Northern Ireland households with Freeview boxes that were previously unable to pick up Channel Five will be able to from tomorrow — but they will lose two other channels in the process.

Thousands of Freeview viewers will have to retune their set top boxes tomorrow as part of a UK-wide exercise to make the service available to more people.

Around 500,000 Freeview households in the UK do not receive Channel Five, including many in Northern Ireland.

To rectify the situation the free-to-air service has had to make changes to the frequencies used to broadcast more than 50 TV channels and 20 radio stations to aerial rooftops across the country.

These changes are also being made to pave the way for high-definition TV channels.

However, the national retune will make some older set top boxes redundant and will result in the loss of ITV3 and ITV4 for some 460,000 viewers. In Northern Ireland 89% of the population has digital TV — of those 36% have Freeview on their main television set.

And while there have been some reports that all set top boxes will stop working unless they retune, a spokeswoman from the organisation told the Belfast Telegraph that this was not correct.

Viewers just won’t be able to receive Channel Five unless they retune, she said.

The digital TV set top boxes that will cease to work from Wednesday are the Daewoo DS608P, the Labgear DTT100, the Triax DVB 2000T, and the Portland DP100.

Combined set top box and video recorders that will not work are the Daewoo SV900 and the Bush IDVCR01.

The switch will not apply to viewers who receive their TV and radio channels from Sky and Virgin Media set top boxes, nor those who have tuned into the Freeview satellite system.

In Northern Ireland there are three TV transmitters which broadcast Freeview to 58% of the population. The Divis transmitter which covers the greater Belfast area covers 508,000 homes.

The Limavady transmitter which transmits Freeview to the North West covers 104,000 homes, and the Brougher Mountain transmitter which transmits to the Enniskillen and Omagh areas covers 37,000 homes.

People who are not covered by one of these three transmitters receive part of the Freeview service via one of the 43 relay transmitters.

The retune will also see the launch of a new channel called Quest, which has been described as a mix of factual lifestyle and entertainment programmes from the archives of the Discovery Channel.