Passive and active
RFS was appointed by Electricas de Medellin in January 2005, and immediately addressed the breadth of the project. “While the actual installation work was to be completed by Electricas de Medellin, all other aspects were our responsibility,” says Amauri Soares, Chief Designer with the RFS WINS design group in its São Paulo, Brazil facility. “Our services scope included site surveying of the tunnel, preliminary and detailed RF system design, equipment delivery and site commissioning, along with the technical training of the Electricas de Medellin installation crew.” On the product supply side, RFS not only provided passive, but also the active RF equipment, such as the two 15-Watt FM transmitters, the two mixers, and the 19-inch rack housings.
Broadband performance was an essential feature demanded of the new in-tunnel RF system—specifically, it was required to support services ranging from the initial FM band (88 to 108-MHz) security and information radio services, through to services at 2.4 GHz. “In the longer term, the Antioquian Government has plans to route at least three other services through the system—‘Cellular’ 850-MHz, personal communications services (PCS) 1900-MHz and UHF maintenance crew radio services, most probably on 450 MHz,” Soares points out.
The RADIAFLEX ultra-wideband RLKU series radiating cable has been specifically designed to provide the genuinely broadband solution required in applications such as the Fernando Gómez Martinez tunnel. It boasts a 75-MHz to 2.65-GHz bandwidth, which is understood to be the world’s largest for a radiating cable. The RLKU series is available in a full range of sizes: 1/2-inch and 7/8-inch variants support typical in-building needs, while the RLKU 1-1/4-inch and 1-5/8-inch sizes are ideal for more demanding tunnel-style applications.
Importantly, the cable selected for the Fernando Gómez Martinez tunnel application —the 1-1/4-inch RADIAFLEX RLKU— incorporated RFS’s JFN-series fire retardant polyethylene jacket. This ensured the installation met the specified requirements for flame and fire retardance, plus stipulations that materials be halogen-free and non-corrosive.
Factory acceptance; on-site training
Once all the material for the project— including the almost 10 kilometers (six miles) of RADIAFLEX RLKU, plus transmitters and mixers—were in place at the RFS São Paulo facility, it was time for the factory acceptance test (FAT). Trial systems were set up in the São Paulo facility to replicate the in-tunnel RF installation planned for the Fernando Gómez Martinez tunnel. “Our performance specification demanded a minimum signal level of -100 dBm at any point within the tunnel,” Soares says. “Our design calculations incorporated a safety margin of 10 to 15 dB. The FAT proved our calculations were accurate—we were achieving around -82 dBm in the FATs.”
Meanwhile, RFS addressed the on-site training requirements for the Electricas de Medellin crew. RFS Brazil’s Field Technical Support Officer set out to Medellin. Over the course of one week he trained eight of the Electricas de Medellin installation crew in areas of RADIAFLEX connectorization, installation, general handling and system commissioning. The RFS training service—and the relative simplicity of the demonstrated RADIAFLEX installation requirements—impressed Electricas de Medellin’s Pérez.
“The tasks of connectorization, earthing and clamping were clearly explained to our personnel,” Pérez says. “As a result of the excellent training provided by RFS, we were quickly able to see that the installation of RADIAFLEX was a very easy task, given its ease of handling and practical, plastic clamp anchoring system.”