John Sayers' Recording Studio Design Forum

RF noise can be a problem even with Humbuckers or stack pickups. I am starting to plan my next build and I would like to virtually eliminate this problem. I am not talking about light dimmers, wiring, computers, CRTs, adding shielding to guitars, type of cables, or any of that sort of stuff I can turn off/on. . . I am talking about RF showing up that is generated outside my building.

Hmmm. . . time to determine the least expensive way to do a good job of a large Faraday cage so we can do distorted rock guitars with minimal RF noise. I found several posts on the topic and some ideas, but there was not a lot there, and some of the links to resources such as mesh size calculators etc. . ., were broken.

My instincts say that perfect would be way too expensive and also that really required. . . so what is a cheap way to go far down the road of shielding without huge expense?

The immediate ideas that come to mind are:

1) some kind of mesh (like chicken wire?), or sheeting (aluminum foil?). I suspect connecting the pieces at low electrical resistance and a really good drain connection to ground would be key. A paper thin copper might be a lot better (would certainly solder), but the copper foil I have seen is really expensive. Tin would certainly work and could be soldered up to a drain cable to a good independent ground. . . I would think that any shielding sheet type material could be incorporated into the construction at some layer so it is invisible in the final look of the building. . . or

2) I could build a steel building as a shell, and build a wood framed studio within the shell. . .

Who has tried and succeeded or failed? What worked, what didn't? What is the lowest cost method with the best results? Suggestions/Ideas?

A long, long time ago, I worked for a communications antenna manufacture. They built a Faraday cage lab on the factory floor. It was a 2by4(inch) frame building, covered inside and out with copper window screen. All soldered or bounded together. It looked a lot like a summer porch.

First question, before I or several other people spend a lot of time collecting data to answer your question, what is your budget for the Faraday cage?

Economically,
Andre

I have never been, and will never be, a budget first person. I attempt to learn about the topic first and look for the point were there is the most benefit at the least cost. Then I pick my place on the price performance curve (sometimes going for the 99.9% solution at high cost, other times 50% of the solution at very low cost depending on the performance), and plan the project / budget. So let's just say less than $20,000 and more than $1,000.

It was not my intention to ask people to "spend a lot of time collecting data". I am hoping there are others who already have information they wish to share or are interested in this topic and wish to gather information for their own purpose as well as sharing.

Great response! Doing back of my head calculations, including specialised labour, it is around $3/ft^2 for basic shielding. It is most often effective, when there is localised problem, to solve it the source.
As options you wrote, a fully lined steel room will do it. The expense with that comes in the sealing of the joints, fully welded being right. Next down is some form of highly conductive mesh. Cost is in the material and the labour to join EVERY strand at EVERY meeting point.


How large is your proposed facility? Where in Canada are you? It would help in helping you?

Andre

There's a Faraday shield in the science museum in our capital. It houses a Van de Graff generator that demonstrates how lightning works.

It's built out of a 3 - 4mm guage, 2" x 2" opening square mesh. All the mesh panels are solder wired together and all earthed heavily (i.e thick earth wires)

That's your $20,000 end

I've also seen it done with chicken wire - your $1,000 end.

If is safe to say, no matter what approach is taken, good electrical bonding and thick gauge connection to an independent ground is of paramount importance, and that system needs to be designed around the shielding layer. So, then the questions that come to mind are:

1) What EMI bands (frequency range) do we need to shield to provide isolation and garner decent results?

2) What are the characteristics of the different materials that can be used for shielding?

3) What about openings for Windows? Does a space opening mean just a small increase in RF making its way in or would it be more like a flood?

I am not sure at all about item 1. . . there is a lot of different EMI out there these days. . . not where to draw the line on what effects unshielded pickups and the sort. . .

Item 2) starts to be a little more intuitive. . . the smaller the grid the higher the frequency, the better the conductor the more drain, and I believe being ferrous does not matter because we are trapping EMI, not a magnetic field (we are not protecting CRTS from a magnet). I know the grid size relates to the undesired frequency of the EMI, the speed of light, and the grid size for mesh. . . I just can't remember it it needs to be a quarter wave or half wave (but I do know smaller is better).

Item 3) is again something I am not sure about at all.

I will continue to dig around on this. . . and post anything I come across.

Howard's questions:

At the low end a few KHz from Switch Mode Power Supplies and Compact Fluorescent Lamps at the high end near 1GHZ from cell-phones, wi-fi and soon wi-max.

Copper, Aluminum and Steel are the common materials, not sure what you need to know.

If the frequency is high and the opening is between the source and the receiver, one square inch is large.

What I would use is copper or aluminum screening. or aluminum cooking foil. I'll leave it to you to bond it all together.

Unfortunately the source of EMI is outside of my control. . . just from our modern day surroundings. I doubt there will be specialized labour because the only thing I can't/won't do is roofing, drywall taping, and I don't like to shovel snow I will tackle pretty much anything else and especially like electrical work.

don't you have an FCC like organization to which you can register complaints? in the US if you're getting hit with EMI you can complain to the FCC and they'll actually look into it.

_________________
Glenn

I am not talking about any more RF noise than you will find in a typical city. Since there is no specific culprit I doubt these authorities will get involved. Single coil pickups with amp gain is simply too good an antennae. If you can keep the guitar player oriented the right way and do some fades as notes trail out, it is not a problem in most songs. . . but I am hoping to reduce this problem by a couple notches.

http://www.twpinc.com/twpinc/control/category/~category_id=TWPCAT_3?gclid=CMruto-K9JACFQ6CPAodL1OQ0g
Copper mesh looks like it is $5-10 per square foot, depending on awg and spacing, at least at this site. Ouch!

Even aluminum screening is almost 50 cents a square foot.

aluminium doesn't work as a faraday shield.

Many shielded cable manufacturers use aluminum foil for shielded pair audio cables. Why won't it work for a Faraday cage?