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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?
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
Friday, 12 June 2015
B
Brian Murray
9:09 PM

Dave Lindsay: Thanks for your help. Reception of COM7 channels is fine, COM8 is non-existent .

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Brian Murray's 7 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

10:09 PM

Brian Murray: According to Digital UK, COM8 launched from Caldbeck only yesterday.

In which case, if you haven't already done so you should go to the manual tune screen and select/enter UHF channel number 35 (if there's an option for DVB-T or DVB-T2 then the latter should be chosen). Don't press the button to scan/add services straight away, instead wait and see what readings of strength and quality you get. If the going's good then add the channel.

According to Digital UK, power levels for Caldbeck channels are:

PSB1, PSB2, PSB3 - 100kW
COM4, COM5, COM6 - 50kW
COM7 - 31.91kW
COM8 - 35.8kW

We do not know whether COM8 is running on its full final power yet.

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

10:12 PM

Brian Murray: Have you confirmed that BBCB is tuned to Caldbeck (England) on UHF channel 30?

And, silly question, but the grid aerial is mounted horizontally and not vertically?

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Dave Lindsay's 5,724 posts GB
Saturday, 13 June 2015
B
Brian Murray
12:48 PM

Dave Lindsay: tried the manual tuning option - unable to tune in any programmes on CH30 or CH35 - tv goes through the process of searching & tells me there is nothing there.
Grid aerial is mounted horizontally (had to wait for daylight to confirm this).

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Brian Murray's 7 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

1:40 PM

Brian Murray: That's odd. So what BBCB(PSB3) is it tuned to? This information (the tuned UHF channel and/or frequency) is given on the signal strength screen. Go to 101 BBC One HD and view the signal strength screen.

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Dave Lindsay's 5,724 posts GB
B
Brian Murray
2:11 PM

Dave Lindsay: I don't have any of the BBCB channels - I tried switching to 101 but just get message on screen saying invalid DVB channel

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Brian Murray's 7 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

2:18 PM

Brian Murray: What you're describing sounds like a TV which doesn't have a Freeview HD (DVB-T2) tuner in-built. Lots of people have been caught out by this. Are you sure it receives the HD channels itself or have you been viewing the HD channels using another tuner such as a PVR?

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Dave Lindsay's 5,724 posts GB
B
Brian Murray
3:07 PM

Dave Lindsay: I think you may be right - one of the tvs connected to this aerial is an old Panasonic, which is the one I have been using to test. I cannot get any of the BBCB channels on this TV, but I am sure I used to be able to get Film4+1on it previously.
The other TV is a fairly new Samsung, whichI have retuned(yet again) and it has "re-found" Film4+1 - the other HD channels are still there, but reception is very iffy- picture breaks up.

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Brian Murray's 7 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

5:18 PM

Brian Murray: As you may know, Film4+1 used to be on one of the COMs (COM5 IIRC) and it's now on BBCB. So even though it's in SD you need a HD receiver to get it. The TV or box you are using for the test must have a HD (DVB-T2) tuner in-built, usually branded as being "Freeview HD".

Retuning is a waste of time if it's tuned correctly -- you need to ascertain that that's the case. So is the Samsung tuned to UHF channel 30 (545.8MHz or 546MHz) for BBC One HD? If it is, what happens with a different aerial?

Perhaps there's a known issue with your model that is causing it to forget Film4+1. Let us know the model number and one of the experts on here might be able to shed light on that.

That said, perhaps the issue is Film4+1 moving multiplex and some remnant of its old multiplex being stored in your TV, this only being cleared out by a factory reset. This still doesn't explain the poor reception.

A grid aerial has low gain (because it has no elements and has wide acceptance angle). So it would seem unlikely that you could possibly be suffering from too high a signal level into your TV. Where this is the case, however, it usually affects HD multiplexes before SD muxes.

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Dave Lindsay's 5,724 posts GB
B
Brian Murray
6:05 PM

Dave Lindsay: Looks like I'll either have to replace the Panasonic or put up with not having those channels then.The Samsung is a fairly new TV,46" screen, purchased Dec2012 and is FreeviewHD with 3D. The Samsung is tuned to UHF channel 30. Haven't tried a different aerial yet as it's a long way up to our roof (big old house) and going up & down ladders isn't my favourite occupation.
However, if you think I would get better reception of UHF channel programmes by changing the aerial from the grid aerial to a Yagi then I will get a new Yagi aerial and change the aerials over.

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Brian Murray's 7 posts GB
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