Freeview Light on the Backwell (North Somerset, England) transmitter
 | Google map |  | Bing map |  | Google Earth |  | 51.441,-2.724 or 51°26'28"N 2°43'25"W |  | BS48 1NY |
The symbol shows the location of the Backwell (North Somerset, England) transmitter which serves 4,600 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.
This transmitter has no current reported problems
The BBC and Digital UK report there are no faults or engineering work on the Backwell (North Somerset, England) transmitter._______
Digital television services are broadcast on a multiplexes (or Mux) where many stations occupy a single broadcast frequency, as shown below.
H/V: aerial position (horizontal or vertical)
The Backwell (North Somerset, England) mast is a public service broadcasting (PSB) transmitter, it does not provide these commercial (COM) channels: 4seven, 5Action, 5STAR, 5USA, Al Jazeera English, Blaze, Blaze +1, Challenge, Channel 5 +1, DMAX, U&Drama, E4 Extra, Film4 +1, Food Network, FRANCE 24 (in English), GREAT! action, GREAT! movies, GREAT! player, GREAT! romance, HGTV, HobbyMaker, ITV2 +1, ITV3 +1, ITV4 +1, ITVBe +1, YAAAS!, Legend, PBS America, POP MAX, Quest +1, Quest Red, Really, Sky Mix, Sky News, Talking Pictures TV, That's Melody, That's TV , That's TV 2, Tiny Pop, TRUE CRIME, TRUE CRIME XTR, U&Dave, U&Yesterday, U&W.
If you want to watch these channels, your aerial must point to one of the 80 Full service Freeview transmitters. For more information see the will there ever be more services on the Freeview Light transmitters? page.
Which Freeview channels does the Backwell 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.
| Mux | H/V | Frequency | Height | Mode | Watts |
| PSB1 BBCA | V max | C25 (506.0MHz) | 125m | DTG- | 19W |
 1 BBC One (SD) West, 2 BBC Two England, 9 BBC Four, 23 BBC Three, 201 CBBC, 202 CBeebies, 231 BBC News, 232 BBC Parliament, plus 17 others | |||||
| PSB2 D3+4 | V max | C28 (530.0MHz) | 125m | DTG- | 19W |
 3 ITV 1 (SD) (West), 4 Channel 4 (SD) South ads, 5 Channel 5, 6 ITV 2, 10 ITV3, 13 E4, 14 Film4, 15 Channel 4 +1 South ads, 18 More4, 26 ITV4, 28 ITVBe, 30 E4 +1, 35 ITV1 +1 (West), 71 That's TV 3, | |||||
| PSB3 BBCB | V max | C22 (482.0MHz) | 125m | DTG- | 19W |
 46 5SELECT, 57 U&Eden, 101 BBC One HD West, 102 BBC Two HD England, 103 ITV 1 HD (ITV Meridian Southampton), 104 Channel 4 HD South ads, 105 Channel 5 HD, 106 BBC Four HD, 107 BBC Three HD, 204 CBBC HD, plus 1 others | |||||
Are you trying to watch these 44 Freeview channels?
The Backwell (North Somerset, England) mast is a public service broadcasting (PSB) transmitter, it does not provide these commercial (COM) channels: 4seven, 5Action, 5STAR, 5USA, Al Jazeera English, Blaze, Blaze +1, Challenge, Channel 5 +1, DMAX, U&Drama, E4 Extra, Film4 +1, Food Network, FRANCE 24 (in English), GREAT! action, GREAT! movies, GREAT! player, GREAT! romance, HGTV, HobbyMaker, ITV2 +1, ITV3 +1, ITV4 +1, ITVBe +1, YAAAS!, Legend, PBS America, POP MAX, Quest +1, Quest Red, Really, Sky Mix, Sky News, Talking Pictures TV, That's Melody, That's TV , That's TV 2, Tiny Pop, TRUE CRIME, TRUE CRIME XTR, U&Dave, U&Yesterday, U&W.
If you want to watch these channels, your aerial must point to one of the 80 Full service Freeview transmitters. For more information see the will there ever be more services on the Freeview Light transmitters? page.
Which BBC and ITV regional news can I watch from the Backwell transmitter?
BBC Points West 0.9m homes 3.4%
from Bristol BS8 2LR, 8km east-northeast (75°)
to BBC West region - 60 masts.
ITV West Country News (East) 0.9m homes 3.4%
from Bristol BS4 3HG, 11km east (90°)
to ITV West region - 61 masts.
All of lunch, weekend and 50% evening news is shared with West Country (West)
How will the Backwell (North Somerset, England) transmission frequencies change over time?
| 1984-97 | 1997-98 | 1998-2010 | 2010-13 | 5 Jun 2019 | |||||
| A K T | A K T | A K T | A K T | A K T | |||||
| C22 | BBC1waves | BBC1waves | BBC1waves | BBCB | BBCB | ||||
| C25 | ITVwaves | ITVwaves | ITVwaves | BBCA | BBCA | ||||
| C28 | BBC2waves | BBC2waves | BBC2waves | D3+4 | D3+4 | ||||
| C32 | C4waves | C4waves | C4waves |
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 24 Mar 10 and 7 Apr 10.
How do the old analogue and currrent digital signal levels compare?
| Analogue 1-4 | 94W | |
| BBCA, D3+4, BBCB | (-6.9dB) 19W |
Which companies have run the Channel 3 services in the Mendip transmitter area
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Tuesday, 9 April 2024
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Paul Dursley11:47 AM
Steve Donaldson:
Hi Steve - filter on the way from Restore TV
I'll report back after receipt and fitment of the filter
Thanks
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Paul Dursley3:33 PM
Paul Dursley:
Steve/Chris - hopefully you are both picking this message up.
Miraculously C22 has returned - it was there when I switched on sometime after midday. It was definitely absent before during the morning period. Coming through with a steady 6/10 for both signal strength and quality.
Not as good as C25 and C28 which are both 10/10 for quality and 7-8/10 for strength
We still have strong winds in the area through this morning and still blowing now. Atmospherics have improved though.
Other than speaking with Restore TV this morning I've done nothing to alleviate the problem.
Mysterious.....
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Wednesday, 10 April 2024
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Steve Donaldson12:32 PM
Paul Dursley: That C22 still has lower quality appears might perhaps imply the issue is still present, just not as bad as it was. With that in mind, it will be interesting to fit the filter and see if the quality for C22 goes up to 10/10 with it fitted and down to its current reading without.
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Paul Dursley6:14 PM
Steve Donaldson:
Evening - waiting on the filter to turn up, keen to get it fitted and see if that helps.
I agree that it's 'odd' that C22 seems to be the only multiplex affected from the Backwell transmitter. Maybe there is some local interference at around the C22 frequency - we'll see if the filter helps.
I'm going to try a new coaxial cable to the TV just as a quick check comparison with the current installation.
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Thursday, 11 April 2024
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Steve Donaldson10:09 PM
Paul Dursley: Bristol Kings Weston is co-channel with Backford and it is on nearly the same bearing for you.
During the 700MHz Clearance, UHF channels 49 to 60 were cleared of TV broadcasts, with all transmitters on those channels having to move down. Consequently, with fewer broadcast channels to go around, some transmitters ended up on the same channel when previously they were not.
In your area, the change happened on 5th June 2019 (except for one of Kings Weston's channels which changed two weeks later).
Backwell used channels 22, 25 and 28 before the change. The COMs of Kings Weston and the PSBs of Ubley changed.
Bristol Kings Weston COMs: 53, 57*, 60- changed to 22, 25*, 28
Backwell: No channel changes. Power up from 18W to 37W.
Ubley: Power up from 15W to 25W. 21+, 24, 27 changed to 22, 25, 28
* Kings Weston C57 changed to C25 on 19/06/19.
Kings Weston is on a bearing of 37 degrees at 7 miles out. Backwell is on a bearing of 31 degrees at 2 miles out.
Like Backwell, Kings Weston is vertically polarised. Kings Weston is 200W, much of which is coming in your direction, the radiation pattern being generally to the south from the tower (see the page on this site for Kings Weston).
I think the power increases at Backwell and Ubley were an effort to counter co-channel interference rather than to increase coverage. Similar power increases occurred elsewhere in similar circumstances.
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Steve Donaldson10:35 PM
Paul Dursley: My apologies, I meant to say 'Backwell', not 'Backford'.
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Saturday, 13 April 2024
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Paul Dursley6:17 PM
Steve Donaldson:
Evening
Inline filter received and fitted - made absolutely no difference to C22 signal strength or quality; C25 and C28 unaffected.
Still, the original issue is 'resolved' in so much that I am receiving the BCC West HD and other C22 TV channels.
Not sure where that leaves the us with the discrepancy of signal strength and quality for C22 vs. C25 and C28 from the Backwell transmitter.
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Steve Donaldson7:31 PM
Paul Dursley: Considering what I have found, which follows below, I'm not surprised the filter has had no effect. I believe this is an issue with reception of Mendip by the Backwell transmitter and needs reporting to the BBC.
The signal path between the Backwell transmitter and Mendip runs close to the ground for around a mile where it goes over the top of Barrow Hill. The signal path is the line through free space between the transmitting aerial of Mendip and the receiving aerial of Backwell. I think this is why there are two receive aerials on the Backwell transmitter.
I suspect the reason you lost reception of PSB3 (C22) and at the same time had lower quality on PSB2 (C28) is because Mendip was broadcasting from its reserve antenna. This is lower down the mast than the main which is at the top. I think that PSB3 came back because Mendip returned to transmitting from its main antenna.
The three Mendip channels for the PSBs are C32 (PSB1), C34 (PSB2) and C35 (PSB3). If your issue is in fact a reception issue for the Backwell transmitter then when you lost PSB3 it was C35 that was worst impacted with C34 less so (you had lower quality on PSB2). If this was because Mendip was on its reserve antenna and now it is on its main, then the quality issue on C22 may in fact be a quality issue on C35 as received by the Backwell transmitter.
Thus, it looks like the objects in the signal path between Mendip and Backwell are acting to the detriment of reception in the frequency range of C35 (around 586MHz). With the lower height of the reserve antenna the obstruction in the path increased, and when this happened the impact on reception on C35 frequencies became more pronounced, spilling over into the adjacent channel, C34.
- Terrain Plots -
I have set out the aerial heights below. Here is a terrain plot with Backwell on the left and Mendip on the right:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
The plotter uses six-figure OS grid references, meaning the locations of the two transmitters are set to the 100m interval closest to where they are. Backwell is set a few tens of metres away from its true location where the ground height is a little higher, so I have compensated by reducing the height of the antenna. For the height of the Mendip antenna I have entered that of the lower/bottom of the reserve, so we can see worst-case scenario, with Mendip transmitting from its lowest antenna.
The yellow line denotes the line-of-sight and the pink line is the outer of the first Fresnel zone. The Fresnel zone is the area between the pink line and yellow line. Anything in this area can have the potential to affect reception. This isn't to say that it will, but we can see that the ground and objects on it are in the Fresnel zone for around a mile, from somewhere about 2.6 miles out to maybe 3.7 miles out from Backwell. This corresponds roughly to a line over Barrow Hill from about The Conygar (around Water Catch Farm) through to the high ground of Yewtree Farm, which is to the south of Freemans Quarry and north of the A38.
The point then is that the lowering in height of the Mendip antenna (by way of switching from main to reserve) increases the level of obstruction in general present in the Fresnel zone (the Fresnel zone having lowered also). Increasing its height by returning to the main reduces the obstruction.
This is a plot from the Backwell receive to the bottom of the Mendip main antenna:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
- Aerial Heights -
Ofcom publishes the average aerial heights of transmitting antennas (main, not reserve). I referred to planning application diagrams for the height of the Backwell receive, and Mendip main and reserve antennas height spans (source reference notes in square brackets):
-- Backwell --
Site height: 96m
Receive aerial height above ground: 23m [1]
-- Mendip --
Site height: 303m
Main antenna height: from 282.3m to 293.7m [2]
Reserve antenna height: from 245.7m to 257.2m [2]
~~
The Mendip source [2] was published in 2013 and therefore with the previous Mendip antennas, as they were subsequently replaced for 700MHz Clearance. However, the current ones are in the same place, so the figures will be still relevant.
As can be seen in photos[3], between the main TV and reserve TV aerials are DAB and FM broadcast antennas. I checked the height of these other antennas and they are between the main TV and reserve TV heights quoted above, so those figures look to be right. The average height of the main TV is given as 288m, which ties in with the above.
We can see from this that the Mendip reserve antenna is 36.6m lower, from the bottom of the main to the bottom of the reserve.
_____
[1] Planning application 15/P/1969/F with North Somerset council, 'Proposed Elevation' document.
[2] Planning application 2013/1080 with Somerset Council, East District (former Mendip District), 'Existing SE Elevation' document.
[3] mb21 - The Transmission Gallery
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Sunday, 14 April 2024
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Paul Dursley9:45 AM
Steve Donaldson:
Hi Steve,
Thank you for your very thorough analysis of the signal transmission and reception between the Mendip and Backwell antenna. The analysis does fit my reported TV reception (or not, initially) symptoms over the past week or so from the Backwell transmitter and in conjunction with engineering works at Mendip.
The ineffective influence of the filter only bolsters the conclusion of your analysis.
You mention reporting the issue of reception by Backwell of the Mendip signal to the BBC - who would be responsible for making that report?
If it's me as a 'customer' of the BBC I will quite happily report this as an issue. Presumably there is no problem with referencing our discourse over the past week or so?
Once again thank you for assisstance with my reception problem.
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Saturday, 20 April 2024
S
Steve Donaldson1:49 AM
Paul Dursley: It's good to hear all Backwell multiplexes have returned to good strength and quality.
The channel allocations of Backwell and Wenvoe COMs lend themselves to combining into one the feeds of an aerial on each transmitter. The main six are: Backwell's PSBs: 22, 25 and 28, and Wenvoe's COMs: 39, 42 and 45. Wenvoe's Cardiff local multiplex is 37 and its PSBs are 41, 44 and 47.
ATV currently lists a single UHF-UHF diplexer[1]. It splits at C38 and according to the photo, is a Fringe Electronics model. Fringe doesn't list such a model on its website[2]. The diplexer attenuates channels neighbouring the split, so this may not be the best one here.
UHF-UHF diplexers are thin on the ground. There is an Antiference UD3437 diplexer listed on eBay. If you put the model number into the eBay search bar you should find it. Its lower input actually goes all the way down to 88MHz, so will pass FM broadcasts too. The UHF channels it passes on the two inputs are 21 to 34 and 37 to 68.
_____
[1] Diplexer Channel 38 (UHF/UHF) A.T.V. Poles, Brackets, Clamps & Aerials
[2] https://fringeelectronics.co.uk/diplexers.html
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