Freeview TV signals are once again subject to interference this weekend due to weather conditions.

From Friday until early Monday, TV signals could be disrupted due to atmospheric conditions linked to high pressure systems.

This may cause some viewers to temporarily lose access to some TV channels or see an increase in blocking and glitching. Interference may last anything from a few minutes to a few hours per day.

Initially coastal areas are most at risk. But unstable reception is possible anywhere in the UK by the end of the weekend, until areas of thunderstorms break the weather pattern early next week. In addition to Freeview, weather conditions may affect other radio and terrestrial communications services.

Interference generated by TV signals passing over water to your location is generally strongest in the afternoon hours. This is on top of any normal tidal interference in coastal areas.

Interference from TV signals bending over landmasses tends to be most noticable early in the day.

But if the interfering signal has had to travel over both land and sea, then interference could peak at any time. Local weather and terrain may also affect when it’s worst.

It comes as most of the UK falls under a ‘heat dome’, a scenario where the hot air is trapped in lower layers of the atmosphere by the high pressure sitting above us. The high pressure acts as a lid stopping the hot air rising. This lid, or boundary between air masses, is where TV signals can bounce, causing the problem.

This is slightly different to other instances when atmospheric conditions can affect Freeview. In winter for example, high pressure can cause widespread fog. The fog or low cloud also creates another atmospheric lid associated with an inversion from which TV signals can bounce off.

Normally, TV signals travel in line of sight or near line of sight between transmitter and aerial. During certain atmospheric conditions, TV signals can bounce off the troposphere sending the signal beyond the horizon where it can interfere with TV services in other regions and countries.

Viewers are advised not to retune, as TV reception will return to normal when the weather conditions change.

Retuning may inadvertently cause viewers to lose channels, receive TV services from another region or country – they’ll have to retune yet again when the weather changes to restore their channel list.

In addition to the UK, viewers in parts of the Republic of Ireland may encounter similar issues with Saorview reception, as the heat extends westwards.

It is not a new problem, but broadcast networks are forced to use fewer frequencies than they used to.

When we used to have analogue TV, this type of interference used to manifest itself in the form of horizontal lines, like venetian blinds. Depending on the severity of the interference, the lines were either very faint or quite noticeable upto the point where the interfering TV signal could break through the lines, leading to some viewers suddenly seeing a different TV channel.

In the digital era, interference can be more disruptive and cause sudden and complete loss of signal.

In addition, with the growth of mobile networks, the frequencies are more intensively used. Some former TV frequencies are now used for 4 and 5G services. The frequencies assigned to terrestrial TV have thus reduced, meaning more transmitters over a smaller area have to reuse the same frequencies. This increases the potential for co-channel interference.

Yes, the same weather condition elsewhere in the world can also disrupt TV reception. France is one such example.

But some countries may have fewer terrestrial TV services, requiring fewer frequencies and thus reducing co-channel interference. Other terrestrial TV networks may use a different configuration to broadcast their multiplexes, providing a more robust signal in exchange for less bandwidth (fewer channels). And in some countries, terrestrial TV is only used by a minority, meaning many viewers aren’t impacted. Sadly, this may impact poorer households who can’t afford pay cable or satellite services.

Homes that are often affected by poor terrestrial reception do have the option of switching to Freesat. Or, for those willing to pay for their TV service, Sky and Virgin Media are also unaffected by this type of interference.

RXTV info | Covering the reception and distribution of UK terrestrial TV (Freeview), cable, satellite and connected TV services for users and installers.

Saorview: Irish DTT  | How to manually tune Sky box | Sky Glass channel list |  UHF channels and centre frequencies

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