In reply to a post by XRaySpeX:

Could you be confusing TV ON with nighttime?

Yes, even I can tell the difference between daytime and nighttime.

SNRM is forced to around 4.3dB, from the ISP's 6.3dB. As already stated above, when I switch the TV on, the SNRM drops by between 0.5 and 1dB. It doesn't cause a re-sync or drop the connection. Granted, in isolation, that's nothing to worry about. Although, you could argue that a single device causing such a marked change could be something to worry about...
At night however, when there's all the other sources of interference present, that extra 0.5 to 1dB could cause re-syncs and /or instability.

@sbrads: The ADSL lead is made from cat5e cable so, noise shouldn't be an issue. Any length of cable can act like an antenna however, the twisted nature of cat5e cable is there to prevent this as it 'rejects' noise.
Regardless, I've put a ferrite core on it already and it made no difference. Thanks for the suggestion though.

@eckiedoo: Yes thanks, I'd already decided against using foil anywhere near the router case. The antenna's would negate its effectiveness anyway.

And I've already fitted a ferrite core to the TV mains cable and it's made no difference. Again, thanks for the suggestions.

@MrSaffron: I agree mains bourne interference affecting noise margins is rare but, I've seen it before with a Thompson Sky receiver.
The issue I have with believing it's airbourne interference is as mentioned above, the distance between the router and TV and that the interference would have to penetrate through 2 floors.
Yes, the ADSL cable is constructed of twisted pair cable. I don't have a ring wire as the master socket is wired directly to the drop wire on the outside of the house via cat5e cable. Only the 'A' and 'B' legs are connected. The 'usual things' have all been taken care of as I was extremely mindful of the network set up when the house was wired up (see first post).

@Zarjaz: Again, yes in isolation 0.5 to 1dB isn't a lot. However, if we examine the big picture and consider what happens at night, that extra reduction could cause instability.

As the SNRM is dropping, I'd expect there to be an increase in errors too.

By way of a further update, I made a mains filter from a delta suppression filter and varistor, wired it across where the TV's spur is wired into the mains and it made precisely no difference. So back to the drawing board.

Paul

Edited by deleted (Sat 07-Jul-12 19:16:33)

Does it not strike you, with all this extra fancy hardware gubbins you fitted not having any effect, that you might be barking up the wrong tree?

Barking up the wrong tree in what sense? Please elaborate...

Paul

Have you used an AM radio to try and identify which bit of kit is the worst offender noise in the home?

That the issue is connected with mains interference and introducing some combination of suppressors, conductors, condensors, resistors, varistors, vibrators or any other electrical "...ors" into the house power supply will cure a BB problem.

Edited by XRaySpeX (Sat 07-Jul-12 20:15:51)

No, not done that yet, mainly because I don't have access to one and that I was convinced it was the TV sticking nastiness up the mains.

If I can get hold of one, I'll certainly use it to pinpoint the exact issue, if it can.

Paul

Maybe so but, that's why I was asking the question(s), in the hope that enlightened people such as yourself could point me up the right tree.

Paul

Yes Plasma telly's have been known to be a source of REIN, but then so have Sky boxes, ethernet switches, communal aerials, robot lawn mowers, electric fences, etc, etc.

Use of an MW radio will most likely convince you that the telly IS the cause, they always kick out a lot of noise, but is it the right sort of noise ?

@Zarjaz: Again, yes in isolation 0.5 to 1dB isn't a lot. However, if we examine the big picture and consider what happens at night, that extra reduction could cause instability.

... but is it causing instability ???

As the SNRM is dropping, I'd expect there to be an increase in errors too.

Well, is it racking up the errors when it lowers ??

In the specific circumstance I'm writing about, It's clear it is the TV. There's no question about it. I can see it clear as day. When I switch the TV on, there's a downward spike in the SNRM of around 1dB. It will then settle around 0.5dB lower than it was when the TV was off.
When I turn the TV off, the SNRM goes straight back up to it's target level again.

Paul