MDS 05-3627A01, Rev. D
LEDR Series I/O Guide
9
The requirement for a clear transmission path depends upon the distance
to be covered by the system. If the system is to cover only a limited dis-
tance, say 5 km (3.1 miles), 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 receiver sensitivity
by an amount known as the fade margin to provide reliable operation
under various conditions.
Detailed information on path planning should be reviewed before begin-
ning an installation. Computer software is also available for this purpose
that can greatly simplify the steps involved in planning a path.
Microwave Data Systems offers path analysis (for paths in the USA) as
an engineering service. Contact the factory for additional information.
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.
The test can be performed by installing a radio at each end of the pro-
posed link and checking the Received Signal Strength Indication (RSSI)
value reported at the front panel LCD screen of each radio. If adequate
signal strength cannot be obtained, it may be necessary to mount the sta-
tion antennas higher, use higher gain antennas, or select a different site
for one or both stations.
A Word About Interference
Interference is possible in any radio system. However, since the LEDR
radio is designed for use in a licensed system, interference is less likely
because frequency allocations are normally coordinated with consider-
ation given to geographic location and existing operating frequencies.
The risk of interference can be further reduced through prudent system
design and configuration. Allow adequate separation between frequen-
cies and radio systems.
C/I Curves
A carrier to interference (C/I) curve can help in frequency and space
coordination. The information in this curve can aid greatly in helping
plan geographic locations and frequency usage for radio systems. Con-
tact the factory for additional information on carrier to interference
curves. A white paper (publication no. 05-3638A01) on the subject is
available from MDS at www.microwavedata.com. Search for the term
“LEDR” under the manuals download area to see this, and all other pub-
lications pertaining to the LEDR series.
