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The effect on that roof tiles and walls have on analogue TV signals is that the picture will degrade slightly. Making the signal slightly weaker will add a 'snow' element to the picture which is mildly irritating. The picture quality drops, but it is usually possible to make out the picture, as demonstrated here:
Many people have preferred this slight loss in picture quality for the perceived benefits of a loft-mounted aerial. Loft aerials are much easier and somewhat safer to install, and the aerial is shielded from wind and rain that can cause damage to rooftop aerials. In some places (such as New Towns) TV aerials have been previously banned from rooftops.
However, the BBC and others state that Freeview reception demands a roof-top aerial. The existing (pre Digital Switchover) Freeview signals are at very low power levels. The use by ITV, Channel 4 and five of "64QAM" mode for their transmission multiplexes to provide more channel choice results in a very lower chance of reception of these channels (multiplex 2 is ITV1, ITV2, ITV3, ITV4, CITV, Channel 4, More4, E4, Film4+1; multiplex A carries five, five Life and five US) with a loft-mounted aerial.
By comparison with the image above of how analogue signals look as the signal grow weaker, digital TV reception will continue to give perfect pictures and sound as the power level drops off, until suddenly the level drops below what the COFDM system can cope with. At this point the picture will become blocky and freeze whilst the sound will appear to come and go. Another tiny drop in signal level will result in no picture or sound and a message saying that "no signal is being received". As the signal can vary with weather conditions, people often find that a loft aerial will work when installed and then suddenly stop some months later.
After switchover new digital signals will replace the existing analogue and digital ones. The new digital signals will be at much higher levels that the current ones (for most people) and this will help with reception. However, all six multiplexes will switch to the 64QAM mode that causes the problems indicated above.
Due to our Climate Change commitments (Kyoto Protocol), the signal levels for these new digital will not be as high as those currently used for analogue. For this reason you should not depend on the increase in power levels after switchover compensating for having a loft aerial.
Wherever possible you should use a rooftop aerial. If this is impossible, you may find that connecting your aerial to your Freeview box or integrated digital television using satellite-grade coaxial cable will compensate for the loss.
Your comments are always welcome. Please use the form below to add your thoughts or questions to this page. We will get back to you as soon as we can.
Peter martelli Monday 31 December 2012 7:20PM
We live in Lostwithiel in Cornwall in Castle view. We can not receive the signal from Carradon with a horizontally polarized aerial only a limited number of channels from the repeater with a vertically polarized aerial. Is it possible to receive the full number of channels from the repeater?
I have a loft aerial with a splitter feeding my Sky to 3 tv's, this worked fine until the switchover, now signal is terrible, coincidence?? Can this be rectified and if so guidance with what would be required would be great, Thanks
Chris Foley: The question is: is this a strength issue or is it a quality issue?
The fact that you could receive the lower power (weaker) signals prior to switchover and split them suggests that it won't be too low a strength. Therefore the only possibility is too high a signal level; knowledge of your location may allow that to be graded as a likelihood.
If it is a quality issue, then that starts at your aerial. Splitting the signal won't affect the quality.
What do you observe when looking at the signal strength screens? Some receivers give more away than others and really you need to find one that gives strength and quality as separate readings.
Chris Foley: Although already having been touched upon, but in all cases where reception is involved its essential for anyone assisting to have knowledge of a persons location, this in the form of a post code or one from nearby such as a shop, as this would then enable the signal reception predictor to be accessed as well as info on the transmitters involved.
Chris Foley: Hi guys, thanks for prompt responce, I do not use my loft aerial although it is connected, i only use the Sky signal, i was wondering could there be an issue with the splitter not being digital? if there is such a thing?
Reading in between the lines, I am wondering whether you are watching the ouput of your Skybox on the other TVs. This uses an analogue signal. Is this what you referred to as being "terrible" after switchover?
If so, then perhaps a digital signal has started up on the UHF channel (frequency) that you have your Sky box set to use. A digital signal interfering with an analogue picture makes it go snowy. You may be able get an idea whether this is the issue by removing the incoming aerial from the Sky box.
I have a loft aerial and my digitalsignal has been fine but of late has started playing up when i change channels its fine and a while later i will change channel and service not running will appear ,next the picture will appear but without sound.I have to turn t.v. off for 30 secs and put it back on and its fine.This is worse in the evening and is getting on my nerves now.our main television is cable but the prob television isnt.any imput would be appreciated.
pamela dudley: You problem is possibly being caused by the signal level received being on the weak side and not really high enough above your TV minimum cut off level.
However its not really possible for anyone to offer advice without having knowledge of either your post code or one from somewhere nearby e.g: a shop, this being used to access info on the station involved.
We have just installed a new digitalaerial in the roof as have been watching freeview channels through sky since switchover, and ow want to watch freeview on a new television ot connected to sky. We have placed the new aerial in the loft in the same location as the old aerial, but do not appear to be receiving a signal. Any ideas?
Karen: Unfortunately what you have said requires a certain amount of clarification, insomuch if new roof aerial has been installed then why are you also using one in the loft? or are you meaning that the loft aerial has been installed purely to be able to watch "freeview" on a second TV thats not connected to the Skybox in the living room?
The other point being, are you able to watch freeview via the roof aerial on the TV that "is" connected into the Sky box as well as being able to view Sky programmes?
But though as your query involves reception then a post code or one from nearby is required such as a shop or a post office, should the latter be near!
Wow. What a useful place you've made! We've just had solar panels installed and would like to move our (Freeview) roof aerial into the loft to reduce shading. We're virtually line-of-sight to the Sandy transmitter (SG8 0QB) - might the signal be strong enough to penetrate a slate roof in our case? Alternatively… do you think we could take the old aerial off the pole? Is it still receiving anything useful?
sarah: By being located at just over 8 miles away from Sandy I don't really think that you have anything whatsoever to worry about by moving the aerial into the loft, that is so long as its not sited close to any control equipment that "may" have been installed associated with the panels which can cause intermittent glitches on the picture.
But though, you would be much better purchasing a log periodic type aerial and fitting that in the loft, these being much easier to position by having an overall length of only 3' 6" / 14" wide, an example of the type referred to in the link.