Noise filter?


Active Member
So I've got an interesting noise issue in the new house. Unforutanately it seems to be mostly affecting the section of the house that has the Server Room so it's a pretty big deal.

I mentioned in another thread that I had a minor issue with Insteon and PowerHome auto-discovery which I solved by moving the PLC to another room for discovery. Now that all the devices are known the PLC is working fine in the Server Room.

The big issue I'm having with it is with noise interfering on my component video signals. I have a 42" plasma wall mounted in the master bedroom, connected to a satellite receiver in the server room via MuxLabs baluns over Cat5. Everything works great excep there is a rolling line and some discoloration in the plasma. I spent several days troubleshooting and finally figured out that the source of the line was the power in the server room. I determined this by using a very long Cat 5 cable and 100' extension cord and moving the satellite receiver around. What I discovered is I could put the receiver pretty much anywhere and if the extension cord was plugged in in the server room, I got the noise. And the opposite is also true. I currently have the satellite receiver mounted in the rack with everything else, and the rack power supply plugged into the extension cord, which runs out of that room across the house to the master bedroom. Everything is fine at this point.

So clearly I have a noise issue on those circuits. It's odd because I have a dedicated subpanel for the server room. I suspect the electrician may have put some other things on it ... need to figure that out. He still owes me a trip back for punchout so we'll see.

Here's my question though. I know noise filters are typically used at the source of the noise. But is there any reason I couldn't put one between the sat receiver and the wall and filter out the noise that way? Ideally, I'd put it between the rack and the wall, thus filtering the noise from anything in the rack.

Am I off base here?

Going by your description of the noise that's being seen on your plasma TV I think you have the dreaded "ground loop" problem. The "rolling bar" is a dead giveaway. I think that is why with your current method of powering the sat receiver via a extension cord to another room the "noise" disappears.

You can test this by powering everything the way you want it to be and placing a "cheater plug" on the power cord for the plasma set in the MB. The "cheater plag is a three-to-two-prong adapter that will temporarily lift the plasma ground. My guess is this will eliminate the ground loop. Now if this does the trick you have three way to attack the problem:

(1) move the breaker in the subpanel that powers the rack power supply to the other phase. Might work and is the cheapest solution.
(2) when you have electrician out for the punch list, show him the problem and have him fix it. Possible, but he may not even see a problem.
(3) get a "gound loop isolator".

Hope this helps.

Switching power supplies are notorious for adding pulse noise to the AC line. They switch at a rate that is similar to the frequency of X10 and other protocols. They also contain harmonics and high energy pulses that are transmitted to the AC line. These power supplies are used in computers, TV's and other devices.

The first thing is to isolate all the different devices in your server room to find which one is the culprit. Cheap computer power supples are first on the list, because to keep the price down they eliminate the filters, bypasses and etc. Filters seldom help clean up these devices because of the high energy levels.

Cliff s
Already tried isolating noise by unplugging everything in the rack excep the sat receiver. It sounds like the ground loop issue is the more likely culprit. I'll try plugging the plasma in without ground to check that out.

What exacty is a ground loop isolator and is this something I would do or the electrician. And if I need to get him to fix the ground loop problem, can someone explain what is wired wrong / the issue in a manner that I can explain it to him?

One thing I should try. I have that subpanel in the server room and each plug has a dedicated circuit (4 plugs each). So I likely already have plugs on different phases. Just need to try some different ones.

Any info you could further educate me with prior to my meeting with the electrician would be useful.
rocco said:
... and switching noise in your server room, causing Insteon to have problems.
I had this problem with an older computer power supply. I used a smarthome FilterLinc and it helped a lot with insteon.
Thanks to all for the input. It sounds like what I should do is two things:

1. Isolate where the ground loop is by using one of the 2 prong adapters (temporarily) and then put in the appropriate ground loop isolator. It sounds like I probably need a component video one between the sat receiver and the plasma TV. Which could get ugly since there is a matrix switch I haven't added to the mix yet. Am I right in thinking I could potentially need one between the matrix switch and each TV?

2. Put a FilterLinc between the rack and the wall to help my Insteon signals.