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Freeview signals: too much of a good thing is bad for you

If you have a high-gain aerial or use signal amplifiers, it is quite common to find that the high-power digital signals provided after switchover will overload your Freeview equipment - and can appear to be "weak signals".

If you have a high-gain aerial or use signal amplifiers, it is
published on UK Free TV

Most people will experience nothing but simplicity and joy with the digital switchover - the process that turns off the old five high power analogue signals, and the existing six low power digital services and replaces them with six new high power Freeview multiplexes.

For those with problems, there are generally three issues.

Eliminating other possible problems first

The first is that very, very old equipment will not function with the digital signals split into 6,817 sub-signals, as it was only designed to work with 1,705 sub-signals. This is known as the "8k mode issue" - see TVs and boxes that do not support the 8k

It is also common that people do not clear out the old channel list (by selecting "first time installation" retune, "Factory Reset" or "Shipping Condition") before doing an "autoscan" for the available broadcast frequencies, and this results in everything from missing channels to no subtitles, programme guide, wrong channel numbers and no text services. If you can't find how to do it see either Freeview Retune - list of manuals or do it this way: My Freeview box has no EPG, is blank, has no sound or the channel line up is wrong .

A third problem is caused by having signals from more than one transmitter - see Digital Region Overlap.

The final very common issue is "too much signal".

Transmitters have much more digital power after switchover

At most transmitters, the digital signals after switchover are considerably more powerful than before. This was because when the analogue and digital services ran together, the digital services were kept low to prevent appearing as snowy interference on television sets using analogue reception.

Here is an example, from Sutton Coldfield, of how the signals change at switchover:

4,000kW of analogue signals are turned off, and the digital services increase in total power from 48kW to 1,200kW - that is an increase of 25 times in numerical terms, also know as +14dB. (The reduction of -7dB from the analogue strength is intended - the digital services require less power to cover the same number of homes).

This large increase in power should cause no effect for most people. A stronger signal does not increase the picture quality (you need Freeview HD for that), sound levels - the only effect should be that more homes that are further away from the transmitter mast can receive a stable digital signal.

High gain aerials and signal boosters

However, many people have been tempted into buying one both high gain aerials and signal boosters.

High-gain aerials were very suitable for places where the Freeview signal before switchover was very weak indeed, but if you have one of these and you are located closer to the transmitter, you will probably now have a signal overload.

Generally speaking, signal booster devices are never really much use for Freeview reception, and much of the time they actually amplify the interference more than they do the signal, causing reception to get worse, not better.

How to tell if you have too much signal

There are almost as many ways for a Freeview box to display the "signal strength" and "signal quality" as there are types of Freeview box. Here are some of them:

Speaking generally, there will be two indicators:

One is signal strength - this shows the power level of the signal entering the Freeview box. Often "0" is the lowest and "10" the highest, but sometimes it can be a percentage, sometimes coloured boxes and so on.

The signal strength should be around 75% - more than this indicates too much signal.

The other measure is the signal quality and this is much more important to high-quality Freeview viewing. Any measures that increase this to the maximum will provide for uninterrupted viewing, lower values will result in "bit errors" that cause the picture to freeze and the sound to mute out.

One problem with over powerful signals is the overload can sometimes show as a low signal because the receiver circuitry will enter a "blown fuse" state to protect itself.

How to deal with too much signal

First, if you have a booster or amplifier - remove it from your system. Don't just unplug the power, as this will result in no signal getting though the device.

If you can't just disconnect the output cable and connect it to the input cable, you might need a coax female-female coupler to connect two male connectors together.

If you don't have a booster or amplifier, you might have to fit an attenuator onto the cable. They come in two types, either a "single attenuator", around five pounds, or a variable attenuator, for around ten pounds. The variable sort has a knob that can be turned to select the required level of signal dampening.

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Saturday, 3 December 2011
9:52 PM

Thanks for your replies, unfortunately I live in a flat and we have a communal aerial so upgrading or pointing it in a different direction would not be my decision although I will relate your comments to the powers that be at the next opportunity.

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Mark's 3 posts GB flag
Tuesday, 13 December 2011
5:04 PM

According to the information for the Belmont transmitter on this site COM5 CH53 & COM6 CH60 are being transmitted at the same power level of 4000 watts. I get 40% strength and 100% quality for COM5 and 20% strength and 0-10% quality for COM6 - surely some mistake?

North Norfolk is getting a raw deal, not only do we not get the programming for the region we live in, we can't receive all the Freeview channels(Yesterday, Film4, ITV4 etc.) because the transmitter is not up to the job.

My Postcode is PE36 6JB

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Mark's 3 posts GB flag
Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Dave Lindsay

5:44 PM

Mark: One thing to be aware of is that Belmont was once (in the days of four-channel analogue) was group A only which means that it only used lower frequencies and that aerials that were installed for it were group A which means that they aren't as sensitive to the higher frequencies.

When Channel 5 came along, it was on C56 from Belmont at 50kW (versus 500kW for the other analogues). So you might have had another aerial fitted to receive it. If you didn't, then perhaps this would explain.

The only other thing I can think is that C60 from Sudbury is causing you interference, which, if it's the case, is ironic because many people in the Suffolk area can't pick it up.

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Dave Lindsay's 5,724 posts GB flag
Carl castleton.
6:59 PM

Just brought a variable tv attenuator would this need to be placed before distrubution amp or at tv getting 85-95 sig strength showing on tv.Keep getting no signal at 1tv but have got signal at outher free view box`s. is this too much. on bellmont transmitter think the aeril is 52 elerment wide band. also had mast head amp disconected last year. Thank you carl. king`s lynn norfolk.

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Carl castleton.'s 1 post GB flag
Sunday, 8 January 2012
Ian McPherson
9:46 PM

Can anyone help, I have a Freeview HD+ recorder with one of those funny little loop through situations at the back with a little jumper cable between RF out 1 (Aerial is connected to RF in 1) and RF in 2 (cable then goes from RF out 2 to my tv). However after a few days the picture has become jumpy and freezes. I have discovered that if I plug the aerial into RF in 1 and tyhen straight from RF out 1 to my TV the picture is crystal clear and no problems. It seems there is a massive loss of signal strength and quality as it goes through the second reciever (however the recording function requires this to be looped as originally set up). My question is would buying a more expensive Freeview+ HD recorder result in better quality or do I need to look at increasing my freeview signal strength?

Or could I supply two seperate signals one to each reciever in the box (rather than the second one getting its signal from the first one via the loop cable), as I have two working aerials on my roof at the moment.

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Ian McPherson's 1 post GB flag
Dave Lindsay

9:50 PM

Ian McPherson: What is the make and model of this HD recorder?

Also, what is your location, preferably post code, so we might check on the likely signal at your location? It would be useful to know what transmitter you are receiving from, or what direction your aerial is pointed in (the latter certainly requiring a location in order to determine the transmitter).

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Dave Lindsay's 5,724 posts GB flag
Dave Lindsay

9:55 PM

Ian McPherson: There is no reason why you can't use one aerial for each tuner in the box; that is the reason for having two inputs. That is, so that you can use different aerials on different transmitters for analogue and digital.

Of course, when analogue is switched off in your area, then you can disconnect the analogue tuner altogether.

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Dave Lindsay's 5,724 posts GB flag
Monday, 16 January 2012
Ian Podmore
12:48 PM

We have recently got a new Sony TV (40HX723) with HD freeview, and live in Lichfield.

We have got a rooftop aerial (X Bow type) that has been there about 17 years.

We have full signal strength and quality but when watching HD channels on the TV, the picture goes black including the 'System Information' overlay if it is on. No problem when watching normal freeview channels or DVD etc.

We are only 5.5 miles from Sutton Coldfield mast and aerial appears to be aligned correctly, and we have never had a problem before.

Could it be an aerial problem, or is the TV shop trying it on? I have also tested the TV on a different site with a new aerial install and get the same there as well.

TV shops threatening that we will have to pay if repair engineer comes out to TV and finds its the aerial!

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Ian Podmore's 1 post CH flag
Dave Lindsay

1:32 PM

Ian Podmore: On the basis that you are so close to a high power station, then the first thing to try must be an attenuator (as shown at the top of this page). I would get a variable one.

The shop you bought your TV from is (I assume) not responsible for your aerial installation. Thus, if someone comes out, then it is not surprising that they will charge if it is found that their product is not at fault.

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Dave Lindsay's 5,724 posts GB flag
Wednesday, 8 February 2012
11:03 AM

We live approximately 10 miles from the Hannington transmitter which started switchover today. We can no longer receive any BBC channels on Freeview (which I understand are the first to be switched).
We have a regular digital aerial in our loft connected to a multiway signal booster to allow us to run 6 TV sets from the one aerial. This has always worked fine in the past. I understand that the strength of the post-switchover signal may be responsible for the missing channels, but will it be sufficiently strong to feed multiple sets without a booster? Or could there be a different problem?

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Iain's 2 posts GB flag
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