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Current Freeview changes make it a little less reliable

Over the next three years, Freeview is shuffling the frequencies it uses to make room for more mobile broadband. Will this mean risking missing a few TV shows?

Please do not blame Freeview.   They are pumping out all the usual signals if this happens to you.      Photograph: UK Free TV
Please do not blame Freeview. They are pumping out all the usual signals if this happens to you. Photograph: UK Free TV
published on UK Free TV

Freeview is reliable

If you enjoy watching TV using Freeview, this means that there is a wire going from the back of your TV set to an aerial on the roof of your home, flat or office.    In the air. the Freeview TV signals travel in straight lines, like light, so the aerial needs to be able to “see” the top of a Freeview transmitter tower. 

From the top of one of these towers is mounted a cylinder that is covered in transmission panels.   This allows the Freeview signals to be sent out in a controlled pattern, for several reasons:

  • It is wasteful to send the signals out into space;
  • It is unhelpful to send signals over a country borders;
  • It is unnecessary to send signals into mountains where no-one can get them;
  • To limit the possibility of interference in a very flat area;
  • Sometimes to synchronise a signal in a single frequency network area.

 

Tropospheric Ducting

It is quite reasonable to think that all the above conditions would remain constant over time.

It was discovered that all TV signals sent horizontally do not always just zoom off into space.   From time to time, changes to air pressure cause “Inversion” and the signals can reflect down as if there were a mirror at cloud level.  Sometimes the signals can be found 800 miles beyond their expected locations.

 

The way the digital TV signals are encoded incorporates ways to reject these unplanned, unexpected interference.    There is a limit to what can be done in all instances.

Whilst it is possible to predict where the “mirrors” can occur in the atmosphere – see http://www.dxinfocentre.com/tropo_nwe.html - the loss of Freeview channels from your box can then depend upon:

  • The Freeview multiplex you are watching (the ones in DVB-T2 mode are safer);
  • The direction your aerial points because which TV transmitters are in a line projecting from your roof to your normal transmitter AND which transmitters are in line 180 degrees from the above one;
  • If your aerial system has an amplifier (that might get overloaded and stop working);

This means that moving a few streets away can make the difference between no Freeview at these times and normal service during a time of Tropospheric Ducting.

People who watch satellite TV can have a similar, random problem caused by heavy rain and snowfall. 

Generally, these Tropospheric Ducting events happen in the UK about the times the clocks go forward and go back, and sometimes when there is a very still, cold winter. 

 

Why the 700MHz changes might be an extra problem

 In simple terms the 700MHz changes will reduce the number of transmission frequencies for Freeview from 40 (C21 to C37, C39 to C48) to just 30 (C21 to C48, C55 and C56).  This is being done in a way that keeps all the channels you can watch.

It does mean, however, that during those times of random Tropospheric Ducting it will be slightly more likely that an interfering signal might occur at any given location.

 

Do not adjust your set

So, please don’t blame Freeview.   They are pumping out all the usual signals if this happens to you.    

If it does happen, please don’t retune your equipment.    It is unlikely that the problem will continue for more than a few hours at the most, and you will most likely be able to watch most other Freeview channels.

 

Do we need an “Inversion Effect” predictor?

Would it be useful to develop a tool to work out how bad a potential Tropospheric Ducting event might be for a given location? 

 

See also https://ukfree.tv/article/1107052352/What_is_the_Inversion_Effect_and_why_does_it_effec



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Comments
Sunday, 18 February 2018
M
MikeB
sentiment_very_satisfiedPlatinum

10:08 PM

John: Why are your blaming individual problems with reception, which is quite likely to be caused by faults within your own system, on Freeview?

If your getting a weak signal, check your system, because thats the most likely cause - your system.

The location of transmitters, geography and the basic physics of how a signal gets to the household has not changed one jot from analogue, and the power output is roughly the same.


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MikeB's 2,568 posts GB
Tuesday, 20 February 2018
N
Nick Anderson
sentiment_satisfiedBronze

3:51 PM

Is there a TV without internet connectivity available which enables those that live in fringe areas of services to connect a second aerial pointing in the direction of another BBC or ITV region to receive both regional services on Channels 1 and 3 respectively? This was always possible in the days of analogue but is seemingly impossible on digital.

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Nick Anderson's 81 posts GB
N
Nick Anderson
sentiment_satisfiedBronze

3:57 PM

Is there a TV set not using internet connectivity that enables one as with analogue to split the signal from two aerials for those living in fringe areas and receiving signals from two TV regions on BBC and ITV on Channels 1 and 3 respectively and so enable the viewer to choose between 2 regional programmes at the time they are being transmitted?

link to this comment
Nick Anderson's 81 posts GB
S
StevensOnln1
sentiment_very_satisfiedPlatinum

5:01 PM

Nick Anderson: You might be able to achieve that with either a diplexer or a coaxial switch, but I've never heard of a TV that can take two separate aerial inputs at the same time.

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StevensOnln1's 2,444 posts GB
M
MikeB
sentiment_very_satisfiedPlatinum

5:06 PM

StevensOnln1: There are one or two, but they tend to be at the top level, with twin freeview and freesat tuners, like the Panasonic OLED, Samsung QLED 8 series, etc. The idea of a non smart TV these days having twin Freeview tuners is zero. Frankly, there are very few non smart TV's around.

Yeah, the easiest way is to use a diplexer or coax switch. Or just have a second digibox.

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MikeB's 2,568 posts GB
Wednesday, 21 February 2018
MikeP
sentiment_very_satisfiedPlatinum

12:03 PM

Nick Anderson:

Further to the answers given by StevensOnln1 and MikeB, do not be copncerned about whether a TV has or does not have an internet connection, you don't have to connect it if that service is not wanted.

I strongly recommend use of a coaxial switch as a diplexer will severely reduce your signal level, due to the way it works. If your signal; levels are very strong on *both* sources then they could be used but it is far better to use a switch. One such is available at Maplins, for example, See https://www.maplin.co.uk/…80b. Other retailers sell such switches for use with UHF TV aerial systems.

If needed, you can buy converter plugs to enable connection of a coaxial plug into an 'F' connector socket, they are very inexpensive.



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MikeP's 2,790 posts GB
Saturday, 24 February 2018
E
Elvin Rose
10:47 AM

Since the update to freeview on the Waltham Transmittter I have been having a problem when I set a timer for series record for the six o'clock news on BBC SD. To give you an example.
Today Saturday 24th February I set a timer on my Sony HDD Recorder for the BBC News which today is 19.00 hrs. I set it at around 5.45 am and immediately the box started recording BBC TW0 SD BBC News and the timer said 3.55 am to 6.00 am. This has happened every day since the update. I usually use a Panasonic DMR HW100 box and I have noticed that it usually records that same day's Six o'clock News but later in evening it deletes the next day's timer for BBC One BBC News and replaces it with above timer on BBC TWO and records it to the HDD the next mornnig. The times do vary but are around 2 hrs. Interestingly on two occasions the timer has been cancelled by the box part way through. I know it may be the EPG updates around that time. A complete mystery, How can a box record something it has no timer set for it. Thought it was the Panasonic problem but now know it is nothing to do with my equipment. It cwertainly needs sorting as it si a real pain having to reset the timer each day.

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Elvin Rose's 2 posts GB
J
js
sentiment_satisfiedGold

11:23 PM

Elvin Rose: Looks like a mistake.

All the following events have series crid = /KCI4LN but the BBC TWO events clearly don't belong in this series - essentially BBC News at Six.


001 BBC ONE N West, Sat 24 Feb 19:00 - 19:10 : BBC News
The latest national and international news from the BBC. Also in HD. [S]
crid = /5A7JNO, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = A15D

001 BBC ONE N West, Sun 25 Feb 18:05 - 18:20 : BBC News
The latest national and international news stories from the BBC News team. Also in HD. [S]
crid = /5A7JR0, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = A174

001 BBC ONE N West, Mon 26 Feb 18:00 - 18:30 : BBC News at Six
The latest national and international news stories from the BBC News team, followed by weather. Also in HD. [S]
crid = /5A7K68, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = AC35

001 BBC ONE N West, Tue 27 Feb 18:00 - 18:30 : BBC News at Six
The latest national and international news stories from the BBC News team, followed by weather. Also in HD. [S]
crid = /5A7K69, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = AC52

001 BBC ONE N West, Wed 28 Feb 18:00 - 18:30 : BBC News at Six
The latest national and international news stories from the BBC News team, followed by weather. Also in HD. [S]
crid = /5A7K6A, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = AC6F

001 BBC ONE N West, Thu 01 Mar 18:00 - 18:30 : BBC News at Six
The latest national and international news stories from the BBC News team, followed by weather. Also in HD. [S]
crid = /5A7K6B, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = AC8A

001 BBC ONE N West, Fri 02 Mar 18:00 - 18:30 : BBC News at Six
The latest national and international news stories from the BBC News team, followed by weather. Also in HD. [S]
crid = /5A7K6C, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = ACA3

001 BBC ONE N West, Sat 03 Mar 18:10 - 18:20 : BBC News
The latest national and international news from the BBC. Also in HD. [S]
crid = /5A7JNP, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = ACBC

002 BBC TWO, Sat 24 Feb 03:55 - 06:00 : BBC News
Joining the BBC's rolling news channel for a night of news, with bulletins on the hour and the headlines every 15 minutes. Also in HD. [S]
crid = /5A7SQD, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = A6D7

002 BBC TWO, Sun 25 Feb 01:00 - 06:00 : BBC News
Joining the BBC's rolling news channel for a night of news, with bulletins on the hour and the headlines every 15 minutes. Also in HD. [S]
crid = /5A7SQE, Type : 31 (item), crid = /KCI4LN, Type : 32 (series)
eventID = ADAA

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js's 617 posts GB
Tuesday, 6 March 2018
M
Mark
10:42 PM

Hi.
We have a number of customers with one particular brand of gym machine with integral freeview hd that have been installedand fine for years. In the past few weeks thay have reported loosing all the hd channels on psb3 mux. from Crystal Palace. Thrre is no problem with bbcnews hd or bbc4hd
As this is at multiple sites acroos london we are ruling out an installation problem and wondering if anything has changed on the mux itself in the past month or so??

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Mark's 1 post GB
Wednesday, 7 March 2018
MikeP
sentiment_very_satisfiedPlatinum

12:19 PM

Mark:

There are no reported problems with the Crystal Palace transmitter. If there were a problem, millions would be complaining, but they are not. So it is either something to do with the installation or a possible fault with the equipment design.



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MikeP's 2,790 posts GB
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