Rebuilding Freeview High Definition from 2019 onwards
As Freeview High Definition users in Cornwall already know, the number of TV channels being broadcast in the UK will be cut back in mid-2020 to make way for the fifth generation of mobile phone data services.
This is because the number of multiplexes being broadcast will be cut back to the original six. The extra two were provided as a “interim service”. A Freeview multiplex is a single broadcast of binary data that occupies a 8MHz frequency range. In the UK each of these can carry 24.1, 27.1 or 40.2Mbps or of data.
Because older TV sets and set-top boxes can only work with 24.1 Mbps, it is only possible for the owners of the multiplexes to use the higher capacity modes when every home has switched to Freeview HD capable equipment. This equipment is marked with “DVB-T2”.
As illustrated, the total bitrate (in a home that can receive all the multiplexes) will change over time.
Meet the multiplexes
Not all the multiplexes are the same:
- only three are broadcast to the whole of the UK;
- a different three are broadcast in the better DVB-T2 mode;
- legally, only BBC channels may appear on BBCA
- also, legally, only public service broadcast channels (ITV, C4, C5) can appear on D3&4
- The HD mode multiplexes have more bits and use a more video efficient encoding system (MPEG-4)
- The current license to broadcast have different end-dates
This can be summaries in this table.
|
Multiplex name |
Expires |
HD mode? |
Coverage |
Mode |
Bitrate today |
||
|
com7 |
21 June 2020 |
Yes |
76% |
6 |
40.2 |
||
|
com8 |
21 June 2020 |
Yes |
76% |
6 |
40.2 |
||
|
D3&4 |
15 November 2022 |
No |
100% |
3 |
24.1 |
||
|
ARQA |
15 November 2026 |
No |
90% |
8 |
27.1 |
||
|
ARQB |
15 November 2026 |
No |
90% |
8 |
27.1 |
||
|
SDN |
15 November 2026 |
No |
90% |
8 |
27.1 |
||
|
BBCB |
16 November 2026 |
Yes |
100% |
6 |
40.2 |
||
|
BBCA |
31 December 2027 |
No |
100% |
3 |
24.1 |
Freeview requires about 2.2Mbps for a standard definition channels and three times that for a high definition one (6.7Mbps).
The Freeview HD EPG problem
One problem for people with Freeview HD receivers will note is that HD channels are grouped together in the program guide, rather than appear as replacements for the standard definition channels as viewers expect. This is because the six channels on the BBCB multiplex (BBC One, BBC Two, CBBC, ITV, Channel 4 and Channel 5) can only be seen on newer boxes, making channel number replacement impossible without breaking the oldest Freeview equipment.
Basically the UK-wide BBCA and D3&4 multiplexes can’t change mode until ALL homes can receive them.
The interim position
There is good news, however, for the SDN, ARQA and ARQB multiplexes. They can switch modes to the high definition whenever they feel that it is commercially practical. This might be at a lower level of Freeview HD box use, perhaps 80% or 90%.
By switching to DVB-T2 mode, each of them can increase their capacity from 27.1 to 40.2Mbps and take advantage of MPEG4.
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So, of the 80Mbps lost when com7 and com8 close, half of that can be got back by SDN, ARQA and ARQB upgrading, which would be enough for an extra 6 full HD services.
The HD public service channels
This diagram explains what will happen to create space six more Freeview HD channels.
The gains for the BBC when everyone has a DVB-T2 receiver are larger. It will:
- No longer need half of the capacity on the BBCB multiplex (20.1Mbps) as it can move these channels to BBCA
- Gain 16.1 Mbps on BBCA due to the mode change;
- Gain 6.6 Mbps from not simulcasting three services in SD and HD
- Use the “gained 22.1Mbps” Be able to supply all the BBC television channels in HD to all UK homes
For the D3&4 multiplex, the gains are similar:
- No longer need the 20.1Mbps on BBCB, making it available for other UK-wide services.
- Gain 16.1 Mbps on D3&4 due to the mode change;
- Gain 6.6 Mbps from not simulcasting three services in SD and HD
- Be able to broadcast ITV, C4 and C5 in HD to all UK homes
I hope that's as clear as possible! Any qestions?
6:28 PM
I, too, have lost all the channels in Com7 in the last couple of weeks, although my transmitter is Ridgehill. Neither my TV nor my PVR can find Channel 55 any more, although it was there a couple of weeks ago.
I took the comments on the Ridge Hill Transmitter page about 'Being removed from Freeview (for 5G use) after November 2020' to mean that Channel 55 was being closed, with the hope that the BBC HD channels would be moved to another channel/mux. However, Freeview today told me that Ridge Hill were still transmitting Channel 55, and that everything on Com 7 was fine.
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2:34 AM
Tony:
As per the post immediately before yours here (now on p15) COM7 has not closed and the post before yours refers to a previous post with details about what happened to COM8 and what is happening to COM7. Please read the linked posts. Information on various transmitter pages on this site is incorrect not just about COM7 but it hasn't been updated in many places with all the 700 MHz Clearance changes.
Ridge Hill has had no reported faults recently and not had any listed Planned Engineering.
There has however been some recent "Tropospheric Ducting", see Effect of tropospheric ducting on Freeview | RTIS for a simplistic explanation. This can affect reception of any multiplex, and not necessarily all, or at the same time, the disruption can last for seconds, minutes, or hours. The interference can come from other transmitters, in Europe, Eire or the UK.
The effects will likely be worse if the normal signals aren't very strong. COM7 is transmitted as an SFN and at lower power than the other multiplexes and to complicate matters with SFNs there can sometimes be some "not spots" where signals are much weaker or can't be received. As you haven't provided a full postcode, I can't advise what your typical predicted reception of COM7 (or other multiplexes) might be.
Depending on your location within the Ridge Hill coverage area, COM7 signals could be affected by eg. signals from Mendip, Wenvoe or Sutton Coldfield, the latter currently having Planned Engineering with "Possible weak signal"
If you've retuned, or your set automatically retunes when you had no signal or badly pixellated reception, this can usually just clear the correct tuning and you'd need to retune again when signals return to normal. It's advised to turn off automatic retuning, it's often more trouble than it's worth, and these days, retuning should be a less frequent occurrence and you'd be advised if one was needed by on-screen pop-ups.
If you have retuned and still don't have COM7, I would try a manual retune of C55 after Wednesday evening when any effects of the Tropospheric Ducting should have subsided. If this doesn't work, post back with a full postcode so we can look at your predicted reception.
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1:35 PM
Bristol
Channel 55 com 7 seems to have disappeared from the Mendip transmitter with BBC4HD. I live within eyesight of the mast, about 10 miles away. Which channel can I receive it on now please?
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Alan's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
12:48 AM
Alan John Richardson:
You can still receive it on COM7 UHF C55. I didn't check myself yesterday but it is fine today. As COM7 carries 3 BBC channels I would have expected a report from them if it had been off-air due to a fault, but I can't find any report, but then again in this covid-19 situation reports can get delayed (or maybe even fail to appear).
if you are still not receiving COM7, have you changed anything in your setup recently? Make sure you don't have any HDMI leads close to aerial and Flyleads as HDMI leads near unscreened/poorly screened flyleads/aerial leads can cause interference, especially with C55.
Otherwise, check your signal strengths and quality of other multiplexes in your TV's tuning section - do these look normal? If not it suggested a potential fault on your installation.
I'd check that your aerial seems intact and pointing in the correct direction and that your downlead looks undamaged (especially if it is old). Also check all your coax plugs, connections, flyleads etc, unplug connectors check for corrosion or other problems and reconnect them. Flyleads are a common problem, try swapping/changing them.
NOTE - Problematic connections, water ingress etc. can seem to affect reception of just an individual or several multiplexes.
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11:54 PM
Hi,
I'm having the same problem with BBC 4 HD and BBC News HD disappearing.
COM7 - Ch55 has zero reception.
Transmitter is Pontop Pike.
I've checked all of my coax and moved HDMIs away from the aerial lead.
Any ideas?
Thanks,
Nick
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8:06 AM
nick:
Last week, Pontop Pike was on Planned Engineering with "Possible weak signal". Earlier this week there was some variable "Tropospheric Ducting" that occurred with the high pressure weather that may have disrupted reception in some parts of the country.
If you retuned when there was no signal (or very badly pixelated) this often just clears correct tuning, it's not recommended as you have to retune again when signals return to normal.
Try a manual tune on C55. Autotune can sometimes miss weak signals, and COM7 is likely to be a weaker signal but a full postcode would be needed to look at predicted reception.
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3:57 PM
Hi
You don't mention the BBC radio stations....
Surely with all the upcomming spare capacity they can all be upgraded to stereo.
At a decent bit rate, like they are on DAB or better like internet.
W Penn
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5:42 PM
Bill: There has been no announcement yet regarding any multiplexes being converted to DVB-T2, so at the moment this mostly hypothetical. Radio stations on a DVB-T2 mux would use AAC audio, which would enable all stations to be broadcast in stereo at the same (or lower) bitrate that is currently used to broadcast in mono using MPEG2.
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3:07 PM
I can confirm that there have been a number of occasions on which the COM7 channel from Mendip appears to be absent (or at least is undecodable).Now I see that COM7 is transmitted as an SFN I can understand why it may disappear from time to time, due to ducting from other more distant transmitters, as the other sites may be far enough away to exceed the COFDM guard interval of the multiplex. I note that today in Burnham-on-Sea it is giving a 100% quality rating and zero errors ( I assume that the error rate of my TV is calculated after FEC has been applied). It will be interesting to see how this varies with the weather, if it ever gets warm again!
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4:47 PM
Peter Jackson:
As I'm sure you appreciated reception of COM7 (indeed any multiplex, but especially COM7 and Local ones) is dependant on location. Your general area shouldn't have any real problems with reception from Mendip but you of course also have very strong reception from Wenvoe. Apart from "Tropospheric Ducting" of which there has been some very variable and very strong on odd occasions recently, Planned Engineering can also have an effect.
The next nearest transmitter with COM7 is probably Ridge Hill, and ducting might have some effect on occasion.
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