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Port tunnel radio reception

  • 18-12-2006 1:27am
    #1
    311
    Closed Accounts Posts: 5,332 ✭✭✭


    I was wondering about the safety broadcasts that will be used in the porttunnel ,I presume normal radio stations will be broadcast through the tunnel ??? so the radio can be left on in the vehicle.

    How can you transmit radio frequencies in such a long tunnel ??


Comments

  • #2
    monkeyfudge
    Registered Users, Registered Users 2 Posts: 23,216 ✭✭✭✭monkeyfudge


    I'd be interested to know what sort of license they are broadcasting under too.


  • #3
    bkehoe
    Registered Users, Registered Users 2 Posts: 2,153 ✭✭✭bkehoe


    Usually something called a 'leaky feeder' is used in tunnels. This is basically a length of coax cable with gaps in the screen which allow the signal to 'leak' out.

    So at one end you've got a transmitter (or transmitters) connected to the cable, and at the other end a dummy load. The ERP of this type of system would be tiny, so it probably isn't an issue with regard to licences.

    For each station being relayed, the tunnel transmitter would use one of the existing alternate frequencies for the station concerned, and would use the stations PI code. This way they can be sure that everyone in the tunnel will be listening to the relayed version. Because of this, they can then take over the broadcast when necessary in emergencies, etc.

    A similar system has recently been installed into the tunnel in Cork.


  • #4
    jmkennedyie
    Registered Users, Registered Users 2 Posts: 678 ✭✭✭jmkennedyie


    Just FYI, there is a sign at the port entrance to the tunnel listing the stations and frequencies that are available inside. Guess one at the other end too. Probably too much info for one sign on a motorway to be honest, but that's a different thread :)


  • #5
    311
    Closed Accounts Posts: 5,332 ✭✭✭311


    bkehoe wrote:
    Usually something called a 'leaky feeder' is used in tunnels. This is basically a length of coax cable with gaps in the screen which allow the signal to 'leak' out.

    So at one end you've got a transmitter (or transmitters) connected to the cable, and at the other end a dummy load. The ERP of this type of system would be tiny, so it probably isn't an issue with regard to licences.

    Thanks bkehoe ,

    Brian.


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