More than 900,000 UK households could be affected by 4G interference to digital TV, according to upcoming Ofcom figures.
Previous figures from the regulator put the worst case scenario at 760,000 households to be affected by 4G mobile. The 800MHz band used by some 4G base stations will be adjacent to the band used for digital terrestrial television, causing interference, according to Ofcom (PDF).
Around 900,000 households will be affected by interference to the extent where a filter will be necessary, ZDNet UK has learnt. A further 10,000 will be affected badly enough to require a change of platform, either to satellite or cable TV. Around 500 households will be affected so badly that technical measures other than a change of platform will be necessary.
The interference could affect blocks of digital channels called 'multiplexes', according to a 2011 Ofcom consultation document. For example, "losing the BBC's main multiplex would result in the loss of BBC One, BBC Two, BBC Three, BBC Four, CBBC, CBeebies, BBC News and BBC Parliament," said the document (PDF).
Mobile operators that win spectrum in a much-delayed auction at the end of 2012 will have to foot the bill to provide technology to interference, the Department for Culture Media and Sport said in a statement on Tuesday.
"There will be some interference when 4G services are rolled out but we will have the solutions in place to eliminate the disruption to television viewers," communications minister Ed Vaizey said in the statement. "More and more of us are using smartphones and tablets to access the internet. Releasing more spectrum is essential to enable industry to meet this growing demand."
Mobile operators will provide £180m funding for a 'help scheme' to provide technology to overcome interference. The operators will also administrate the scheme, said DCMS.
"A number of households may need to change platform, which could mean shifting from DTT to cable or satellite viewing, and this will be funded by the help scheme," said the statement. "For a small number of homes, the provision of filters or shifting to another platform will not solve the interference. In these cases, up to £10,000 per household will be used to find a solution."
The filters will "plug into the back of a TV", a DCMS spokesman told ZDNet UK on Tuesday.
ZDNet UK understands that households that need to change platforms will be eligible for products such as a Freesat set-top box, which retail at around £200. In a worst-case scenario, interference may mean new fibre will need to be laid, or a relay transmitter installed to boost signal range, up to a cap of £10,000 per household.