Arqiva now has responsibility for digital networks for all public service broadcasters, having previously announced deals with the BBC and ITV-owned SDN, which broadcasts Five.
The three contracts cover the roll-out of a network to all 1,154 UK terrestrial transmitter sites in preparation for digital switchover.
Under the latest deal, the network will supply 98.5% of the UK population and will carry ITV1, ITV2, ITV3, ITV4, Channel 4, E4 and More4. The contract is set to run until 2034.
Digital 3 & 4's project director Mike Hughes said: 'This all-important contract will mean that ITV's and C4's terrestrial transmission costs will fall compared to today's levels as we transition to a fully digital network.
'This is a complex deal and we have total confidence that Arqiva will deliver according to our needs. It forms a crucial part of the [switchover] project and will ensure that these public-service channels are available to almost everyone in the UK through a roof-top aerial.'
Digital 3 & 4 is a consortium of regional ITV companies and Channel 4.