All posts by Steve Donaldson
Below are all of Steve Donaldson's postings, with the most recent are at the bottom of the page.
Jon Henderson: It sounds like it may be sporadic, which could imply interference from some source. It could be mobile phone interference, whether a mast or mobile device.
Another thing to be aware of is that other types of cable, such as HDMI, USB and Ethernet, running close to or parallel with aerial cables can sometimes affect the TV signal running in the aerial cable.
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Jon Reardon Smith: Carry out a manual tuning scan of UHF channel 42.
According to the posting above yours, DAB and FM from Ludlow were off-air between 05:50 to 06:20 on 22nd December. This was sourced from BBC Reception [bbc.co.uk/reception]. No indication is given above that TV was off-air, although I should say that this doesn't necessarily mean the BBC page didn't say it. The above postings from 'Transmitter engineering' are taken from the BBC page, so it's possible that the BBC page said something that the bot on this site didn't get.
A common reason for different types of broadcasts (e.g. FM, TV, DAB) to go off air at relay sites such as this is a power outage. Unlike the high power main transmitters, they don't have a generator for back-up power.
Having checked the BBC Reception page, it's worth checking the power-cut map of the electricity distribution network operator for the transmission site, which is National Grid Electricity Distribution (formerly Western Power Distribution): https://powercuts.nationalgrid.co.uk/
The postcode for the transmitter site for use on the power-cut map is SY8 2HD, which is shown at the top of this UK Free TV page. Power cuts may not be shown once they have been restored.
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nick horrex: I think we need to find or come by the bilateral agreement between the UK and the Netherlands for TV transmitters post 700MHz Clearance. We can then see whether you are on a bearing out from the transmitter where there is a notch in the radiation pattern as a mitigator against co-channel interference in the Netherlands, probably in the area north of Amsterdam.
Ofcom published the following with respect to the 800MHz Clearance:
UK Digital Terrestrial Television: International Coordination Agreements - Ofcom
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Chris.SE: Heathfield doesn't use C37. Heathfield uses 41, 44, 47, 40, 43 and 46.
Prior to 700MHz Clearance on 18/07/18 Heathfield and Tunbridge Wells were SFNs for all six channels. The COMs are now different, Tunbridge Wells on 29, 31 and 37.
The WEDDIP V8.1 maps by UHF channel, dated 29th April 2016, shows Tunbridge Wells as having been allocated 40, 43 and 46, the same as Heathfield, so a decision must have been made to change Tunbridge Wells' COMs to 29, 31 and 37 after that date.
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Jon Henderson: This is good news.
It's also been interesting to hear about your experience. It helps to understand the problem, the learnings of which may be of help to others with similar symptoms.
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nick horrex: There are bilateral agreements made between neighbouring nations with respect to co-ordination of TV transmitter channels. They specify restrictions placed on transmitters so as to mitigate the chances of co-channel interference in the neighbouring state. Where a transmitter uses a particular UHF channel in one country, it may have to emit a lower signal level in the direction of another transmitter on the same channel in the neighbouring country.
The reason for saying that this may be relevant in your case is to see if Sudbury is putting out less signal in your direction. That is, whether its output is down on the 100kW on your bearing out from the transmitter.
I haven't managed to find the agreement between the United Kingdom and the Netherlands. I have the ones between the UK and France for both 800MHz and 700MHz Clearances, and the one for the UK and Ireland for 700MHz Clearance.
With respect to the latter, and by way of example, ComReg, the regulator in Ireland, has published the memorandum of understanding between the United Kingdom and Ireland on co-ordination TV transmitter channels post 700MHz Clearance:
https://www.comreg.ie/publication/mou-co-ordinate-dtt-frequency-plans-ofcom-comreg
You will see that this document contains a table for each channel by country. In the tables are entries for transmitters on the respective channel, along with the agreement detail, which is how many dBs down it is to be between specified numbers of degrees. Further on in the document are radiation patterns for each transmitter channel showing these numbers of dB down that the transmitter must be.
ComReg has also published the DTT channel plan post 700MHz Clearance for Belgium, France, Germany, Ireland, Luxembourg, the Netherlands and the United Kingdom (the document itself dated 29 April 2016). This consists of maps by each UHF channel with pins for the transmitters on that channel:
https://www.comreg.ie/publication/dtt-frequency-plan-band-470-694-mhz-administrations-belgium-france-germany-ireland-luxemberg-netherlands-united-kingdom
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nick horrex: If you haven't already done so, then as per Chris.SE's advice, get a 700MHz filter from Restore TV. It could prove to be mobile phone interference, and it is best to have a filter installed so it can't cause issues.
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Charlie S: Malvern's PSBs on 41, 44 and 47 are now co-channel with The Wrekin's COMs @ 10kW. At your location The Wrekin is about 70 degrees clockwise of Ridge Hill and you have or are not far off line-of-sight at 46 miles.
A few years ago TV transmitter channels were reorganised to clear the 700MHz band for use by mobile phone services. This meant clearing channels 49 to 60 of TV. As part of this programme, on 7th March 2018 Malvern's PSBs changed to 41, 44 and 47. The Wrekin did not change any time during the 700MHz Clearance.
Additionally, Oxford changed to the same six channels as Malvern uses, meaning the two are co-channel on all six channels, but you have a lot of terrain in the way.
As your aerial is horizontal, it may be picking up a higher level of interfering signal from The Wrekin than if it had been VP, and this is acting against successful reception of the Malvern PSB signals which are VP. The question is: can you receive Malvern's COMs on 29, 31 and 37?
Malvern is/was used in Worcester. To counter the problem of co-channel interference in the area as a result of the change, a new transmitter was installed at Elbury Park Reservoir. It is a single-frequency network (SFN) with Ridge Hill, meaning it uses the same six channels without each interfering with one another.
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Charlie S: (Read my earlier comment in response to yours, where I explain the situation from March 2018 onwards with respect to The Wrekin causing co-channel interference to the PSB channels of Malvern.)
Reading between the lines, I think you might be about to tell us that your mother is using Malvern and that the programme channels she has variable reception on are those carried on the three PSB multiplexes, meaning channels including all the BBC ones, ITV, Channel 4, Channel 5, ITV2, ITV3, ITV4, E4, Film4, More4 and all the HD channels.
I think you have made the observation that you are unable to pick up Malvern on your horizontal aerial directed to Ridge Hill when you would expect to and perhaps could do in the past. I don't think your intention is to receive Malvern at your property, other than for test purposes, in effort to understand why your mother has intermittent reception on some channels.
If I am correct then the only solution may be to change your mother's aerial to face another transmitter, such as Lark Stoke or Sutton Coldfield, if these or any other can be received at her property.
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Tuesday 26 December 2023 1:02AM
Adrian Crafer : If you are still in Walcot then you and your neighbours using Oxford may benefit by switching to Seagry Court. As a relay of Mendip, Seagry Court's regions are BBC West and ITV West, so unless you prefer Oxford's, then change transmitter. I can see on Street View that some houses on what may still be your road have made the switch.
In February 2018, TV reception in Swindon was improved. Seagry Court got a 10x power boost and became a full-service transmitter, with the COMs added. At the same time, the Wroughton transmitter opened, also a full-service transmitter, this to serve an area not reached by Seagry Court.