Construction of a replacement TV and radio transmitter for the fire-damaged Bilsdale mast has started.
About 100 people began construction of the new 262ft (80m)-high temporary mast on Monday, operator Arqiva said.
A spokesman said it was hoped to be operational within 21 days and will provide a Freeview TV signal to 90% of those served by the Bilsdale mast, which was hit by a blaze on 10 August.
Meanwhile, services across Teesside were disrupted by work at Eston Nab.
The transmitter near Middlesbrough, which was boosted after the Bilsdale mast fire, was turned off up to 20 times for a minute at a time on Tuesday as Ofcom investigated an interference problem.
The new temporary Bilsdale mast is on land 2,200ft (670m) above sea level and will only operate until winter, Arqiva said.
Paul Donovan from the firm said it was hoped to be up and running within 21 days.
The new mast is being built in a quarry close to the Bilsdale transmitter, which, at 1,032ft (315m) tall, is the 10th tallest structure in the UK.
Construction will involve more than 100 helicopter trips to bring materials to the site, Mr Donovan said.
Once the temporary tower is in place, work will begin on a permanent replacement on the existing Bilsdale mast site.
Work will include excavation of heather, which will be re-seeded in the area later, and installation of stone that has the right levels of acidity for the surrounding environment, Arqiva said.
A spokeswoman said: "Arqiva's priority is now on working with organisations across the affected area including local councils, housing associations and charities to reach and support those who may remain without signal following the mast build, and to prioritise the most vulnerable people affected."
Adrian Twyning, chief of operations at Arqiva, said: "We are working 24/7 to restore services to as many people as possible across the North East and North Yorkshire.
"This is complex work, involving multiple agencies and highly-skilled teams. We are fully committed to the task at hand."
Further advice regarding services can be found here.