User Manual

User Reference and Installation Manual 3-8

MDS 5800 II

• Receive Antenna Gain: Enter 23 for the internal antenna or enter the gain of the external

antenna if used.

• 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

: The primary

consideration for the outdoor interconnect cable from the ODU to SDIDU

is the distance

and route between the ODU and SDIDU

. This cable should not exceed 330 feet using

Times Microwave LMR-200 cable. Longer lengths and distances are possible, but require

higher quality cable.

• ODU/IDU Cable Length: Enter the cable length in feet between the ODU and IDU.

Maximum cable lengths are listed in 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.