The final stage of the switchover to digital broadcasts from the Angus television transmitter will begin early on Wednesday.
After the ending of the BBC Two analogue service on August 4, all the remaining analogue channels will be stopped permanently from around midnight.
The Angus transmitter serves most of Angus and Dundee along with parts of Perthshire and Fife.
Anyone receiving its signals should be able to get more than 40 channels on the digital Freeview service.
Its 23 relay transmitters will not be able to carry as many TV channels and they are expected to broadcast only around 15, from the BBC, STV/ITV, Channel Four and Five, although they will also carry radio and text services.
The switch means that anyone who relies on broadcast television and has not yet fitted their set with a Freeview set-top box, or bought a TV with an internal Freeview decoder, will lose all reception.
The changes taking place to the transmitter and its relays mean that all Freeview viewers will need to do a re-scan to pick up their services.
Freeview should be back on air from the Angus transmitter by 6am and also from the Perth and Tay Bridge relays.
The rest of the relays will be upgraded during the day, with Grandtully and Methven expected to be the last added by late afternoon.
Viewers receiving their TV service by satellite or cable will not be affected by the switchover.