Further information
Ofcom study

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Thursday, 3rd May 2012
Ofcom publishes feasibility study for rollout of local digi multiplexes

The radio regulator, Ofcom, has outlined ways to ensure that radio listeners can receive local digital radio stations, by a build-out of the transmitter network.

The study - intended as a report-back to Government - makes it clear that people like to listen to neighbouring stations and to catch traffic information on-route. Local DAB - like FM - should provide overlapping signals so that stations broadcasting to adjacent counties stand a good chance of being heard, for these reasons.

The report highlights the requirements for DAB coverage to match that of FM - so that digital switchover can be met - by offering ways that this could be achieved.

It also looks at using block 5A in some parts of the country for local DAB: Oxfordshire, for example, so the risk of interference between multiplexes is minimised (currently blocks 10B to 12D are used to broadcast DAB; Using 5A would require a full scan on a DAB receiver, which may cause confusion to customers with older radio models).

The study also examines in-depth changes that might be necessary to existing local digi multiplexes to make it possible for each local area to get DAB. The report suggests a change to the broadcast block for Manchester from 11C to 10B, London III from 11B to 10B, Liverpool from 11B to 10C, Plymouth from 11B to 10D and Humberside from 11B to 10D. This would put greater geographical distance between blocks, minimising the chances of interference between stations broadcasting on the same DAB frequency.

Responses from multiplex operators and radio groups about combining local digi multiplexes to serve large areas were muted, with stations raising concerns about increased costs and difficulties in carrying local advertisements, if their stations were to serve a wider geographical area.

It was also found that actual DAB signal degrades less than originally calculated over the same distance. The possibility of receiving a robust signal (or getting listenable reception, without the bubbling sound) is much better than was originally predicted: put simply, the signals travel further than first thought, particularly for national BBC and commercial stations. This could reduce the number of transmitters needed to build-out the local network.

This also means that the postcode checker for DAB might be a bit pessimistic on whether you'll get reception.
Possible blocks for local DAB coverage
The report looks at how DAB blocks can be best arranged to cover the UK's population

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