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Loft aerials

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

One of the most common problems people have with Freeview recep
published 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

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.

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Do I need to buy a booster?1
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Comments
Friday, 16 November 2012
C
Chris Dickson
7:30 PM

I have a loft tv aerial. Now I have digital through my cable supplier, do I need the aerial and should I dispose of it?

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Chris Dickson's 1 post GB
Monday, 31 December 2012
P
Peter martelli
7:20 PM

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?

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Peter martelli's 1 post GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

7:28 PM

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

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Dave Lindsay's 5,724 posts GB
Sunday, 3 February 2013
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Chris Foley
1:00 PM

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

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Chris Foley's 3 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

1:12 PM

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.

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Dave Lindsay's 5,724 posts GB
J
jb38
sentiment_very_satisfiedPlatinum

1:40 PM

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.

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jb38's 7,179 posts GB
Monday, 4 February 2013
C
Chris Foley
1:35 PM

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?

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Chris Foley's 3 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

1:47 PM

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.

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Dave Lindsay's 5,724 posts GB
C
Chris Foley
2:10 PM

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

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Chris Foley's 3 posts GB
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