Around a million people in the North East of England in areas from Sunderland to Whitby, including Hartlepool, Darlington and Middlesborough came home from work on 10 August to find that their Freeview TV, DAB radio and FM radio services had disappeared. This was caused by a fire at the Bilsdale mast in the North Yorkshire moors. At the time of writing, it is still unclear whether the masts's structure is sound and as an interim, transmission company Arqiva are putting a number of mitigations in place to try and restore services.

One of the main mitigations which has already been put in place is to move the DTT services from Bilsdale to a mast at Eston Nab. Eston Nab was previously a relay station used to provide fill-in TV coverage to a few homes around Eston, Teesville and Wilton who, ironically, could not receive a service from Bilsdale as the Nab itself blocked the line-of-sight. The relay station originally had a transmitter power of just 3 Watts (compare this to the 100,000 Watts which Bilsdale used)

Eston Nab was also used as a high power FM transmitter for Smooth Radio on 107.7 with a power of 2.5 kW. Most of the rest of the FM stations in the region were transmitted from the Bilsdale mast at a power of 5 kW. Though TV services which previously ran at Bilsdale have been relocated to Eston Nab, the transmitter power in use is far lower. One report claims that the power of the new DTT TV transmitters at Eston Nab are just 20 Watts.

Wireless Waffle wondered how the coverage from Eston Nab would compare to Bilsdale if it ended up being needed in the long term due to the Bilsdale mast needing to be re-built completely. Though it is not a direct like-for-like comparison, the Associated Broadcasting Consultants web-site provides coverage maps for FM radio services based on the parameters provided by Ofcom. As such, it is possible to compare the coverage of the Smooth Radio 107.7 FM service from Eston Nab with, for example, the previous coverage of the Heart FM 100.7 FM service from Bilsdale.



The map above compares the coverage of the Smooth and Heart FM services from the two transmitter sites. Coverage from Bilsdale is in green and yellow, and coverage from Eston Nab is in blue and aqua. When it comes to the larger cities in the region (Darlington, Middlesborough and Hartlepool) it is clear that it may be possible to restore service from the Eston Nab transmitter as this provides reasonable coverage in these areas. Across the North Yorkshire Moors however, the Eston Nab transmitter does not provide much by the way of coverage. For these locations, an alternative may be necessary.

Note that the map compares coverage for FM transmitters and at the UHF frequencies used by television, coverage would be far more patchy, however it does suggest that a higher power site at Eston Nab may restore coverage in some of the more densely populated affected areas. Note that in these areas, the direction of the Eston Nab transmitter would be different to Bilsdale which would require the re-pointing of TV antennas for many people (this is not an issue for FM reception as most antennas, such as those on cars, are not directional).

An additional plan being considered is to use the BT microwave tower at Arncliffe Wood to restore service in and around Northallerton, Thirsk and Malton. Again, re-pointing of antennas may be necessary in these areas. It is possible that further sites may be identified which, working together, could restore coverage to the original Bilsdale coverage area without the need to re-build the mast (should this prove necessary). Such schemes have been used before. In Portugal, for example, the national DTT service is provided from a network of cellphone towers, rather than the large hill-top sites previously used for the analogue service.

Useful links:

• Arqiva update on the Bilsdale mast incident
• Measured coverage area maps
• MB21 updates on plans to restore service
• UKfreeTV page on the Bilsdale transmitter
• Twitter feed of a516digital providing additional information on the situation