Few things are more frustrating than a TV picture that breaks up for no obvious reason. The aerial looks fine, the cable is sound and the weather is calm, yet channels pixelate at random. In many cases the culprit is not your aerial at all but the mobile signals travelling through the same air.
Some 4G and 5G services use frequencies that sit close to those used for digital television. In a dense city like London, with masts on rooftops and street furniture, that proximity can cause real problems. This guide explains why, how to recognise it, how it is fixed and when you need an engineer.
Why mobile signals affect TV
Radio spectrum is shared out between uses, and the mobile networks have been given frequencies close to the top of the television band. Your aerial and amplifier are built to pick up TV, but they are not perfect at ignoring strong signals just outside that range.
When a mobile signal is powerful enough, particularly from a mast close by, it can overload the amplifier's front end. The amplifier then distorts everything passing through it, including your TV channels, and the tuner sees errors.
Freeview now occupies UHF channels 21 to 48, below mobile spectrum released through television clearance programmes. The problem is not that a mobile mast broadcasts a television programme on your channel. Rather, an unwanted strong signal can exceed the handling capacity of receiving equipment, creating distortion or reducing its ability to recover the wanted broadcast.
Signs that interference is the cause
Intermittent pixelation, freezing and sound loss can indicate interference, but none proves a mobile network is responsible. Electrical appliances, damaged screening, weak reception and amplifier overload can produce similar symptoms. Note the timing and affected channels without assuming that evening breakup is caused by busy mobile traffic; measurements are needed to distinguish the possibilities.
Another hint is timing. If trouble started after a new mast or network upgrade nearby, or after you added an amplifier, interference becomes more likely. Breakup that is worse in the evening is a classic report from customers.
Why older systems suffer most
Aerials and amplifiers installed years ago were designed before mobile services moved into neighbouring frequencies, so they often have no built-in filtering. They receive and amplify everything, including signals they should reject.
Cheap boosters are particularly vulnerable. A budget amplifier with high gain and poor filtering can turn a manageable mobile signal into a picture-wrecking one, which is why replacing it often fixes what adding more gain cannot.
How filtering fixes the problem
A filter fitted between the aerial and the amplifier or TV blocks the unwanted mobile frequencies while letting television pass. It is a small, inexpensive component, but placement and choice matter: fitted in the wrong place, it will not fully protect the amplifier.
Choose a filter designed for the current television band and the unwanted mobile frequencies, including the 700 MHz band where relevant. An older filter intended only for 800 MHz interference may not provide the protection required. The filter also needs to suit the installation's connectors, signal levels and any masthead amplifier power feed.
If a masthead amplifier is already overloaded, a filter placed after it cannot undo distortion that has been created. Protection normally needs to be ahead of the vulnerable component. Roof-mounted equipment should be assessed by an engineer; do not climb up to move a filter or disconnect a power supply without understanding the system.
How we diagnose it
We use a professional meter that shows both signal level and quality. A strong signal with poor quality is a classic sign of interference or overload, whereas weak signal and weak quality suggests a path or cable problem.
We test at the aerial, at the amplifier and at the sockets, and where necessary add a filter temporarily to see whether the picture recovers. That gives certainty before any permanent fix.
What you can try first
If you have an amplifier, check whether the picture improves when it is bypassed, but only if your installer or manual says that is safe. Make a note of when breakup happens and which channels are affected, and whether every TV is affected or just one.
Avoid buying stronger boosters in the hope of fixing it. More gain rarely cures interference and often makes it worse. A quick call with those notes in hand helps us diagnose faster.
Check for transmitter engineering notices before changing equipment, and avoid repeated retunes while the signal is breaking up. A retune cannot remove radio interference and can lose stored services when reception is absent. Keep roof access and shared distribution cupboards off limits; safe checks are limited to accessible leads, receiver settings and observations about the fault.
Getting help in North London
Restore TV provides advice and support for eligible television reception problems caused by mobile services using cleared television spectrum. Check its current eligibility and assistance arrangements before buying equipment, as support depends on the circumstances. A letter about local mobile changes is useful background information, but still does not prove that every reception fault is mobile interference.
Call us on 0800 206 2385 and describe the pattern. We will test, explain the findings plainly and quote a clear price before any work starts.