User Reference and Installation Guide
3-9
© 2006 Microwave Data Systems Inc. All Rights Reserved.
MDS FOUR.9 Series
05-4561A01, Rev. A
•
Link Distance: Enter distance in miles or kilometers (must select the correct units: miles or
kilometers)
•
Fresnel Clearance Ratio: This is a factor indicating the radio line of sight. A clear radio
line of site has a Fresnel clearance ratio of +0.60. As the curvature of the earth or other
obstacles degrade the radio line of sight, the ratio can drop to –1. A separate spreadsheet
is provided to calculate the appropriate ratio. In this spreadsheet the path length, tower
heights and heights of any obstructions or ridges in the path of the link are entered.
•
Climate Factor: Enter 0.1 for dry, 0.25 for average and 0.5 for humid environments
•
Terrain Factor: Enter 0.25 for mountainous, 1 for average, and 4 for smooth (water)
•
Determine the Length of Interconnect Cable from ODU to SDIDU
TM
: The primary
consideration for the outdoor interconnect cable from the ODU to SDIDU
TM
is the distance
and route between the ODU and SDIDU
TM
. Maximum cable lengths are listed in
176H173H
Table
3-1.
Table 3-1. Maximum cable lengths
Loss at (dB/100 m)
Cable Type
140 MHz
350 MHz
Maximum
Length*
LMR-200
12.6
20.1
100 m
LMR-300
7.6
12.1
165 m
LMR-400
4.9
7.8
256 m
RG-214
8
13.1
153 m
Belden 7808
8.6
14
143 m
* Does not account for connector loss.
The link availability, dispersive fade margin and expected signal strength readings are calculated
based on the entered parameters. Maximum link distances based on the antenna and transmitter
power settings are also displayed.
Summary of Contents for FOUR.9 Series
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