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Long distance hops
 The resulting network utilizes frequency channels in the 5-GHz band
for all links, except for the initial link between Jinan
and the first peak at Juezishan. For this short five-kilometer (3-mile) hop,
the 11-GHz band was used. Most of the hops span much greater distances, with
three of around 100 kilometers (62 miles) through mountainous territory. “These
are very long distances for digital microwave point- to-point links,” says
Fei, “and they required some special engineering.”
Common techniques used to improve the signal-to-noise ratio for very
long hops are space and/or frequency diversity. The hop essentially consists
of two parallel point-to-point links, operating on different channels within
the band, and separated by a vertical distance of about 10 meters (33 feet).
For the Shandong Broadcast microwave backhaul network, a combination of
space and frequency diversity were used for all hops greater than 35 kilometers
(22 miles) in length.
The RFS antennas used in the installation were predominantly 10-foot
single-polarized high-performance microwave antennas, optimized for use
in the 5-GHz band (model DA10-44AD). In addition to a robust and wind-resistant
construction, these antennas feature low voltage standing wave ratio (VSWR)
feed, planar radome, and shroud for improving side lobe suppression. More
than 30 antennas were deployed throughout the network in varying combinations
of vertical and horizontal polarization.
Lengths of RFS FLEXWELL premium elliptical waveguide EP46J connect
the tower-mounted antennas with the Alcatel LSY 9600 radio in the
equipment room at the tower base. Featuring superior transverse stability,
flexibility and crush strength, the FLEXWELL waveguide was installed in
continuous lengths between 50 and 100 meters (164 to 328 feet)— depending on
the height of the tower—eliminating flange discontinuities and facilitating
installation. The premium version is specially designed for high-
capacity radio systems, where low loss and a very low VSWR is required.
Total system optimized
The complete RFS system—from the output of the radio to the antenna—was
fully optimized to meet the technical specifications determined by Alcatel
Shanghai Bell. According Fei, RFS won the contract based on the superior
performance of the complete system, which offers unsurpassed reliability
and longevity. “RFS also provided supervision on site to ensure the
installation team was correctly instructed in how to assemble the system,” Fei
says. “This included mounting of the antenna in the correct position
and techniques for connecting the waveguide.” Installation took a
total of 21 days, with another day for testing and commissioning at each
site.
The network finally went on-air in April 2005, and is currently supporting
the existing analog television services. “The system is performing
very well,” says Fei. “It has all the capacity it needs and
more. Now Shandong Broadcast is one step closer to realizing the full potential
of DTV.”
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