When the first cars drive through the Fehmarn tunnel in 2029, they will not lose connection to mobile phones or car radios. This is what engineer and independent telecommunications analyst Torben Rune says:
– In tunnels, safety always has the absolute top priority. And both mobile phones, mobile data, and car radios are vital in a possible emergency, he says.
Takes over the car radio in an emergency
It goes without saying that it is important to be able to call for help if you have a traffic accident in the tunnel, especially since the emergency telephones along the motorway were abolished many years ago. But in the event of a major emergency, where it becomes necessary to evacuate the tunnel, the car radio plays an important role. Here, the traffic control in the tunnel can “take over” the car radio via RDS (Radio Data System) in the same way that traffic information can be sent out to motorists today.
FM radio 40 meters down
Det forudsætter naturligvis, at der er radiodækning i tunnelen, og det er ikke helt så ligetil. Det vil man vide, hvis man for eksempel lytter til sin bilradio, når man passerer under eksempelvis Guldborgsundtunnelen mellem Lolland og Falster. Så mister radioen nemlig signalet cirka midt i tunnelen. Det kan man leve med i en tunnel på beskedne 460 meter som Gulborgsundtunnelen. Men i en tunnel på 18 kilometer, 40 meter under havoverfladen, så er radiodækning kritisk.
Advisor at Silvertown
Torben Rune has just returned from the Silvertown tunnel project in London, where he is an external advisor:
– On Thursday (September 29, 2022, ed.) they had drilled 20 of a total of 1,400 meters, so there is still a long way to go, and it bears no comparison with the Fehmarn project. But we are in the process of technical planning, he says.
Antenna cable with holes
In tunnels, a technology called radiating cables or leaking coax is used. In practice, it is a long coax cable, like the ones we know from the old antenna cables, with a lot of holes in it. When you send the radio signal through the cable, it will radiate through the holes. The signal that radiates out is not very strong. But since the distance to the receiver is also very short, the signal will be strong enough to reach the car radio or mobile phone. This way, the cable will function as one – very long – antenna.
Reliable and fireproof
As safety is the top priority, all cabling must be reliable. The cables must also be made of fireproof material.
No WiFi above 50 km/h
The FSC consortium, which will provide radio coverage in the Fehmarn Tunnel. Must establish both mobile coverage, WiFi, FM, DAB, and GPS coverage under the Fehmarn Belt. However, motorists or train passengers will not be able to use WiFi. It does not work if you move more than 50 kilometers per hour. In return, the technical installations will communicate with each other and the outside world via the wireless network.
