Interference happens when a TV signal is distorted by other signals or objects before it reaches your TV aerial. It can be caused by electrical equipment, radio communications or the weather. |
Electrical interference
Effects of electrical interference on the TV screen include:
ragged, moving horizontal patterns
random white dots or flashes
buzzes and clicks on the sound
 The interference can be caused by anything powered by electricity, such as domestic appliances, switches, central heating thermostats and computers.
To work out what is causing the interference, leave the TV on and switch off or disconnect your electrical appliances - including the central heating or boiler - one at a time to see if reception improves. You may have a faulty appliance or thermostat that needs repairing or replacing.
An unusual colour effect on the TV screen may be caused by the magnets inside a hi-fi speaker, so don't put speakers on or near the TV.
Sometimes, high-voltage electrical equipment outside your home can cause interference.
Radio interference
Effects of radio interference on the TV screen include:
moving, wavy or herringbone patterns
a 'waffle' effect
S patterns
loss of colour
 This type of interference is usually caused by equipment that emits radio waves, as used by taxis and emergency services, amateur and citizens' band radio, and mobile phone services. Most of this equipment is properly licensed and filtered, though some is not.
Radio interference can also be caused by equipment connected to your TV set, such as a video or DVD recorder or a signal booster. Try disconnecting these and plugging the aerial lead directly into the TV. If the problem disappears, one of the units is causing the problem - reconnect each one until the problem recurs to find out which one.
Co-channel interference
(caused by the weather)
 Smooth, evenly spaced horizontal bars on the TV screen - a 'Venetian blind' effect - are a sign of co-channel interference. This is caused by signals from different transmitters overlapping, which happens when high air pressure allows signals to travel further than normal. Reception will only improve when the weather changes.
Ofcom interference investigation service
If you cannot trace the source of interference, you may want to ask Ofcom to investigate. If the interference is caused by something outside your control, they will give advice and take action if possible. Note that they may charge a fee if they find it is something within your control. Ofcom is also responsible for licensing radio users and preventing illegal broadcasting.
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