Pixellation

#1
Just lately I have been getting severe pixellation (most recently on BBC2). I live in North London.

My house is being redecorated and there is scaffolding up to high level. Is this enough to cause the problem, or should I be looking for another cause? Certainly, I have had no problems until last week, which is when the scaffolding went up. If it is likely to be another cause, what causes should I look for (and how do I look for them)? There was the thunderstorm last Friday, but a much more severe storm a few weeks ago did not cause any problem. It is also possible that the scaffolders somehow moved the aerial or disturbed the connection.
 

MymsMan

Ad detector
#2
It is also possible that the scaffolders somehow moved the aerial or disturbed the connection.
Seems the most likely to me, though the scaffolding could be causing interference

Either way you need to have a word with the decorators/scaffolders so that you can check it out before you have no scaffolding left and have to resort to high ladders.

You can use the Humax as a signal strength meter using the Menu->Settings->Installation->Manual Search to see a live Signal strength display so you can shout to someone on the scaffold when they make the signal better or worse!
 
OP
OP
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#3
Thanks for that help. I would guess that a connection got disturbed.

Current signal strength is around 25%, so no wonder things are bad.
 

prpr

Well-Known Member
#6
The scaffolders have knackered the cable or knocked the aerial (my money's on the former, although I expect they'll plead ignorance if you try and challenge them). Probably worth replacing both as you've got access. I would expect both are quite old.
 
OP
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#7
I have to get to see the decorators and ask them to take a look. (It's not that easy to see them, as the house is divided into flats, and I'm not sure exactly where they are working.) As the scaffolders are a different firm from the decorators, I don't think they will feel the need to say "Can't have been us".

Antone know of a good aerial firm covering North London (Hampstead)? I had a very good firm fitting the original aerial a long time ago, but I think they said that for cable issues it would be cheaper to find someone more local.
 
OP
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#8
My decorators have taken a look and reckon that it is actually the scaffolding that is causing an issue, in particular one pole running very close to the cable. They tried adjusting the position of the cable a little, and in some positions the signal was much better. But in the end they gave up, and it isn't good. I think I'll have to wait until that part of the scaffolding comes down.

By the way, what are the channels one sees under Signal Detection? Evidently they refer to a bunch of what a casual user would call a channel. Channels 23, 26, and 30 seem to be active, some of the others have nothing.
 

Ezra Pound

Well-Known Member
#9
The 23, 26, 30 etc. are the UHF TV 'Channel' numbers, in the days before digital TV each one would relate to a single TV station e.g. BBC1, however since digital TV took over each one of these 'Channels' carries a multiplex or MUX, this is a group of TV channels bundled together, there are currently 8 MUXs transmitted from Cystal Palace carrying in excess of 100 TV and radio programmes
EDIT
Here is a list showing what is on each 'MUX'
http://www.digitaluk.co.uk/channels/channel_listings
 
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Black Hole

May contain traces of nut
#10
By the way, what are the channels one sees under Signal Detection? Evidently they refer to a bunch of what a casual user would call a channel. Channels 23, 26, and 30 seem to be active, some of the others have nothing.
The numbers are the actual broadcast channels, and relate to transmission frequency by the formula:

Frequency (MHz) = 8 x Channel + 306

In the pre-digital days, there was one TV service (BBC1, BBC2, ITV, Channel 4, Channel 5) per broadcast channel. Digital broadcasting enables multiple TV, radio, and data services to be multiplexed onto one datastream, and the datastream is modulated onto one carrier wave at the transmission frequency. That's why I prefer to refer to them as services not channels (see Glossary - click, entry LCN).

When you run an automatic retune, the tuner scans all the broadcast channels looking for DVB-T datastreams, then again looking for DVB-T2 datastreams. The numbers in the list under Signal Detection are the channels datastreams were found on when you last did a retune. You seem to be missing a few now!

Find out what you should have here (and note that with the current round of channel shuffling going on to clear the way for 5G, channels are being moved out of the bandwidths of aerials that used to be perfectly OK for the "local group" of analogue services):

https://hummy.tv/forum/link-forums/digital-uk-coverage-checker.41/
 

prpr

Well-Known Member
#11
My decorators have taken a look and reckon that it is actually the scaffolding that is causing an issue, in particular one pole running very close to the cable. They tried adjusting the position of the cable a little, and in some positions the signal was much better. But in the end they gave up, and it isn't good
It's definitely been crushed by the scaffolding then and must be replaced. You WILL regret it if you don't, as it'll be even more expense if left until you've got no signal at all.
 
OP
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#13
I've just heard from my downstairs neighbour that they may well need a new aerial too. So having it done for the two of us while the scaffolding is up sounds a good idea.

My decorators also say that the bolts on my current aerial are rusted away. Do you think I need a new aerial or just a pole or mast to refasten the old aerial, together with a new cable? How long should one expect aerials to last? I reckon mine must be pretty old, but don't remember quite how old.
 
#14
Can you receive the Channels that are broadcast on the Com7 and Com 8 MUXes eg BBC 4 HD ?

With recent channel moves these are now on channels that cant be received by some without a new aerial,
Aerials don't last forever so now might be a good excuse to replace the whole aerial system, a competent installer should give honest advice and not just try to sell for the sake of it,
 

Black Hole

May contain traces of nut
#15
My decorators also say that the bolts on my current aerial are rusted away. Do you think I need a new aerial or just a pole or mast to refasten the old aerial, together with a new cable? How long should one expect aerials to last? I reckon mine must be pretty old, but don't remember quite how old.
It's not so much the antenna itself that fails, as the terminals to the cable (dissimilar metals, galvanic corrosion). If you are going to the expense of having the pole and cable dealt with, not fitting a new antenna at the same time (however OK it might look) seems like penny-pinching.
 

prpr

Well-Known Member
#16
Do you think I need a new aerial or just a pole or mast to refasten the old aerial, together with a new cable?
There is no point not replacing the aerial. It's almost certainly group A and you'll probably want a wideband for COM7/8. Unless you've got any local obstructions, I believe CP to Hampstead will probably romp in on almost any wideband aerial (I'd have a log periodic but your installer may have different ideas).
 
OP
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#18
Thanks for all the advice. I am asking a couple of aerial installers to give me a quote. Anyone got a rough idea of the cost, or does it depend too much on the actual building.

In the short term (that is, until I get a replacemnt aerial) my decorators seem to have adjust things so that I get a tolerable signal. At least that's true of BBC1 and 2, though Yesterday is much poorer.
 

Trev

The Dumb One
#19
Make sure that they use good quality coax, even if you have to pay a bit more. WF100 is generally considered to be the best.
 
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