In areas of high atmospheric pressure, or atmospheric turbulence caused by very heavy rain, the effective range of signals between transmitters can be reduced, so the terrestrial transmission chain is broken. This usually occurs when the lower atmosphere is stable, but the middle and upper atmosphere is unstable. This is most pronounced at night and also ahead of warm fronts.
Alternatively, there may be a technical fault in your local area. Your local transmitter will detect this and, rather than show a blank screen, will default to programming from the London region which has been sent to your local transmitter via satellite.
Note: The BBC News channel simulcasts with BBC One at certain times of day. If BBC One shows local news during these times, BBC News - which has only one nationwide feed - shows BBC London programming.
For further help you can Contact Us.
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