Loft aerials

Published on 11th January 2007 at 16:31 by Brian Butterworth on UK Free TV

One of the most common problems people have with Freeview reception relates to the use of "loft" aerials.

Because the analogue TV transmitter network uses very high power transmissions (the total ERP for the UK is 64 megawatts) many people have installed their TV aerial in places such as lofts, or have used other  Indoor Aerials.

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

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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?

1 post

Dave Lindsay
Monday 31 December 2012 7:28PM

Peter martelli: No because it doesn't broadcast all Freeview channels!!!

3,928 posts

Chris Foley
Sunday 3 February 2013 1:00PM

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

3 posts

Dave Lindsay
Sunday 3 February 2013 1:12PM

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.

3,928 posts

jb38
Sunday 3 February 2013 1:40PM

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.

4,570 posts

Chris Foley
Monday 4 February 2013 1:35PM

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?

3 posts

Dave Lindsay
Monday 4 February 2013 1:47PM

Chris Foley: No, the splitter works by frequency and isn't bothered whether signals are analogue or digital.

Reading in between the lines, I am wondering whether you are watching the ouput of your Sky box 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.

3,928 posts

Chris Foley
Monday 4 February 2013 2:10PM

Dave Lindsay: Thanks Dave, I think you could be right, i will disconnect my aerial when i get home and let you know the outcome, thanks again, Chris

3 posts

Dave Lindsay
Monday 4 February 2013 2:14PM

Chris Foley: The procedure to change the output channel of a Sky box is here:

 How do I change the RF output channel on a Sky Digibox? | ukfree.tv - 10 years of independent, free digital TV advice

3,928 posts

pamela dudley
Tuesday 19 March 2013 12:47PM

I have a loft aerial and my digital signal 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.

2 posts

jb38
Tuesday 19 March 2013 5:30PM

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.

4,570 posts

Karen
Friday 5 April 2013 8:08PM

We have just installed a new digital aerial 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?

1 post

jb38
Saturday 6 April 2013 8:17PM

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 Sky box 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!

4,570 posts

sarah
Thursday 18 April 2013 8:59AM Royston

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?

2 posts

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jb38
Thursday 18 April 2013 9:40AM

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.

 Online TV FM DAB Aerial sales

4,570 posts

sarah
Thursday 18 April 2013 11:01AM

jb38, that's very reassuring; I'll look at the log type aerial and assess local installers. Thank you!

2 posts