Radio Frequency Interference

dminches · Apr 20, 2018

I think my phono pre is picking up RFI from my Ethernet switch and access point in my listening room. Other than trying to locate it as far as possible from the pre amp is there anything else I can do? Are there Ethernet switches that are less prone to leakage?

mountainjoe · Apr 20, 2018

First I would try to isolate whether it's your ethernet switch or the AP (access point). Selectively turn one off then the other and see if one of them is the primary culprit or if both are contributing.

Also a lot of ethernet radiation can come from the cables (i.e. they make good antennas) - you could try using shielding ethernet cabling or just moving them around to see if things get better or worse.

You can also try putting a ferrite around the power cord to the switch or AP as the power cords can also radiate.

These are some easy things to try - I can suggest other experiments depending on what you find after taking these steps.

Cheers, Joe

dminches · Apr 20, 2018

Thanks Joe.

I am going to play with this tomorrow. I will take some of your suggestions into the process. I am going to start by moving the switch away from its current location. And I should get some shielded cables.

rockitman · Apr 20, 2018

What does RFI sound like in your system ?

dminches · Apr 20, 2018

rockitman said:
What does RFI sound like in your system ?

Intermittent bursts of air. That’s the best way to describe it. I need to experiment to make sure that’s what it really is.

Tango · Apr 20, 2018

I have many phono cables. My RFI problem comes when I position my phono cables in a wrong place.

King regards,
Tang

dminches · Apr 20, 2018

Tango said:
I have many phono cables. My RFI problem comes when I position my phono cables in a wrong place.

King regards,
Tang

Tanh, what do you mean by in the wrong place? Near other wires or power cords?

Tango · Apr 20, 2018

dminches said:
Tanh, what do you mean by in the wrong place? Near other wires or power cords?

Not the power cables. I have a big glass window. The RFI comes from the public radio station nearby. Placing a my phono cable a foot to the right can capture RFI. One of my phono cable I even have to scotch taped to the left leg of my rack to get a complete absent of rfi. It is annoying I understand. I had to play around quite a bit. If you look at the latest pic of my syste, you will see that I have moved my EMT to the right and move AF1 in the middle. This position somehow gives me no RFI. In the back of my system you will see a big glass window.

Tang

dminches · Apr 20, 2018

I see. You have a lot of great looking and sounding equipment!

Ron Resnick · Apr 21, 2018

Amateur radio people call the search for RFI or illegal transmitting stations "fox-hunting."

An AM radio with a telescoping antenna tuned in between radio stations can be used to find RFI sources.

Ron Resnick · Apr 21, 2018

Tango said:
. . . I have a big glass window. The RFI comes from the public radio station nearby. . . . In the back of my system you will see a big glass window.
. . .

Tang

Maybe the big glass window can be removed and replaced with a big slab of aluminum. The aluminum can be grounded to an earth ground. This should block RF from entering your room through that window.

A less family-friendly solution would be to wallpaper every millimeter of the inside walls, floor and ceiling of the room in which your audio system is located with thick aluminum foil. This would create a Faraday cage and should inoculate the entire room from RFI.

Tango · Apr 21, 2018

Ron Resnick said:
Maybe the big glass window can be removed and replaced with a big slab of aluminum. The aluminum can be grounded to an earth ground. This should block RF from entering your room through that window.

A less family-friendly solution would be to wallpaper every millimeter of the inside walls, floor and ceiling of the room in which your audio system is located with thick aluminum foil. This would create a Faraday cage and should inoculate the entire room from RFI.

Ms Tinka must be so kind, understanding, and super supportive of you Ron. Don’t ever let her down.

Kindest regards,
Tang

Ron Resnick · Apr 21, 2018

Hahahaha!

Yes, she is!

No, I won’t.

Marcus · Apr 21, 2018

Ron Resnick said:
A less family-friendly solution would be to wallpaper every millimeter of the inside walls, floor and ceiling of the room in which your audio system is located with thick aluminum foil. This would create a Faraday cage and should inoculate the entire room from RFI.

FWIW, there are much beeter solutions than thick aluminium foils. Check this: http://www.aaronia.com/products/shielding-screening/

Sablon Audio · Apr 21, 2018

For the truly committed - https://lessemf.com/personal.html

GMKF · Apr 21, 2018

Ron Resnick said:
Maybe the big glass window can be removed and replaced with a big slab of aluminum. The aluminum can be grounded to an earth ground. This should block RF from entering your room through that window.

A less family-friendly solution would be to wallpaper every millimeter of the inside walls, floor and ceiling of the room in which your audio system is located with thick aluminum foil. This would create a Faraday cage and should inoculate the entire room from RFI.

Thats my plan someday... I woulnd't use aluminum, but Mu-Metal's. Behind the acoustic treatments. Or even a double brick wall with a big metal plate in between.

dminches · Apr 21, 2018

I really hadn’t thought about the notion that the RFI could be coming from outside my house. There are no towers nearby but I guess my neighbor could have something causing this. I do remember a couple years ago that my Technics RS-1500 RTR would pick up a radio signal. It was bizarre.

microstrip · Apr 21, 2018

Ron Resnick said:
Maybe the big glass window can be removed and replaced with a big slab of aluminum. The aluminum can be grounded to an earth ground. This should block RF from entering your room through that window.

A less family-friendly solution would be to wallpaper every millimeter of the inside walls, floor and ceiling of the room in which your audio system is located with thick aluminum foil. This would create a Faraday cage and should inoculate the entire room from RFI.

You would have to have a power generator inside the Faraday cage - otherwise you risk the mains wires will be introducing RF in your precious room!

GMKF · Apr 21, 2018

microstrip said:
You would have to have a power generator inside the Faraday cage - otherwise you risk the mains wires will be introducing RF in your precious room!

Shielded mains wires ? Amps outside the room ?

Speedskater · Apr 21, 2018

When it comes to noise and interference, the go-to expert is Jim Brown. He was past AES committee co-chair on EMI/RFI and is a Ham radio operator. He has about 50 papers and PowerPoints. Many deal with fighting RFI.

http://www.audiosystemsgroup.com/publish.htm

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