As summer returns to many parts of the UK, broadcasters are warning of a side-effect that may stop you watching TV.
- Atmospheric conditions may result in TV and radio interference affecting Freeview TV. It may affect your FM/DAB radio reception, too.
- This may result in the temporary loss of services, or an increased risk of picture/sound glitches. Don’t retune.
- Eastern England most likely to be affected, but unstable reception conditions are set to last until the weekend.
- Such interference is more widespread now thanks to more intense usage of frequencies.
The BBC and Freeview are warning viewers that the current spell of fine weather may result in problems receiving terrestrial TV and radio services.
This is a result of co-channel interference from more distant transmitters, which can become more severe under high pressure weather patterns.
Broadcasters advise viewers not to retune during this time, as reception will return back to normal when weather conditions change. Signals may fluctuate at various times of the day while the current weather persists.
▶ What is co-channel interference? Co-channel interference occurs when signals from a more distant transmitter are boosted by atmospheric conditions. When they use the same frequencies as those used by your local transmitter, they can interfere with your reception. Under normal weather conditions, terrestrial TV and FM/DAB signals rely on line of sight or near line of sight to the transmitter. Under high pressure, tropospheric ducting can cause the signals to be bounced over the horizon and received many miles outside of their intended coverage area.
Worst hit areas
Parts of Eastern England may see some of the strongest levels of interference, which may result in viewers inadvertently receiving TV and radio signals from continental Europe. The south coast is expected to see worse than usual interference levels. But there is a warning that reception troubles could crop up in most parts of the UK.
In the days of analogue TV, high pressure weather conditions would result in some viewers seeing horizontal lines over their picture. This was known as the ‘venetian blinds’ effect. On digital TV, interference is manifest through pixelation, glitches and loss of signal.
Worse than before
And the problem has got worse over the years, as the number of frequencies available for terrestrial TV services has reduced to make way for new 4G and 5G mobile services.
This has increased the number of transmitters forced to operate on the same frequencies, potentially causing interference when atmospheric conditions reflect the signal further.
Arguably, the broadcasters are not too fussed about it, as they’re keen to get viewers switching over to their streaming services. Both the BBC and Freeview are advising viewers of streaming services as an alternative method of access.
But what can also affect TV and radio signals can also affect mobile signals which use some of the frequencies previously used for TV. Some areas with a marginal phone signal may see variations in their reception. And there’s an increased possibility of inadvertent roaming in coastal areas of South East England.
Satellite and cable based platforms are not affected.