Existing digital television services could be affected by the national switchover to all-digital television, Ofcom has warned.
The communications regulator will review its Code of Practice to govern the switchover to digital and the switch off of analogue television, which will take place from 2008 to 2012. It has outlined some of the problems that could be encountered.
The set up of nationwide digital terrestrial television (DTT) to replace analogue television could affect current DTT services, which only some households use.
"The digital switchover (DSO) programme may affect the coverage of existing DTT and analogue services," said the discussion paper on the Code issued by Ofcom. "Several years before switchover, the existing digital antenna may need to be removed to enable the construction of new DSO-ready antennas (e.g. to make room on the mast)."
There could also be problems with interference as digital signals are broadcast more widely, and into areas where analogue signals are still live.
Analogue switch off will be performed on a region by region basis, according to the ITV franchise areas. The Borders area will be first, in 2008, because it is a relatively self-contained broadcast area. Other areas such as the south east of England are far more complicated because they have much greater population density and because the spectrum used must inter-lock with other countries' spectrum, such as that of nearby France.
"As the regions are scheduled to switch over at different times the transmissions using the new digital switch over frequency channels being adopted in one region may cause interference that would affect the reception of existing DTT or analogue services in another region," said the discussion paper.
Ofcom has announced that it will change its Code of Practice to ensure that problems such as these are minimised. The parties involved have until March to contribute ideas to Ofcom for possible inclusion in the revised Code.
The Code says that where this disruption denies viewers access to television, and where a DTT service will not be available, the operators of the digital television network must offer those people an alternative paid for by the operator. That is likely to be a satellite television service, which does not rely on DTT transmission networks.