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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.

Help with Freeview, aerials?
Can I attach a Freeview digibox to a Combi TV/Video unit?1
My high gain aerial can't get all the Freeview channels I expected2
I can't get Freeview yet, when will it start in my area?3
Are there plans to extend the range of regional variations on Freeview?4
How can I Receive Freeview on two TVs using one box?5
In this section
Should the UK close down the TV networks to allow for more mobile broadband? 1
UK Digital switchover ends - Northern Ireland completes on 24th October 20122
The last day of analogue television in the UK - goodbye PAL3
2 days left of analogue television - goodbye teletext4
3 days of analogue to go - goodbye to NICAM 7285
Changes to Saorview frequencies and power levels, 24th October 20126

Comments
Sunday, 11 November 2018
MikeP
sentiment_very_satisfiedPlatinum

1:00 PM

Tony:

Excessive signal is unlikely to cause internal damage to your Freeview equipment unless it is at a signal level of several volts! It is usually a few millivolts. However, excessive signal will overload the tuner so it cannot work properly and will give either no reception al all of else all the pictures will break up (pixilation). You ideally need a signal strength shown on your TV of between 60% and 85%,



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MikeP's 2,929 posts GB
Wednesday, 6 February 2019
P
Phil Glen
11:21 PM

Hi I have a tv signal of 94% and quality 100% since recent retune at Craigkelly transmitter which causes pixelation problems on occasion.
Can you tell me what attenuator I.e. 2db 4db 6db etc. I woulld require to achieve an acceptable signal.

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Phil Glen's 7 posts GB
Thursday, 7 February 2019
MikeP
sentiment_very_satisfiedPlatinum

7:58 PM

Phil Glen:

You should try a 3dB one first and if that is not sufficient then try a 6dB one. I'm not a fan of the variable types as they seem to be uncertain quality.



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MikeP's 2,929 posts GB
Friday, 8 February 2019
D
duncan
11:49 AM

Our problem..We have two TV's so fitted a 2 way splitter "F" type.
Worked fine but then today main TV has "no signal so I " Unscrewed "F" connector and when the copper cable touched the outer case of splitter TV had signal 50%+ strength and 100% quality but as soon as I connect it back I lose signal. Is it a faulty splitter ?

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duncan's 1 post GB
MikeP
sentiment_very_satisfiedPlatinum

9:44 PM

Duncan:

It may be but there are things to check first.

Start by checking that the F connectors are all fitted correctly and that there are no stray filaments of the outer touching the inner conductor. Do that check on all the connectors. Then use an F coupler to join the aerial feed cable to just one of the TV feed cables and check the signal strength for all multiplexes on that TV. Then do the check connected to the other TV without the splitter.

I that all works, then connect both TVs again using the splitter - ensuring that all the connections are perfect again. Then check both TVs.

If all is working then the problem was oxidation on the contacts - it happens more often than people realise. If all is not working then it is likely to be a fault in the splitter. Make sure you never try to use the splitter with just one outlet connected - they are designed to have all outlets in use to ensure there is the correct impedance matching.

Let us know how you get on, please?



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MikeP's 2,929 posts GB
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