Hannington Home>  Station Plates>  Aerials Index>  Supersize Images>  UHF Coverage Map  






Medium Size Images


Large Size Images



(In order of site visit with narrative)





At most main UHF transmitter sites in the UK, the re-engineering of the transmission structures for Digital Switchover generally comprised two key requirements - the replacement of the main analogue UHF antenna at the top of the structure and the installation of a UHF reserve aerial system in a position normally just below the main antenna, the latter replacing some or all of any existing aerials for the pre-switchover digital television network and other panels where in place (such as separately deployed aerials for analogue Channel 5 as featured at Hannington).

Whereas at most sites this was implemented by the relatively simple process of installing the new reserve aerial system first and then replacing the main antenna (with the former carrying all services whilst the latter was replaced), achieving these goals at Hannington was complicated by two space factors - one spectrum based and the other physical.





The spectrum issue dated back to the original digital UHF service from Hannington, with the two channels allocated to Multiplexes C and D (Channels 44 and 41 respectively) being co-channel with the Guildford relay transmitter, sited some twenty miles to the east and attached to the London region as a dependent of the Crystal Palace main station.

 In order to prevent Hannington causing interference in the Guildford service area, digital transmissions from Hannington were limited to the western arc of its transmission range.

  This was achieved by installing digital aerials only on the western face of the mast, which comprised eight tiers of panels installed just below the main UHF analogue antenna.

(Right: The original main UHF analogue aerial cylinder and the eight-tier digital panels positioned below).






Frequency planning ensured the co-channel issue would cease upon Digital Switchover at both Hannington and Guildford, with no future channel sharing within their respective post-switchover multiplexes.  However, Hannington was scheduled to complete switchover on 22 February 2012 whilst Guildford, as part of the London region, was not due to complete until 18 April 2012.  Between these dates, the issue would continue based on the Hannington Commercial (COM) frequencies (Channel 41,44 and 47) being co-channel with pre-switchover Guildford.  Accordingly, the COM multiplexes at Hannington would for the interim period have to be transmitted from the existing western facing set of panels, meaning the space they occupied on the mast would not be available for a permanent all-direction post-switchover reserve aerial until after the London region switchover.

Meanwhile, back in 2010, work commenced on the first stage of aerial re-engineering which was the installation of a reserve UHF aerial to carry all analogue transmissions whilst the main antenna at the top of structure was replaced.  With no other space on the mast available, this could only be achieved by removing the bottom of the four tiers carrying the station's FM Band II transmissions, allowing space for a temporary four-tier circulating UHF reserve aerial.  This arrangement amounted to an extreme compromise, not only because of the potential detrimental effect on the station's FM service, but also this position was much lower on the mast at around 100 metres above ground level.  Coupled with the fact there was only room for four UHF tiers, the service this would provide was likely to have been barely adequate in places.




The removal of the bottom FM tier and its replacement with a four tier UHF reserve aerial marked the first significant stage in re-engineering the mast and was observed as complete in August 2010.

(Far Left: The FM Band II aerials in four-tier configuration - image from May 2008)

(Immediate Left: The FM Band II aerials with the  bottom tier now replaced with the temporary four-tier UHF reserve - image from August 2010)







The removal of the main analogue UHF antenna at the top of the structure and its replacement with a new eleven tier digital aerial took place in October 2010.

  Once this work was complete and the new main antenna was in service, the temporary four-tier UHF reserve was removed allowing the restoration of the bottom FM tier to its original position.

(Right: Before and after replacement of the main UHF aerial in October 2010.  Note that the distinctive black-grey shroud at the bottom of the old cylinder was also removed as part of the re-fit).




Upon Digital Switchover on 22 February 2012, the COM multiplexes commenced transmission from the existing west-facing eight tier digital UHF aerial (left) as planned.

Once Guildford completed Digital Switchover on 18 April 2012 and thereafter ceased to share any channels with Hannington, the COM multiplexes at Hannington (now able to broadcast in all directions) moved to the main UHF antenna.

  This rendered the original west-facing eight-tier digital aerial redundant, allowing work to proceed on its replacement with a permanent all-direction UHF reserve aerial.

 The first stage of this work involved creating additional space on the mast by reducing the aperture of the four-tier FM Band II installation, which was achieved by closing the gaps between each tier.  This work was observed when near completion in May 2012.

(Left: Photographed in May 2012, work-in-progress to close the gaps between the four FM tiers).
















In the following two months (June/July 2012), the west-facing eight-tier UHF set was removed and replaced by the permanent all-direction eight tier reserve aerial system.

This marked the completion of the switchover refurbishment.

(Left to Right: The original eight-tier west-side panels replaced by the permanent all-direction system)








One loose end also attended to was the four-tier UHF panel used for the limited Channel 5 analogue service to the North Hampshire/Berkshire border area, which was removed from its position 30 metres above ground on the north face.

(Right: The now-removed Channel 5 panels).







Medium Size Aerial Images

Large Size Aerial Images



HANNINGTON at mb21 - including the replacement of the main UHF aerial




Hannington Home>  Station Plates>  Aerials Index>  Supersize Images>  UHF Coverage Map  



Hannington Home

Site Home