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BBC Four HD mux. change
- Thread starter prpr
- Start date
OP
prpr
Well-Known Member
It can't be both. As bandwidth goes up, gain comes down. The law of diminishing returns applies if you try increasing the aerial size, and you make the side-lobes worse and increase the windage.
Owen Smith
Well-Known Member
I can tell that is after a retune due to COM5 on UHF 36, that moved today.
You are also missing COM4 on UHF 51, as well as COM7 and COM8 on 55 and 56.
Sandy Heath in the analogue days needed a Group A aerial, and even when C5 was added from the Maddingley transmitter it was on UHF 35 which was receivable on many Group A aerials and certainly Group A extended ones.
When pre DSO digital TV came along on Sandy Heath all the muxes were up in Group B, C and D for example one mux was originally right at the top on UHF 68. You needed a wideband aerial to have any hope of receiving these at low pre DSO power levels, and I had to put a masthead amp in as well.
COM4 will move to UHF 33 some time next year as part of 700 Mhz clearance, at which point you should get all six main muxes based on your results above. If you want COM4, 7 and 8 before then you probably need a wideband aerial. COM4 is at the same power as COM5 so only frequency is a good explanation of why you can't get it.
Try manual tuning UHF 35 as well, that is the Cambridge local mux. Power is low but the modulation is QPSK which is incredibly robust so doesn't need much power.
Black Hole
May contain traces of nut
I get the impression the planners are shortsightedly looking at the whole broadcast spectrum for placing the transmission frequencies instead of considering the needs of aerial groups!
Owen Smith
Well-Known Member
Actually when this is all finished, all muxes on Sandy Heath should be receivable on Group A except maybe COM6 on UHF 48. They've done quite a nice job compared to what Sandy Heath had in the past with channels from 21 to 68 pre DSO.
And also once 700Mhz clearance is finished, aerial groups become pointless. The range will be 21 to 48 which is easily receivable on a Group K which can have quite decent gain unlike widebands.
The alternative sticking strictly to aerial groups would possibly have resulted in only five muxes post 700 Mhz clearance, that was the original proposal. Given we'll be losing COM7 and 8 anyway, if ignoring aerial groups is the price to pay for retaining the main six muxes then I believe it is worth paying.
Last.To.Know
Member
Again, you are right.
Looking at
https://ukfree.tv/transmitters/tv/Sandy_Heath
I can see I used to have those stations, though I never watched them, so I am not bothered about trying to restore them.
I am more miffed about losing the HD channels, which I hope will be shuffled to the six main muxes you describe.
Owen Smith
Well-Known Member
They gave us COM7 and 8 to encourage people to swap their TVs and boxes for DVB-T2 capable ones by offering extra channels that only DVB-T2 systems can receive. I believe this has mostly been a failure because most people don't care due to the utter dross that accounts for most of the channels on COM7 and 8. If it weren't for BBC4 HD I wouldn't be bothered if I couldn't receive COM7 and 8.
What the plan needed to work was for some decent channels like Film4 HD and ITV3 HD (for hidef repeats of Morse and Poirot etc) to come onto COM7 and 8. But the financials of keeping HD behind a Sky paid service vs. free to air on muxes with only 75% national coverage and then only receivable by those with DVB-T2 gear made that a failure.
The purpose of trying to get us to upgrade our equipment to DVB-T2 was so that by the end of 700Mhz clearance it would be less controversial to switch more of the main six muxes to DVB-T2. Eg. the BBC need at least one more mux to go to DVB-T2 in order to keep BBC4 HD and BBC News HD.
What I suspect the BBC would like is an entire DVB-T2 mux to themselves which can probably fit everything they currently broadcast given no need for SD simulcasting. And then something like PSB3 but for SD where there is a DVB-T mux that carries BBC1, BBC2, ITV1, C4 and Five (and no doubt a load of crap) so that DVB-T only devices can still receive the main five channels.
Owen Smith
Well-Known Member
I cannot explain your loss of COM4 on UHF 51. It has been on UHF 51 for years and it has not changed power level. Maybe the recent high pressure weather means you have lost it temporarily due to interference from distant transmitters? Maybe your aerial installation inc. cabling has degraded with time and weather?
The HD channels on COM7 and 8 will not be shuffled onto the main six muxes until well into 2020 when 700Mhz clearance is due to finish. Decisions will be made based on whether and when COM7 and 8 are switched off. Part of moving them to SFNs may be to try to persuade Ofcom there is space to keep them permanently, that only needs 16MHz from the vast swathes of bandwidth that the mobile evangelists insist they must have or the world will end.
Owen Smith
Well-Known Member
Oh yes, COM7 and COM8 transmitting gear is recycled from the low power pre DSO transmitters for the main muxes. Part of the justification was that COM7 and 8 could be created cheaply by such re-use. So they are already old-ish transmitters, who knows how much realistic life they have left in them. Though Arquiva should have plenty of spare units, since it is only two muxes and only at a subset of locations.
MymsMan
Ad detector
A huge number of people rarely stray far from the old channels 1-5 and even the BBC still does last minute schedule changes to move Andy Murray at Wimbledon from BBC2 to BBC1
Owen Smith
Well-Known Member
People don't stray far from the old channels 1-5 because there is so much absolute crap on the other channels. And shown in blocky LegoVision too since they are so heavily compressed. It really has become a race to the bottom.
One of the rare occasions I venture away from the main 101 to 105 HD channels plus BBC4 HD is to watch new seasons of Red Dwarf. It is unfortunate it is on Dave in LegoVision, it should be on the BBC where it started.
Personally the only reason I care what channel something is on is the picture and sound quality the channel broadcasts with. I watch programmes not channels. It's just the best programmes tend to be on the main channels which have the budgets to afford them. This means like you I am baffled when something switches from BBC2 to BBC1 at the last minute. Who cares? They're both on the same muxes with similar vision and sound quality. And it pisses off people trying to record things, so why do it?
Black Hole
May contain traces of nut
...and while you're at it, why cover something on BBC1/2 that is "news" and is being adequately covered on BBC NEWS???
MymsMan
Ad detector
It is over 50 years since BBC2 launched and at the time homosexuality was a criminal offence but now same sex marriage is legal.
Some attitudes can change radically but the BBC still thinks people will refuse to switch channel to watch Andy Murray but routinely announce 'coverage will continue on BBC2' for lesser players - bizarre!
Last.To.Know
Member
SFNs?
I was thinking today that if I did want to register my annoyance over the loss of HD channels, who would I direct my ire at?
The BBC?
Freeview?
Who took the decision that led to my losing those HD channels and who has the power to remedy the situation?
MikeSh
Well-Known Member
Until 2020 or so you do probably, by changing/improving your aerial system as I did.
Beyond that ... if they have a plan they haven't published it, in any detail anyway.
MikeSh
Well-Known Member
That doesn't mean everyone is happy about it. There is still a proportion of the population who think that the latter is a terrible thing, and despite changing technology there will be a proportion who still watch telly as though remote controls had never been invented.
One difference is that there are no laws to stop you complaining vigorously about watching TV.
Trev
The Dumb One
That's a shame. Another case of the tiny minority influencing every one else's lives and trying to change their beliefs.
Owen Smith
Well-Known Member
SFN = Single Frequency Network. I thought I gave the name in full earlier in the thread.
An SFN is where multiple transmitters all use the same UHF channel for a particular mux. The UK national DAB networks are all SFNs. COM7 and 8 on 55 and 56 are SFNs.
An SFN is where multiple transmitters all use the same UHF channel for a particular mux. The UK national DAB networks are all SFNs. COM7 and 8 on 55 and 56 are SFNs.