Analogue TV – The effects of weather

A 'Venetian blind' effect - smooth, evenly spaced horizontal bars - is a sign of co-channel interference. This is caused by signals from different transmitters overlapping, and happens when high air pressure (which brings fine weather) allows signals to reach areas they would not normally reach.

High air pressure can also cause the signal to become weaker in low-lying areas.

Other effects may be a generally poor picture, or in extreme conditions you may see other pictures in the background or the picture may 'roll'. It may be only one or two channels that are affected.

Unfortunately, there is no solution to this kind of interference. Broadcasters can't prevent it, and adjusting your aerial will make no difference. Reception will only improve when the weather changes.

If your TV reception deteriorates during heavy rain and is still poor when the rain has passed, it may be that water has got into the aerial or the cable running down from it. Check first to see if it is only your TV that is affected, for example by asking a neighbour. Also check today's transmitter work to see if there is a transmitter problem.