Campaigners today wage a fight to protect traditional TV and radio amid fears of a looming terrestrial switch off.
Signals through aerials are only guaranteed until 2034 - fuelling worries that services could be wound down from the mid-2030s.
More than 17 million adults in Britain watch Freeview TV through an aerial every week.
A coalition of groups under the Broadcast 2040+ umbrella has written to Culture Secretary Michelle Donelan urging the Government to protect traditional TV and radio services to 2040 and beyond.
The organisation is led by broadcast infrastructure company Arqiva.
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Chief executive Shuja Khan said “broadcast TV and radio are part of the daily routine of tens of millions of people across the UK”.
He added: “Now is a critical moment to guarantee them for the long-term.
“The Government is only committed to these services until the early 2030s - on questions of critical national infrastructure, that is closer than it seems.”
The letter is signed by groups including the Children’s Media Foundation, the Rural Services Network and Silver Voices.
Its director Dennis Reed told the Mirror: “Silver Voices is right behind the Broadcast 2040+ campaign to save Freeview. People don't realise that the future of Freeview TV and terrestrial radio is hanging by a thread if digital and streaming services are given more broadcasting space. "
Viewers who watch TV through satellite or broadband providers would not be affected by a potential terrestrial switch-off because they do not receive channels via an aerial.
A Strand Partners/Arqiva poll of 5,066 voters in 12 key Tory-held seats - six in the Red Wall where Labour is the main challenger and six in the South West where the Lib Dems are the major opposition - found 75% of voters want their MP to “actively support the continued provision of digital terrestrial TV and broadcast radio”.
Two-thirds said it should be classed as “critical national infrastructure”, while 26% were worried about the cost of TV subscriptions - rising to 40% of those on lower incomes.
Half said they could not afford subscription services or do not believe they offer value for money, while 52% were not interested in switching from Freeview to streaming apps.
Conservative MP Selaine Saxby, whose North Devon constituency was one of those surveyed, said local people “rely on their terrestrial TV service”.
She added: “We must protect terrestrial TV services for the long-term, and I will be pressing that case with government.”
Industry regulator Ofcom is currently considering what the UK’s negotiating position will be at next year’s World Radiocommunication Conference, where countries will decide whether the spectrum of radio frequencies currently used for TV broadcasting should instead be allocated to other technologies, such as mobile phones.
Decisions at previous summits led to cuts in the spectrum protected for digital terrestrial TV - meaning more services squeezed into fewer bands.
Experts said the UK would “fight” to “preserve its broadcast services”.
Arqiva added: “To have the technical capacity to deliver these services later down the line, the Government must commit to protect them now and ensure that there is no change in the spectrum allocated to television broadcasting.”
Colin Browne, chairman of the public service broadcasting group Voice of the Listener & Viewer, said only digital terrestrial can guarantee that “viewers and listeners across the UK are able to access high quality television and radio into the future”.
A DCMS spokeswoman said: "Terrestrial TV and radio are hugely important and will continue to be for years to come.
“We're committed to ensuring UK audiences can access these platforms in the long term."
