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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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Thursday, 10 November 2011

10:25 PM

Graham Clarke: Please see the article at the top of the page.

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Briantist's 38,907 posts GB flag
Saturday, 19 November 2011
MK Malc
5:21 PM
Milton Keynes

We live in Milton Keynes MK5, so on the outskirts of Sandy Heath transmitter.
We have 100% quality on Mux1 and 0% quality on mux2 channels.
The only channels we have apart from mux1 are arqB.(e.g. ITV4)
Strangely, ITV1 was ok for a while after 2030 last night.
It's been like this for over a week and we are getting a little frustrated !!
The website says Sandy Heath receivers are liable to interruption, but it seems to have been a long time.
Any advice would be very welcome.

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MK Malc's 2 posts GB flag
MK's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
MK Malc
5:34 PM
Milton Keynes

Just thought I'd add :
we have a booster, but signal strength is only 60% on all channels with it on.
When we tried to retune with the booster turned right down, ITV1 and the other mux2 channels disappeared completely.
We turned it up about half way to enable us to get ITV1 back, albeit not watchable.
Hope this helps with a diagnosis.

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MK Malc's 2 posts GB flag
MK's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
10:30 PM


My parents have lost a couple of their freeview channels last week (Film 4 and Yesterday). They live in Colchester and prior to last week, they were able to recieve these channels. Any ideas why they would loose them and how it can be fixed?

They have retuned both their recorder and tv, and this happened at about the time the Sudbury transmitter was switched on.


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Dan's 1 post GB flag
Tuesday, 22 November 2011
9:08 PM

We cannot get a tv signal atall on my daughters television. We have tried all sorts of aerials and Freeview boxes but to no avail. The signal wasn't great before the switchover, however, now we have no signal atall. We live in South Lanarkshire in Scotland (ML9 area). Any help would be appreciated.

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Jeanette's 1 post GB flag
Dave Lindsay

9:31 PM

Jeanette: Is there not a roof-top aerial?

What do the neighbours get?

Are these aerials you've referred to set-top ones or fixed/roof-top ones?

The post code might be helpful in giving a more accurate response.

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

9:32 PM

Jeanette: In general, roof-top aerial is advised, although that is not to say that a set-top aerial will work in certain locations (to a certain degree).

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Dave Lindsay's 5,724 posts GB flag
Friday, 2 December 2011
6:11 PM

I live in Hunstanton, North Norfolk (East Anglia). Almost unbelievably the only signal we get is from somewhere in Yorkshire and as a result we get Yorkshire local TV. As if that's not bad enough since switchover we have now lost channels like Yesterday et al. I despair and am now looking at SKY or FREESAT as the only way of receiving programming from my home region unless someone can offer a solution.

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Mark's 3 posts GB flag
Dave Lindsay

6:19 PM

Mark: I believe you!

See here for the response I made to someone else in Hunstanton with the same query:

Freeview on Tacolneston TV transmitter | - independent free digital TV advice

If you have lost Yesterday etc then it could be because you have a Group A aerial on Belmont. The commercial channels are not in Group A and as such that is probably why such an aerial is less sensitive to picking them up.

If you would like a fuller explanation, please let me know. Your post code might help give a more accurate prediction.

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Dave Lindsay's 5,724 posts GB flag

8:08 PM

Mark: Have you tried receiving a signal from the King's Lynn relay which is sited at Sandringham? Mux BBCA for East Anglia is currently transmitted on C49- (due to change to C40 in 2013, date TBA). Aerial needs to point South and set for vertical polarisation.

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KMJ,Derby's 1,811 posts GB flag
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