INTERFERENCE AFFECTING PAGE 888 SUBTITLES ON TERRESTRIAL ANALOGUE TV:
The reasons why page 888 subtitles fail are many and varied and all scenarios cannot all be covered in a short outline such as this. Reasons can range from technical issues, placement of aerials through to variations in weather conditions.
Two specific scenarios relating to two different forms of interference are outlined here, and we know from experience that these causes account for a major proportion of the reception issues reported to us.
Page 888 subtitles on our analogue terrestrial platforms ( to distinguish them from DVB subtitles on newer digital platforms ) are the subject of this article.
CHECK YOUR TELETEXT QUALITY:
If you can receive error-free teletext pages, then you will receive reliable page 888 subtitles. If on the other hand your teletext pages fail to display or display with corrupted elements, then you will not receive reliable page 888 subtitles.
You must receive a good quality TV signal to receive reliable page 888 subtitles. As the quality of a received signal deteriorates beyond a critical threshold page 888 subtitles will begin show errors. Displayed text will become 'corrupt' and subtitles may in a worst case fail completely.
This is not to say that those receiving a less than perfect TV signal cannot receive page 888 subtitles. In many cases those with a 'somewhat weak' signal, can still receive perfect page 888 subtitles provided the signal quality is not otherwise compromised.
Conversely, those located close to a TV transmitter, who are receiving a strong TV signal may suffer from signal impairments that will preclude them from decoding page 888 subtitles reliably.
INTERFERENCE - What is it ?:
Interference is an unwanted signal that interacts with your received TV signal.
Some interference can be transient, such as "co-channel interference" while other types may be a permanent feature of your location such as "reflections" due to buildings or local terrain.
Both of these are discussed below.
CO-CHANNEL INTERFERENCE - Effects of Weather :
Atmospheric conditions usually associated with High Pressure fronts will introduce interference known as co-channel interference. This affects all areas of the country, however it is more prevalent in the North and East of the country due to the closer proximity of these regions to UK transmitters.
Co-channel interference regularly happens during really fine weather in the Summer months and can continue for extended periods.
These weather conditions allow TV signals travel way beyond their planned service areas and when this happens, unwanted distant TV transmissions will interfere with your RTE reception.
Co-channel interference manifests itself as a 'venetian-blind' effect with smooth evenly spaced horizontal bars across your picture.
Co-channel interference will always impair page 888 subtitles even when the received picture and sound remains 'watchable'.
There is no solution to this type of interference. Broadcasters can't prevent it and adjusting your aerial will make no difference. Reception will only improve when the atmospheric conditions change. In some cases re-tuning to an adjacent RTE channel may provide a short-term "fix" of the problem, but not all viewers will have this option available to them.
REFLECTIONS - Location Location :
In some unique areas it is impossible to receive a 'clean' direct TV signal from your local transmitter. This is due to signal components that have been reflected from local features such as mountains and valleys or other man-made structures such as buildings and bridges.
These reflections may not appear to impair your received picture too severely, but will create difficulties in decoding teletext pages and subtitles.
In many cases, there is not a lot can be done to solve this type of interference.
Solutions to try :
. Check if you can receive an improved signal from an alternate RTE transmitter
. Install a different type of aerial or
. Relocate / redirect your aerial to reduce the level of the reflected interference.
Your local dealers will be familiar with the reception issues in your area and are well placed to advise you on possible solutions.
All should be aware that the newer digital platforms will also accommodate subtitles and these new digital transmissions will be far more resilient to the interference types outlined above.
Audio Description will be available on our Christmas movie 'UP' transmitting on Christmas Day