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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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Wednesday, 14 September 2011

5:16 AM

I thought I might have problems when Oliver's Mount switched over.

I'm only a mile or so from the transmitter (line of site) and was getting full signal before the switch over. My TV (Sony Bravia) seems to be coping fine though. No problems at all.

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Phil's 39 posts GB flag
Phil's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage

8:12 AM

Phil: Olivers Mount is, however, only a 2kW/1kW transmitter, which is much less than Sutton Coldfield, for example, which is 200kW.

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Briantist's 38,915 posts GB flag
9:01 AM

I live in ox28 1fz and the north Oxford Tx change over to digital Overnight. Lost all channels this morning so retuned and initially all was well. Then selected channel 5 and found that all channels other than BBC channels have awful interference. I have a mains powered signal amp in the loft; do you think that the signal is now so strong that it's causing the apparent interference?

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Ewan's 1 post GB flag
Ewan's: ...
peter batey
10:28 AM

just like to put in my bit in my experience the strength of signal is directly linked to quality of signal in my area pontop pike on my Panasonic TV BBC is about 70% strength and 100% quality and itv 2 is 50% strength and between 30% to 50% quality with break up ! so in my book strength and quality have to be linked. don't know about the techy stuff,just my opinion.

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peter batey's 1 post GB flag
peter's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage
1:52 PM

Hi. I live in filey, north yorkshire. Belmont has switched and we now recieve the HD channels and the signal is ok. Still can get blocky on channel 4 and 5 etc. I noticed my tv is telling me to re-tune. I assume this is because we also can recieve signals from Emley Moor. So I will re-tune again on the 21st Sept. My main point/question is, whilst watching itv 1 HD, I noticed that I am getting Granada news? Why? Also when is the last analog signal finnaly switch off nation wide? Thank you.

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Gary's 2 posts GB flag

1:55 PM

Gary: Please see ITV1+1, ITV1HD, BBC One HD regional services on Freeview | - independent free digital TV advice to answer your main question.

The last date in England for analogue TV is 26 September 2012, the dates for Northern Ireland are yet to be announced.

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Briantist's 38,915 posts GB flag

2:26 PM

peter batey: As they say, the plural of "anecdote" is not "data".

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Briantist's 38,915 posts GB flag

2:27 PM

Ewan: It could be, it is also possible that when all the services are at full power in two weeks time the problem will go away.

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Briantist's 38,915 posts GB flag

3:06 PM

There is an upside to all this,in the fact that where i install TV aerials in South-east Shropshire.Within this area,i can receive useble signals from the Winter Hill transmitter in the north-west,in many locations,approx 85-100 miles,and because the line of direction is very close to the line of direction of The Wrekin i can bring in channels from Aquiva A.Aquiva A and B have been nulled here fro the Wrekin as not to interfere with two analogue channels at Brierley Hill(channels 57 and 53).This will all change on the 28th Sept,allilluliah!where all channels will be picked up omni-directionally from The Wrekin,final channel numbers and powers.
My point is,that it is good to receive an alternative BBC/ITV region,inthe 800's.
Incidently received a 41dB signal strength,with good quality of Moel-y-Parc BBCA mux,ch 45,from a favoured spot near the Shropshire/Worcestershire border.

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Aerialman's 140 posts GB flag
4:05 PM

Ok so after losing half my freeview channels today (september 14th) after many rescans and factory resets and still no luck....i just checked my signal quality and signal strength....

My signal quality is a 10 outer 10 (Green bar)

My singal strength sais its 10 outer 10 (grey bar) BUT the flashing bar meter is at roughly 75%

Ive also tried manual retune.

Stations ive lost are Dave,Dave +1, E4+1,Sky News,Realy,Babestation and others.

Soooo....what now? =).

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Matt's 17 posts GB flag
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