BBC had channel loss

[foxhole]

After recent retune some of the HD channels have gone, tv says they are no longer available, namely BBC channels like news and bbc4 and CBeebies.? Also a hd shopping channel and RT news.

 

[Lucid]

BBC HD news....................COM 7
BBC 4 HD.........................COM 7
CBeebies HD.....................COM 7
RT news HD......................COM 7

HD shopping channels
QVC HD...........................COM 7
QVC Beauty HD................COM 7
Shopping Quarter..............PSB3 (BBC B)

There's a pattern here. You're missing a lot of the COM7 channels. You weren't specific about which shopping channels though, so Shopping Quarter on the PSB3 mux could be a red herring. I've only included it here because it's (a) shopping and (b) HD. If you're still getting BBC 1 HD, BBC 2 HD, ITV HD, CH4 HD, Ch5 HD then you're still getting PSB3 and so Shopping Quarter shouldn't be affected unless it has changed to a different mux.


[Background info:] COM 7 is a temporary mux. It is used as a holding space while there's a lot of shuffling going on to do with clearing the 700MHz band ready for selling off to the mobile phone operators. The longer term plan is for the channels it carries to be folded in to the existing muxes. This has already happened with COM 8.

COM 7 is still broadcasting from my local transmitter; Winter Hill, N.West England - Granada region - but I don't know if that's the same for you. You haven't mentioned in this thread which your local transmitter is. At a guess you could be receiving from Crystal Palace or Bluebell Hill (located north of Maidstone). You can look this up for yourself though using your postcode in the Wolfbane site http://www.wolfbane.net/cgi-bin/tvd.exe? From there we can work out if there have been any changes at your local transmitter.


Causes of specific mux (frequency) loses:

Broken or loose aerial plug connections resulting in more resistance and lower signal level, this then affects the weaker muxes first (The digital cliff)

Damage to some cable - kinked, bent, trapped, crushed - causing a frequency notch that affects some muxes but not all of them

Changes in the frequencies being used, and that making them a poorer fit with the aerial type installed at your property https://www.freeview.co.uk/help/4-nov-2020-channel-changes

The aggregate effect of an aging aerial system, possibly combined with some of the above, pulling the overall signal level down and so the weaker muxes are affected first

Aerial has moved and is now pointing such that the signal level is generally lower, but some muxes fall below the receivable threshold earlier than others (The digital cliff)
Aerial has moved and is now pointing such that the signal level is generally higher, but some muxes exceed the receivable threshold earlier than others (The digital cliff)

Damage to some cable - kinked, bent, trapped, crushed - causing a frequency notch that affects some muxes but not all of them

The TV doesn't erase the previous channel allocations on retuning. It simply looks to refresh what it already 'knows' and so misses the shift in mux frequencies

Engineering work at the transmitter (Google search for that)

Atmospheric conditions (high pressure) making it possible to receive signals from distant transmitters normally considered too far away to cause issues. This results in frequency clashes that disrupt certain muxes. (Crystal Palace and Bluebell Hill both use RF ch 55 (746MHz) for COM 7). This is usually a temporary phenomenon.

Changes to transmitters in other nearby countries causing some interference e.g. French transmitters affecting UK coastal reception in the S.East

Some other issue



I'd always go with the simple stuff first. Check plugs if they're the DIY fit type. Where you're using moulded cables you won't be able to do this, and you should be mindful that these are prone to unseen breakages in the centre conductor where it is soldered to the centre pin. The result of that is a much higher resistance but the signal still continues to work because of capacitive coupling at high frequency. If you have a multimeter, do a continuity test on the centre pin.

I would avoid a wholescale retune. Try instead going for a manual tune of the specific mux carrying COM 7 for your local transmitter. If that fails then have a look at the signal levels on the other muxes.


As always, if this or any other answer helped, please click the THANKS button on those posts. It costs you nowt to do and is quicker than typing a post with the words "thanks"

 

[ericmark]

With my boxes no problem, but direct on TV every time I return it seems different, I will guess some times vertical and some times horizontal polarised, possibly a voltage fault with TV. From what I am lead to believe the LNB is set to vertical or horizontal by the supply voltage, all my set bottom boxes get the full range, but not the TV, since I use a Sky Q box with that TV it does not matter to me that the TV satellite input seems faulty.

As to freeview well I am using the Moel y Sant (Powys, Wales) mast which is a public service broadcasting (PSB) transmitter, it does not provide these commercial (COM) channels: 4Music, 4seven, 5SELECT, 5STAR, 5USA, Aljazeera English, BBC Four HD, BBC News HD, Blaze, Blaze +1, CBeebies HD, CBS Drama, CBS Justice, CBS Reality, Together TV +1, Challenge, Channel 5 +1, CITV, Dave, Dave ja vu, DMAX, Drama, E4 +1, Film4 +1, Food Network, Forces TV, FreeSports, HGTV, Horror Channel, ITV2 +1, ITV3 +1, ITV4 +1, ITVBe +1, More4 +1, NOW 80s, Paramount Network, PBS America +1, pick, Quest +1, Quest Red, Quest Red +1, Really, RT HD, Sky Arts, Sky News, Smithsonian Channel, Sony Movies Action, Talking Pictures TV, TCC, Together TV, Yesterday +1.

So it will depend on your local transmitter, maybe not tuned into same one as before? I did live in North Wales and when returning some times it would pick up Winter Hill and some times Moel-y-parc even when aerial aimed at Winter Hill.

Kent is rather flat, lived is Suffolk for a time, and had a problem with isotropic weather, where it would tune into Dutch instead of English TV, so it is possible it has picked up a different transmitter. Where I live now, freeview is useless, so never bother with it. Freeveiw is clearly local so only some one else living in Kent can really say what goes on down there.

 

[foxhole]

Smart tv so the missing channel have returned. Signal is from Crystal Palace and line of site map shows the side street my aerial point down curved right thru direct line of site and rises on elevation (we are in low lying spot near stream ).

 

[Lucid]

Smart tv so the missing channel have returned.

I'm not sure if it's just odd grammar, or if it's actually what you intended to write, but the fact that yours is a smart TV has nothing to do with the signal returning.

Your signal for Com 7 (RF ch 55, 746MHz) is marginal. There could be a few reasons for this. It transmits at about 1/4 of the power of the main muxes for a start.

Depending on your distance from the transmitter, - and competing signals, - perhaps some local noise getting in to some poorly shielded cable or unshielded wall plates, - a kinked or damaged cable, - a bit of loss through one of the molded coax fly leads, - some aerial misalignment, - a bit of system degredation with age, there's all sorts of things, your COM7 signal could be close to the threshhold where a very small change in signal level is enough to tip the reception over the edge of the digital cliff. Once the signal picks up again then it looks like the problem has magically fixed itself. That's until it dips once again.

To give you an idea of how much difference ancillaries and cable damage can make, I've just done a job in Nantwich that involved putting a TV on the wall and concealing the cables. The local transmitters for this area are Winter Hill (Granada) and The Wrekin (Central TV). WH is more powerful (max 100kW) but further away at 39 miles. The Wrekin transmitter is closer (27 miles) but less powerful at 20kW max. The field strength for both is about the same according to Wolfbane. The property is a new build, about five years old.

The homeowners told me that their TV picks up Granada, but they were having trouble with some stations breaking up (Quest - RF ch 29).

I identified three issues: the wall socket was unshielded; the cable to it in the backbox was kinked; and they were using a molded fly lead from the wall plate to the TV. Fixing all that allowed me to get sufficient signal level to do a two-way split and still get 52-55dB at the TV aerial socket with 100% signal quality across the board.