How do I know if the 4G broadband will overload my Freeview?
Back in June 2011, we looked at how Ofcom moves to protect Freeview interference from 4G mobile .
Since then, the television Digital Switchover has been finished and 4th generation (4G) mobile broadband services - also known as Long Term Evoluition (LTE) have launched all over the world, including a service from Everything Everywhere (EE) in the UK.
To understand why and how these 4G broadband services will cause problems during 2013, you need to take into consideration a number of technical factors.
Understanding the radio spectrumThe Radio spectrum is the name given to the frequencies of the electromagnetic spectrum that can be usefully used to transmit radio, television and data services.
The top bar on the diagram below (or download) shows a selection of the services used in the UK, with old-fashioned long-wave radio, then medium-wave radio, though FM radio, the digital DAB radio services up to those used for television broadcasting. (See here for a really complex chart).
The highest frequencies on the diagram, the "ultra high frequencies" (or UHF) band is shown enlarged as the lower purple bar. In this range we can see TV "channels C21 to C60" (blue), second- and third- generation mobile phones (2G orange, 3G pink) and the location for the 4G services.
It is important to note that some of the 2G capacity in the "1800MHz" range has already been converted to 4G operation by Everything Everywhere (EE). The other two yellow boxes show the "800MHz" (to the left) "2.6GHz" (on the right).
For the purpose of Freeview reception, only the 800MHz range need be considered. The other two ranges will not cause Freeview problems.
Protecting Freeview receivers against overloadAs we have seen already - Freeview signals: too much of a good thing is bad for you - Freeview boxes are designed to protect themselves against signal overloads. When they do this they close down and people often incorrectly diagnose the problem as being "no signal" when there is too much.
The problem that has to be solved as the 4G services launch, is that the new mobile broadband signals can cause overloads onto the frequencies that are being used for Freeview.
One particular problem is that a very common type of Freeview signal decoder, a superheterodyne receivers are sensitive to signals being present nine channels (72MHz) away.
In addition to overloads, 4G may also cause Signal-Interference Noise Ratio degradation, where reception breaks down because the receiver can no longer decode the digital information in the transmission.
Knowing who will win the 4G auctionUntil the 4G auction takes place, no one will know which company has the right to use the 800MHz channels for mobile devices. The following companies have qualified to bid:
- Everything Everywhere Limited (UK)
- HKT (UK) Company Limited (a subsidiary of PCCW Limited)
- Hutchison 3G UK Limited
- MLL Telecom Ltd
- Niche Spectrum Ventures Limited (a subsidiary of BT Group plc)
- Telefonica UK Limited
- Vodafone Limited
Viewing high power television and using low power mobilesUsing the 'Sitefinder' Mobile Phone Base Station Database you can compare the locations of existing mobile phone "masts" with those used for Freeview Transmitters. Here is an example from Brighton and Hove, where a medium-sized single mast (Whitehawk Hill) can cover a whole city, but where hundreds of mobile phone base-stations cover a many smaller-by-comparison areas.
This illustrates two points. Firstly, that Freeview broadcasts are high powered and one-to-many - mobile devices are low power and peer-to-peer. The mast your TV signal comes from may be miles, sometimes tens or miles away, for your mobile perhaps only meters away.
The second point is that if an existing 2G/3G mobile supplier wins a 800MHz 4G slot, they will wish to use their existing "phone mast" locations (especially the 900MHz ones) as this would be most economical for them. Until the action winners emerge, and then plan their network, only idle speculation about possible interference can be made.
Using the TV frequencies for 4G masts and phonesResearch (see here) shows that a 4G mast in relative close proximity, or a mobile 4G handset closer than a meter to an unfiltered Freeview box will cause overloading on many tested devices. The following diagram shows the relationship between the 4G use and the old TV channel designations.
Those Freeview transmitters that use channels above C52 are most likely to have receivers that get overloaded by the use of 4G signals in the 800MHz area. FDD is Frequency-division duplexing - the transmitter and receiver operate at different carrier frequencies.
Interpreting the aerial and mast locationsOnce the proposed mast locations for 4G services are known, it will then be possible to predict which homes will need to fit the special filters in areas where Freeview uses the higher channel numbers (the C52 to C60 range).
If you then have a rooftop aerial without a signal amplifier, to get an overload you will need the 4G mast to be in the line-of-sight between your Freeview transmitter and the aerial, or possibly "directly behind" the aerial.
If you then have a rooftop aerial and an amplifier, or perhaps have lower-grade cables, you are likely to need to protect from a 4G overload if the phone mast is close to your rooftop aerial.
Finding transmitters that use the higher range frequenciesSome powerful transmitters and many relays use the high frequencies: Sudbury, Oxford, Belmont, Winter Hill, Tacolneston, Pontop Pike, Mendip, Emley Moor, Clermont Carn, Truskmore and Maghera.
Click below to find out the transmitters in with high frequency allocations:
- C60 is used by 126 transmitters - including Sudbury, Oxford, Belmont;
- C59 is used by 142 transmitters - including Winter Hill and Tacolneston;
- C58 is used by 100 transmitters - including Winter Hill, Sudbury, Pontop Pike and Mendip;
- C57 is used by 131 transmitters - including Clermont Carn, Truskmore, Oxford;
- C56 is used by 73 transmitters - including Mendip, Sudbury;
- C55 is used by 139 transmitters - including Maghera, Winter Hill and Tacolneston ;
- C54 is used by 104 transmitters - including Mendip, Pontop Pike and Winter Hill;
- C53 is used by 131 transmitters- including Truskmore, Belmont, Oxford;
- C52 is used by 81 transmitters - including Emley Moor, Sandy Heath, Clermont Carn and Mendip.
Protecting Freeview boxes and sets, cables, amplifiers from 4G devicesAgain in areas where Freeview uses the higher channel numbers (C52 and above) you may have to protect your Freeview devices from signals from a 4G handset (such as mobile phone, tablet, or USB "dongle").
This may, once again, require the fitting of a special filter, or the upgrading of the "fly leads" used to connect your aerial to the set top box or TV. This may be a particular problem if you have used an indoor aerial or signal amplifier.
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ian from notts: People who experience interference will be supplied with one filter only:
The Problem with 4G LTE 800 and Freeview | at800
Additional filters will be at viewers' own expense. Where a single aerial is used for multiple sets, it may be possible (and best practice) to fit one filter before the powered or unpowered splitter/amplifier.
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5:52 PM Wigan
I appreciate that an awful lot of activity is taking place, i.e., 4G and all that sort of rot, but can anyone explain why, recently when attempting to automatically set up channels on new TVs found that Channel 62 (which apparently takes in all of the BBC channels) has completely ignored Winter Hill and instead given me crummy or nil reception from Yorkshire (ID302d). Right now the only way I can be in possession of all available channels is to manually search. Not that much of a problem but I'm still curious. My postcode is WN4 9LG.
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Charlie: Some of the more recent tuners give an option to select your first choice of region for storage in the LCN (normal) positions in the EPG, with any alternatives placed in the 800s. Older receivers frequently put the first set of services found at the head of the EPG, in your location this is BBC from Emley Moor, with any subsequent options (BBC from Winter Hill) being placed in the 800s. Manual tuning, when available, gives the viewer the option of selecting which muxes they wish to store and depending on the design of the tuner if more than one region is chosen,will place either the first or sometimes the last option selected in the LCN positions and the alternatives in another vacant location in the channel list, usually the 800s - this you find out for yourself when carrying out a manual tune. Thinking back to analogue days you would still have found the Emley Moor signals first, but they would have been either ignored or stored on spare buttons, Winter Hill signals then being chosen for buttons 1 to 5.
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We feed several TV receivers from a single Freeview aerial via amplified spitters. At various times each receiver may be tuned to a different channel. If 4G interference results in a Freesat installation being required how will multi-channel reception continue to be provided?
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Ted: Each satellite receiver requires an individual feed from the dish other wise everything is just the same as with Freeview.
But though it cant be taken as a foregone conclusion that a person is going to be affected by 4G as there is a great deal of quite unnecessary panicking going on about this issue, as its totally dependant on where a person resides in relation to the 4G mast as well as the channels used by the Freeview transmitters that cover their area.
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If is any consolation to those who will lose their TV signal, the companies that intend to run 4G are likely to be running at a considerable loss for a considerable period of time.
The business case for 4G is so weak and the advantages to the users so restricted we may see the companies happy to hand back the license. After all, if 4G users do not want to watch TV on a mobile, a 4G phone has little to offer.
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KMJ Derby: Thank you for your very detailed reply, but with respect, I can't say that I fully understand it - mainly because it appears from your explanation that, for my area, the true BBC source is Emley Moor. I had no idea where Emley Moor is situated but on checking I find it is near Leeds. Now, this Yorkshire-located source for BBC is probably the culprit for my poor to non-existent reception. However, when opting for manual channel selection the situation is well and truly corrected, and everything in expected channel number order, by achieving Winter Hill's output for everything, including BBC programmes, and this being confirmed by checking the signal information. I don't know whether I'm just slow on the uptake here or what . . . Kind Regards
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