Why can't I use a mobile phone on the Underground?

Asked by: Sam Short, Enfield

Mobile phones operate on a high-frequency signal that's easily blocked by soil or concrete. Signals further down the spectrum travel relatively unhindered. For instance, medium wave radio stations can be heard in motorway tunnels, while higher-frequency FM stations cut out. Mobile phones operate in an even higher range and can't work underground without a prohibitively large networkof repeaters to maintain consistent coverage.

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