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6.4 Digital Terrestrial TV (Freeview) Reception

Digital Terrestrial Television does not suffer from the picture impairments described in Section 6.1 that occur on analogue TV.  Provided you have sufficient signal level to overcome interference, the picture quality will be at the same level as that transmitted wherever you are in the coverage area.
There are now many types of digital terrestrial TV boxes and equipment you can connect to your TV. The hundreds of possible combinations and specifications mean we cannot offer you individual advice about your equipment. We have prepared some information with answers to the most common problems people experience.

First, try this…
Whatever the problem (lost channels, BBCi stopped working, picture and sound out of sync), we have found that a reboot/rescan often cures the fault. Most Freeview problems can be cured by following a number of simple instructions.


h2Reboot
A Freeview box/IDTV has a micro-processor at its heart and like many computers it can suffer from occasional glitches. In many cases, a simple reset is all that is needed to fix the problem. This means unplugging the equipment from the mains power supply for about 10 minutes. Plugging the power back in reboots (restarts) the software and often cures the problem.


h3Rescan/retune
If a reboot fails to fix the problem then a rescan/retune can often restore lost channels or features. Follow the instructions below to clear the memory and rescan all channels. This may not work for all digital receivers but will not damage your equipment. Users should refer to their manuals for further information if required.

  • Disconnect the equipment from the mains power supply and leave unplugged for 10 minutes.
  • Remove the aerial from the rear of the equipment and leave it unplugged.
  • Reconnect the mains power supply (but NOT the aerial); switch the equipment back on.
  • Set your box/IDTV to rescan/retune all channels (you may need to refer to your manual). When complete, the equipment should show 'no channels found'.
  • Switch off the equipment and reconnect the aerial; switch the equipment back on.
  • Now set your box/IDTV to rescan/retune all channels; this should find all channels available to you.

If the problem continues, please refer to the manual or contact the manufacturer of your equipment.

mugMissing channels or pictures breaking up
 
If you are missing or have lost channels you think you should have, or if the picture breaks up, there may be a problem either with your aerial installation or with your set-top box.  First try a reboot or rescan: this often cures box glitches.
Check which channels are predicted to be available in your area using http://www.dtg.org.uk/retailer/coverage.html
If you are in an area bordered by more than one digital transmitter, different signals may be confusing your equipment. When Freeview boxes/IDTVs retune, typically they automatically scan from the lowest channel number to the highest. In some areas where receivers can pick up signals from more than one transmitter this may mean the equipment tunes to the first signal it finds and ignores a better signal at a higher frequency. This may result in a box picking up the wrong region or, if the signal tuned to is a weak one, in reception problems on some services.
A correctly fitted benchmarked digital aerial pointed towards the preferred transmitter should ensure the best possible reception and avoid many types of problems. Please contact your equipment manufacturer if you need further advice on how your receiver performs a retune.
The following advice is aimed at digital users who are comfortable with setting up their equipment. Viewers who are unsure of how to tune in and check channel details should seek advice from professionals.

  • To establish if your equipment is tuned to the correct transmitter, visit the DTG digital coverage predictor web page http://www.dtg.org.uk/retailer/coverage.html and perform a coverage check. This will show the predicted transmitters covering your postcode. Note down the name of the transmitter shown (if you are covered by more than one transmitter, note down the name of the one offering the most services).
  • Now visit the DTG transmitter information web page http://www.dtg.org.uk/retailer/transmitters.html and look up the details of the transmitter you have noted from the predictor. Make a list of channel numbers each multiplex is broadcast on. These numbers are the frequencies your equipment should be tuned to in order to ensure the best possible reception.
  • Your manual or manufacturer should tell you how to check that your equipment is tuned to these multiplexes. If your equipment is tuned to the wrong frequency channels you may not get the best reception possible or you may miss out on TV channels that would otherwise be available to you. Some boxes/IDTVs have a facility that allows the user to manually tune the equipment to specific user-defined multiplexes (refer to your manual or manufacturer for details). This feature can resolve the issue. However, a correctly fitted benchmarked digital aerial pointed towards the preferred transmitter should ensure the best possible reception and help to avoid this type of problem.

Please contact your equipment manufacturer if you need further advice on how your receiver performs a retune.  Freeview channels are broadcast in groups of six separate bundles. Each bundle of channels is called a multiplex. If you can only receive some of the channels in a multiplex (e.g. BBC One and BBC Two but not BBC Three), it is not due to bad reception but is more likely to be a problem with your set-top box.  If this happens, try resetting your box.

If you cannot receive any channels in one or more multiplexes, or the pictures break up or freeze, there may be a problem with your aerial or the connections coming from it.
Digital TV has what can be described as a narrow cliff-edge of reception. This means that as long as the equipment is picking up enough signal to decode (even if it is a relatively poor signal) it will produce a good picture. However, if the signal strength drops below a certain level that the receiver can process, you may get no picture at all, or one with very noticeable problems (e.g. blocking, pixellation, clicking sounds).
The difference between an acceptable signal strength and one that will cause your box to fail can be very slight. The strength of the signal itself can also vary depending on the weather or atmospheric or local conditions. This means the picture could effectively come and go over time. In addition, aerials may pick up some frequencies better than others; this means some multiplexes can appear to be working normally while others produce no pictures at all.
If you have problems with the reception of digital as mentioned above we would recommend contacting a CAI registered aerial installer for further advice.
We have prepared a number of detailed factsheets to provide additional information to help in resolving reception difficulties.  They are available from the BBC website on http://www.bbc.co.uk/reception/factsheets/index.shtml
General factsheets                             
q Analogue TV problems                      
w  DAB reception difficulties                                             
r Digital TV problems                                                 
e Radio aerials and good reception                                  
o Radio reception on the move and overseas                            
                                                                          
Technical factsheets                                                 
y TV aerials and reception                                           
u The effect of trees on reception                                  
j The impact of large buildings and structures (including wind farms) on terrestrial TV reception            
                                                                                                                 
You can also get information on Digital TV at the DTG website [3] which includes a post code checker, information on digital TV, retailers and receivers

 

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