Freeview reception relies on line of sight or near line of sight to the transmitter, at least at roof-top level. The location and height of the transmitter mast determines the maximum theoretical range of the transmitter – i.e. how far away it can be received.
That’s why most prominent Freeview transmitters are located on high ground, in a location overlooking low-lying land.
The second factor is a viewer’s own aerial. It will be set up, usually on a roof-top or in a loft to point at a particular transmitter. So if the transmitter is in completely the wrong direction, the aerial will either a) not receive the signal or b) not receive enough signal to provide a stable picture.
So when an incident at a transmitter site occurs, the only way to completely restore services is to reinstate services from the same site, with a mast of the same height. Move the mast a few miles on one side of the hill, and viewers on the other side lose reception. Reduce the height of the mast, and the signal won’t travel as far or reach as far into valleys.
For viewers in North Yorkshire, Teesside and parts of County Durham, this means only the current set-up at Bilsdale will restore reception to exactly how they were before.
However, with the site in a conservation area – such a mast would probably not get planning permission if it was being proposed today – the work at restoring services will be difficult. Weather conditions through autumn and winter will make work on the fire-damaged mast very dangerous. In the meantime, a temporary mast will need to be connected to the electricity supply – lying cables in a remote area, let alone a conversation area is tricky – and the temporary mast will need to be at a safe distance, should the existing mast fall down, or need to be demolished.
Eston Nab temporary tower
With the process looking set to drag on, transmitter operator Arqiva have already deployed another temporary tower, which will give some viewers a TV service. But it isn’t the perfect solution:
The Eston Hills to the east of Middlesbrough is normally home to the Eston Nab relay. It usually provides a TV service to a few hundred households immediately in the shadow of the hills, which blocks Bilsdale. The site is now the main focus of efforts to restore Freeview across a number of densely populated areas along Teesside. A temporary tower joined existing masts on the site last week. Initially, the signal from the mast was able to reach Hartlepool and Redcar. An upgrade to the broadcast antenna will start sending signals westwards towards Darlington, as well.
The Eston Nab temporary tower is built on a 240 metre high hill. This compares to the 379 metre high hill Bilsdale mast is built on. In addition, the Bilsdale mast is another 314.6 metres high, meaning the top of the damaged mast is nearly 700 metres above sea level. The height difference will result in a reduction in possible coverage. It makes it impossible for the Eston Nab signal to travel over the North York Moors to reach all the affected households in North Yorkshire, for example.
However, it is high enough to deliver a signal across all areas immediately to the north of the Moors. For viewers in the west, close to the A1, the signal will be coming in at an angle to the direction most aerials are pointing in. As a result, reception could be patchy.
The good news is that following the Bilsdale outage, some households in the area have reported being able to receive a weak, but usable signal from alternative transmitters. That’s despite the aerial is pointing in the complete opposite direction. This gives some hope for reception from Eston Nab, which will be less than 90 degrees away from the direction of the Bilsdale mast.
Not all channels for everyone…
Priority is given to Public Service Broadcasters when restoring coverage. This means services from the BBC, ITV, Channel 4 and Channel 5. Therefore reception of entirely commercial channels, such as Dave, Sky News and Quest may well continue to be more difficult. These are restricted to a much smaller area. Some services, such as the Teesside local television service are currently completely absent.
Alternative platforms…
Most Freeview channels are available via satellite without a subscription. Therefore, some viewers may find it advantageous to switch to Freesat. Sky or Virgin Media customers aren’t generally affected by the Bilsdale outage. But secondary TVs not connected to multiroom will remain blank.