Full Freeview on the Divis (Northern Ireland) transmitter
 | Google Streetview |  | Google map |  | Bing map |  | Google Earth |  | 54.607,-6.009 or 54°36'24"N 6°0'34"W |  | BT17 0NG |
The symbol shows the location of the Divis (Northern Ireland) transmitter which serves 440,000 homes. The bright green areas shown where the signal from this transmitter is strong, dark green areas are poorer signals. Those parts shown in yellow may have interference on the same frequency from other masts.
Are there any planned engineering works or unexpected transmitter faults on the Divis (Northern Ireland) mast?
Divis transmitter - Divis transmitter: Possible effect on TV reception week commencing 25/09/2023 Pixelation or flickering on some or all channels 
_______
Digital television services are broadcast on a multiplexes (or Mux) where many stations occupy a single broadcast frequency, as shown below.
64QAM 8K 3/4 27.1Mb/s DVB-T MPEG2
DTG-12 QSPK 8K 3/4 8.0Mb/s DVB-T MPEG2
H/V: aerial position (horizontal or vertical)
Which Freeview channels does the Divis transmitter broadcast?
If you have any kind of Freeview fault, follow this Freeview reset procedure first.Digital television services are broadcast on a multiplexes (or Mux) where many stations occupy a single broadcast frequency, as shown below.
64QAM 8K 3/4 27.1Mb/s DVB-T MPEG2
DTG-12 QSPK 8K 3/4 8.0Mb/s DVB-T MPEG2
H/V: aerial position (horizontal or vertical)
Which BBC and ITV regional news can I watch from the Divis transmitter?
BBC Newsline 0.6m homes 2.5%
from Belfast BT2 8HQ, 1,044km northeast (51°)
to BBC Northern Ireland region - 46 masts.
Are there any self-help relays?
| Chapel Fields | Transposer | Central Belfast | 61 homes |
How will the Divis (Northern Ireland) transmission frequencies change over time?
| 1950s-80s | 1984-97 | 1997-98 | 1998-2012 | 2012-13 | 4 Mar 2020 | ||||
| VHF | A K T | A K T | A K T | K T | W T | ||||
| C1 | BBCtvwaves | ||||||||
| C21 | C4waves | C4waves | C4waves | +D3+4 | D3+4 | ||||
| C23 | SDN | SDN | |||||||
| C24 | ITVwaves | ITVwaves | ITVwaves | BBCB | BBCB | ||||
| C26 | ArqA | ArqA | |||||||
| C27 | BBC2waves | BBC2waves | BBC2waves | BBCA | BBCA | ||||
| C29 | ArqB | ||||||||
| C30 | LBT | ||||||||
| C31 | BBC1waves | BBC1waves | BBC1waves | ||||||
| C33 | com7 | ||||||||
| C34 | com8 | ||||||||
| C36 | _local | ||||||||
| C48 | NIMM | NIMM | |||||||
| C55tv_off | com7tv_off | ||||||||
| C56tv_off | COM8tv_off |
tv_off Being removed from Freeview (for 5G use) after November 2020 / June 2022 - more
Table shows multiplexes names see this article;
green background for transmission frequencies
Notes: + and - denote 166kHz offset; aerial group are shown as A B C/D E K W T
waves denotes analogue; digital switchover was 10 Oct 12 and 24 Oct 12.
How do the old analogue and currrent digital signal levels compare?
| Analogue 1-4 | 500kW | |
| BBCA, D3+4, BBCB | (-7dB) 100kW | |
| SDN, ARQA, ARQB | (-10dB) 50kW | |
| com8 | (-16dB) 12.7kW | |
| com7 | (-16.1dB) 12.4kW | |
| LBT | (-20dB) 5kW | |
| Mux 1*, Mux 2*, Mux A*, Mux B* | (-23.4dB) 2.3kW | |
| Mux C* | (-24dB) 2kW | |
| Mux D* | (-24.9dB) 1.6kW | |
| NIMM | (-47dB) 10W |
Which companies have run the Channel 3 services in the Divis transmitter area
|
|
Tuesday, 6 November 2012
M
Mike Dimmick2:48 PM
John Durrell: The difference in what your TV reports is *probably* down to using an external receiver rather than having the HD tuner built in to the set.
This is complicated by the fact that, on Freeview HD, the encoding hardware, and therefore the transmissions, can dynamically switch between 1080i50 and 1080p25 modes for every Group of Pictures (GoP). A GoP is a sequence of 15-25 pictures that are encoded using differences between the pictures, only one whole picture being sent in the set. The encoder switches mode based on how well the content compresses in each mode - if the source material was actually captured in progressive mode, or if there isn't much motion, it should compress better in progressive mode than interlaced. If there is fast motion, it will look better in interlaced mode.
It is never anything to do with your aerial - the decision of whether to choose i or p mode for a group of pictures is taken by the encoding and multiplexing hardware in London (and the BBC's backup location somewhere in the Midlands). For BBC One Northern Ireland HD, and UTV HD, a lightly-compressed high-bitrate signal is sent to the code-and-mux centre for compression and multiplexing. The resulting multiplex is sent back to Divis, where Service Information for the other multiplexes is added. It is then transmitted from Divis and carried via line feeds to Limavady and Brougher Mountain, which also transmit it. The other, relay, transmitters receive off-air from one of those three and retransmit. (Similarly, BBC One NI and BBC Two NI in standard definition are sent to the BBC's code-and-mux centres, while UTV and UTV+1 in SD are sent to ITV/C4 facilities elsewhere in London.)
The reason code-and-mux is done in England is simply that the majority of channels on most of the multiplexes only have one version for the whole UK, mostly played out or originated in London, and it makes more sense to bring in the few differences rather than send out the greater amount of content that is the same. Also, the same content is uplinked to satellites for satellite reception, where all the content for a single transponder has to be combined into one multiplex and uplinked from a single location.
The raw, uncompressed data rate for 1080p25 is the same as for 1080i50. 1080p25 means that 1080 lines are refreshed in full 25 times per second, taking 1/25th of a second, while 1080i50 means that half of the 1080 lines are refreshed in 1/50th of a second, followed by the other half in the next 1/50th of a second. In both modes, any specific line is only refreshed 25 times per second. 1080p50 doubles that to 50 times per second. Much equipment drops the '50' from the end of the indication and just reports 1080i or 1080p.
When a GoP is encoded progressively, the receiver can still send it on to the TV in interlaced mode: it just sends the lines in a different order to how it received them. There is no loss in picture quality and no difference in the apparent motion of the picture.
It may be possible to set up your receiver to send 1080p50 to the TV, if both support it. To receive the 'HD Ready' or 'HD TV' logos, and even the 'Full HD Ready' or 'Full HD TV' logos, the TV only has to support 1080i50 input - it does not have to support 1080p50. They only have to support 1080p50 in order to receive the 'HD Ready 1080p' or 'HD TV 1080p' logos. (The word 'Full' indicates that the TV itself has 1080 display lines, without that word it might have only 720 lines.)
| link to this comment |
Thursday, 8 November 2012
K
Keith4:30 AM
Hi i live in Blackrock, Co.Louth. I am using a wideband aerial which i mounted in the loft, but can not get any luck in keeping up signal from Divis. My mate lives only 3 miles away in dundalk and hes getting signal without any amplifiers at all.
I have tried adding 2 differnet masthead amplifiers but still no joy.
Anybody having any ideas as to what i am doing wrong?
| link to this comment |
J
John Durrell9:04 AM
Coleraine
Many thanks to Mike Dimmick for his very detailed post. From what Mike has said it seems to me that the interaction of the TV and external i-Can receiver is the issue. The Sharp Aquos TV was bought in 2007 and plays blurays perfectly well in 1080p but I suppose it is getting a pure signal. From what Mike has said the broadcast signal is slightly different and I imagine that the technology in the TV cannot cope with this. The answer seems to be a new TV when this one 'dies'. Thanks agin Mike for all your help. I can now stop worrying about aerials.
| link to this comment |
John's: mapJ's Freeview map terrainJ's terrain plot wavesJ's frequency data J's Freeview Detailed Coverage
Keith: Divis uses only Group A channels and wideband yagi aerials are less efficient on those channels.
Use a Group A aerial:
Rowridge Transmitter
Digital TV Transmitters
| link to this comment |
P
Peter Henderson1:12 PM
Keith: I'd also think about getting the aerial mounted outside on the chimney. It should make quite a bit of a difference.
| link to this comment |
D
David6:08 PM
Keith: My mother lives in Blackrock and is picking up all freeview muxes from Divis on a chimney mounted group A aerial.
| link to this comment |
Friday, 9 November 2012
K
Keith5:15 AM
Thanks guys. I'll have to get myself a group a aerial.
Another question, to get the saorview signal from Claremont Carn I will need a c/d group aerial, is this correct or will I be able to continue using my wideband aerial (which is picking up soarview perfectly now) and how do I wire the 2 aerials into 1 coax cable??
Thanks again for your help.
| link to this comment |
Keith: The sensitivity (gain) of an aerial isn't the same across all UHF channels/frequencies. For yagi aerials, the shape of the curve is broadly the same. See here for examples that illustrate my point:
Gain (curves), Again
The gain of wideband yagi aerials on Group A channels is much lower than C/D ones. That is why there is no such thing as a high gain wideband aerial that has "high" gain on Group A channels.
More gain in one direction is simply at the expense of more "loss" in others. So the "beam" of a higher gain aerial is narrower.
If your wideband aerial is sufficient for Clermont Carn, then there is no reason not to continue using it. The reason for suggesting use of a Group A aerial for Divis is because of the lower gain of the wideband aerial on its channels and the poor reception you are experiencing.
You need a diplexer to combine the two feeds:
Online TV Splitters, Amps & Diplexers sales
For Divis and Clermont Carn, get a diplexer that "splits" at C38. This will allow you to receive a multiplex from Divis on C36 should it ever come to fruitition.
| link to this comment |
Saturday, 10 November 2012
M
MEM1:24 AM
Does anyone have any idea why I can get the RTE radio stations via Digital TV but not through my DAB radio?
I live in the Newry area, prior to DSO I could get a very weak signal from the RTE radio stations on my DAB set but it would never tune in. I would get a service not available message.
After the DSO I retuned my DAB radio in the hope of getting a better signal but I have now lost all the RTE channels.
I would appreciate any help thanks.
| link to this comment |
MEM: Because the DAB signal and the TV signal are different signals. The TV switchover didn't mean any difference to DAB radio.
See:
Digital Radio Ireland » Can I get DAB
Maybe you need a directional aerial.
| link to this comment |
Select more comments
Your comment please