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RF comms keep trains in touch ‘down under’ Advanced confined coverage technology supports rail tunnel train radio systems below Australia’s new Federation Square. An advanced confined coverage RF solution ensures that trains passing beneath the new Federation Square in Melbourne, Australia, maintain continuous, uninterrupted radio communication. Designed and integrated by Radio Frequency Systems, the turnkey solution is based on its latest broadband radiating cable technology—a technology already in service in rail systems throughout the world. Working with the Federation Square Rail Project Manager, Thiess Infraco, RFS completed the covered area’s RF installation at the end of 2000. 12 CONFINED COVERAGE The new system supports the 400 to 450 MHz train radio systems operating in the rail tunnels passing beneath the Federation Square deck and adjacent roadway. The new RF network interfaces directly with the Metropolitan and Non-Urban Train Radio systems to provide continuous signal coverage under the deck and nearby Princes Bridge for a distance of approximately 580 metres (1,900 feet). The system has been designed to accommodate future coverage expansions. The RFS solution is based upon the company’s radiating cable technology—a technology designed to facilitate radio communications in enclosed environments where RF penetration is severely limited by the surrounding structure. A vital requirement of the new system was that it provide reliable communications in the presence of the high ambient RF signals typically found in large cities. It was also important that the network easily accommodate future coverage expansions and the addition of new wireless services, without compromising the reliability or quality of communications. Additional future services could include commercial paging, mobile telephones, and the State’s Police and Mobile Radio network. “Our solution is based upon RFS broadband radiating cable technology, providing a passive solution that offers optimal system availability,” explained Tony Danino, RFS South-East Asia’s Wireless Distributed Communications Product Manager. “Gaining access to the train tunnels for upgrades or maintenance is difficult. As a result, we believed it was essential to provide a high Mean Time Between Failures (MTBF) ‘future proof’ solution, ensuring we kept any need to access the tunnel in the future to an absolute minimum.” Although the system specification required a bandwidth of 150 to 900 MHz, RFS’s radiating cable can support services from 70 MHz to the 1800 MHz cellular band. This ensures the infrastructure will accommodate additional services well beyond the original brief of train communications, without needing to install additional or replacement radiating cable. As a total turnkey design/install/commission project, RFS scope of supply also includes the head end combiners to support different train radio system signals plus associated The new system supports the 400-500 MHz train radio operating in the rail tunnels beneath the Square and adjacent roadway. power dividers and directional couplers. Small RFS omni antennas are also used in two large void areas of the tunnel, where the mechanical support of radiating cables is difficult. Although other solutions had been proposed, Danino believes the radiating cable architecture provides far greater coverage uniformity, plus the added advantage of its broadband nature. “The inherently high MTBF of the passive system also provides a reduction in life-cycle costs,” Danino concluded.
RFS tools— introducing X-tilt and CELcalc Continuing STAY CONNECTED’s review of the RFS tools software family, we explore the tilt calculation tool X-tilt and RF utilities package CELcalc. In this issue we look at two important software tools from the RFS tools family—X-tilt and CELcalc. Both packages are now available for Palm Operating Systems—any Personal Digital Assistant (PDA) running on the PalmOS can easily run both programs, presenting huge advantages to the travelling RF professional. All RFS tools may be downloaded from the www.rfsworld.com—simply choose ‘software solutions’ at the RFSWorld homepage, then select ‘RF Software’ from the drop down menu. X-tilt X-tilt, the first RFS tool in the series, allows RF engineers to determine quickly and easily the approximate coverage zone for various values of downtilt. X-tilt calculates the coverage of a downtilted antenna where the height above average terrain (HAAT) and vertical 3 dB beamwidth of the antenna are known. With X-tilt, the user simply enters the antenna’s 3 dB vertical beamwidth and its height above average terrain (HAAT). X-tilt then presents a matrix showing where the main beam’s lower and upper 3 dB points will intersect the earth, scaled in miles away from the site. X-tilt also provides a measure of where the beam peak intersects the earth for each degree of tilt. This is provided for each degree of tilt from 0 to 20 degrees. As X-tilt is a simple program, it is based on flat terrain and no obstructions. Most cellular networks are based on line of site propagation, ensuring this ‘flat earth’ approximation is adequate in the vast majority of applications. The user then chooses a value of tilt that provides the desired coverage and enters that value of downtilt into the propagation software. It’s that simple—there is no longer any need to plug complex trigonometric functions into a calculator or iterate through a set of guessed tilt values! The user’s propagation software can then be used to complete the design using tilt values providing optimal coverage. The CELcalc downtilt calculator determines the lower, centre and upper 3 dB point plus radio horizon of a given antenna and tilt. SOFTWARE 13 RFS CELcalc provides handy calculation of VSWR, return loss (dB), percentage reflected power and reflection loss. CELcalc also offers a wide range of handy unit conversions for the RF engineer. CELcalc CELcalc provides a handy ‘grab bag’ of calculations and conversions for the busy RF engineer. These include: • VSWR, return/reflection loss: Calculates Voltage Standing Wave Ratio (VSWR), return loss (dB), percentage reflected power and reflection loss (dB) based on known forward and reflected power. • Wavelength calculator: Calculates wavelength in inches, feet and metres, based on the known carrier frequency. • Antenna vertical isolation: Determines an approximate measure of isolation in dB, based on the known vertical separation distance and frequency. • Antenna horizontal isolation: Provides a measure of horizontal isolation between two antennas (in dB), based on their separation distance, gain and frequency. • Conversions: dB/Watts/Volts conversions, plus VSWR/dB return loss and Celsius /Fahrenheit. • Downtilt: Calculates the location of the main beam’s centre, and lower and upper 3 dB intersect points (in miles and kilometres), based on the antenna’s HAAT, vertical beamwidth and nominated downtilt. Minimum system specifications: Both CELcalc and X-tilt may be used on an IBM compatible PC 486 or better, running Windows 95 operating system or above. The user must have installation rights (administrator) on the machine.
Page 1 and 2: The Radio Frequency Systems Bulleti
Page 3 and 4: IMPRINT Happy 3rd anniversary STAY
Page 5 and 6: RFS dual band & broadband 3G antenn
Page 7 and 8: New office heralds South African bu
Page 9 and 10: use the 2.5 to 2.7 GHz range; or to
Page 11: Photos by Sergei Karpuchin. © Reut
Page 15 and 16: Performance milestones RF cable tec
Page 17 and 18: operational windspeed for this size
Page 19 and 20: It’s show time! Radio Frequency S

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