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Freeview reception has changed?

Why should my Freeview reception change when I have not changed anything?

Why should my Freeview reception change when I have not changed
published on UK Free TV

From time to time people find that their Freeview box, integrated set (idTV) or Personal Video Recorder (PVR) has lost many channels without any apparent changes.

There are a number of factors to consider

Freeview is broadcast on digital multiplexes. This means that, once broken down into a stream of bits, each television channel is combined into a single transmission of 1s and 0s. This means that reception is of the multiplex first if this is lost it affects all the channels in the multiplex in the same way.



The signal strength received by the box or TV for a particular multiplex from a given transmitter determines if the data can be received or not. So, a poor signal results in no data, an adequate signal in perfect data and a low signal in either none or all.

Poor digital signal levels do not result, as they do with old-fashioned analogue television, in a sub-standard picture or sound. Poor signals often result in a perfect data-stream, but are prone to periods of no reception. Sometimes this will be for hours, but can also be several times a minute when caused by induction from fridges, freezers, central heating systems, two-stroke scooters, baby monitors and so on.

If you have lost ALL your Freeview channels

First disconnect the aerial lead from the Freeview box or TV set and reconnect it and then follow this reset procedure to scan for channels again. If this does not result in services being restored, check the Freeview transmitters page to see if there are any engineering problems with your local transmitter.

How to check all cables, connectors and aerials

The RF connectors need to be in very good condition to work. There are two general types:

Factory-fitted connectors are very reliable as they cannot easily be taken apart, but they can be damaged by wear and tear. On the female-type the central section is often composed of two parts which can often be forced apart, resulting in a poor connection you can push them back together if this has happened with a pair of tweezers. On male connectors if the central pin is damaged, you will need a new cable. If there are any loose partials in the connector, remove them.

Another problem with these cables is that quite easy to sprain the connector at the back which causes little obvious external damage, but disconnects the internal connection. This happens often when a set-top box is pushed backwards into a cabinet.

Hand made cables can also suffer from similar problems to factory made ones and they are also prone to accidental damage from a cable being pulled. If such a connector is not firmly attached to the cable, the connector may need refitting.

Cables

Make a visual check of the cables. There are a few basic checks:

If the cable has been slashed or cut, it will not be very effective or reliable. If such a cable is fitted externally, this can allow rainwater to enter the cable and this will reduce the signal levels.

You can easily damage an RF cable by crushing it, for example in a door. If the outside of the cable has a permanent kink in the cable or has been very tightly looped, this could be the site of damage.

Aerial

For reliable and effective Freeview reception, a rooftop aerial is required. It is hard to make a visual check of such an aerial without putting yourself in potential danger.

You can make a visual check of the route between the aerial and the transmitter. Any form of obstruction will damage the digital signals. In particular trees coming into leaf, as these will leech the signal before it reaches your aerial. This applies to both trees adjacent to the aerial and at a distance.

Another common problem in cities is building work. A large crane will often change position many times during the day, and if this is between your aerial and the transmitter this can reduce the signal levels in an unpredictable way.

If your system uses a booster, the power may have failed. Check the fuse to the power to the booster.

Weather problems

There are two main weather problems that effect Freeview reception.

The Inversion Effect: please see What is the Inversion Effect and why does it effect my Freeview TV reception?



Wind: high winds sometime can dislodge the aerial this results in a poor signal.

Rain: poor or old cables can fill with water and this results in a poor signal. If this happens, the cables will require replacement.

Help with Freeview, aerials?
How do I get a test card with Freeview1
I would like to know if it is possible to receive UK terrestrial Freeview servic2
I have been told I would receive too much singal from my Freeview tansmitter as 3
Can my Freeview box receive more than one BBC and ITV region?4
Is it true that my 87 year old mother is entitled to a FREE upgrade when the ana5
In this section
Official aerial installers guide to the TV spectrum future1
Which free digital TV system will give me the most reliable reception?2
High pressure causing channel loss through "Inversion"3
Digital Region Overlap4
Two frequency interference 5
Single frequency interference6

Comments
Thursday, 25 August 2011
D
David
5:01 PM

jb38: Thanks very much. The manual suggests that it should be capable of seeing Freeview HD. I will try the booster and report back . Thanks very much for all of your input.

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David's 4 posts GB flag
Saturday, 27 August 2011
L
lorraine dobson
4:07 PM

at about 11.00a.m this morning all the t.vs in the house had no signal on the screens, this has happened in the past but lasted only a few moments, then all ok, this time has gone on for 5 hours so far, can only get bbc1 and bbc2. just wandering if anything to do with the transmission in hemel hempstead.

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lorraine dobson's 1 post GB flag
Sunday, 28 August 2011
D
DavidHufton
7:21 PM

My HumaxPVR9200 shows BBC channels to have lower signal Powers than other channels. This results in occasional drops in signal Quality accompanied by drop out of picture and sound. Why should this be when all non-BBC channels don't suffer even when they share a multiplex with the BBC? BBC Powers register about 60 and non-BBC 80.
Thanks, DH

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DavidHufton's 5 posts GB flag
J
jb38
sentiment_very_satisfiedPlatinum

9:31 PM

DavidHufton: But they dont share the same multiplex and thats why the signal strengths can be different, normal main stations using 6 multiplexes with two of them being BBC and the rest commercial concerns.

Freeview "light" stations having limited services because only three multiplexes are involved, two of them used by the BBC, with one being for HD transmissions.

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jb38's 7,179 posts GB flag
Monday, 29 August 2011
M
Mike Dimmick
sentiment_very_satisfiedPlatinum

12:23 AM

DavidHufton: The only non-BBC channels sharing a BBC multiplex are Sky Sports 1 and 2, if your region hasn't yet switched over, or ITV1 HD and 4hd if it has (STV HD rather than ITV1 HD in Scotland, or S4C Clirlun rather than 4hd in Wales).

If you provide a full postcode we can offer more information. At some pre-switchover transmitters, the BBC main multiplex (Mux 1) is on lower power than others; Multiplex B (the second one) is often lower than Mux 1, 2 and A.

In general, higher frequencies travel less well than lower ones, in air but particularly along cables. Aerials generally have higher gain at higher frequencies within the group, which offsets this a bit. There is also a phenomenon called Frequency-Selective Fading which can mean some frequencies are more affected by reflections than others - those reflections can either add to or subtract from the signal, depending on the distance of the reflective surface from the normal path.

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Mike Dimmick's 2,486 posts GB flag
J
jb38
sentiment_very_satisfiedPlatinum

8:06 AM

DavidHufton: Or can I put it another way David, if two different signal strengths are seen on what you are looking at then you are comparing two different multiplex transmitters, so rather than just looking at the signal strengths also look at the multiplex channel numbers (not EPG programme ones) associated with them.



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jb38's 7,179 posts GB flag
A
Alan Kiddell
8:30 AM

I receive my signal from tacolneston, Norfolk.
In the last few day I have been getting a very poor signal on a number of channels including BBC 1.
There is indication if engineering work last weekend.
Is there any chance this could be the cause?

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Alan Kiddell's 1 post GB flag
Tuesday, 30 August 2011
Briantist
sentiment_very_satisfiedOwner

1:54 PM

Alan Kiddell: There has been no work since then, I would have a look at Single frequency interference | ukfree.tv - independent free digital TV advice .

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Briantist's 38,910 posts GB flag
Friday, 2 September 2011
W
William Mchugh
3:11 PM

Caravan freeview reception sites Y025 8TZ Skipsea most have lost channels Mux C Sky news etc. Retuned several times use to get 85 T V channels now only 45? Belmont transmitter, any ideas please. William McHugh

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William Mchugh's 2 posts GB flag
Jeff
3:18 PM

I am in AL5 Harpenden and get Freeview from Crystal Palace. Since 31 August I have lost the HD channels on Ch31, I assume this is due to Sandy Heath starting to use this channel. Would a more directional aerial solve the problem. If not I guess thos of us up to the North East of London will have to wait till 18th April next year for the saerice to return.

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Jeff's 3 posts GB flag
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