Viewers may lose some or all Freeview channels in southern England this bank holiday weekend due to high pressure weather conditions. Disruption will then extend to cover areas surrounding the Irish Sea.
Freeview has told viewers not to retune if they lose services.
Atmospheric conditions linked to high pressure can cause TV signals to travel further than normal in a process called tropospheric ducting, interfering with signals from local transmitters. This can result in Freeview signals breaking up or disappearing altogether.
Southern England and areas around the Irish Sea, including parts of Wales and Northern Ireland, will be most prone to interference. But coastal areas everywhere are at increased risk, with signals travelling over the sea creating interference to local services.
- Viewers are advised not to retune, as services will return when weather conditions change.
- Normally, not all channels are affected at the same time.
- Affected viewers can continue watching TV services via streaming or via satellite or cable.
The areas most prone to interference can be predicted by analysing the atmospheric forecasts for the next few days. The interference is also likely to be worse in areas where there is high reuse of the same frequencies. This creates what’s known as ‘co-channel interference’.
This is particularly the case in Southern England. Here, local Freeview transmitters are subject to interference from services from the near continent. Generally, public service channels are allocated frequencies less likely to suffer from interference. The reuse of frequencies has intensified as bandwidth available for terrestrial TV is reduced for 4G and 5G mobile services.
How many people will be affected?
- There’s no clear figure. Each TV aerial set up is different and interference levels will vary, even within the same area.
- Some households need to choose between receiving Freeview from a main transmitter carrying more channels, but more prone to weather-related interference or receiving a local relay with fewer channels, but with a more reliable signal.
- Additionally, there’s no impact for viewers using online streaming, Sky, Freesat or Virgin Media.
While clusters of households in southern England are most prone to interference and it could affect thousands of viewers at any one time, it is highly unlikely that millions of households will lose Freeview reception as a direct result of this type of interference.
The BBC has published a video presented by BBC Weather’s Matt Taylor on why fine weather can cause TV reception problems.
DAB and FM Radio services are also subject to interference for the same reasons.
In the Republic of Ireland, cross-border Freeview reception and local Saorview reception may be impacted in some locations. With the Republic only having two terrestrial TV multiplexes, the risk of interference is reduced, but not completely eliminated.