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 04/12/2023 Pixelation or flickering on some or all channels 
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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
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Thursday, 17 January 2013
L
Lynn Steenson3:08 PM
Dave Lindsay: I have discovered the antenna levels for the Coms *before* scan are:
COM 4: antenna level 58 quality 0
COM 5: antenna level 50 quality 0
COM 6: antenna level 38 quality 0
The Coms we cant get are listed in the guide but once you select them there is no picture.
On doing this I was able to get another reading of the strength/quality of the channel.
E.g.
Dave in COM 5: signal strength 92 quality 0
Quest in COM 4: signal strength 95 quality 0
and to compare
UTV in PSB2: signal strength 99 quality 100
BBC1HD in PSB3: signal strength 96 quality 100
Does this shed any light on what is goin on?
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Lynn Steenson: The COM strengths would be expected to be the same whether you go through the manual tune screen and enter the UHF channel or (with the services, e.g. Dave, stored) bring up the signal strength screen, so I'm not sure why you got lower readings then. The only thing to say is that you might have to give it a few seconds (10 maybe) to settle.
That said, the strengths being in the mid to high 90s could perhaps be an indication that they are too great, presumably being driven that high due to your amplifier. I suggest that you try reducing the level of amplification so you get around 75% to 80%. It isn't critical; quality is the important thing with digital reception.
If the signals are on the high side, say verging on excessive (for what your tuner can cope with), then that is akin to turning the volume right up to maximum on your hifi. What happens is the sound distorts and quality is lost. The COMs use a signal type that isn't as rugged as the PSBs, which could explain why they are lost and the PSBs aren't - this is my suggested explanation if you find that reducing the level of amplification does the trick.
You may even find that the amp isn't needed at all. You are around 30 miles from the transmitter and I believe that you even reside in the area coloured green in the map above.
You should also be able to combine the feed from the Divis aerial and that of, Monaghan I guess, so you can view both Saorview services and Freeview services on the same/all receivers. For this you will need a diplexer - probably one that splits at C51.
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Friday, 18 January 2013
L
Lynn Steenson12:19 AM
Dave Lindsay:
I have tried to bypass the amplifier but if I do that i get no channels at all.
Its an old one- Fringe Electronics Hi-Current P1290, its either on or off no turning up or down!
Yes we are indeed in the green area on the map above!
We are currently receiving all saorview channels and (freeview apart from the coms.)
Do you think if we were getting the coms before the DSO with current aerial/amp that maybe it could be the power strength that Divis is broadcasting the coms? It being only half the strength of the psbs?
I used the digital tv postcode checker for coverage of a BT postcode BT603DP in N.Ireland which is close to us.We are not far from the border!
It shows good reception for the psbs and variable reception for the channels we are missing!?
Thanks for all your help so far.
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Sunday, 20 January 2013
Lynn Steenson: The Digital UK predictor essentially provides a statistic on the likelihood of success. COM6 is "good" but the other two are considered "variable". I imagine that this is more down to the way in which it calculates the likelihood of interference from other transmitters that use the same channel. I wouldn't be too concerned about that.
The Fringe P1290 is a power supply for an amplifier and not an amplifier. The amplifier is probably on the roof or near to the aerial. Turning the power of to the amplifier will likely result in no signal coming out.
You appear not to have many more options left without getting into it deeper. Removing the amplifier, or turning it down (if possible), is probably the next thing that needs trying.
The lower power COMs will affect some fringe viewers - that is those who can "only just" pick up the PSBs. This would appear not to be an issue for you. You may have line-of-sight or not far off which is why I'm thinking that the amplifier isn't necessary, or at least at the current magnitude.
An attenuator on the aerial lead may reduce the signal strength sufficiently if you can't get to remove the amp or reduce its level. An attenuator reduces the signal level which is the opposite of an amplifier. Therefore an attenuator would be acting to cancel out some of the amplification of the amp.
Various ones are available. Here is one such example that is variable:
TV Aerial Attenuator Variable 0-20Db Freeview Digital | eBay
Try to reduce the signal strength (to say 75 or 80%) and see if the quality of the COMs increases and they become available to you.
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Monday, 21 January 2013
L
Lynn Steenson6:11 PM
Armagh
Dave Lindsay:
We also have a Fringe Mini 4 Distribution Unit 40 - 860 Mhz.
It has one input and 4 x 6db. outputs.
Would the amplifier be built into this?
I also tried to bypass this but no success!
I think I will get the suggested variable attenuator and take it from there.
Thank you!
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Lynn's: mapL's Freeview map terrainL's terrain plot wavesL's frequency data L's Freeview Detailed Coverage
Tuesday, 22 January 2013
Lynn Steenson: The distribution unit does have a degree of amplification (+6dB). Cables, for example, have a degree of loss (i.e. minus so many dB, depending on type and length). The objective of an attenuator is to reduce the signal further.
Is this fed directly from the aerial or via a Sky box?
I've had another thought: I wonder if your receiver might not be built to receive the COM channels.
The COM channels use a different mode to the PSBs, and different to that which their equivalent multiplexes used before switchover.
The UK's standard definition networks and Ireland's Saorview network both use the DVB-T system (it standing for "Digital Video Broadcasting - Terrestrial").
However, there are a number of modes, which are sub-standards or parts of the DVB-T standard. The UK PSBs and UK COMs operate using a different mode.
If the receiver you are using is not Freeview approved then I wonder if it could be the case that it isn't designed to operate in the mode used for the COMs. The result could perhaps be that signal strength is registered but no quality, as is what you are getting.
I'm not a professional so am simply wondering whether such devices might exist. I know that some really old digital receivers were rendered useless at switchover because they weren't designed to comply with the DVB-T standard in full.
What's the make and model of the receiver you are using? It might be possible to find the specifications and work out whether this might be the cause.
Presumably you having a distribution amp means that you have more than one receiver. What do the others do?
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Wednesday, 23 January 2013
L
Lynn Steenson8:27 PM
Dave Lindsay: This distribution unit is fed directly from the 48 Element High Gain Digital TV Aerial.
The receiver is built into the tv Samsung LE40D503F7W.It picks up the saorview channels fine.
I also have an Echostar HDT610RGB which picks up the HD channels and saorview as well.
All other tvs just have cheap Freeview boxes eg Alba/Bush but im mainly concerned with the main tv and echostar.
I can see i have the option of DVB-T and DVB-T2 in the echostar box but once i choose DVB-T2 on channel 23 the signal strength 0 and quality 0.
with DVB-T on channel 23 for example I have 58 signal level and 0 quality.
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Thursday, 24 January 2013
J
jb388:14 AM
Lynn Steenson: On reading back through your various postings on the issue of zero quality being indicated on all of the COM channels, it would be interesting to know the outcome if you first of all blanked out all channels already stored in the TV's memory by carrying out an auto-tune with the aerial connection removed, checking the EPG list on completion of the scan to ensure that nothing is being indicated, then follow this by going into the TV's manual tune facility and entering Ch23 and check if the quality is still zero, if though it isn't then carry out a scan on this channel then when completed select ITV3 and check if a picture is showing.
By the way regarding your Echostar, if you scan channel 23 whilst its set on DVB-T2 than that will result in a zero indication, as the tuner will not recognise the signal.
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Saturday, 26 January 2013
L
Lynn Steenson7:59 PM
Dave Lindsay: I got the suggested attenuator but not having any success.
It reduces the signal strength only. for example on ITV3 (within the guide), original signal strength is 96 and quality is 0.
When I use the attenuator and I reduce signal to say 75 the quality remains at 0.
The attenuator seems to have no effect on the signal quality at all.
There is a very distorted jumpy picture on ITV3 when signal strength is at 96!
Do I maybe need a bigger amplifier?
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L
Lynn Steenson8:08 PM
Jb38: I did a retune with the aerial disconnected.Then the list of channels is empty. Then after connect aerial ch23 quality is still zero. As you can see above I tried an attenuator but to no avail. Any other ideas?
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