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Full Freeview on the Mendip (Somerset, England) transmitter

first published this on - UK Free TV
sa_streetviewGoogle Streetviewsa_gmapsGoogle mapsa_bingBing mapsa_gearthGoogle Earthsa_gps51.237,-2.626 or 51°14'12"N 2°37'33"Wsa_postcodeBA5 3LB

 

The symbol shows the location of the Mendip (Somerset, England) transmitter which serves 720,000 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.

This transmitter has no current reported problems

The BBC and Digital UK report there are no faults or engineering work on the Mendip (Somerset, England) transmitter.

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

Which Freeview channels does the Mendip 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.

MuxH/VFrequencyHeightModeWatts
PSB1
BBCA
 H max
C32 (562.0MHz)591mDTG-3100,000W
Channel icons
1 BBC One (SD) West, 2 BBC Two England, 9 BBC Four, 201 CBBC, 202 CBeebies, 231 BBC News, 232 BBC Parliament, 250 BBC Red Button, plus 16 others

PSB2
D3+4
 H max
C34 (578.0MHz)591mDTG-3100,000W
Channel icons
3 ITV (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, 25 ITV4, 29 E4 +1, 34 ITV +1 (West),

PSB3
BBCB
 H max
C35 (586.0MHz)591mDTG-6100,000W
Channel icons
72 Shopping Quarter , 101 BBC One HD (England no regional news), 102 BBC Two HD (England), 103 ITV HD (ITV Meridian Southampton), 104 Channel 4 HD South ads, 105 Channel 5 HD, 204 CBBC HD, plus 1 others

COM4
SDN
 H max
C48 (690.0MHz)591mDTG-8100,000W
Channel icons
 CCXTV, 12 Quest, 20 Drama, 21 5USA, 28 ITV2 +1, 31 5STAR, 32 Paramount Network, 41 GREAT! movies action, 45 Channel 5 +1, 55 5SELECT, 57 ITVBe +1, 58 ITV3 +1, 59 ITV4 +1, 63 Blaze, 66 CBS Reality, 68 Horror Channel, 73 Drama +1, 77 TCC, 80 Blaze +1, 203 CITV, 211 Ketchup TV, 212 YAAAS!, plus 15 others

COM5
ArqA
 H max
C33 (570.0MHz)591mDTG-8100,000W
Channel icons
11 Sky Arts, 17 Really, 19 Dave, 30 4Music, 35 pick, 39 Quest Red, 42 Food Network, 46 Film4 +1, 47 Challenge, 48 4seven, 56 Smithsonian Channel, 69 Quest +1, 74 Yesterday +1, 82 Together TV, 233 Sky News, plus 9 others

COM6
ArqB
 H max
C36 (594.0MHz)591mDTG-8100,000W
Channel icons
23 Dave ja vu, 26 Yesterday, 33 GREAT! movies, 38 DMAX, 40 CBS Justice, 43 HGTV, 67 CBS Drama, 81 Talking Pictures TV, 84 PBS America, 234 RT, 235 Aljazeera English, plus 18 others

LBS
 H -10dB
C51 (714.0MHz)591mDTG-1210,000W
Channel icons
from 22nd September 2014: 7 Made in Bristol,

com7
 H -1.4dB
C55 (746.0MHz)591mDTG-672,400W
Channel icons
 Together TV +1,  Merit, 64 FreeSports, 70 Quest Red +1, 76 Now 70s, 86 More4 +1, 87 PBS America +1, 89 Court TV, 96 Forces TV, 106 BBC Four HD, 107 BBC News HD, 113 RT HD, 114 Quest HD, 205 CBeebies HD, plus 2 others

DTG-3 64QAM 8K 2/3 24.1Mb/s DVB-T MPEG2
DTG-6 256QAM 32KE 2/3 40.2Mb/s DVB-T2 MPEG4
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 Mendip transmitter?

regional news image
BBC Points West 0.9m homes 3.4%
from Bristol BS8 2LR, 25km north (3°)
to BBC West region - 60 masts.
regional news image
ITV West Country News (East) 0.9m homes 3.4%
from Bristol BS4 3HG, 23km north (11°)
to ITV West region - 61 masts.
All of lunch, weekend and 50% evening news is shared with West Country (West)

Are there any self-help relays?

CheddarTransposer15 km E Weston-super-Mare1674 homes
LuccombeActive deflector6 km w Minehead38 homes

How will the Mendip (Somerset, England) transmission frequencies change over time?

1984-971997-981998-20102010-132013-182013-1727 Feb 2018
C/D EEEC/D EC/D E TW TW T
C30_local
C32BBCA
C33com7com7
C34D3+4
C35com8com8
C36ArqB
C37C5wavesC5waves
C48SDNSDNSDNSDN
C49tv_off BBCABBCA
C51tv_offLBSLBS
C52tv_offArqBArqBArqB
C54tv_offC4wavesC4wavesC4wavesD3+4D3+4D3+4
C55tv_offcom7tv_off
C56tv_offArqAArqAArqACOM8tv_off
C58tv_offBBC1wavesBBC1wavesBBC1wavesBBCBBBCBBBCB
C61ITVwavesITVwavesITVwavesBBCA
C64BBC2wavesBBC2wavesBBC2waves

tv_off Being removed from Freeview (for 5G use) after November 2020 - 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 500kW
Analogue 5(-6dB) 126kW
SDN, ARQA, ARQB, BBCA, D3+4, BBCB(-7dB) 100kW
com7(-8.4dB) 72.4kW
com8(-8.6dB) 69.1kW
Mux 1*, Mux 2*, Mux A*, Mux B*, Mux C*, Mux D*, LBS(-17dB) 10kW

Which companies have run the Channel 3 services in the Mendip transmitter area

Jan 1958-Jul 1968Television Wales and the West
Jul 1968-Feb 2004Harlech Television
Feb 2004-Dec 2014ITV plc
Feb 1983-Dec 1992TV-am•
Jan 1993-Sep 2010GMTV•
Sep 2010-Dec 2014ITV Daybreak•
• Breakfast ◊ Weekends ♦ Friday night and weekends † Weekdays only. Mendip 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.

Comments
Sunday, 8 November 2020
A
Alan_C
2:53 PM

Chris.SE:
Chris:

Figures with amp connected (Commtel 4 channel amp/distribution device) in the loft, connected between the aerial lead and the cable running down to the wall plate, built in to the wall):

32 Q 60 L 100
34 Q 65 L 100
35 Q 0 L 100
48 Q 55 L 100
33 Q 30 L 100
36 Q 35 L 100
55 Q 0 L 95
30 Q 0 L 0

Note the increase in signal level across the band (including ch55); but also note the loss of quality across the band, with the exception of ch48 which benefits.

I know the Freeview map shows good coverage in my locality but the truth is there are many pockets in Somerton where people are slightly lower down and do not get good signals. Our installation situated on the plateau doesn't have unobstructed LOS to Mendip. It is also notable that about 50% of the properties around have two aerials - the other being directed to Stockland Hill. While this could be because they identify with SW rather than W region, it also apparent that we're about halfway between the two transmitters - and the direction to Stockland isn't far from -180 degree endfire on my aerial (I wonder what its reception pattern is like out of the back?). And I would add we get very poor FM radio even with a separate dedicated outdoor antenna, and no usable DAB. But that's off topic except that it does indicate we're not so well served by Mendip.

Thanks for the suggestions re. VCR, etc. We do have a VCR connected using SCART - I'd forgotten about the RF modulators in these things. Switching off the VCR and a DVD player, and removing an HDMI lead, made no difference to the signal / quality measures.

Interesting thought about standing waves in the cables. I've checked and swapped around all leads; also tried a long cable from the loft instead of the installed cable and wall plate. No changes seen.

The position in the loft is rather constrained, it needs to point through the gable end rather than the tiles because we have solar PV, and there aren't many places with enough headroom. The DC cable for the solar panels does run perpendicular to the aerial axis, close to the pole.

I'll wait for any further thoughts and comments before attempting to realign the aerial or move it sideways., as without any kind of analogue meter up there with me this is a bit of a trial and error activity. Initial alignment was just based on the required bearing!

Slight change of topic, but are we to expect Com7 to be switched off sometime in 2020?

Again, very grateful for your inputs (were you really typing at 4-5am?!!).

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Alan_C's 9 posts GB
Monday, 9 November 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

2:27 AM

Alan_C:

It's probably fair to say that none of the coverage maps or predictors are 100% accurate, the less variable the local terrain, the more likely they are to give some believable figures, that said the Freeview Detailed Coverage Checker doesn't show any variation across the 6 main muxes, only COM7 very marginally less reliable for your postcode.
It does also show very good reception from Stockland Hill (bearing 223 degrees) and as it happens some good and variable reception from Wenvoe (bearing 320degrees)! Stcckland Hill is 38km from you, Mendip 22km, Wenvoe 59km.

The aerial is likely to have some moderate side lobes to the rear sides, I'd try just out of curiosity to see what you could pick up without moving the aerial (with the amp connected). Stockland Hill's UHF channels are C26+, C23+, C29+, C25-, C22-, C28- for PSBs1-3, COMs4-6, no COM7 or Local. Don't worry about the +/- offsets, TVs tune quite happily.

Now, well done for trying the long cable, all that you did were useful checks. One query in relation to the amp, when you had the aerial connected directly (first set of figures), was the amp still switched on/powered up? IF so, try the aerial connected direct again with the amp powered off and see if there's any differences (this should make sure that the amp isn't causing any interference).

The set of figures with the amp in circuit are now suggesting too much signal, hence the drop in the quality figures, that's why you found some improvement when you introduced that splitter giving some attenuation as mentioned in your original post. Although this C48 problem is still another issue (eg. it could be aerial position in relation to maybe your solar PVs or other things, if it wasn't a problem with the amp itself which the check I've just mentioned should confirm).

Its also worth considering other possible sources of interference that may be affecting C48 if the amp is eliminated. Try switching off anything that might be running constantly when you've been looking at figures or having problems with reception (not fridges/freezers/central heating as these go on and off) but any lighting running off transformers, fluorescent fittings, compact fluorescents, LEDs, or any other discharge lighting eg.outside. Anything else that has any electronic control that's powered all the time.

As you have a 4-way amp/splitter, I assume you may have at least one other TV elsewhere in the house. Does it show similar relative figures for each UHF channel?

If there doesn't appear to be any problems with the amp, then it would probably a good idea to get one of these eBay item: 310039226920, Coax TV Aerial Attenuator Adjustable Variable Between 0-20 dB Reduces signal | eBay
IF the amp does turn out to be an issue then any replacement might usefully have a variable gain control.

If we've got to the point that everything else that could be causing interference or poor reception has been eliminated, then we are most likely down to aerial position. Whilst absence of a meter might making things somewhat tricky with a bit of trial and error, initially we're only interested in whether reception is being adversely affected by position. Without the amp in circuit, I would initially take it off the pole and remove the pole and just move the aerial sideways and say back away from the solar PVs and just have it sitting on the beams/loft floor doesn't matter if it say overhangs your loft access or whatever, to start with we're just looking for what significant (if any) changes there are in signals.

If you've got a 2nd set and it was showing similar relative figures to your main set, maybe you could position it somewhere nearer the loft which would make any to-ing and fro-ing a bit easier.

If you can post back with the info about whether the amp was on when you did the first figures and any differences if so, and any comparison with a second set, checks on other potential sources of interference etc. I can see if any of that modifies my thoughts.

I replied to your DAB post, yes I was up, had been watching news on the US election then decided to watch a film (sad I know!). COM7 is not likely to close in 2020, it's anticipated that the earliest would be later in 2021 IF any MNOs buy the SDL frequencies when the auction is held scheduled in the new year, they could then give 3 months notice to be able to use the frequencies, but equipment would need to be installed as well as suitable handsets available and this won't happen overnight. That said, Arqiva closed COM8 for commercial reasons primarily due to loss of advertising revenue in the covid-19 situation and broadcasters being uncertain about the future wanting to cut costs, so that might have a future effect on COM7, personally I don't think it's a high probability.

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Chris.SE's 2,365 posts GB
Tuesday, 10 November 2020
A
Alan_C
5:29 PM

Chris.SE:

A quick but partial answer...

I like the idea of seeing what signal I can pick up from Stockland Hill using side lobes, without realigning the aerial - I'll do that at the weekend (don't want to get in the bad books of my wife). That'll also be the best time for me to try some rotation / repositioning of the aerial. And that's probably my best time for switching other things off. Like most people I guess, I have a few things which are "always on", like the wifi router. I don't think there's anything which has been put in fairly recently, though, except central heating (which has all wired thermostats, nothing radio-connected). My neighbour has been doing a lot of work in his house - I hope he hasn't installed anything operating on 690MHz!

Going back to the amplifier; when I tested with the amp disconnected it was moved away from the leads and fully powered down, and the aerial lead and the cable to the wallplate joined using a female-female back to back connector. As you've said, the figures show that the amp does provide gain ;-) which is probably not needed, and causes overloading of the tuner. But they do seem to suggest that the signal out of the aerial on Ch 48 is genuinely quite a bit lower than other channels; which isn't in line with the aerial gain curve?

Actually I don't have any other TVs anywhere - I installed the amp when my daughter came back to live for a while, and I put in an aerial point in another room for her - but since she left we haven't had a second TV. So I can carry on without the amp, but do you think it might be worth trying to put in some variable gain and find a sweet spot where Ch 48 is improved without overload on the others?

I'll do some more playing around next weekend.

Thanks for your continued assistance. Is this a hobby? I am impressed by your tolerance and politeness when responding to people with a wide range of attitudes!

Alan


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Alan_C's 9 posts GB
Wednesday, 11 November 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

10:56 PM

Alan_C:

It's not specifically anything "operating" on 690MHz, it's anything that might possible generate some interference to that frequency. In the expression "electronic control"/ powered all the time that would include anything with a SMPS (perhaps I could have been more explicit) so things like Mobile Phone chargers, USB power supplies etc. could all be suspects.

As it seems that the amp is not a likely source of issues for the C48 problems, unless repositioning of the aerial causes a significant uplift of the signal for the other multiplexes, not just SDN and COM7 (C48 & C55) then it's probable that you'd benefit from some amplification but not (necessarily) the full amount the amp can give.
You might find for example that you can get an uplift in C48 & C55 moving the aerial but you might get a slight drop in the others, so amplification to bring them all up would be a good idea.

By using a variable attenuator, you can hopefully tweak it to get the best compromise. You'd put it between the amp and the set, not aerial and amp. If you highlight the whole of that eBay url and open it in a new tab say, or search eBay for the item number - just the number, no words, it'll take you straight to it. There are other suppliers on eBay and on other sites, but not necessarily at such a good price for that - quite good - brand. If you go elsewhere, watch that you want coax connectors not F-connectors.

Hobby? Haaa, well, it was onetime work, these days it helps keep the brain active, but it's sometimes difficult to remain polite when you get some posts like two on the previous 2/3 pages here!

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Chris.SE's 2,365 posts GB
Saturday, 14 November 2020
A
Alan_C
7:56 PM
Somerton

Chris.SE:

An interesting and initially frustrating day spent tweaking things and hoping to improve reception of channel 48 from my loft aerial.

I tried checking for signal from Stockland Hill and Wenvoe (without turning the aerial) and unamplified, I found nothing on any of the relevant channels (26+ etc.).

I tried isolating any possible source of interference, switching various things off - I think I found all the switch mode power supplies in the house. A search online suggested that the solar PV inverter in the loft (which is a switching design) was a potential problem, and I considered where I might add ferrites - but turning it off made no difference to the signal on Channel 48.

So I looked at the effects of rotating the aerial. I checked signal quality and strength as reported by the TV for Channel 48, and also Channel 33 as a reference. As well as rotation, I also moved the aerial a small amount along its axis (up to about 15cm) and sideways (about 5cm) but these didn't seem to make any difference. What did make a difference was when I lowered it a small amount (7cm) to allow enough room for it to turn. This resulted in noticeably lower signals on my reference channel.

I plotted all the results on a graph and it showed that the signal strength on Channel 33 had a maximum at 22 degrees; Channel 48 seemed to indicate a peak around 30 degrees but it never rose enough to get a decent signal quality; the maximum was about 25.

So I concluded that the aerial was already pointing in the best direction possible for that location, but then I thought again about the height effects and put it as high as possible while horizontal; then angled it up by 15 degrees. The results are as follows:

Channel Horiz. Quality Horiz. Strength +15deg Quality +15deg Strength
32 95 60 100 70
34 100 70 100 75
35 45 60 60 60
48 50 65 95 70
33 95 70 100 70
36 55 65 85 65

As you can see, angling it upwards has improved the signal across the board, presumably because it is capturing signal which is coming through the tiles rather than the gable wall.

So I now have satisfactory reception on Channel 48, as well as the others. It hasn't explained why that channel was so much more affected by the wall than the others.

In closing, very many thanks for your help and support, and I'm glad to say the outcome is looking good.

Alan


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Alan_C's 9 posts GB
C
Chris.SE
sentiment_very_satisfiedPlatinum

8:35 PM

Alan_C:

Sounds like you've been very thorough in the checks that you've done.
In many respects, I'm not surprised that the signal is better through the tiles rather than a wall, even with all the rain today!!

Yes tilting the aerial slightly can improve signals in some circumstances. Did you try any slight rotation as well whilst it is tilted or isn't there enough headroom for that?

Any signal on C55 now?
Getting any side-lobe signal for Stockland Hill without any amplification was probably expecting a bit much. I still say you have a scope for improving things with the amp, but use a variable attenuator between amp and TV (located at the TV end) should enable you to tweak things to get optimum signal without overload.
It'd give you more chance of a reasonably reliable signal for C55 but improve reliability for C35 going by those figures.

You never know, you might even get a Stockland Hill signal!

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Chris.SE's 2,365 posts GB
C
Chris.SE
sentiment_very_satisfiedPlatinum

8:40 PM

Alan_C:

For the sake of clarity, when I said "to tweak things to get optimum signal without overload" it really means to get the Quality figures up, ideally to 100% without overload.

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Chris.SE's 2,365 posts GB
Wednesday, 2 December 2020
A
Alan_C
6:46 PM
Somerton

Chris.SE:

I've obtained an attenuator (-20dB max) and done some more experiments. I connected aerial to amplifier to attenuator to TV and recorded signal quality and level at every whole turn of the attenuator knob - assumed to be a change of about 4dB per turn. Disappointingly, there was no attenuation setting at which the signal quality on Channels 35 and 48 was improved. I also tried it with the connections the other way around: antenna-attenuator-amplifier-TV; the results weren't any better.

I still don't understand why I'm getting poor reception on channels 35 and 48, yet 36 is excellent. I'm fairly sure that the LOS to Mendip transmitter grazes the top of a heavily-wooded hilltop. I think it looks as though I shall have to venture outside and try installing the aerial on the gable end wall, or failing that the chimney.

I suppose there's still one other thing I could try, and that's turning the antenna to point to Stockland Hill (you may remember I looked to see whether there was any signal on the Stockland channels but I did this without turning the aerial, just to see whether it had any sensitivity out of rear lobes!). Or I could knock a hole in the gable end!

By the way, I'm not clear about 55 - is it correct to say that this has now gone for good?

Alan

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Alan_C's 9 posts GB
Friday, 4 December 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

4:32 AM

Alan_C:

Sorry for the delay getting back to you, C55 is very much alive (but not transmitted from Stockland Hill), the suggestion on many transmitter pages on this site that it was going in November is wrong. For the situation as it was back in June see Rebuilding Freeview High Definition from 2019 onwards | free and easy and the updated situation is that the Clearance programme was eventually completed in August. OFCOM have scheduled the auction for sometime in January 2021. The rest of the situation is as previously suggested, until the auction is completed, we won't know if any MNO will have bought the Centre Frequencies (allocated for SDL use), nor will we know what timescale will be involved for such a purchaser to commission such equipment to use the frequencies and so give any 3 month notice as stated in the current multiplex licence.

Going back to previous posts, you said the aerial was a 48 element, was that a typo as the link is actually a 40 element, there doesn't appear to be a similar 48 element. That aside, the aerial spec. shows a pretty flat response across the spectrum, so from an aerial point of view no obvious reason for the C35 and C48 performance, also C36 didn't look that good.

Looking at those figures with the aerial tilted up 15 deg. C48 wasn't bad, it was C35 & C36 that weren't that good, but that was without the amp. So with the amp in circuit and the attenuator at the set end, nothing improved for any setting of the attenuator!! Very disappointing.
Having the attenuator at the aerial end will most likely degrade the S/N ratio a bit but otherwise not much difference.
Give the attenuator at the set end another try. Up until Wednesday evening there'd been some tropo around again which could well have been upsetting the apple cart!

Trees on the LOS can sometimes cause multipath (again, not at all frequencies), but at this time of year I would have expected signals to have been more stable and when the trees are some considerable distance away even less of an effect. So I'm thinking that it's some issue with the position in the loft, I don't known if it's worth tweaking direction a bit, or position back/forth/sideways but keeping the 15 deg. tilt.
PS. If I recall correctly you looked for Stockland Hill pointed at Mendip without the amp?

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Chris.SE's 2,365 posts GB
Tuesday, 8 December 2020
A
Alan_C
9:23 PM
Somerton

Chris.SE:

Hi Chris, thanks for commenting back. I've only got a few notes to add at the moment; it seems I need another session of trial-and-error to see whether there's any way of getting an improvement. Unfortunately I don't think I have enough nerve to go up on the roof, so I'm stuck with trying the loft!

Thanks for clarifying the Ch55 story. It's academic to me at the moment, since I'm not getting anything on that channel, but I shall keep checking it and include it when I make comparisons!

I don't recall describing the aerial I bought as 48 element - it's an XB10K, "12 element" (10 directors, dipole and reflector), X-beam design (but I might have to go up and do a recount).

We've been getting worse reception / more pixellation the last couple of days, even though the weather is now dominated by a weak low pressure system. So I really will have to try changing the position. I guess the small changes I've tried aren't really enough in wavelength terms. Unfortunately it is very hard to find space for it to move - the reflector is right against the rafters as close to the apex as it'll go, so any attempt to move it means I have to position it lower.

I did wonder whether all cable on the market these days is 75 ohm impedance, and hence matched to the antenna (which has a balun)? If not, then maybe I've got a rogue length of 50 ohm or something!

I don't think all the trees have lost their leaves yet.

Best wishes,

Alan

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Alan_C's 9 posts GB
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