Noisy environment / PLC noise on earth/ground

[pysco68]

Hi everyone,

I'm facing a kind-of-weird problem. I just moved into a shared new office building and I'm having some trouble with RF noise that my test equipment happily picks up.
The long story is that I was just tracking down some issues in the power supply of a product we're currently designing. During the measurements I noticed spikes all over the place overlaying the expected signals. After eliminating all causes that could be related to the DUT I tracked down the issue to what seemingly is one of my neighbour's powerline/PCL adapter modulating on the main's earth causing some weird trouble. 

Basically the HomePlug AV1200 standard introduced the possibility to use the earth/ground wire for MIMO purposes. They didn't think or didn't worry about people relying on a clean earth apparently.
So while I understand how to filter RF noise on hot and neutral I have no clue how to deal with this issue 

Any clue?

The attached trace is from a Micsig handheld scope's probe compensation generator, just with added mains earth reference. Having the scope floating the traces go back to normal.

P.S.: I hope I'm posting this in the right section

[shteii01]

Can you try putting UPS between powerline and your equipment?

[pysco68]

Hi, thanks for your reply,

could you elaborate a bit on how that should help? In my understanding a UPS *should* maintain a direct path to earth, or am I missing a point?

[Kleinstein]

There are special approved inductors as filters for the PE. However just an inductor does not make a good filter, so the function is limited. The main purpose is more like breaking RF ground loops. Using common mode chokes (e.g. Ferrite rings around the power cable) can also help.

The best solution would be getting rid of PLC all together. Maybe talk to your neighbors. In principle PLC is emitting too much RF noise and should be turned down if it causes trouble - but this is gray theory and not good for making friends.

[pysco68]

Yeah, talking to the neighbours didn't work out that great.

While the two employees were rather sorry for the trouble caused, their boss was VERY unhelpful. He was very angry about the 5minutes I asked them to stream some YT videos to generate some traffic... I even offered them help to do the wiring and configuration for a *real* network, but no he was not really interested in understanding what my issue is 

Anyhow. I already hit the buy button on a modestly expensive Schaffner line filter that has a earth line choke, but as you stated, I doubt it will have a huge effect. On the other hand we're talking about ~120mV peak at at few MHz. So who knows... Maybe I'll throw a few ferrite rings at it too.

I'll report if that works out as soon as I get my hands on the hardware.

[Pinkus]

Hellp pysco68,
Please PM me with your email adress - I cannot reach you, as your mailbox is full (see screenshot attached).
Pinkus