Expecting 4G interference? Tests now show that you have a one in 300 chance
Brian Butterworth published on UK Free TV Looking back the the original posting, Ofcom moves to protect Freeview interference from 4G mobile, we can see the Ofcom suggested that:
Of the 16.3 million UK homes with a standard (unamplified, unshared) Freeview reception, 110,000 (0.67%) would be effected.
Of the 5.2 million homes using communal aerials systems, 550,000 (10.6%) will have problems.
Of the 5.6 million homes using amplified Freeview reception, 100,000 (1.8%) will experience problems.
Today, at800 have published the results of the tests in London, Brighton and Hove and York - at800 updates estimate of likely impact of 4G at 800 MHz on Freeview:
"Following tests conducted across the country, at800, the organisation responsible for protecting Freeview when 4G at 800 MHz is rolled out across the UK, has provided a new estimate of the likely scale of the impact. If national rollout reflects the results seen during its tests, at800 expects no more than 90,000 households, with Freeview as their primary TV service, to experience disruption caused by 4G at 800 MHz. Whatever the level of disruption, at800 is ready to restore Freeview to viewers.
at800 has now sent postcards to households in London and the surrounding areas in preparation for the activation of 4G at 800 MHz masts over the coming weeks and months. at800 is also sending postcards to other areas of the UK ahead of masts switching on. at800’s mailing does not mean that 4G services will be available to consumers. For information about the availability of 4G services, people should contact their mobile operators.
In London, in particular, Freeview received from the Crystal Palace transmitter is unlikely to be affected by mast activation because of the strong terrestrial television signal and its relatively large frequency separation from 4G at 800 MHz. However, at800 is sending postcards and running a publicity campaign to ensure anyone who does experience new disruption to their Freeview service knows how to get in touch."
So with 26.50 million TV households in the UK (see Monthly universe summary - BARB) 90,000 represents 0.340% of them - that's a ONE IN THREE HUNDRED chance.
It seems that you are most likely to need a filter if:
a) you are a long way from a high power Freeview transmitter; and
b) you are very close to a 4G mobile phone mast; and
c) you are using a booster.
That's good news for Freeview viewers.
If you have had a postcode from at800 - see Received a postcard from at800?
Ken Campbell: I write on here as a technical bod rather than an aerial installer.
An aerial amplifier (booster) without any power going into it usually gives nothing out. Where the signal going in is very strong then a little signal might come out.
Therefore, in order to test without the amplifier it must be removed from the feed. It could be, and indeed it would be best, that you have a masthead amplifier (i.e. one that is close to the aerial - with only a short piece of cable between it and the aerial) in which case the box, perhaps behind the TV, into which mains electricity flows is merely a power supply which feeds the amp adjacent to the aerial. So turning it off, or even removing it for test purposes, still leaves the amplifier connected.
A look at your road on Streetview (photos taken June 2012) shows it to be a new development with few TV aerials and some satellite dishes. Indeed, the only TV aerial I spotted is on number 48 and judging by the photo it appears to be little above the apex of the roof.
I then placed myself on Marcroft Road near to the end with Tir John North Road and observed that Marcroft Road slopes downwards, so the roof line of that house and quite a few others are likely to below those I'm stood next to.
With that in mind and with the fact that you are at the bottom of a drop which is causing difficulty with reception from Kilvey Hill, I wonder if, as well as getting the aerial up as high as possible, having it sloping upwards a little might be worthwhile, this assuming that the bracket allows.
With digital reception there are two factors: strength and quality. Quality is digits all present and correct so as to allow the picture to be built up. A small (low strength) signal of good quality can be made bigger with an amplifier. A poor quality signal of any magnitude cannot be made better with an amplifier. See here for an explanation:
Television Aerial Boosters / Amplifiers, Splitters, Diplexers & Triplexers
A high gain aerial has a narrower acceptance angle because its gain (increased sensitivity in one direction) comes from having less gain elsewhere. That is, if it were used to send out a signal (transmit) it would emit a narrower more concentrated beam than one of lower gain:
Aerials, TV Aerial and Digital Aerial
Where there is no line-of-sight such as because one is at the bottom of a slope which blocks view of the transmitter, there is obviously no beam to focus on (signals travel in straight lines). Consider car headlights coming towards you but which are not visible because there is higher ground between you and them. Over the brow you can see light and if the light were brighter it would light where you are because it bends at the point it meets the brow. Such a situation would be like sunlight which lights all parts of a room, even though not all parts are in direct line-of-sight to the sun.
Now remember the points about digital signal quality and the fact that higher gain aerials have narrower acceptance angles. These aerials are therefore looking across a narrower angle and therefore rely on the quality across that (narrower) angle being good. If there is a momentary drop in quality across that angle, the quality of the signal going down the lead will dip. If, however, a wider angle of viewing is available, that drop in quality may be across a smaller proportion of the total angle, hence the average quality of the signal (that which goes down the lead) doesnt drop as much. The signal level may be lower, but an amplifier can improve that. This is why in situations such as yours that an aerial that isnt high gain accompanied with an amplifier is better. Indeed, one of the experts on here suggests a log periodic (rather than a yagi) with an amplifier can be effective:
Aerials, TV Aerial and Digital Aerial
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10:43 AM
Ken Campbell. Having studied Dave Lindsay's comments I thought I'd have a look at the Digital UK coverage checker using your postcode. Certainly you are only 1KM from the mast, but also the information is that you are likely to get 'Variable Reception' from the 'main' muxes, and the other muxes (COM 4,5 & 6) are not even rated. The information also states that the aerial group is AV. I always understood the 'V' to indicate polarisation, which in this cases implies Vertical, which is surprising as I always understood Vertical polarisation was only used by 'relay' stations. The information also refers to the Huntshaw Cross transmitter on a bearing of 192 degrees, but as you use an installer I would be reluctant to suggest you might see if you can pick up something from Huntshaw, not only as the aerial would need to be changed from Vertical to Horizontal and swung around to a different angle, but also the frequencies at Huntshaw are at the other end of the spectrum to those from Kilvey. Also the Huntshaw mast is only 538 ft high and Exmoor might be in the way. Have you asked your neighbours how they manage? You might find they are all with Sky or Freesat, very few terrestrial aerials can be seen using 'Streetview', I could only find one, it might be yours! You might like to use Sitefinder Mobile Phone Base Station Database
to see where your nearest mobile phone masts are, unfortunately it doesn't give information about 4G.
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10:52 AM
Swansea
Dave Lindsay: Thanks for the info Dave. My neighbour has an indoor aerial and an excellent reception, so it seem that my location is the main problem. Will look to increase height of mast and check direction(angle). The amplifier is in-house not mast head and when testing, I completely removed it form the system. However will post result of implementing your suggestions.
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Ken's: mapK's Freeview map terrainK's terrain plot wavesK's frequency data K's Freeview Detailed Coverage
11:04 AM
Swansea
Jack Luxon: Actually there are quite a few aerials around - as a new development street view has not kept up to speed with installations. As previously stated I think the problem is location - my house is just out of sight of the transmitter so will try a higher mast for my aerial. As an aside, we do have Freesat as well as Freeview and of course the former is 100% on all criteria.
As the interference occurs erratically, it could be months in between good reception I will make enquiries with 3G and 02, who have masts nearby if they are using or testing for 4G.
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Ken's: mapK's Freeview map terrainK's terrain plot wavesK's frequency data K's Freeview Detailed Coverage
2:54 PM
Ken Campbell: As you've said it's been going on for a while it is definitely not 4G, so don't waste time worrying about it.
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5:03 PM
I've just had another look at the Kilvey Hill details on Digital UK website, it only pumps out 2KW compared with 20Kw at Huntshaw Cross and 100Kw at Wenvoe and Mendip. In view of your neighbour's success with an indoor aerial I'm wondering if your problem may be with the co-ax cable from your aerial? Perhaps you might ask him if he would be prepared to plug his indoor aerial into your TV just to see what happens? Another thought: you say your problem is intermittent. Is there any possibility that rainwater is getting into the co-ax connection on your aerial? I once came across a case of the co-ax from an outside aerial insufficiently secured so that it was able to move around in the wind, this resulted in the co-ax wearing through where it was in contact with the edge of a roof tile allowing moisture penetration.
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6:02 PM
Brighton
I have lost my signal for my freeveiw i have no channels ad havent since Friday
whats going to be done about this and when will it be fixed by
ad i ever got a warning
disgusting
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sarah's: ...
6:15 PM
Brighton
i want my tv fixed by tomoz !!!!
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sarah's: mapS's Freeview map terrainS's terrain plot wavesS's frequency data S's Freeview Detailed Coverage
6:33 PM
sarah lee: what makes you think it's 4g. It could be your tv or your aerial have you have had them checked to make sure they are working right.
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sarah lee: Typing in capitals (as in your 6:02PM posting) is rude and shouting. Perhaps you should push off and acquire some respect and manners for others.
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