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Full Freeview on the Divis (Northern Ireland) transmitter

first published this on - UK Free TV
sa_streetviewGoogle Streetviewsa_gmapsGoogle mapsa_bingBing mapsa_gearthGoogle Earthsa_gps54.607,-6.009 or 54°36'24"N 6°0'34"Wsa_postcodeBT17 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 27/11/2023 Pixelation or flickering on some or all channels Digital tick

Choose from three options: ■ List by multiplex ■ List by channel number ■ List by channel name

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.

 H max
C27 (522.0MHz)551mDTG-100,000W
Channel icons
1 BBC One (SD) Northern Ireland, 2 BBC Two Northern Ireland, 9 BBC Four, 23 BBC Three, 201 CBBC, 202 CBeebies, 231 BBC News, 232 BBC Parliament, plus 14 others

 H max
C21+ (474.2MHz)551mDTG-100,000W
Channel icons
3 UTV (SD) (UTV), 4 Channel 4 (SD) NI ads, 5 Channel 5, 6 ITV 2, 10 ITV3, 13 E4, 14 Film4, 15 Channel 4 +1 NI ads, 18 More4, 26 ITV4, 28 ITVBe, 30 E4 +1, 35 UTV +1 (UTV),

 H max
C24 (498.0MHz)551mDTG-100,000W
Channel icons
46 5SELECT, 101 BBC One HD Northern Ireland, 102 BBC Two HD Northern Ireland, 103 UTV HD (UTV), 104 Channel 4 HD NI ads, 105 Channel 5 HD, 106 BBC Four HD, 107 BBC Three HD, 204 CBBC HD, 205 CBeebies HD, plus 1 others

 H -3dB
C23 (490.0MHz)551mDTG-850,000W
Channel icons
20 Drama, 21 5USA, 29 ITV2 +1, 32 5STAR, 33 5Action, 38 Channel 5 +1, 41 Legend, 42 GREAT! action, 57 Dave ja vu, 58 ITVBe +1, 59 ITV3 +1, 64 Blaze, 67 TRUE CRIME, 68 TRUE CRIME XTRA, 78 TCC, 81 Blaze +1, 89 ITV4 +1, 91 WildEarth, 209 Ketchup TV, 210 Ketchup Too, 211 YAAAS!, 267 Al Jazeera English, plus 35 others

 H -3dB
C26 (514.0MHz)528mDTG-850,000W
Channel icons
 Smithsonian Channel, 11 Sky Mix, 17 Really, 19 Dave, 31 E4 Extra, 36 Sky Arts, 40 Quest Red, 43 Food Network, 47 Film4 +1, 48 Challenge, 49 4seven, 60 Drama +1, 65 That's Christmas, 70 Quest +1, 74 Yesterday +1, 75 That's 90s, 233 Sky News, plus 11 others

 H -3dB
C30 (546.0MHz)528mDTG-850,000W
Channel icons
 Quest Red +1,  Classic Hits, 12 Quest, 25 W, 27 Yesterday, 34 GREAT! movies, 39 DMAX, 44 HGTV, 52 GREAT! christmas, 56 That's TV (UK), 61 GREAT! movies extra, 63 GREAT! christmas mix, 71 That’s 60s, 73 HobbyMaker, 82 Talking Pictures TV, 83 Together TV, 84 PBS America, 235 Al Jazeera Eng, plus 20 others

 H -13dB
C36 (594.0MHz)528mDTG-125,000W
Channel icons
from 29th September 2014: 7 NvTv,

 H -40dB
C48 (690.0MHz)551mDTG-10W
Channel icons
from 4th September 2019: 53 TG4, 54 RTÉ One, 55 RTÉ Two,

DTG-8 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?

regional news image
BBC Newsline 0.6m homes 2.5%
from Belfast BT2 8HQ, 1,044km northeast (51°)
to BBC Northern Ireland region - 46 masts.
regional news image
UTV Live 0.6m homes 2.5%
from Belfast BT7 1EB, 1,044km northeast (51°)
to UTV region - 46 masts.

Are there any self-help relays?

Chapel FieldsTransposerCentral Belfast61 homes

How will the Divis (Northern Ireland) transmission frequencies change over time?

1950s-80s1984-971997-981998-20122012-134 Mar 2020

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

Oct 1959-May 2006Ulster Television
May 2006-Dec 2014UTV plc
Feb 1983-Dec 1992TV-am•
Jan 1993-Sep 2010GMTV•
Sep 2010-Dec 2014ITV Daybreak•
• Breakfast ◊ Weekends ♦ Friday night and weekends † Weekdays only. Divis was not an original Channel 3 VHF 405-line mast: the historical information shown is the details of the company responsible for the transmitter when it began transmitting Channel 3.

Sunday, 27 January 2013

8:47 AM

Lynn Steenson: Thanks for the update on that test, but on once again reading over your various replies made I cant actually see you having mentioned that you receive the COM channels on anything at all, and so the question is do you? because if you don't then the issue of your main TV does not really come into the equation as the problem is purely one concerning signal levels.

The other point is that the substitute post code that you provided indicates as being roughly 41 miles away from Divis and at that distance its unlikely that anyone could suffer from an excessive signal level, this backed up by the fact of you being able to receive the PSB's OK and yet they transmit with twice the ERP of the COM's, and so dependant on your answer to my initial question insomuch whether or not you can receive the COM's on any of your devices, if the answer is no then I have a suspicion that you might well be suffering from an effect that sometimes happens with viewers at distances when a transmitter increases power insomuch that the signal received can actually drop.

Although this type of thing can be caused by the way the signal is radiated by the transmitter mast, it can also be an indication that the signal that was previously received had relied on a strong element of reflection from something such as a hill or a tall building, but that the increased signal power has changed the angle of reflection whereby someone further away than you might now be receiving a superior level of signal at your expense.

The problem is, that if the strength appears as being high but with no quality being indicated then amplification will not help the situation one iota, the only thing that's liable to have any effect (but not guaranteed to do so) is experimenting with aerial positions, and in cases where this type of situation applies high gain aerials make the situation worse as these work on the principle of focusing on the signal source.

Anyway, the latter comments will obviously not be applicable in your case "if" you can receive the Com's on your other boxes.

link to this comment
jb38's 7,179 posts GB flag
Lynn Steenson
12:06 PM

jb38: No we can not get the COMs on any other boxes.
Only wen i add the channel manually will it appear in the tv list (using main tv or echostar) then once i check the signal within the guide its level varies but quality always 0 e.g. ITV3
Before the DSO we got ALL channels at the same set up/position of aerial.
Yes we are about 42miles from Divis and are within the green area on the map above.
So you reckon we need to maybe move the aerial slightly? even though before DSO we got all channels fine?
Thanks for your help!

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Lynn Steenson's 15 posts IE flag

5:09 PM

Lynn Steenson: I suspected that this might be the case and as such the comments I made regarding angle of reflections etc is very likely to be the reason for your difficulty, this type of problem not being quite so uncommon as some may think because in many cases it just reduces the level of the signal but with the minimum of variation in its quality, albeit that its lower than it previously was, however in severe cases it results in what you are experiencing and with this being a very difficult type of situation to resolve except in some cases by experimenting with alternative aerial positions, but though with this NOT necessarily meaning higher but a few feet either way in the horizontal plane.

That said, it does have to be admitted and without wishing to appear as a prophet of doom, but in some cases its never really satisfactorily resolved because if a better position is found for the aerial giving the impression that the problem has gone it very seldom ever lasts due to seasonal changes killing it again, as these changes always have an effect on reception levels albeit but with this not really causing any problems to most who reside closer to the transmitting station, but DTT signals coupled to being received at long distances always invites a variety of problems to spring up.

I also experienced exactly the same difficulty as yourself when one of the transmitters that I receive from switched over to high powered operation, as one of its COM channels that I could previously receive dropped out of the box and with no amount of aerial repositioning resolving the problem, and as an engineer I have everything at my proverbial finger tips for carrying out tests and so set about touring the area to find exactly where the signal could be received, it wasn't! however nature itself has assisted as when the weather changed for the worst this improved the situation to a certain extent by providing a terrain that the signal could skip along thereby lifting the level of the signal to just above the reception cut off threshold, something which once again enabled viewing of the channel albeit with the expected number of glitches.

By the way, these green areas seen on the maps are only approximate as indeed are the forecasts made for the expected signal strengths at certain locations in the official trade reception predictor, as no one can accurately predict how an RF signal will behave once its left the mast.

I really regret not being able to be more positive about your problem but its the near to zero quality issue that's the killer, because amplification no matter how powerful never makes any difference in these cases.

link to this comment
jb38's 7,179 posts GB flag

6:32 PM

Lynn Steenson: Also meant to add to my already somewhat lengthy posting, that to give an idea of the chances of success by experimenting with moving the aerial it would be prudent at this time to make an enquiry at a neighbours or some other property located close by to find out if the occupiers of same can receive the commercial channels from Divis, secondly, and although a long shot, but it would also be beneficial if you could eliminate the possibility (albeit remote) of a fault having developed on your Fringe mini distribution unit, this done by first of all by removing both coax leads from the Fringe 1290 power supply and connecting them both together (in other words by-passing the unit) then on your Fringe mini distribution unit removing the input from the aerial and also the coax cable from the unit that would go to the 1290 and linking both of these together, this action resulting in the aerial going directly into the TV without passing through anything else, then once done carry out a rescan on the TV.

My only reason for suggesting that you try this is not because I suspect that you are receiving an excessive signal level but just in case Divis's PSB's are triggering some form of instability within the mini distribution amp that's affecting anything of a lesser level than the PSB's passing through it, a tall order but not impossible!

What's been said is on the assumption that your Fringe 1290 is located near to the TV.

link to this comment
jb38's 7,179 posts GB flag
Lynn Steenson
10:48 PM

jb38: I bypassed the fringe dist unit and I get no signal at all.
Both neighbours nearby have sky so I cant compare freeview Coms with them!
I now think my only option is to get an engineer out to reposition the aerial and hope for the best!
Thanks for all your help and taking the time to respond :)

link to this comment
Lynn Steenson's 15 posts IE flag
Monday, 28 January 2013

12:01 AM

Lynn Steenson: Well, provide that it was by-passed in exactly the method described then yes! the only option you have left is to try repositioning the aerial, its a pity though that no one around you receives Freeview from Divis, because if they like yourself could not receive the COMs either then there would be no point in trying any tests with the aerial being repositioned as its an area problem.

But thanks anyway for the update, and maybe you could possibly give a further one once some aerial repositioning experiments have been carried out as I would be interested in the results.

link to this comment
jb38's 7,179 posts GB flag
Lynn Steenson
12:34 AM

jb38: Yes i by-passed it exactly as you described above, rescanned and no channels were found!
Actually I have a friend who lives approx 1 -2miles from here and they receives all the freeview channels!
Im hoping based on the fact that we used to get all channels before DSO,that we can get them again!
Once I have an update I'll post it here.
Thanks again.

link to this comment
Lynn Steenson's 15 posts IE flag

11:50 PM

Lynn Steenson: OK! will watch out for your update, but as far as your friend is concerned, unfortunately they really reside too far away for their findings to have any bearing on your problem, because experimenting with alternative aerial positions in most cases only involves moving it a few feet either side of where its presently installed and with height not always coming into the equation, this being why I suggested checking with a neighbour as it would at least have indicated if there was liable to be any chance of success by moving the aerial, this type of exercise by its very nature being hit and miss and therefore nothing is guaranteed.

The other point being, that if the zero quality that's seen indicated on the COM channels was associated with a very low signal level then a 15db (min) booster in line "might" bring results, but not in cases where the signal level is already high as that's a symptom of a corrupted signal.

I did also suspect the possibility of a problem existing where the coax downlead is joined into your aerial and that your reception being OK before switchover was purely coincidental, however should anything of this nature apply then this will soon be revealed once an aerial engineer gets involved.

Anyway, and as initially said, I will watch out for an update.

link to this comment
jb38's 7,179 posts GB flag
Friday, 1 February 2013
10:57 PM

Lynn Steenson, this may have been suggested already, have you tried plugging the receiver in question into a known to be working aerial socket?
Sounds too simple a test I know, but just wondering.

link to this comment
flipdee's 6 posts GB flag
Tuesday, 5 February 2013
Wayne Cochran
1:23 PM

Lynn Steenson, are you sure you're getting Freeview from Divis? Your PSB muxes are definitely on UHF chs. 21, 24 & 27?

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Wayne Cochran's 8 posts IE flag
Wayne's: mapW's Freeview map terrainW's terrain plot wavesW's frequency data W's Freeview Detailed Coverage
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