Televisions in more than 800,000 East Midlands homes may have been affected by work to upgrade transmitters.
Several transmitters, centred on Waltham near Melton Mowbray, Leicestershire, were switched off from midnight.
Anyone affected will need to retune their Freeview boxes to restore services. Some may lose channels for several hours.
The work is being done to improve the 4G mobile phone service.
Waltham, along with smaller relay transmitters at Belper, Stanton Moor and Birchover, serves an area from western Lincolnshire, across Leicestershire and Nottinghamshire and into Derbyshire.
Work was expected to be completed by 06:00 BST on Wednesday at the Waltham mast, noon at Belper and Stanton Moor, and later in the afternoon at Birchover.
Homes using transmitters at Leicester, Derby, Eastwood, Bolehill, Matlock, Darley Dale, Stamford, Little Eaton, Nottingham, Ashbourne, Ambergate, Parwich and Ashford in the Water were expected to lose channels for several hours but would not need to retune.
About 815,000 homes in the region were expected to have been affected.
Television services should display messages warning of the changes.
David Scott, chief executive of Digital UK, said: "It's a good idea to retune your Freeview TV or box regularly to make sure your channel list is up to date.
"It usually only takes a few minutes but if anyone is unsure what to do, there's plenty of information available on our website or from our advice line team."