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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
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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, 27 March 2013
Dave Lindsay

5:03 PM

Louise Irvine: I don't think there's much more to suggest. It may be worth trying the troublesome TV directly into the aerial wall socket (without the cables that feed different rooms connected). Failing that, perhaps stick with PSB-only Tay Bridge via the set-top aerial.

From Angus, there are six broadcast channels (frequencies/signals), including the HD one. Does it affect them all?

PSB1 - BBC One
COM5 - Pick TV
COM6 - Film4

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Dave Lindsay's 5,724 posts GB flag
Saturday, 27 April 2013
1:19 AM

How do you tell if an aerial is giving "too much signal"?

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Tim's 1 post GB flag
Tim's: mapT's Freeview map terrainT's terrain plot wavesT's frequency data T's Freeview Detailed Coverage
Monday, 29 April 2013
m newhouse
1:25 PM

hi, our bush digibox 500gb worked fine till the change over. we returned it to argos for the same . it still will not hold bbc tv picture . tv picture from airial is great.signal strength on tuning is low but if i put airial into rf out on digibox the signal increases but still will not hold bbc1 . can you help?argos helpline is useless. i did see that looking for bbc1 durther up the ch list may work

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m newhouse's 2 posts GB flag
Dave Lindsay

3:19 PM

m newhouse: The issue of receivers 'forgetting' channels when they are powered down usually happens where they have run out of tuning memory. The forgotten channels are picked up last during the automatic tuning scan and also the signals from other transmitters have been picked up before. The trick is usually to prevent a receiver from storing the signals from other transmitters so as to have enough room for the wanted one.

Without knowledge of your location (preferably in the form of a postcode or nearby postcode such as that of a shop) and transmitter it isn't possible to tell whether this may be the reason for your difficulty.

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Dave Lindsay's 5,724 posts GB flag

4:28 PM

It is rare for an aerial to give 'too much' signal without a booster/amplifier unless you are very close to a main transmitter.
In analogue days you would see strong cross modulation patterns on the screen but with digital you can only go by the signal strength and quality guides. If the signal is too strong then the Strength will be 100% but the quality will be very low. You can check it by inserting a coaxial attenuator in the aerial lead, preferably at the TV UHF input for this test purpose. They are available with different attenuation, typically 6dB, 12dB or even 18dB. If by trying one the strength stays high but the quality improves significantly then there may be too strong a signal.

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MikeP's 3,056 posts GB flag
Wednesday, 12 June 2013
11:02 PM

I've recently had an extension built on my house and installed a tv in the kitchen. With the existing aerial it seemed to pick up the main channels ok but additional ones were ropes and hd was a non event. I bought a high gin aerial which sorted the hd out perfectly however th other freeview channels are very temperamental. On retune will give itv and associated channels but the bbc channels are awful and vice versa. I have now bought a booster which gives me great bbc service now but itv, channel 4 & 5 etc are horrendous. I'm pretty sure the problem is too much signal on UHF channel 44. Bottom line is I'm confused as to what else I can do. The only thing I can thnk of now is that when the cable has been split and run to the new socket it has been bodged and stuck with tape rather than using a y connecter or splitter. Can anybody help here please?

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Richard's 2 posts GB flag

11:56 PM

Richard: Its not really possible for anyone to be able give advice on a problem of this nature unless a persons location is known, post code or one from nearby (e.g: a shop / post office) as this is required for the purpose of accessing info on the transmitter covering the area plus the signal levels expected at the given location.

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jb38's 7,179 posts GB flag
Thursday, 13 June 2013
9:54 AM

Thanks jb38, I realised after I posted that I needed to include that info! My mistake.

Anyway we live in S21, 9 miles outside Sheffield. The aerial is a philex 48 element high gain mounted in the loft.

Hope you can help

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Richard's 2 posts GB flag
Wednesday, 24 July 2013
11:56 AM

what is the perfect signal quality i live in liverpool england thanx

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rob's 1 post GB flag
Monday, 19 August 2013
11:06 AM

I recently got bt youview and an SL x 48DW Gold 48 Element Digital aerial installed in my loft space. theres plenty of room up there and i can see the TV mast from my house. However I only get 39 channles Inc radio ones which is really frustrating. Do I need to put the aerial on the roof or am i getting to much signal? I have 30 - 40% signal strength and 100% signal quality on the channels I do receive according to the bt box.

My post code is LL401GA

may have to pay an proper installer and stop being a tight ass

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Kieren's 2 posts GB flag
Kieren's: mapK's Freeview map terrainK's terrain plot wavesK's frequency data K's Freeview Detailed Coverage
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