About the project
On one of the European rail corridors currently being modernized in Romania - a new line designed for 160 km/h and prepared for the European Train Control System (ETCS) - a 600 m tunnel needed GSM-R radio coverage: the critical communications network that keeps the train driver, the traffic controller and the safety systems permanently connected. Working within an international construction consortium, Claritech was the radiating-cable specialist: design, installation along both tracks and testing.
Project requirements
Inside a tunnel, radio signal does not penetrate - a radiating element must be installed to provide coverage. The standard solution is the radiating cable (“leaky feeder”): a special coaxial cable with calibrated slots that radiates signal uniformly along its entire length.
The cable was positioned at the height set in the design, on the walls of a double-track tunnel, outside the clearance gauge, a few meters from the 25 kV electrified contact line - with a strict earthing regime, surge protection and fire-retardant cabling. At the end of the project, the radio coverage provided by the radiating cable was measured with a signal generator and a portable spectrum analyzer.
Project type
Radiating-cable route design, installation along both tracks and acceptance measurements - as part of an international consortium.
Location
A 600 m railway tunnel on a main line modernized to European standard, with a 25 kV contact line.
Technologies
GSM-R - critical railway communications, on a line designed for 160 km/h and prepared for ETCS.
The solution
~1,230 m of radiating cable
Two 1-1/4” radiating-cable runs, one for each track, mounted on opposite walls of the tunnel - uniform coverage along the full length, in both directions of travel.
Positioned to the design height
Routes designed and executed outside the clearance gauge, with brackets and clamps sized for the railway environment - vibration, air blasts from passing trains, humidity.
Safety next to 25 kV
A dedicated earthing regime, surge arresters at the cable ends and fire-retardant cabling - the requirements of an electrified railway environment.
Continuity at the portals
At each portal, the radiating cable connects to the outdoor radio stations - the transition between in-tunnel coverage and the line’s network happens without any break in communication.
The portal area: the radiating cable and its end equipment, mounted on the tunnel wall.
Runs installed on both walls - one radiating cable for each track.
System commissioning
Every radiating-cable section was verified with dedicated analyzers - return loss and cable-loss measurements, plus radio-coverage checks on each track, against the design parameters. The results were documented and handed over as part of the project’s acceptance file.
Field RX-level measurement: the GSM-R carrier at 925 MHz, received through the radiating-cable system.
What we delivered
| Component | Details |
|---|---|
| Radiating cable 1-1/4” | ~1,230 m, in two runs (one for each track) |
| Tunnel length covered | 600 m, both directions of travel |
| Protection | Surge arresters, dedicated earthing |
| Cabling | Fire-retardant, outside the clearance gauge |
| Verification | Acceptance measurements on every section |
The results
Critical communications without interruption. Continuous GSM-R coverage through the tunnel - the link between the train and the traffic controller stays continuous along the full length of the tunnel.
Executed in a real railway environment. Works coordinated with the line’s construction site, under the safety conditions of an electrified main line (AFER certification).
Detailed documentation. Measurements on every section, included in the acceptance file.
Why Claritech
Radiating cable is one of our specialties: the same technology we install in railway tunnels also covers metro tunnels, underground car parks and technical galleries. See the DAS project portfolio →