West of England viewers retune 28th March 2012

Viewers receiving services via the Mendip transmitter near Wells in Somerset are required to retune their Freeview, Top Up TV or BT Vision boxes or integrated digital TVs on the 28th March 2012 due to a frequency change that will affect Freeview channels including Dave and Sky News.

On 28th March 2012, the Arqiva A (COM5) multiplex that carries channels such as Sky News, Challenge and Dave will move frequencies - from UHF channel 67 to UHF channel 56. Viewers who do not retune will lose these channels. Changes to the frequency are currently expected to be made between 00:00 and 06:00 on the 28th March, so that viewers receiving from Mendip should be able to retune Freeview at breakfast time.

From 28th March, the UHF broadcast channels at Mendip for manual tuning purposes will be:

BBC-A: 61
D3&4: 54
BBC-B: 58 (DVB-T2 devices only^)
SDN: 48
Arqiva A: 56
Arqiva B: 52

^ Freeview HD multiplex.

This retune is required nearly two years after digital switchover occurred in the ITV West region. Until now, being sandwiched between the Central, Westcountry, Meridian and Wales TV regions, it has not been possible to provide a suitable frequency at Mendip to broadcast some commercial TV services at full power without clashing with neighbouring regions, especially those that had not completed switchover where frequencies were required for both low power digital and high power analogue TV.
In line with the final switchover event in the Central region last September, two of Mendip's multiplexes moved to their final frequencies, leaving one multiplex on a temporary frequency. Now that the neighbouring Meridian region is undergoing switchover and turning off analogue, Mendip can turn up the power and move Arqiva A to its final frequency.

Power boosts
One day before the retune -  on 27th March -  the SDN multiplex on UHF channel 48 (which carries 5*, QVC and Quest among others) will have its power turned up from 70.7 kilo Watt (kW) Effective Radiated Power (ERP) to 100 kW ERP. A technical change will also take place which will alter the Forward Error Correction (FEC), creating more bandwidth for one extra TV channel in the future. Usually a change to the FEC affects reception in fringe areas, but the added signal boost will counteract this.

On the 28th March  both the Arqiva A and Arqiva B (COM6) multiplexes will be turned up to full power. Arqiva A will increase from the current 12.5 kW ERP on its old frequency to 100 kW ERP on its new frequency. Arqiva B will be increased from 25.7 kW ERP to 100 kW ERP whilst remaining on the same frequency.  Viewers in fringe areas who have received the BBC and main ITV services without problems from Mendip, but who have found reception of Dave, Sky News as well as ITV4, Film 4, VIVA - and Sky Sports via BT Vision or Top Up TV -  to be very unreliable may benefit.  The Arqiva A multiplex will also undergo the same technical change to the FEC rate as described above for the SDN multiplex.

Amplifiers may need to be removed if the signal boost causes a signal overload (symptoms include picture break up and appears on screen as if the signal is too weak, when the opposite is true).

Another frequency change due next year
In 2013 viewers in the region will need to retune when the BBC's services from Mendip move from UHF channel 61 to UHF channel 49 in order to clear the top of the waveband for 4G mobile broadband. This can't be done at the same time as the above retune on 28th March, as the neighbouring Wenvoe transmitter needs to clear its services off UHF channel 49 first to make way for Mendip's move. Wenvoe's channel change in turn can't be done until other transmitters start moving frequencies.

The exact date of this event is yet to be announced by Digital UK.

The clearance of UHF channel 61 and 62 for 4G was a late addition to the switchover process and was not originally factored in. Only UHF channels 63 - 68 were originally to be cleared for alternative use. Since switchover started, 4G technology has developed and a consensus reached in Europe (both EU and non-EU countries) to use UHF channel 61 upwards for 4G, hence the retrospective changes for most regions that underwent switchover before the autumn of 2011.

More reading:
Digital UK Newsletter about the changes.
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  1. According to my information, and just to clarify, Arqiva A moves from channel 56 to channel 52, to allow Arqiva B to move from channel 67 to 56.
    Is this not correct?

  2. No, Arqiva A is currently on UHF channel 67 and will move as indicated in the article. However, Arqiva B was temporaily on that frequency before a move last September. There has been a lot of contradictory information about the frequency allocations at Mendip.

    Digital UK have published the following flyer, which you may find of interest. http://www.digitaluk.co.uk/transmitternetwork/tools__and__resources/almanac/special_editions/Special_edition-installers_Mendip_retune_event_March2012_Final_rev23March.pdf


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