Tuesday, 3 July 2012

Technical TV Glitch

There's a potential electrical storm on the horizon. The 800MHz spectrum band (around 791 to 862 MHz in practice) is the frequency which is being auctioned off for 4G use by industry regulator.

4G - fourth generation - is a system designed to provide mobile high speed broadband Internet access, to such equipment as laptops with USB wireless modems, smartphones, and other mobile devices. It's being auctioned off by Ofcom in the UK, and Jersey Telecoms over here is also trialling 4G systems.

But the 4G spectrum band is close to the 700MHz spectrum used to transmit Freeview signals and there has been growing concern in the UK that many households are likely to need to move to cable or satellite services as a result. According to the Daily Mirror, there could be between 2.3 and 3 million homes affected.

The interference can be offset, but only with special filters which may cost around £212 to install, considerably more than a £25 Freeview box. Without this there will be major problems. You will get significant pixellation and the picture will break up and you won't be able to carry on watching," says Freeview chief Ilse Howling. The cost may be greater, as if homes with a good signal use portable aerials for children's rooms, those will need their own filters.

According to the BBC, for some houses, fitting the filter will be relatively easy and can be done by the householder. But for the majority - 83% - an aerial installer will need to complete the installation.

The reason is the kind of aerial. The Ofcom reports notes that:

"Existing DDT receivers (that's digital TV receivers) ... and aerials were designed to receive signals across the UHF band 470 to 862 megahertz. That included the whole of the 800 megahertz band. That means, in addition to receiving the wanted digital TV signal, they will also receive the unwanted signal from new mobile phone base stations, resulting in interference and degradation to DTT reception."

Frequency Cast explains this as follows:

"If you've got a standard TV aerial up on the roof and a Freeview box, and you happen to be in range of one of these new 4G base stations when they come out, the signal from the 4G base station is effectively going to leak into your Freeview box. If that signal is particularly loud, it's going to upset your Freeview box, and it won't be able to receive the Freeview channels." (3)

The key is range. The interference won't effect homes outside a certain distance, but everyone living within 1.2 miles (around 2 km)of a 4G transmitter will face serious interference to the Freeview digital signal.

A BBC Director has called on the mobile companies to pay for the costs of filters to stop 4G services interfering with Freeview:

"John Tate, Director of Policy and Strategy for the BBC, told The Independent that operators should be forced to pay the costs of signal filter equipment under the 'polluter pays' principle, especially as the launch of 4G services will be highly lucrative for the mobile industry."(2)

In the Channel Islands, the 4G roll-out has started. On 23 May 2012, JT, reported that its new 4G network, on offer in St Helier and St Peter Port, boasts the fastest mobile connections in the islands.

It is not yet known if this is causing any significant impact on Freeview signals, despite the fact that virtually a quarter of the island will be close to a circle of radius 1.2 miles. This may depend on the power of the transmitter, and as other phone networks also come online, the frequency range may be more likely to cause interference.

It also depends on how it is done. In the UK, for example, Everywhere, which operates the Orange and T-Mobile brands, is hoping to roll out 4G services ahead of the 4G auction, using its existing 3G network. 4G delivered in this way will not cause interference. Telecoms may be using this means of providing 4G.

If you've suffered any problems with Freeview in the St Helier area, why not post a comment.

(1) http://www.mirror.co.uk/money/personal-finance/three-million-freeview-viewers-face-1095074
(2) http://advanced-television.com/index.php/2012/07/02/bbc-says-mnos-must-pay-for-freeview-filters/
(3) http://www.frequencycast.co.uk/4ginterference.html


Anonymous said...

It will affect Gorey, La Collette and St.Brelade's Bay viewers - not those using Fremont.
The channels that were above ch60 have already been moved to ch59 or lower.
The 4G over here is above 2GHz, the 800MHz 4G band has yet to be used.

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