sight transmission path between the central MDS iNET 900
unit and its associated iNET station site
(s) is highly desirable and pro-
vides the most reliable communications link.
Much depends on the minimum signal strength that can be tolerated in
a given system. Although the exact figure will differ from one system to
another, a Received Signal Strength Indication (RSSI) of –77 dBm or
stronger will provide acceptable performance in many systems. While
the equipment will work at lower-strength signals, signals stronger than
– 77 dBm provide a “fade margin” of 15 dB to account for variations in
signal strength that may occur from time-to-time. RSSI can be measured
with a terminal connected to the
COM1 Port or with a HTTP browser to
the
LAN (Ethernet) connector. (See “Antenna Direction Optimization”
on Page 93 for details.)
5.1.4 Antenna & Feedline Selection
Antennas
The equipment can be used with a number of antennas. The exact style
used depends on the physical size and layout of a system. Contact your
MDS representative for specific recommendations on antenna types and
hardware sources.
To Next Page
Loading...
