Hundreds of thousands of televisions in many parts of the Anglia region will need re-tuning if they get their signals from the main Sandy Heath transmitter.
About 1,000,000 homes in Cambridgeshire, Bedfordshire, Hertfordshire and Northamptonshire get their terrestrial television signal from the Sandy Heath transmitter.
Some parts of west Norfolk and west Suffolk also receive signals from Sandy Heath. Satellite and cable television is not affected.
The changes are being made to the transmitter network to transfer some of the frequencies currently used by television to mobile phones.
This is for Freeview viewers and those using other digital terrestrial TV services like BT TV and YouView.
Viewers may need to perform a retune of your set top box on Tuesday.
If you are having TV reception problems after Tuesday 17 July, you are advised to call the Freeview Advice Line free on 0808 100 0288.