Faraday Cage

Cpyder

Has anyone considered putting their gear in a Faraday cage?

An effective design should stop outside EM interference from reaching the circuit boards in your equipment. This may correlate with reduced noise.

Or are good pieces of equipment already shielded adequately?

Tour2ma

Gear? No...

I did once consider making a pair of grounded, expanded metal grids to put between my SRS's and TV after they gaussed the beejesus out of one CRT, but spitting the SRS's an extra foot apart was all that was necessary.

BlueFox

No need to get fancy. Technology to the rescue.

http://www.musicdirect.com/product/81909
and
http://www.musicdirect.com/product/74266

steveinaz

It's on my to-do list, right after "construct tin-foil hat." :biggrin:

jinjuku

They make paint also that you just make sure is connected to a ground.

halo71

^ Some guitars electronics cavities are painted with that type paint. Some are lined with copper sheeting/foil making a faraday cage as well. :biggrin:

mhardy6647

steveinaz wrote: »

It's on my to-do list, right after "construct tin-foil hat." :biggrin:

They go together...

inspiredsports

Cpyder wrote: »

Has anyone considered putting their gear in a Faraday cage?

An effective design should stop outside EM interference from reaching the circuit boards in your equipment. This may correlate with reduced noise.

Or are good pieces of equipment already shielded adequately?

Seems a bit excessive considering what amounts of EMI most experience in their homes.

TECHNOKID

Cpyder wrote: »

Has anyone considered putting their gear in a Faraday cage[/URL]?

Goodness, I have not heard of Faraday cage in ages! Hum, this reminds me time is catching up with me. :eek:

carwashguy

Hilarious, we usually discuss these on the firearms forum I frequent.

CoolJazz

steveinaz wrote: »

It's on my to-do list, right after "construct tin-foil hat." :biggrin:

http://zapatopi.net/afdb/

zingo

Just get one of these copper baskets from Lowes in their kitchen section:

Cpyder

inspiredsports wrote: »

Seems a bit excessive considering what amounts of EMI most experience in their homes.

That may be, but some people spend tens of thousands of dollars on equipment alone. If a good faraday cage, costing only a tiny fraction of that, could block any/all EMI from reaching your equipment, I'd call it a success. However, unless your equipment is hidden, it may look ridiculous to visitors.

carwashguy wrote: »

Hilarious, we usually discuss these on the firearms forum I frequent.

Why firearm forums?

BlueFox wrote: »

No need to get fancy. Technology to the rescue.

http://www.musicdirect.com/product/81909
and
http://www.musicdirect.com/product/74266

I really don't see how this could reduce EMI, according to the laws of physics. If you are going to try to actively cancel a wave out (EMI being a random wave), you need to measure the wave first and then apply another wave at the same amplitude and frequency 180 degrees out of phase. This is very difficult, especially at high frequencies. See: Wave addition.

That, or you need something to absorb the wave like a good ol' fashion faraday cage.

This product seems to only produce a wave at one frequency @ 7.83 Hz. This would likely have no effect on any EMI. This would be similar to trying to cancel out music playing from your speakers by playing a single tone. Wave addition doesn't work like that.

I'm not saying that product produces no positive results, but it most definitely would not cancel out EMI like a faraday cage.

mhardy6647

Cpyder wrote: »

However, unless your equipment is hidden, it may look ridiculous to visitors.

This product seems to only produce a wave at one frequency @ 7.83 Hz. This would likely have no effect on any EMI. This would be similar to trying to cancel out music playing from your speakers by playing a single tone. Wave addition doesn't work like that.

I'm not saying that product produces no positive results, but it most definitely would not cancel out EMI like a faraday cage.

1) my hifi already looks pretty ridiculous to most normal visitors - they dont quite get the idea of speakers roughly as large as phone booths (heck, the younger ones don't even know what a phone booth is!).

2a) 7.83 Hz... perilously close to the Brown Note. http://en.wikipedia.org/wiki/Brown_note
2b) yeah, wave addition (superposition) does work like that - that's exactly how noise cancelling headphones work. Arthur C. Clarke wrote a witty short story on the subject in the early 1950s called Silence Please.
2c) If you have EMI with a fundamental frequency of 7.83 Hz it could (in principle) work pretty well...

inspiredsports

Cpyder wrote: »

. . . that may be, but some people spend tens of thousands of dollars on equipment alone . . .

Yes, they do. 5 digits would almost cover my cables and IC's.

I'm convinced and will start shopping now :rolleyes:

Cpyder

mhardy6647 wrote: »

2b) yeah, wave addition (superposition) does work like that - that's exactly how noise cancelling headphones work. Arthur C. Clarke wrote a witty short story on the subject in the early 1950s called Silence Please.

What I meant was that you cannot cancel out a wideband wave with a single tone of one frequency. In my example, you could not silence music coming from a speaker with another speaker playing a single tone of any one frequency. In order to cancel music coming from a speaker, you would need to play the exact same song file but with the waveform inverted. Even this would be difficult because you would not get perfect cancellation as the music would be coming from two point sources.

It would be easy to do using software and one speaker. Open up a song in Audacity twice. Invert one and playback both simultaneously. There will be no sound.

Noise cancelling gets very difficult at higher frequencies because you cannot know ahead of time what noise you have to cancel (unlike my example in the previous paragraph). You must measure it actively, and then create an inverted wave to cancel out the noise.

mhardy6647 wrote: »

2c) If you have EMI with a fundamental frequency of 7.83 Hz it could (in principle) work pretty well...

Even if the interference was at 7.83 Hz, this would only work if you measured the interference and aligned the produced tone 180 degrees out of phase with the actual interference. Otherwise, instead of a wave addition that results in noise cancelling, you could just as easily amplify the interference.

But common sources of EMI come from the radio bandwidth (KHz and MHz range), Wi-Fi (GHz) and cell phones, etc. These frequencies are well above the 7.83 Hz tone produced by that device.

mhardy6647

Cpyder wrote: »

What I meant was that you cannot cancel out a wideband wave with a single tone of one frequency. In my example, you could not silence music coming from a speaker with another speaker playing a single tone of any one frequency. In order to cancel music coming from a speaker, you would need to play the exact same song file but with the waveform inverted. Even this would be difficult because you would not get perfect cancellation as the music would be coming from two point sources.

It would be easy to do using software and one speaker. Open up a song in Audacity twice. Invert one and playback both simultaneously. There will be no sound.

Noise cancelling gets very difficult at higher frequencies because you cannot know ahead of time what noise you have to cancel (unlike my example in the previous paragraph). You must measure it actively, and then create an inverted wave to cancel out the noise.

exactly so.

Even if the interference was at 7.83 Hz, this would only work if you measured the interference and aligned the produced tone 180 degrees out of phase with the actual interference. Otherwise, instead of a wave addition that results in noise cancelling, you could just as easily amplify the interference.

But common sources of EMI come from the radio bandwidth (KHz and MHz range), Wi-Fi (GHz) and cell phones, etc. These frequencies are well above the 7.83 Hz tone produced by that device.

I think you might be surprised by the spectral distribution of electromagnetic noise.

carwashguy

The guns guys use them as protection for their electronics from the EMP that will accompany the Nuclear Holocaust that is bound to happen any day now.

mhardy6647

carwashguy wrote: »

The guns guys use them as protection for their electronics from the EMP that will accompany the Nuclear Holocaust that is bound to happen any day now.

Heh, vacuum tube electronics will laugh at the EMF pulse when the Big One comes! That's why the Soviets never stopped using vacuum tubes in military electronics... it wasn't backwardness, it was insight :-)

I never stopped using them, either. Well, OK, I stopped for a while, but I regained my senses. Fortunately there are still new production tubes available, largely thanks to the Russians and the Chinese :-)

Yeah, the CDP will go Tango Uniform when the nukes fly, but I'll cue up We'll Meet Again on the record player a la Dr. Strangelove and settle back in a comfy chair to meet the false dawn.

Tour2ma

carwashguy wrote: »

The guns guys use them as protection for their electronics from the EMP that will accompany the Nuclear Holocaust that is bound to happen any day now.

Mmmmm-kay...

mhardy6647 wrote: »

Heh, vacuum tube electronics will laugh at the EMF pulse when the Big One comes!

... I'll cue up We'll Meet Again on the record player a la Dr. Strangelove and settle back in a comfy chair to meet the false dawn.

Sounds like a better plan... only lacks an 18-yo single malt... and maybe a generator...

carwashguy

Love the false dawn bit.

mhardy6647

carwashguy wrote: »

Love the false dawn bit.

Stole that (slightly modified) from Arthur C. Clarke's Childhood's End

And the island rose to meet the dawn