3. Pre-Installation Procedures
3-6
© 2012 Moseley, Inc. All Rights Reserved.
602-16620-01, Rev. A
3.4
Facility Requirements
The site selected to house the DTV LINK should follow conventional microwave practice
and should be located as close to the antenna as possible. This will reduce the RF
transmission line losses, minimize possible bending and kinking of the line, and allow for
the full range potential of the radio link.
The building or room chosen for installation should be free from excessive dust and
moisture. The area should not exceed the recommended temperature range, allow for
ample air flow, and provide room for service access to cables and wiring.
3.5
Antenna Planning
Larger antennas have the advantage of providing narrower beam widths and high
isotropic gain, which yields better link performance (higher fade margin, better
availability), and improves immunity to spatial interference (due to the smaller beam
widths). However, larger antennas are more costly to purchase and install than smaller
antennas and in some cases, they require special equipment for installation due to
narrower beam widths. They are also more easily affected by wind.
Select where the cable will enter the building from the outside.
Determine the length of cable required. Allow three extra feet on each end to allow
for strain relief, as well as any bends and turns.
3.6
Transmit Power Setup
Setting the transmit power is conditional on the band and application. The
installer of this equipment is responsible for proper selection of allowable
power settings. If there are any questions on power settings refer to your
professional installer in order to maintain the FCC legal ERP limits.
This warning is particularly true for the 5.3 GHz and 5.8 GHz bands and special
instructions are provided below for these bands. For the broadcast auxiliary service (BAS)
applications the power should not exceed that necessary to render for satisfactory
service.
It is also noted that as QAM mode order increases the linearity requirements also
increase. As a rule to maintain requisite signal quality the transmit power should be
lowered 1 dB for every order increase in QAM mode order. For instance, the maximum
power for the EVENT 5800 is 27 dBm in QPSK mode. Therefore the maximum power
backoff would follow Table 3-2 below:
Table 3-2. Maximum Output Power vs. Modulation Order for EVENT 5800
Modulation
Backoff
(dB)
Max. Output Power (dBm)
0.5W Systems
QPSK 0
27
16 QAM
-1
26
32 QAM
-2
25
64 QAM
-3
24
128 QAM
-4
23
256 QAM
-5
22
Содержание Event 5800
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