In reply to a post by MHC:

A power supply should be "quiet" in an EMI (Electro-Magnetic Interference) sense. There will be noise albeit at a low level on a well designed and manufactured unit. However, it is often the case that ones designed and built cheaply or a failing PSU will create a lot of noise and that can be from Hertz right up to several MegaHertz in frequency - some will be radiated and other conducted along the attached cables. So, even if disconnected there could be transmitted EMI which a a phone line could pick up.

I've heard that argument relating to other Sky boxes connected to the same LNB, but never to broadband/phone problems.

Thanks! I'll give it a try - can't hurt! Probably need to wait until the crackling is back, though may test to see if SNRM changes anyway.

Switched mode power supplies are well-known as sources of RFI noise problems.

In reply to a post by Stevenage_Neil:

In reply to a post by MHC:

A power supply should be "quiet" in an EMI (Electro-Magnetic Interference) sense. There will be noise albeit at a low level on a well designed and manufactured unit. However, it is often the case that ones designed and built cheaply or a failing PSU will create a lot of noise and that can be from Hertz right up to several MegaHertz in frequency - some will be radiated and other conducted along the attached cables. So, even if disconnected there could be transmitted EMI which a a phone line could pick up.

I've heard that argument relating to other Sky boxes connected to the same LNB, but never to broadband/phone problems.

Give me one good reason why it should not be the case with a VDSL line and modem?

We used to see a lot of it wrt ADSLx. Then Sky brought out newer/updated kit and it has largely gone away. PSUs can always gradually fail however, and the OP appears possibly to have earlier kit anyway.

It is unlikely to be the cause of his problem, but the possibility has to be eliminated .

In reply to a post by AndyPandy:

Would switching of a sky box upstairs affect a router downstairs? (The one upstairs is old, and probably close to failing!)

Possibly. There have been reports here before where a dodgy TV has effected a whole neighbourhood.

"Close to failing" - this is the type of kit that can produce lots of interference!

In reply to a post by MHC:

In reply to a post by Stevenage_Neil:

Give me one good reason why it should not be the case with a VDSL line and modem?

The Sky box transmits a 22Khz, (and if a dodgy PSU, other frequencies), signal up through a shielded cable

Edited by deleted (Wed 05-Nov-14 15:41:35)

In reply to a post by Stevenage_Neil:

In reply to a post by MHC:

In reply to a post by Stevenage_Neil:

Give me one good reason why it should not be the case with a VDSL line and modem?

The Sky box transmits a 22Khz, (and if a dodgy PSU, other frequencies), signal up through a shielded cable

And the power supply cable is shielded too? I would guess not. The PSU and Sky box are unlikely to be screened either.

In reply to a post by b4dger:

In reply to a post by AndyPandy:

Would switching of a sky box upstairs affect a router downstairs? (The one upstairs is old, and probably close to failing!)

Possibly. There have been reports here before where a dodgy TV has effected a whole neighbourhood.

"Close to failing" - this is the type of kit that can produce lots of interference!

A few years back I was seeing a company on a non-related issue and they mentioned problems with their ADSL modems resetting and rebooting "randomly". I gave them half an hour of my time ...they were in a comms room, on a shelf adjacent to a stud wall - foil backed board too. The company on the other side of the wall had a plasma TV mounted close by and when it was switched on or the channel changed it killed the ADSL signal and the modems had to resync.

In reply to a post by MHC:

I gave them half an hour of my time...

Very generous of you